[deliverable/binutils-gdb.git] / gdb / btrace.c

/* Branch trace support for GDB, the GNU debugger.

   Copyright (C) 2013-2017 Free Software Foundation, Inc.

   Contributed by Intel Corp. <markus.t.metzger@intel.com>

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "btrace.h"
#include "gdbthread.h"
#include "inferior.h"
#include "target.h"
#include "record.h"
#include "symtab.h"
#include "disasm.h"
#include "source.h"
#include "filenames.h"
#include "xml-support.h"
#include "regcache.h"
#include "rsp-low.h"
#include "gdbcmd.h"
#include "cli/cli-utils.h"

#include <inttypes.h>
#include <ctype.h>
#include <algorithm>

/* Command lists for btrace maintenance commands.  */
static struct cmd_list_element *maint_btrace_cmdlist;
static struct cmd_list_element *maint_btrace_set_cmdlist;
static struct cmd_list_element *maint_btrace_show_cmdlist;
static struct cmd_list_element *maint_btrace_pt_set_cmdlist;
static struct cmd_list_element *maint_btrace_pt_show_cmdlist;

/* Control whether to skip PAD packets when computing the packet history.  */
static int maint_btrace_pt_skip_pad = 1;

/* A vector of function segments.  */
typedef struct btrace_function * bfun_s;
DEF_VEC_P (bfun_s);

static void btrace_add_pc (struct thread_info *tp);

/* Print a record debug message.  Use do ... while (0) to avoid ambiguities
   when used in if statements.  */

#define DEBUG(msg, args...)                                             \
  do                                                                    \
    {                                                                   \
      if (record_debug != 0)                                            \
        fprintf_unfiltered (gdb_stdlog,                                 \
                            "[btrace] " msg "\n", ##args);              \
    }                                                                   \
  while (0)

#define DEBUG_FTRACE(msg, args...) DEBUG ("[ftrace] " msg, ##args)

/* Return the function name of a recorded function segment for printing.
   This function never returns NULL.  */

static const char *
ftrace_print_function_name (const struct btrace_function *bfun)
{
  struct minimal_symbol *msym;
  struct symbol *sym;

  msym = bfun->msym;
  sym = bfun->sym;

  if (sym != NULL)
    return SYMBOL_PRINT_NAME (sym);

  if (msym != NULL)
    return MSYMBOL_PRINT_NAME (msym);

  return "<unknown>";
}

/* Return the file name of a recorded function segment for printing.
   This function never returns NULL.  */

static const char *
ftrace_print_filename (const struct btrace_function *bfun)
{
  struct symbol *sym;
  const char *filename;

  sym = bfun->sym;

  if (sym != NULL)
    filename = symtab_to_filename_for_display (symbol_symtab (sym));
  else
    filename = "<unknown>";

  return filename;
}

/* Return a string representation of the address of an instruction.
   This function never returns NULL.  */

static const char *
ftrace_print_insn_addr (const struct btrace_insn *insn)
{
  if (insn == NULL)
    return "<nil>";

  return core_addr_to_string_nz (insn->pc);
}

/* Print an ftrace debug status message.  */

static void
ftrace_debug (const struct btrace_function *bfun, const char *prefix)
{
  const char *fun, *file;
  unsigned int ibegin, iend;
  int level;

  fun = ftrace_print_function_name (bfun);
  file = ftrace_print_filename (bfun);
  level = bfun->level;

  ibegin = bfun->insn_offset;
  iend = ibegin + VEC_length (btrace_insn_s, bfun->insn);

  DEBUG_FTRACE ("%s: fun = %s, file = %s, level = %d, insn = [%u; %u)",
                prefix, fun, file, level, ibegin, iend);
}

/* Return the number of instructions in a given function call segment.  */

static unsigned int
ftrace_call_num_insn (const struct btrace_function* bfun)
{
  if (bfun == NULL)
    return 0;

  /* A gap is always counted as one instruction.  */
  if (bfun->errcode != 0)
    return 1;

  return VEC_length (btrace_insn_s, bfun->insn);
}

/* Return non-zero if BFUN does not match MFUN and FUN,
   return zero otherwise.  */

static int
ftrace_function_switched (const struct btrace_function *bfun,
                          const struct minimal_symbol *mfun,
                          const struct symbol *fun)
{
  struct minimal_symbol *msym;
  struct symbol *sym;

  msym = bfun->msym;
  sym = bfun->sym;

  /* If the minimal symbol changed, we certainly switched functions.  */
  if (mfun != NULL && msym != NULL
      && strcmp (MSYMBOL_LINKAGE_NAME (mfun), MSYMBOL_LINKAGE_NAME (msym)) != 0)
    return 1;

  /* If the symbol changed, we certainly switched functions.  */
  if (fun != NULL && sym != NULL)
    {
      const char *bfname, *fname;

      /* Check the function name.  */
      if (strcmp (SYMBOL_LINKAGE_NAME (fun), SYMBOL_LINKAGE_NAME (sym)) != 0)
        return 1;

      /* Check the location of those functions, as well.  */
      bfname = symtab_to_fullname (symbol_symtab (sym));
      fname = symtab_to_fullname (symbol_symtab (fun));
      if (filename_cmp (fname, bfname) != 0)
        return 1;
    }

  /* If we lost symbol information, we switched functions.  */
  if (!(msym == NULL && sym == NULL) && mfun == NULL && fun == NULL)
    return 1;

  /* If we gained symbol information, we switched functions.  */
  if (msym == NULL && sym == NULL && !(mfun == NULL && fun == NULL))
    return 1;

  return 0;
}

/* Allocate and initialize a new branch trace function segment.
   PREV is the chronologically preceding function segment.
   MFUN and FUN are the symbol information we have for this function.  */

static struct btrace_function *
ftrace_new_function (struct btrace_function *prev,
                     struct minimal_symbol *mfun,
                     struct symbol *fun)
{
  struct btrace_function *bfun;

  bfun = XCNEW (struct btrace_function);

  bfun->msym = mfun;
  bfun->sym = fun;
  bfun->flow.prev = prev;

  if (prev == NULL)
    {
      /* Start counting at one.  */
      bfun->number = 1;
      bfun->insn_offset = 1;
    }
  else
    {
      gdb_assert (prev->flow.next == NULL);
      prev->flow.next = bfun;

      bfun->number = prev->number + 1;
      bfun->insn_offset = prev->insn_offset + ftrace_call_num_insn (prev);
      bfun->level = prev->level;
    }

  return bfun;
}

/* Update the UP field of a function segment.  */

static void
ftrace_update_caller (struct btrace_function *bfun,
                      struct btrace_function *caller,
                      enum btrace_function_flag flags)
{
  if (bfun->up != NULL)
    ftrace_debug (bfun, "updating caller");

  bfun->up = caller;
  bfun->flags = flags;

  ftrace_debug (bfun, "set caller");
  ftrace_debug (caller, "..to");
}

/* Fix up the caller for all segments of a function.  */

static void
ftrace_fixup_caller (struct btrace_function *bfun,
                     struct btrace_function *caller,
                     enum btrace_function_flag flags)
{
  struct btrace_function *prev, *next;

  ftrace_update_caller (bfun, caller, flags);

  /* Update all function segments belonging to the same function.  */
  for (prev = bfun->segment.prev; prev != NULL; prev = prev->segment.prev)
    ftrace_update_caller (prev, caller, flags);

  for (next = bfun->segment.next; next != NULL; next = next->segment.next)
    ftrace_update_caller (next, caller, flags);
}

/* Add a new function segment for a call.
   CALLER is the chronologically preceding function segment.
   MFUN and FUN are the symbol information we have for this function.  */

static struct btrace_function *
ftrace_new_call (struct btrace_function *caller,
                 struct minimal_symbol *mfun,
                 struct symbol *fun)
{
  struct btrace_function *bfun;

  bfun = ftrace_new_function (caller, mfun, fun);
  bfun->up = caller;
  bfun->level += 1;

  ftrace_debug (bfun, "new call");

  return bfun;
}

/* Add a new function segment for a tail call.
   CALLER is the chronologically preceding function segment.
   MFUN and FUN are the symbol information we have for this function.  */

static struct btrace_function *
ftrace_new_tailcall (struct btrace_function *caller,
                     struct minimal_symbol *mfun,
                     struct symbol *fun)
{
  struct btrace_function *bfun;

  bfun = ftrace_new_function (caller, mfun, fun);
  bfun->up = caller;
  bfun->level += 1;
  bfun->flags |= BFUN_UP_LINKS_TO_TAILCALL;

  ftrace_debug (bfun, "new tail call");

  return bfun;
}

/* Return the caller of BFUN or NULL if there is none.  This function skips
   tail calls in the call chain.  */
static struct btrace_function *
ftrace_get_caller (struct btrace_function *bfun)
{
  for (; bfun != NULL; bfun = bfun->up)
    if ((bfun->flags & BFUN_UP_LINKS_TO_TAILCALL) == 0)
      return bfun->up;

  return NULL;
}

/* Find the innermost caller in the back trace of BFUN with MFUN/FUN
   symbol information.  */

static struct btrace_function *
ftrace_find_caller (struct btrace_function *bfun,
                    struct minimal_symbol *mfun,
                    struct symbol *fun)
{
  for (; bfun != NULL; bfun = bfun->up)
    {
      /* Skip functions with incompatible symbol information.  */
      if (ftrace_function_switched (bfun, mfun, fun))
        continue;

      /* This is the function segment we're looking for.  */
      break;
    }

  return bfun;
}

/* Find the innermost caller in the back trace of BFUN, skipping all
   function segments that do not end with a call instruction (e.g.
   tail calls ending with a jump).  */

static struct btrace_function *
ftrace_find_call (struct btrace_function *bfun)
{
  for (; bfun != NULL; bfun = bfun->up)
    {
      struct btrace_insn *last;

      /* Skip gaps.  */
      if (bfun->errcode != 0)
        continue;

      last = VEC_last (btrace_insn_s, bfun->insn);

      if (last->iclass == BTRACE_INSN_CALL)
        break;
    }

  return bfun;
}

/* Add a continuation segment for a function into which we return.
   PREV is the chronologically preceding function segment.
   MFUN and FUN are the symbol information we have for this function.  */

static struct btrace_function *
ftrace_new_return (struct btrace_function *prev,
                   struct minimal_symbol *mfun,
                   struct symbol *fun)
{
  struct btrace_function *bfun, *caller;

  bfun = ftrace_new_function (prev, mfun, fun);

  /* It is important to start at PREV's caller.  Otherwise, we might find
     PREV itself, if PREV is a recursive function.  */
  caller = ftrace_find_caller (prev->up, mfun, fun);
  if (caller != NULL)
    {
      /* The caller of PREV is the preceding btrace function segment in this
         function instance.  */
      gdb_assert (caller->segment.next == NULL);

      caller->segment.next = bfun;
      bfun->segment.prev = caller;

      /* Maintain the function level.  */
      bfun->level = caller->level;

      /* Maintain the call stack.  */
      bfun->up = caller->up;
      bfun->flags = caller->flags;

      ftrace_debug (bfun, "new return");
    }
  else
    {
      /* We did not find a caller.  This could mean that something went
         wrong or that the call is simply not included in the trace.  */

      /* Let's search for some actual call.  */
      caller = ftrace_find_call (prev->up);
      if (caller == NULL)
        {
          /* There is no call in PREV's back trace.  We assume that the
             branch trace did not include it.  */

          /* Let's find the topmost function and add a new caller for it.
             This should handle a series of initial tail calls.  */
          while (prev->up != NULL)
            prev = prev->up;

          bfun->level = prev->level - 1;

          /* Fix up the call stack for PREV.  */
          ftrace_fixup_caller (prev, bfun, BFUN_UP_LINKS_TO_RET);

          ftrace_debug (bfun, "new return - no caller");
        }
      else
        {
          /* There is a call in PREV's back trace to which we should have
             returned but didn't.  Let's start a new, separate back trace
             from PREV's level.  */
          bfun->level = prev->level - 1;

          /* We fix up the back trace for PREV but leave other function segments
             on the same level as they are.
             This should handle things like schedule () correctly where we're
             switching contexts.  */
          prev->up = bfun;
          prev->flags = BFUN_UP_LINKS_TO_RET;

          ftrace_debug (bfun, "new return - unknown caller");
        }
    }

  return bfun;
}

/* Add a new function segment for a function switch.
   PREV is the chronologically preceding function segment.
   MFUN and FUN are the symbol information we have for this function.  */

static struct btrace_function *
ftrace_new_switch (struct btrace_function *prev,
                   struct minimal_symbol *mfun,
                   struct symbol *fun)
{
  struct btrace_function *bfun;

  /* This is an unexplained function switch.  We can't really be sure about the
     call stack, yet the best I can think of right now is to preserve it.  */
  bfun = ftrace_new_function (prev, mfun, fun);
  bfun->up = prev->up;
  bfun->flags = prev->flags;

  ftrace_debug (bfun, "new switch");

  return bfun;
}

/* Add a new function segment for a gap in the trace due to a decode error.
   PREV is the chronologically preceding function segment.
   ERRCODE is the format-specific error code.  */

static struct btrace_function *
ftrace_new_gap (struct btrace_function *prev, int errcode)
{
  struct btrace_function *bfun;

  /* We hijack prev if it was empty.  */
  if (prev != NULL && prev->errcode == 0
      && VEC_empty (btrace_insn_s, prev->insn))
    bfun = prev;
  else
    bfun = ftrace_new_function (prev, NULL, NULL);

  bfun->errcode = errcode;

  ftrace_debug (bfun, "new gap");

  return bfun;
}

/* Update BFUN with respect to the instruction at PC.  This may create new
   function segments.
   Return the chronologically latest function segment, never NULL.  */

static struct btrace_function *
ftrace_update_function (struct btrace_function *bfun, CORE_ADDR pc)
{
  struct bound_minimal_symbol bmfun;
  struct minimal_symbol *mfun;
  struct symbol *fun;
  struct btrace_insn *last;

  /* Try to determine the function we're in.  We use both types of symbols
     to avoid surprises when we sometimes get a full symbol and sometimes
     only a minimal symbol.  */
  fun = find_pc_function (pc);
  bmfun = lookup_minimal_symbol_by_pc (pc);
  mfun = bmfun.minsym;

  if (fun == NULL && mfun == NULL)
    DEBUG_FTRACE ("no symbol at %s", core_addr_to_string_nz (pc));

  /* If we didn't have a function or if we had a gap before, we create one.  */
  if (bfun == NULL || bfun->errcode != 0)
    return ftrace_new_function (bfun, mfun, fun);

  /* Check the last instruction, if we have one.
     We do this check first, since it allows us to fill in the call stack
     links in addition to the normal flow links.  */
  last = NULL;
  if (!VEC_empty (btrace_insn_s, bfun->insn))
    last = VEC_last (btrace_insn_s, bfun->insn);

  if (last != NULL)
    {
      switch (last->iclass)
        {
        case BTRACE_INSN_RETURN:
          {
            const char *fname;

            /* On some systems, _dl_runtime_resolve returns to the resolved
               function instead of jumping to it.  From our perspective,
               however, this is a tailcall.
               If we treated it as return, we wouldn't be able to find the
               resolved function in our stack back trace.  Hence, we would
               lose the current stack back trace and start anew with an empty
               back trace.  When the resolved function returns, we would then
               create a stack back trace with the same function names but
               different frame id's.  This will confuse stepping.  */
            fname = ftrace_print_function_name (bfun);
            if (strcmp (fname, "_dl_runtime_resolve") == 0)
              return ftrace_new_tailcall (bfun, mfun, fun);

            return ftrace_new_return (bfun, mfun, fun);
          }

        case BTRACE_INSN_CALL:
          /* Ignore calls to the next instruction.  They are used for PIC.  */
          if (last->pc + last->size == pc)
            break;

          return ftrace_new_call (bfun, mfun, fun);

        case BTRACE_INSN_JUMP:
          {
            CORE_ADDR start;

            start = get_pc_function_start (pc);

            /* A jump to the start of a function is (typically) a tail call.  */
            if (start == pc)
              return ftrace_new_tailcall (bfun, mfun, fun);

            /* If we can't determine the function for PC, we treat a jump at
               the end of the block as tail call if we're switching functions
               and as an intra-function branch if we don't.  */
            if (start == 0 && ftrace_function_switched (bfun, mfun, fun))
              return ftrace_new_tailcall (bfun, mfun, fun);

            break;
          }
        }
    }

  /* Check if we're switching functions for some other reason.  */
  if (ftrace_function_switched (bfun, mfun, fun))
    {
      DEBUG_FTRACE ("switching from %s in %s at %s",
                    ftrace_print_insn_addr (last),
                    ftrace_print_function_name (bfun),
                    ftrace_print_filename (bfun));

      return ftrace_new_switch (bfun, mfun, fun);
    }

  return bfun;
}

/* Add the instruction at PC to BFUN's instructions.  */

static void
ftrace_update_insns (struct btrace_function *bfun,
                     const struct btrace_insn *insn)
{
  VEC_safe_push (btrace_insn_s, bfun->insn, insn);

  if (record_debug > 1)
    ftrace_debug (bfun, "update insn");
}

/* Classify the instruction at PC.  */

static enum btrace_insn_class
ftrace_classify_insn (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  enum btrace_insn_class iclass;

  iclass = BTRACE_INSN_OTHER;
  TRY
    {
      if (gdbarch_insn_is_call (gdbarch, pc))
        iclass = BTRACE_INSN_CALL;
      else if (gdbarch_insn_is_ret (gdbarch, pc))
        iclass = BTRACE_INSN_RETURN;
      else if (gdbarch_insn_is_jump (gdbarch, pc))
        iclass = BTRACE_INSN_JUMP;
    }
  CATCH (error, RETURN_MASK_ERROR)
    {
    }
  END_CATCH

  return iclass;
}

/* Try to match the back trace at LHS to the back trace at RHS.  Returns the
   number of matching function segments or zero if the back traces do not
   match.  */

static int
ftrace_match_backtrace (struct btrace_function *lhs,
                        struct btrace_function *rhs)
{
  int matches;

  for (matches = 0; lhs != NULL && rhs != NULL; ++matches)
    {
      if (ftrace_function_switched (lhs, rhs->msym, rhs->sym))
        return 0;

      lhs = ftrace_get_caller (lhs);
      rhs = ftrace_get_caller (rhs);
    }

  return matches;
}

/* Add ADJUSTMENT to the level of BFUN and succeeding function segments.  */

static void
ftrace_fixup_level (struct btrace_function *bfun, int adjustment)
{
  if (adjustment == 0)
    return;

  DEBUG_FTRACE ("fixup level (%+d)", adjustment);
  ftrace_debug (bfun, "..bfun");

  for (; bfun != NULL; bfun = bfun->flow.next)
    bfun->level += adjustment;
}

/* Recompute the global level offset.  Traverse the function trace and compute
   the global level offset as the negative of the minimal function level.  */

static void
ftrace_compute_global_level_offset (struct btrace_thread_info *btinfo)
{
  struct btrace_function *bfun, *end;
  int level;

  if (btinfo == NULL)
    return;

  bfun = btinfo->begin;
  if (bfun == NULL)
    return;

  /* The last function segment contains the current instruction, which is not
     really part of the trace.  If it contains just this one instruction, we
     stop when we reach it; otherwise, we let the below loop run to the end.  */
  end = btinfo->end;
  if (VEC_length (btrace_insn_s, end->insn) > 1)
    end = NULL;

  level = INT_MAX;
  for (; bfun != end; bfun = bfun->flow.next)
    level = std::min (level, bfun->level);

  DEBUG_FTRACE ("setting global level offset: %d", -level);
  btinfo->level = -level;
}

/* Connect the function segments PREV and NEXT in a bottom-to-top walk as in
   ftrace_connect_backtrace.  */

static void
ftrace_connect_bfun (struct btrace_function *prev,
                     struct btrace_function *next)
{
  DEBUG_FTRACE ("connecting...");
  ftrace_debug (prev, "..prev");
  ftrace_debug (next, "..next");

  /* The function segments are not yet connected.  */
  gdb_assert (prev->segment.next == NULL);
  gdb_assert (next->segment.prev == NULL);

  prev->segment.next = next;
  next->segment.prev = prev;

  /* We may have moved NEXT to a different function level.  */
  ftrace_fixup_level (next, prev->level - next->level);

  /* If we run out of back trace for one, let's use the other's.  */
  if (prev->up == NULL)
    {
      if (next->up != NULL)
        {
          DEBUG_FTRACE ("using next's callers");
          ftrace_fixup_caller (prev, next->up, next->flags);
        }
    }
  else if (next->up == NULL)
    {
      if (prev->up != NULL)
        {
          DEBUG_FTRACE ("using prev's callers");
          ftrace_fixup_caller (next, prev->up, prev->flags);
        }
    }
  else
    {
      /* PREV may have a tailcall caller, NEXT can't.  If it does, fixup the up
         link to add the tail callers to NEXT's back trace.

         This removes NEXT->UP from NEXT's back trace.  It will be added back
         when connecting NEXT and PREV's callers - provided they exist.

         If PREV's back trace consists of a series of tail calls without an
         actual call, there will be no further connection and NEXT's caller will
         be removed for good.  To catch this case, we handle it here and connect
         the top of PREV's back trace to NEXT's caller.  */
      if ((prev->flags & BFUN_UP_LINKS_TO_TAILCALL) != 0)
        {
          struct btrace_function *caller;
          btrace_function_flags flags;

          /* We checked NEXT->UP above so CALLER can't be NULL.  */
          caller = next->up;
          flags = next->flags;

          DEBUG_FTRACE ("adding prev's tail calls to next");

          ftrace_fixup_caller (next, prev->up, prev->flags);

          for (prev = prev->up; prev != NULL; prev = prev->up)
            {
              /* At the end of PREV's back trace, continue with CALLER.  */
              if (prev->up == NULL)
                {
                  DEBUG_FTRACE ("fixing up link for tailcall chain");
                  ftrace_debug (prev, "..top");
                  ftrace_debug (caller, "..up");

                  ftrace_fixup_caller (prev, caller, flags);

                  /* If we skipped any tail calls, this may move CALLER to a
                     different function level.

                     Note that changing CALLER's level is only OK because we
                     know that this is the last iteration of the bottom-to-top
                     walk in ftrace_connect_backtrace.

                     Otherwise we will fix up CALLER's level when we connect it
                     to PREV's caller in the next iteration.  */
                  ftrace_fixup_level (caller, prev->level - caller->level - 1);
                  break;
                }

              /* There's nothing to do if we find a real call.  */
              if ((prev->flags & BFUN_UP_LINKS_TO_TAILCALL) == 0)
                {
                  DEBUG_FTRACE ("will fix up link in next iteration");
                  break;
                }
            }
        }
    }
}

/* Connect function segments on the same level in the back trace at LHS and RHS.
   The back traces at LHS and RHS are expected to match according to
   ftrace_match_backtrace.  */

static void
ftrace_connect_backtrace (struct btrace_function *lhs,
                          struct btrace_function *rhs)
{
  while (lhs != NULL && rhs != NULL)
    {
      struct btrace_function *prev, *next;

      gdb_assert (!ftrace_function_switched (lhs, rhs->msym, rhs->sym));

      /* Connecting LHS and RHS may change the up link.  */
      prev = lhs;
      next = rhs;

      lhs = ftrace_get_caller (lhs);
      rhs = ftrace_get_caller (rhs);

      ftrace_connect_bfun (prev, next);
    }
}

/* Bridge the gap between two function segments left and right of a gap if their
   respective back traces match in at least MIN_MATCHES functions.

   Returns non-zero if the gap could be bridged, zero otherwise.  */

static int
ftrace_bridge_gap (struct btrace_function *lhs, struct btrace_function *rhs,
                   int min_matches)
{
  struct btrace_function *best_l, *best_r, *cand_l, *cand_r;
  int best_matches;

  DEBUG_FTRACE ("checking gap at insn %u (req matches: %d)",
                rhs->insn_offset - 1, min_matches);

  best_matches = 0;
  best_l = NULL;
  best_r = NULL;

  /* We search the back traces of LHS and RHS for valid connections and connect
     the two functon segments that give the longest combined back trace.  */

  for (cand_l = lhs; cand_l != NULL; cand_l = ftrace_get_caller (cand_l))
    for (cand_r = rhs; cand_r != NULL; cand_r = ftrace_get_caller (cand_r))
      {
        int matches;

        matches = ftrace_match_backtrace (cand_l, cand_r);
        if (best_matches < matches)
          {
            best_matches = matches;
            best_l = cand_l;
            best_r = cand_r;
          }
      }

  /* We need at least MIN_MATCHES matches.  */
  gdb_assert (min_matches > 0);
  if (best_matches < min_matches)
    return 0;

  DEBUG_FTRACE ("..matches: %d", best_matches);

  /* We will fix up the level of BEST_R and succeeding function segments such
     that BEST_R's level matches BEST_L's when we connect BEST_L to BEST_R.

     This will ignore the level of RHS and following if BEST_R != RHS.  I.e. if
     BEST_R is a successor of RHS in the back trace of RHS (phases 1 and 3).

     To catch this, we already fix up the level here where we can start at RHS
     instead of at BEST_R.  We will ignore the level fixup when connecting
     BEST_L to BEST_R as they will already be on the same level.  */
  ftrace_fixup_level (rhs, best_l->level - best_r->level);

  ftrace_connect_backtrace (best_l, best_r);

  return best_matches;
}

/* Try to bridge gaps due to overflow or decode errors by connecting the
   function segments that are separated by the gap.  */

static void
btrace_bridge_gaps (struct thread_info *tp, VEC (bfun_s) **gaps)
{
  VEC (bfun_s) *remaining;
  struct cleanup *old_chain;
  int min_matches;

  DEBUG ("bridge gaps");

  remaining = NULL;
  old_chain = make_cleanup (VEC_cleanup (bfun_s), &remaining);

  /* We require a minimum amount of matches for bridging a gap.  The number of
     required matches will be lowered with each iteration.

     The more matches the higher our confidence that the bridging is correct.
     For big gaps or small traces, however, it may not be feasible to require a
     high number of matches.  */
  for (min_matches = 5; min_matches > 0; --min_matches)
    {
      /* Let's try to bridge as many gaps as we can.  In some cases, we need to
         skip a gap and revisit it again after we closed later gaps.  */
      while (!VEC_empty (bfun_s, *gaps))
        {
          struct btrace_function *gap;
          unsigned int idx;

          for (idx = 0; VEC_iterate (bfun_s, *gaps, idx, gap); ++idx)
            {
              struct btrace_function *lhs, *rhs;
              int bridged;

              /* We may have a sequence of gaps if we run from one error into
                 the next as we try to re-sync onto the trace stream.  Ignore
                 all but the leftmost gap in such a sequence.

                 Also ignore gaps at the beginning of the trace.  */
              lhs = gap->flow.prev;
              if (lhs == NULL || lhs->errcode != 0)
                continue;

              /* Skip gaps to the right.  */
              for (rhs = gap->flow.next; rhs != NULL; rhs = rhs->flow.next)
                if (rhs->errcode == 0)
                  break;

              /* Ignore gaps at the end of the trace.  */
              if (rhs == NULL)
                continue;

              bridged = ftrace_bridge_gap (lhs, rhs, min_matches);

              /* Keep track of gaps we were not able to bridge and try again.
                 If we just pushed them to the end of GAPS we would risk an
                 infinite loop in case we simply cannot bridge a gap.  */
              if (bridged == 0)
                VEC_safe_push (bfun_s, remaining, gap);
            }

          /* Let's see if we made any progress.  */
          if (VEC_length (bfun_s, remaining) == VEC_length (bfun_s, *gaps))
            break;

          VEC_free (bfun_s, *gaps);

          *gaps = remaining;
          remaining = NULL;
        }

      /* We get here if either GAPS is empty or if GAPS equals REMAINING.  */
      if (VEC_empty (bfun_s, *gaps))
        break;

      VEC_free (bfun_s, remaining);
    }

  do_cleanups (old_chain);

  /* We may omit this in some cases.  Not sure it is worth the extra
     complication, though.  */
  ftrace_compute_global_level_offset (&tp->btrace);
}

/* Compute the function branch trace from BTS trace.  */

static void
btrace_compute_ftrace_bts (struct thread_info *tp,
                           const struct btrace_data_bts *btrace,
                           VEC (bfun_s) **gaps)
{
  struct btrace_thread_info *btinfo;
  struct btrace_function *begin, *end;
  struct gdbarch *gdbarch;
  unsigned int blk;
  int level;

  gdbarch = target_gdbarch ();
  btinfo = &tp->btrace;
  begin = btinfo->begin;
  end = btinfo->end;
  level = begin != NULL ? -btinfo->level : INT_MAX;
  blk = VEC_length (btrace_block_s, btrace->blocks);

  while (blk != 0)
    {
      btrace_block_s *block;
      CORE_ADDR pc;

      blk -= 1;

      block = VEC_index (btrace_block_s, btrace->blocks, blk);
      pc = block->begin;

      for (;;)
        {
          struct btrace_insn insn;
          int size;

          /* We should hit the end of the block.  Warn if we went too far.  */
          if (block->end < pc)
            {
              /* Indicate the gap in the trace.  */
              end = ftrace_new_gap (end, BDE_BTS_OVERFLOW);
              if (begin == NULL)
                begin = end;

              VEC_safe_push (bfun_s, *gaps, end);

              warning (_("Recorded trace may be corrupted at instruction "
                         "%u (pc = %s)."), end->insn_offset - 1,
                       core_addr_to_string_nz (pc));

              break;
            }

          end = ftrace_update_function (end, pc);
          if (begin == NULL)
            begin = end;

          /* Maintain the function level offset.
             For all but the last block, we do it here.  */
          if (blk != 0)
            level = std::min (level, end->level);

          size = 0;
          TRY
            {
              size = gdb_insn_length (gdbarch, pc);
            }
          CATCH (error, RETURN_MASK_ERROR)
            {
            }
          END_CATCH

          insn.pc = pc;
          insn.size = size;
          insn.iclass = ftrace_classify_insn (gdbarch, pc);
          insn.flags = 0;

          ftrace_update_insns (end, &insn);

          /* We're done once we pushed the instruction at the end.  */
          if (block->end == pc)
            break;

          /* We can't continue if we fail to compute the size.  */
          if (size <= 0)
            {
              /* Indicate the gap in the trace.  We just added INSN so we're
                 not at the beginning.  */
              end = ftrace_new_gap (end, BDE_BTS_INSN_SIZE);

              VEC_safe_push (bfun_s, *gaps, end);

              warning (_("Recorded trace may be incomplete at instruction %u "
                         "(pc = %s)."), end->insn_offset - 1,
                       core_addr_to_string_nz (pc));

              break;
            }

          pc += size;

          /* Maintain the function level offset.
             For the last block, we do it here to not consider the last
             instruction.
             Since the last instruction corresponds to the current instruction
             and is not really part of the execution history, it shouldn't
             affect the level.  */
          if (blk == 0)
            level = std::min (level, end->level);
        }
    }

  btinfo->begin = begin;
  btinfo->end = end;

  /* LEVEL is the minimal function level of all btrace function segments.
     Define the global level offset to -LEVEL so all function levels are
     normalized to start at zero.  */
  btinfo->level = -level;
}

#if defined (HAVE_LIBIPT)

static enum btrace_insn_class
pt_reclassify_insn (enum pt_insn_class iclass)
{
  switch (iclass)
    {
    case ptic_call:
      return BTRACE_INSN_CALL;

    case ptic_return:
      return BTRACE_INSN_RETURN;

    case ptic_jump:
      return BTRACE_INSN_JUMP;

    default:
      return BTRACE_INSN_OTHER;
    }
}

/* Return the btrace instruction flags for INSN.  */

static btrace_insn_flags
pt_btrace_insn_flags (const struct pt_insn *insn)
{
  btrace_insn_flags flags = 0;

  if (insn->speculative)
    flags |= BTRACE_INSN_FLAG_SPECULATIVE;

  return flags;
}

/* Add function branch trace using DECODER.  */

static void
ftrace_add_pt (struct pt_insn_decoder *decoder,
               struct btrace_function **pbegin,
               struct btrace_function **pend, int *plevel,
               VEC (bfun_s) **gaps)
{
  struct btrace_function *begin, *end, *upd;
  uint64_t offset;
  int errcode;

  begin = *pbegin;
  end = *pend;
  for (;;)
    {
      struct btrace_insn btinsn;
      struct pt_insn insn;

      errcode = pt_insn_sync_forward (decoder);
      if (errcode < 0)
        {
          if (errcode != -pte_eos)
            warning (_("Failed to synchronize onto the Intel Processor "
                       "Trace stream: %s."), pt_errstr (pt_errcode (errcode)));
          break;
        }

      memset (&btinsn, 0, sizeof (btinsn));
      for (;;)
        {
          errcode = pt_insn_next (decoder, &insn, sizeof(insn));
          if (errcode < 0)
            break;

          /* Look for gaps in the trace - unless we're at the beginning.  */
          if (begin != NULL)
            {
              /* Tracing is disabled and re-enabled each time we enter the
                 kernel.  Most times, we continue from the same instruction we
                 stopped before.  This is indicated via the RESUMED instruction
                 flag.  The ENABLED instruction flag means that we continued
                 from some other instruction.  Indicate this as a trace gap.  */
              if (insn.enabled)
                {
                  *pend = end = ftrace_new_gap (end, BDE_PT_DISABLED);

                  VEC_safe_push (bfun_s, *gaps, end);

                  pt_insn_get_offset (decoder, &offset);

                  warning (_("Non-contiguous trace at instruction %u (offset "
                             "= 0x%" PRIx64 ", pc = 0x%" PRIx64 ")."),
                           end->insn_offset - 1, offset, insn.ip);
                }
            }

          /* Indicate trace overflows.  */
          if (insn.resynced)
            {
              *pend = end = ftrace_new_gap (end, BDE_PT_OVERFLOW);
              if (begin == NULL)
                *pbegin = begin = end;

              VEC_safe_push (bfun_s, *gaps, end);

              pt_insn_get_offset (decoder, &offset);

              warning (_("Overflow at instruction %u (offset = 0x%" PRIx64
                         ", pc = 0x%" PRIx64 ")."), end->insn_offset - 1,
                       offset, insn.ip);
            }

          upd = ftrace_update_function (end, insn.ip);
          if (upd != end)
            {
              *pend = end = upd;

              if (begin == NULL)
                *pbegin = begin = upd;
            }

          /* Maintain the function level offset.  */
          *plevel = std::min (*plevel, end->level);

          btinsn.pc = (CORE_ADDR) insn.ip;
          btinsn.size = (gdb_byte) insn.size;
          btinsn.iclass = pt_reclassify_insn (insn.iclass);
          btinsn.flags = pt_btrace_insn_flags (&insn);

          ftrace_update_insns (end, &btinsn);
        }

      if (errcode == -pte_eos)
        break;

      /* Indicate the gap in the trace.  */
      *pend = end = ftrace_new_gap (end, errcode);
      if (begin == NULL)
        *pbegin = begin = end;

      VEC_safe_push (bfun_s, *gaps, end);

      pt_insn_get_offset (decoder, &offset);

      warning (_("Decode error (%d) at instruction %u (offset = 0x%" PRIx64
                 ", pc = 0x%" PRIx64 "): %s."), errcode, end->insn_offset - 1,
               offset, insn.ip, pt_errstr (pt_errcode (errcode)));
    }
}

/* A callback function to allow the trace decoder to read the inferior's
   memory.  */

static int
btrace_pt_readmem_callback (gdb_byte *buffer, size_t size,
                            const struct pt_asid *asid, uint64_t pc,
                            void *context)
{
  int result, errcode;

  result = (int) size;
  TRY
    {
      errcode = target_read_code ((CORE_ADDR) pc, buffer, size);
      if (errcode != 0)
        result = -pte_nomap;
    }
  CATCH (error, RETURN_MASK_ERROR)
    {
      result = -pte_nomap;
    }
  END_CATCH

  return result;
}

/* Translate the vendor from one enum to another.  */

static enum pt_cpu_vendor
pt_translate_cpu_vendor (enum btrace_cpu_vendor vendor)
{
  switch (vendor)
    {
    default:
      return pcv_unknown;

    case CV_INTEL:
      return pcv_intel;
    }
}

/* Finalize the function branch trace after decode.  */

static void btrace_finalize_ftrace_pt (struct pt_insn_decoder *decoder,
                                       struct thread_info *tp, int level)
{
  pt_insn_free_decoder (decoder);

  /* LEVEL is the minimal function level of all btrace function segments.
     Define the global level offset to -LEVEL so all function levels are
     normalized to start at zero.  */
  tp->btrace.level = -level;

  /* Add a single last instruction entry for the current PC.
     This allows us to compute the backtrace at the current PC using both
     standard unwind and btrace unwind.
     This extra entry is ignored by all record commands.  */
  btrace_add_pc (tp);
}

/* Compute the function branch trace from Intel Processor Trace
   format.  */

static void
btrace_compute_ftrace_pt (struct thread_info *tp,
                          const struct btrace_data_pt *btrace,
                          VEC (bfun_s) **gaps)
{
  struct btrace_thread_info *btinfo;
  struct pt_insn_decoder *decoder;
  struct pt_config config;
  int level, errcode;

  if (btrace->size == 0)
    return;

  btinfo = &tp->btrace;
  level = btinfo->begin != NULL ? -btinfo->level : INT_MAX;

  pt_config_init(&config);
  config.begin = btrace->data;
  config.end = btrace->data + btrace->size;

  config.cpu.vendor = pt_translate_cpu_vendor (btrace->config.cpu.vendor);
  config.cpu.family = btrace->config.cpu.family;
  config.cpu.model = btrace->config.cpu.model;
  config.cpu.stepping = btrace->config.cpu.stepping;

  errcode = pt_cpu_errata (&config.errata, &config.cpu);
  if (errcode < 0)
    error (_("Failed to configure the Intel Processor Trace decoder: %s."),
           pt_errstr (pt_errcode (errcode)));

  decoder = pt_insn_alloc_decoder (&config);
  if (decoder == NULL)
    error (_("Failed to allocate the Intel Processor Trace decoder."));

  TRY
    {
      struct pt_image *image;

      image = pt_insn_get_image(decoder);
      if (image == NULL)
        error (_("Failed to configure the Intel Processor Trace decoder."));

      errcode = pt_image_set_callback(image, btrace_pt_readmem_callback, NULL);
      if (errcode < 0)
        error (_("Failed to configure the Intel Processor Trace decoder: "
                 "%s."), pt_errstr (pt_errcode (errcode)));

      ftrace_add_pt (decoder, &btinfo->begin, &btinfo->end, &level, gaps);
    }
  CATCH (error, RETURN_MASK_ALL)
    {
      /* Indicate a gap in the trace if we quit trace processing.  */
      if (error.reason == RETURN_QUIT && btinfo->end != NULL)
        {
          btinfo->end = ftrace_new_gap (btinfo->end, BDE_PT_USER_QUIT);

          VEC_safe_push (bfun_s, *gaps, btinfo->end);
        }

      btrace_finalize_ftrace_pt (decoder, tp, level);

      throw_exception (error);
    }
  END_CATCH

  btrace_finalize_ftrace_pt (decoder, tp, level);
}

#else /* defined (HAVE_LIBIPT)  */

static void
btrace_compute_ftrace_pt (struct thread_info *tp,
                          const struct btrace_data_pt *btrace,
                          VEC (bfun_s) **gaps)
{
  internal_error (__FILE__, __LINE__, _("Unexpected branch trace format."));
}

#endif /* defined (HAVE_LIBIPT)  */

/* Compute the function branch trace from a block branch trace BTRACE for
   a thread given by BTINFO.  */

static void
btrace_compute_ftrace_1 (struct thread_info *tp, struct btrace_data *btrace,
                         VEC (bfun_s) **gaps)
{
  DEBUG ("compute ftrace");

  switch (btrace->format)
    {
    case BTRACE_FORMAT_NONE:
      return;

    case BTRACE_FORMAT_BTS:
      btrace_compute_ftrace_bts (tp, &btrace->variant.bts, gaps);
      return;

    case BTRACE_FORMAT_PT:
      btrace_compute_ftrace_pt (tp, &btrace->variant.pt, gaps);
      return;
    }

  internal_error (__FILE__, __LINE__, _("Unkown branch trace format."));
}

static void
btrace_finalize_ftrace (struct thread_info *tp, VEC (bfun_s) **gaps)
{
  if (!VEC_empty (bfun_s, *gaps))
    {
      tp->btrace.ngaps += VEC_length (bfun_s, *gaps);
      btrace_bridge_gaps (tp, gaps);
    }
}

static void
btrace_compute_ftrace (struct thread_info *tp, struct btrace_data *btrace)
{
  VEC (bfun_s) *gaps;
  struct cleanup *old_chain;

  gaps = NULL;
  old_chain = make_cleanup (VEC_cleanup (bfun_s), &gaps);

  TRY
    {
      btrace_compute_ftrace_1 (tp, btrace, &gaps);
    }
  CATCH (error, RETURN_MASK_ALL)
    {
      btrace_finalize_ftrace (tp, &gaps);

      throw_exception (error);
    }
  END_CATCH

  btrace_finalize_ftrace (tp, &gaps);

  do_cleanups (old_chain);
}

/* Add an entry for the current PC.  */

static void
btrace_add_pc (struct thread_info *tp)
{
  struct btrace_data btrace;
  struct btrace_block *block;
  struct regcache *regcache;
  struct cleanup *cleanup;
  CORE_ADDR pc;

  regcache = get_thread_regcache (tp->ptid);
  pc = regcache_read_pc (regcache);

  btrace_data_init (&btrace);
  btrace.format = BTRACE_FORMAT_BTS;
  btrace.variant.bts.blocks = NULL;

  cleanup = make_cleanup_btrace_data (&btrace);

  block = VEC_safe_push (btrace_block_s, btrace.variant.bts.blocks, NULL);
  block->begin = pc;
  block->end = pc;

  btrace_compute_ftrace (tp, &btrace);

  do_cleanups (cleanup);
}

/* See btrace.h.  */

void
btrace_enable (struct thread_info *tp, const struct btrace_config *conf)
{
  if (tp->btrace.target != NULL)
    return;

#if !defined (HAVE_LIBIPT)
  if (conf->format == BTRACE_FORMAT_PT)
    error (_("GDB does not support Intel Processor Trace."));
#endif /* !defined (HAVE_LIBIPT) */

  if (!target_supports_btrace (conf->format))
    error (_("Target does not support branch tracing."));

  DEBUG ("enable thread %s (%s)", print_thread_id (tp),
         target_pid_to_str (tp->ptid));

  tp->btrace.target = target_enable_btrace (tp->ptid, conf);

  /* We're done if we failed to enable tracing.  */
  if (tp->btrace.target == NULL)
    return;

  /* We need to undo the enable in case of errors.  */
  TRY
    {
      /* Add an entry for the current PC so we start tracing from where we
         enabled it.

         If we can't access TP's registers, TP is most likely running.  In this
         case, we can't really say where tracing was enabled so it should be
         safe to simply skip this step.

         This is not relevant for BTRACE_FORMAT_PT since the trace will already
         start at the PC at which tracing was enabled.  */
      if (conf->format != BTRACE_FORMAT_PT
          && can_access_registers_ptid (tp->ptid))
        btrace_add_pc (tp);
    }
  CATCH (exception, RETURN_MASK_ALL)
    {
      btrace_disable (tp);

      throw_exception (exception);
    }
  END_CATCH
}

/* See btrace.h.  */

const struct btrace_config *
btrace_conf (const struct btrace_thread_info *btinfo)
{
  if (btinfo->target == NULL)
    return NULL;

  return target_btrace_conf (btinfo->target);
}

/* See btrace.h.  */

void
btrace_disable (struct thread_info *tp)
{
  struct btrace_thread_info *btp = &tp->btrace;
  int errcode = 0;

  if (btp->target == NULL)
    return;

  DEBUG ("disable thread %s (%s)", print_thread_id (tp),
         target_pid_to_str (tp->ptid));

  target_disable_btrace (btp->target);
  btp->target = NULL;

  btrace_clear (tp);
}

/* See btrace.h.  */

void
btrace_teardown (struct thread_info *tp)
{
  struct btrace_thread_info *btp = &tp->btrace;
  int errcode = 0;

  if (btp->target == NULL)
    return;

  DEBUG ("teardown thread %s (%s)", print_thread_id (tp),
         target_pid_to_str (tp->ptid));

  target_teardown_btrace (btp->target);
  btp->target = NULL;

  btrace_clear (tp);
}

/* Stitch branch trace in BTS format.  */

static int
btrace_stitch_bts (struct btrace_data_bts *btrace, struct thread_info *tp)
{
  struct btrace_thread_info *btinfo;
  struct btrace_function *last_bfun;
  struct btrace_insn *last_insn;
  btrace_block_s *first_new_block;

  btinfo = &tp->btrace;
  last_bfun = btinfo->end;
  gdb_assert (last_bfun != NULL);
  gdb_assert (!VEC_empty (btrace_block_s, btrace->blocks));

  /* If the existing trace ends with a gap, we just glue the traces
     together.  We need to drop the last (i.e. chronologically first) block
     of the new trace,  though, since we can't fill in the start address.*/
  if (VEC_empty (btrace_insn_s, last_bfun->insn))
    {
      VEC_pop (btrace_block_s, btrace->blocks);
      return 0;
    }

  /* Beware that block trace starts with the most recent block, so the
     chronologically first block in the new trace is the last block in
     the new trace's block vector.  */
  first_new_block = VEC_last (btrace_block_s, btrace->blocks);
  last_insn = VEC_last (btrace_insn_s, last_bfun->insn);

  /* If the current PC at the end of the block is the same as in our current
     trace, there are two explanations:
       1. we executed the instruction and some branch brought us back.
       2. we have not made any progress.
     In the first case, the delta trace vector should contain at least two
     entries.
     In the second case, the delta trace vector should contain exactly one
     entry for the partial block containing the current PC.  Remove it.  */
  if (first_new_block->end == last_insn->pc
      && VEC_length (btrace_block_s, btrace->blocks) == 1)
    {
      VEC_pop (btrace_block_s, btrace->blocks);
      return 0;
    }

  DEBUG ("stitching %s to %s", ftrace_print_insn_addr (last_insn),
         core_addr_to_string_nz (first_new_block->end));

  /* Do a simple sanity check to make sure we don't accidentally end up
     with a bad block.  This should not occur in practice.  */
  if (first_new_block->end < last_insn->pc)
    {
      warning (_("Error while trying to read delta trace.  Falling back to "
                 "a full read."));
      return -1;
    }

  /* We adjust the last block to start at the end of our current trace.  */
  gdb_assert (first_new_block->begin == 0);
  first_new_block->begin = last_insn->pc;

  /* We simply pop the last insn so we can insert it again as part of
     the normal branch trace computation.
     Since instruction iterators are based on indices in the instructions
     vector, we don't leave any pointers dangling.  */
  DEBUG ("pruning insn at %s for stitching",
         ftrace_print_insn_addr (last_insn));

  VEC_pop (btrace_insn_s, last_bfun->insn);

  /* The instructions vector may become empty temporarily if this has
     been the only instruction in this function segment.
     This violates the invariant but will be remedied shortly by
     btrace_compute_ftrace when we add the new trace.  */

  /* The only case where this would hurt is if the entire trace consisted
     of just that one instruction.  If we remove it, we might turn the now
     empty btrace function segment into a gap.  But we don't want gaps at
     the beginning.  To avoid this, we remove the entire old trace.  */
  if (last_bfun == btinfo->begin && VEC_empty (btrace_insn_s, last_bfun->insn))
    btrace_clear (tp);

  return 0;
}

/* Adjust the block trace in order to stitch old and new trace together.
   BTRACE is the new delta trace between the last and the current stop.
   TP is the traced thread.
   May modifx BTRACE as well as the existing trace in TP.
   Return 0 on success, -1 otherwise.  */

static int
btrace_stitch_trace (struct btrace_data *btrace, struct thread_info *tp)
{
  /* If we don't have trace, there's nothing to do.  */
  if (btrace_data_empty (btrace))
    return 0;

  switch (btrace->format)
    {
    case BTRACE_FORMAT_NONE:
      return 0;

    case BTRACE_FORMAT_BTS:
      return btrace_stitch_bts (&btrace->variant.bts, tp);

    case BTRACE_FORMAT_PT:
      /* Delta reads are not supported.  */
      return -1;
    }

  internal_error (__FILE__, __LINE__, _("Unkown branch trace format."));
}

/* Clear the branch trace histories in BTINFO.  */

static void
btrace_clear_history (struct btrace_thread_info *btinfo)
{
  xfree (btinfo->insn_history);
  xfree (btinfo->call_history);
  xfree (btinfo->replay);

  btinfo->insn_history = NULL;
  btinfo->call_history = NULL;
  btinfo->replay = NULL;
}

/* Clear the branch trace maintenance histories in BTINFO.  */

static void
btrace_maint_clear (struct btrace_thread_info *btinfo)
{
  switch (btinfo->data.format)
    {
    default:
      break;

    case BTRACE_FORMAT_BTS:
      btinfo->maint.variant.bts.packet_history.begin = 0;
      btinfo->maint.variant.bts.packet_history.end = 0;
      break;

#if defined (HAVE_LIBIPT)
    case BTRACE_FORMAT_PT:
      xfree (btinfo->maint.variant.pt.packets);

      btinfo->maint.variant.pt.packets = NULL;
      btinfo->maint.variant.pt.packet_history.begin = 0;
      btinfo->maint.variant.pt.packet_history.end = 0;
      break;
#endif /* defined (HAVE_LIBIPT)  */
    }
}

/* See btrace.h.  */

const char *
btrace_decode_error (enum btrace_format format, int errcode)
{
  switch (format)
    {
    case BTRACE_FORMAT_BTS:
      switch (errcode)
        {
        case BDE_BTS_OVERFLOW:
          return _("instruction overflow");

        case BDE_BTS_INSN_SIZE:
          return _("unknown instruction");

        default:
          break;
        }
      break;

#if defined (HAVE_LIBIPT)
    case BTRACE_FORMAT_PT:
      switch (errcode)
        {
        case BDE_PT_USER_QUIT:
          return _("trace decode cancelled");

        case BDE_PT_DISABLED:
          return _("disabled");

        case BDE_PT_OVERFLOW:
          return _("overflow");

        default:
          if (errcode < 0)
            return pt_errstr (pt_errcode (errcode));
          break;
        }
      break;
#endif /* defined (HAVE_LIBIPT)  */

    default:
      break;
    }

  return _("unknown");
}

/* See btrace.h.  */

void
btrace_fetch (struct thread_info *tp)
{
  struct btrace_thread_info *btinfo;
  struct btrace_target_info *tinfo;
  struct btrace_data btrace;
  struct cleanup *cleanup;
  int errcode;

  DEBUG ("fetch thread %s (%s)", print_thread_id (tp),
         target_pid_to_str (tp->ptid));

  btinfo = &tp->btrace;
  tinfo = btinfo->target;
  if (tinfo == NULL)
    return;

  /* There's no way we could get new trace while replaying.
     On the other hand, delta trace would return a partial record with the
     current PC, which is the replay PC, not the last PC, as expected.  */
  if (btinfo->replay != NULL)
    return;

  /* We should not be called on running or exited threads.  */
  gdb_assert (can_access_registers_ptid (tp->ptid));

  btrace_data_init (&btrace);
  cleanup = make_cleanup_btrace_data (&btrace);

  /* Let's first try to extend the trace we already have.  */
  if (btinfo->end != NULL)
    {
      errcode = target_read_btrace (&btrace, tinfo, BTRACE_READ_DELTA);
      if (errcode == 0)
        {
          /* Success.  Let's try to stitch the traces together.  */
          errcode = btrace_stitch_trace (&btrace, tp);
        }
      else
        {
          /* We failed to read delta trace.  Let's try to read new trace.  */
          errcode = target_read_btrace (&btrace, tinfo, BTRACE_READ_NEW);

          /* If we got any new trace, discard what we have.  */
          if (errcode == 0 && !btrace_data_empty (&btrace))
            btrace_clear (tp);
        }

      /* If we were not able to read the trace, we start over.  */
      if (errcode != 0)
        {
          btrace_clear (tp);
          errcode = target_read_btrace (&btrace, tinfo, BTRACE_READ_ALL);
        }
    }
  else
    errcode = target_read_btrace (&btrace, tinfo, BTRACE_READ_ALL);

  /* If we were not able to read the branch trace, signal an error.  */
  if (errcode != 0)
    error (_("Failed to read branch trace."));

  /* Compute the trace, provided we have any.  */
  if (!btrace_data_empty (&btrace))
    {
      /* Store the raw trace data.  The stored data will be cleared in
         btrace_clear, so we always append the new trace.  */
      btrace_data_append (&btinfo->data, &btrace);
      btrace_maint_clear (btinfo);

      btrace_clear_history (btinfo);
      btrace_compute_ftrace (tp, &btrace);
    }

  do_cleanups (cleanup);
}

/* See btrace.h.  */

void
btrace_clear (struct thread_info *tp)
{
  struct btrace_thread_info *btinfo;
  struct btrace_function *it, *trash;

  DEBUG ("clear thread %s (%s)", print_thread_id (tp),
         target_pid_to_str (tp->ptid));

  /* Make sure btrace frames that may hold a pointer into the branch
     trace data are destroyed.  */
  reinit_frame_cache ();

  btinfo = &tp->btrace;

  it = btinfo->begin;
  while (it != NULL)
    {
      trash = it;
      it = it->flow.next;

      xfree (trash);
    }

  btinfo->begin = NULL;
  btinfo->end = NULL;
  btinfo->ngaps = 0;

  /* Must clear the maint data before - it depends on BTINFO->DATA.  */
  btrace_maint_clear (btinfo);
  btrace_data_clear (&btinfo->data);
  btrace_clear_history (btinfo);
}

/* See btrace.h.  */

void
btrace_free_objfile (struct objfile *objfile)
{
  struct thread_info *tp;

  DEBUG ("free objfile");

  ALL_NON_EXITED_THREADS (tp)
    btrace_clear (tp);
}

#if defined (HAVE_LIBEXPAT)

/* Check the btrace document version.  */

static void
check_xml_btrace_version (struct gdb_xml_parser *parser,
                          const struct gdb_xml_element *element,
                          void *user_data, VEC (gdb_xml_value_s) *attributes)
{
  const char *version
    = (const char *) xml_find_attribute (attributes, "version")->value;

  if (strcmp (version, "1.0") != 0)
    gdb_xml_error (parser, _("Unsupported btrace version: \"%s\""), version);
}

/* Parse a btrace "block" xml record.  */

static void
parse_xml_btrace_block (struct gdb_xml_parser *parser,
                        const struct gdb_xml_element *element,
                        void *user_data, VEC (gdb_xml_value_s) *attributes)
{
  struct btrace_data *btrace;
  struct btrace_block *block;
  ULONGEST *begin, *end;

  btrace = (struct btrace_data *) user_data;

  switch (btrace->format)
    {
    case BTRACE_FORMAT_BTS:
      break;

    case BTRACE_FORMAT_NONE:
      btrace->format = BTRACE_FORMAT_BTS;
      btrace->variant.bts.blocks = NULL;
      break;

    default:
      gdb_xml_error (parser, _("Btrace format error."));
    }

  begin = (ULONGEST *) xml_find_attribute (attributes, "begin")->value;
  end = (ULONGEST *) xml_find_attribute (attributes, "end")->value;

  block = VEC_safe_push (btrace_block_s, btrace->variant.bts.blocks, NULL);
  block->begin = *begin;
  block->end = *end;
}

/* Parse a "raw" xml record.  */

static void
parse_xml_raw (struct gdb_xml_parser *parser, const char *body_text,
               gdb_byte **pdata, size_t *psize)
{
  struct cleanup *cleanup;
  gdb_byte *data, *bin;
  size_t len, size;

  len = strlen (body_text);
  if (len % 2 != 0)
    gdb_xml_error (parser, _("Bad raw data size."));

  size = len / 2;

  bin = data = (gdb_byte *) xmalloc (size);
  cleanup = make_cleanup (xfree, data);

  /* We use hex encoding - see common/rsp-low.h.  */
  while (len > 0)
    {
      char hi, lo;

      hi = *body_text++;
      lo = *body_text++;

      if (hi == 0 || lo == 0)
        gdb_xml_error (parser, _("Bad hex encoding."));

      *bin++ = fromhex (hi) * 16 + fromhex (lo);
      len -= 2;
    }

  discard_cleanups (cleanup);

  *pdata = data;
  *psize = size;
}

/* Parse a btrace pt-config "cpu" xml record.  */

static void
parse_xml_btrace_pt_config_cpu (struct gdb_xml_parser *parser,
                                const struct gdb_xml_element *element,
                                void *user_data,
                                VEC (gdb_xml_value_s) *attributes)
{
  struct btrace_data *btrace;
  const char *vendor;
  ULONGEST *family, *model, *stepping;

  vendor = (const char *) xml_find_attribute (attributes, "vendor")->value;
  family = (ULONGEST *) xml_find_attribute (attributes, "family")->value;
  model = (ULONGEST *) xml_find_attribute (attributes, "model")->value;
  stepping = (ULONGEST *) xml_find_attribute (attributes, "stepping")->value;

  btrace = (struct btrace_data *) user_data;

  if (strcmp (vendor, "GenuineIntel") == 0)
    btrace->variant.pt.config.cpu.vendor = CV_INTEL;

  btrace->variant.pt.config.cpu.family = *family;
  btrace->variant.pt.config.cpu.model = *model;
  btrace->variant.pt.config.cpu.stepping = *stepping;
}

/* Parse a btrace pt "raw" xml record.  */

static void
parse_xml_btrace_pt_raw (struct gdb_xml_parser *parser,
                         const struct gdb_xml_element *element,
                         void *user_data, const char *body_text)
{
  struct btrace_data *btrace;

  btrace = (struct btrace_data *) user_data;
  parse_xml_raw (parser, body_text, &btrace->variant.pt.data,
                 &btrace->variant.pt.size);
}

/* Parse a btrace "pt" xml record.  */

static void
parse_xml_btrace_pt (struct gdb_xml_parser *parser,
                     const struct gdb_xml_element *element,
                     void *user_data, VEC (gdb_xml_value_s) *attributes)
{
  struct btrace_data *btrace;

  btrace = (struct btrace_data *) user_data;
  btrace->format = BTRACE_FORMAT_PT;
  btrace->variant.pt.config.cpu.vendor = CV_UNKNOWN;
  btrace->variant.pt.data = NULL;
  btrace->variant.pt.size = 0;
}

static const struct gdb_xml_attribute block_attributes[] = {
  { "begin", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
  { "end", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_attribute btrace_pt_config_cpu_attributes[] = {
  { "vendor", GDB_XML_AF_NONE, NULL, NULL },
  { "family", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
  { "model", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
  { "stepping", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_pt_config_children[] = {
  { "cpu", btrace_pt_config_cpu_attributes, NULL, GDB_XML_EF_OPTIONAL,
    parse_xml_btrace_pt_config_cpu, NULL },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_pt_children[] = {
  { "pt-config", NULL, btrace_pt_config_children, GDB_XML_EF_OPTIONAL, NULL,
    NULL },
  { "raw", NULL, NULL, GDB_XML_EF_OPTIONAL, NULL, parse_xml_btrace_pt_raw },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

static const struct gdb_xml_attribute btrace_attributes[] = {
  { "version", GDB_XML_AF_NONE, NULL, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_children[] = {
  { "block", block_attributes, NULL,
    GDB_XML_EF_REPEATABLE | GDB_XML_EF_OPTIONAL, parse_xml_btrace_block, NULL },
  { "pt", NULL, btrace_pt_children, GDB_XML_EF_OPTIONAL, parse_xml_btrace_pt,
    NULL },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_elements[] = {
  { "btrace", btrace_attributes, btrace_children, GDB_XML_EF_NONE,
    check_xml_btrace_version, NULL },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

#endif /* defined (HAVE_LIBEXPAT) */

/* See btrace.h.  */

void
parse_xml_btrace (struct btrace_data *btrace, const char *buffer)
{
  struct cleanup *cleanup;
  int errcode;

#if defined (HAVE_LIBEXPAT)

  btrace->format = BTRACE_FORMAT_NONE;

  cleanup = make_cleanup_btrace_data (btrace);
  errcode = gdb_xml_parse_quick (_("btrace"), "btrace.dtd", btrace_elements,
                                 buffer, btrace);
  if (errcode != 0)
    error (_("Error parsing branch trace."));

  /* Keep parse results.  */
  discard_cleanups (cleanup);

#else  /* !defined (HAVE_LIBEXPAT) */

  error (_("Cannot process branch trace.  XML parsing is not supported."));

#endif  /* !defined (HAVE_LIBEXPAT) */
}

#if defined (HAVE_LIBEXPAT)

/* Parse a btrace-conf "bts" xml record.  */

static void
parse_xml_btrace_conf_bts (struct gdb_xml_parser *parser,
                          const struct gdb_xml_element *element,
                          void *user_data, VEC (gdb_xml_value_s) *attributes)
{
  struct btrace_config *conf;
  struct gdb_xml_value *size;

  conf = (struct btrace_config *) user_data;
  conf->format = BTRACE_FORMAT_BTS;
  conf->bts.size = 0;

  size = xml_find_attribute (attributes, "size");
  if (size != NULL)
    conf->bts.size = (unsigned int) *(ULONGEST *) size->value;
}

/* Parse a btrace-conf "pt" xml record.  */

static void
parse_xml_btrace_conf_pt (struct gdb_xml_parser *parser,
                          const struct gdb_xml_element *element,
                          void *user_data, VEC (gdb_xml_value_s) *attributes)
{
  struct btrace_config *conf;
  struct gdb_xml_value *size;

  conf = (struct btrace_config *) user_data;
  conf->format = BTRACE_FORMAT_PT;
  conf->pt.size = 0;

  size = xml_find_attribute (attributes, "size");
  if (size != NULL)
    conf->pt.size = (unsigned int) *(ULONGEST *) size->value;
}

static const struct gdb_xml_attribute btrace_conf_pt_attributes[] = {
  { "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_attribute btrace_conf_bts_attributes[] = {
  { "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_conf_children[] = {
  { "bts", btrace_conf_bts_attributes, NULL, GDB_XML_EF_OPTIONAL,
    parse_xml_btrace_conf_bts, NULL },
  { "pt", btrace_conf_pt_attributes, NULL, GDB_XML_EF_OPTIONAL,
    parse_xml_btrace_conf_pt, NULL },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

static const struct gdb_xml_attribute btrace_conf_attributes[] = {
  { "version", GDB_XML_AF_NONE, NULL, NULL },
  { NULL, GDB_XML_AF_NONE, NULL, NULL }
};

static const struct gdb_xml_element btrace_conf_elements[] = {
  { "btrace-conf", btrace_conf_attributes, btrace_conf_children,
    GDB_XML_EF_NONE, NULL, NULL },
  { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
};

#endif /* defined (HAVE_LIBEXPAT) */

/* See btrace.h.  */

void
parse_xml_btrace_conf (struct btrace_config *conf, const char *xml)
{
  int errcode;

#if defined (HAVE_LIBEXPAT)

  errcode = gdb_xml_parse_quick (_("btrace-conf"), "btrace-conf.dtd",
                                 btrace_conf_elements, xml, conf);
  if (errcode != 0)
    error (_("Error parsing branch trace configuration."));

#else  /* !defined (HAVE_LIBEXPAT) */

  error (_("XML parsing is not supported."));

#endif  /* !defined (HAVE_LIBEXPAT) */
}

/* See btrace.h.  */

const struct btrace_insn *
btrace_insn_get (const struct btrace_insn_iterator *it)
{
  const struct btrace_function *bfun;
  unsigned int index, end;

  index = it->index;
  bfun = it->function;

  /* Check if the iterator points to a gap in the trace.  */
  if (bfun->errcode != 0)
    return NULL;

  /* The index is within the bounds of this function's instruction vector.  */
  end = VEC_length (btrace_insn_s, bfun->insn);
  gdb_assert (0 < end);
  gdb_assert (index < end);

  return VEC_index (btrace_insn_s, bfun->insn, index);
}

/* See btrace.h.  */

int
btrace_insn_get_error (const struct btrace_insn_iterator *it)
{
  return it->function->errcode;
}

/* See btrace.h.  */

unsigned int
btrace_insn_number (const struct btrace_insn_iterator *it)
{
  return it->function->insn_offset + it->index;
}

/* See btrace.h.  */

void
btrace_insn_begin (struct btrace_insn_iterator *it,
                   const struct btrace_thread_info *btinfo)
{
  const struct btrace_function *bfun;

  bfun = btinfo->begin;
  if (bfun == NULL)
    error (_("No trace."));

  it->function = bfun;
  it->index = 0;
}

/* See btrace.h.  */

void
btrace_insn_end (struct btrace_insn_iterator *it,
                 const struct btrace_thread_info *btinfo)
{
  const struct btrace_function *bfun;
  unsigned int length;

  bfun = btinfo->end;
  if (bfun == NULL)
    error (_("No trace."));

  length = VEC_length (btrace_insn_s, bfun->insn);

  /* The last function may either be a gap or it contains the current
     instruction, which is one past the end of the execution trace; ignore
     it.  */
  if (length > 0)
    length -= 1;

  it->function = bfun;
  it->index = length;
}

/* See btrace.h.  */

unsigned int
btrace_insn_next (struct btrace_insn_iterator *it, unsigned int stride)
{
  const struct btrace_function *bfun;
  unsigned int index, steps;

  bfun = it->function;
  steps = 0;
  index = it->index;

  while (stride != 0)
    {
      unsigned int end, space, adv;

      end = VEC_length (btrace_insn_s, bfun->insn);

      /* An empty function segment represents a gap in the trace.  We count
         it as one instruction.  */
      if (end == 0)
        {
          const struct btrace_function *next;

          next = bfun->flow.next;
          if (next == NULL)
            break;

          stride -= 1;
          steps += 1;

          bfun = next;
          index = 0;

          continue;
        }

      gdb_assert (0 < end);
      gdb_assert (index < end);

      /* Compute the number of instructions remaining in this segment.  */
      space = end - index;

      /* Advance the iterator as far as possible within this segment.  */
      adv = std::min (space, stride);
      stride -= adv;
      index += adv;
      steps += adv;

      /* Move to the next function if we're at the end of this one.  */
      if (index == end)
        {
          const struct btrace_function *next;

          next = bfun->flow.next;
          if (next == NULL)
            {
              /* We stepped past the last function.

                 Let's adjust the index to point to the last instruction in
                 the previous function.  */
              index -= 1;
              steps -= 1;
              break;
            }

          /* We now point to the first instruction in the new function.  */
          bfun = next;
          index = 0;
        }

      /* We did make progress.  */
      gdb_assert (adv > 0);
    }

  /* Update the iterator.  */
  it->function = bfun;
  it->index = index;

  return steps;
}

/* See btrace.h.  */

unsigned int
btrace_insn_prev (struct btrace_insn_iterator *it, unsigned int stride)
{
  const struct btrace_function *bfun;
  unsigned int index, steps;

  bfun = it->function;
  steps = 0;
  index = it->index;

  while (stride != 0)
    {
      unsigned int adv;

      /* Move to the previous function if we're at the start of this one.  */
      if (index == 0)
        {
          const struct btrace_function *prev;

          prev = bfun->flow.prev;
          if (prev == NULL)
            break;

          /* We point to one after the last instruction in the new function.  */
          bfun = prev;
          index = VEC_length (btrace_insn_s, bfun->insn);

          /* An empty function segment represents a gap in the trace.  We count
             it as one instruction.  */
          if (index == 0)
            {
              stride -= 1;
              steps += 1;

              continue;
            }
        }

      /* Advance the iterator as far as possible within this segment.  */
      adv = std::min (index, stride);

      stride -= adv;
      index -= adv;
      steps += adv;

      /* We did make progress.  */
      gdb_assert (adv > 0);
    }

  /* Update the iterator.  */
  it->function = bfun;
  it->index = index;

  return steps;
}

/* See btrace.h.  */

int
btrace_insn_cmp (const struct btrace_insn_iterator *lhs,
                 const struct btrace_insn_iterator *rhs)
{
  unsigned int lnum, rnum;

  lnum = btrace_insn_number (lhs);
  rnum = btrace_insn_number (rhs);

  return (int) (lnum - rnum);
}

/* See btrace.h.  */

int
btrace_find_insn_by_number (struct btrace_insn_iterator *it,
                            const struct btrace_thread_info *btinfo,
                            unsigned int number)
{
  const struct btrace_function *bfun;

  for (bfun = btinfo->end; bfun != NULL; bfun = bfun->flow.prev)
    if (bfun->insn_offset <= number)
      break;

  if (bfun == NULL)
    return 0;

  if (bfun->insn_offset + ftrace_call_num_insn (bfun) <= number)
    return 0;

  it->function = bfun;
  it->index = number - bfun->insn_offset;

  return 1;
}

/* See btrace.h.  */

const struct btrace_function *
btrace_call_get (const struct btrace_call_iterator *it)
{
  return it->function;
}

/* See btrace.h.  */

unsigned int
btrace_call_number (const struct btrace_call_iterator *it)
{
  const struct btrace_thread_info *btinfo;
  const struct btrace_function *bfun;
  unsigned int insns;

  btinfo = it->btinfo;
  bfun = it->function;
  if (bfun != NULL)
    return bfun->number;

  /* For the end iterator, i.e. bfun == NULL, we return one more than the
     number of the last function.  */
  bfun = btinfo->end;
  insns = VEC_length (btrace_insn_s, bfun->insn);

  /* If the function contains only a single instruction (i.e. the current
     instruction), it will be skipped and its number is already the number
     we seek.  */
  if (insns == 1)
    return bfun->number;

  /* Otherwise, return one more than the number of the last function.  */
  return bfun->number + 1;
}

/* See btrace.h.  */

void
btrace_call_begin (struct btrace_call_iterator *it,
                   const struct btrace_thread_info *btinfo)
{
  const struct btrace_function *bfun;

  bfun = btinfo->begin;
  if (bfun == NULL)
    error (_("No trace."));

  it->btinfo = btinfo;
  it->function = bfun;
}

/* See btrace.h.  */

void
btrace_call_end (struct btrace_call_iterator *it,
                 const struct btrace_thread_info *btinfo)
{
  const struct btrace_function *bfun;

  bfun = btinfo->end;
  if (bfun == NULL)
    error (_("No trace."));

  it->btinfo = btinfo;
  it->function = NULL;
}

/* See btrace.h.  */

unsigned int
btrace_call_next (struct btrace_call_iterator *it, unsigned int stride)
{
  const struct btrace_function *bfun;
  unsigned int steps;

  bfun = it->function;
  steps = 0;
  while (bfun != NULL)
    {
      const struct btrace_function *next;
      unsigned int insns;

      next = bfun->flow.next;
      if (next == NULL)
        {
          /* Ignore the last function if it only contains a single
             (i.e. the current) instruction.  */
          insns = VEC_length (btrace_insn_s, bfun->insn);
          if (insns == 1)
            steps -= 1;
        }

      if (stride == steps)
        break;

      bfun = next;
      steps += 1;
    }

  it->function = bfun;
  return steps;
}

/* See btrace.h.  */

unsigned int
btrace_call_prev (struct btrace_call_iterator *it, unsigned int stride)
{
  const struct btrace_thread_info *btinfo;
  const struct btrace_function *bfun;
  unsigned int steps;

  bfun = it->function;
  steps = 0;

  if (bfun == NULL)
    {
      unsigned int insns;

      btinfo = it->btinfo;
      bfun = btinfo->end;
      if (bfun == NULL)
        return 0;

      /* Ignore the last function if it only contains a single
         (i.e. the current) instruction.  */
      insns = VEC_length (btrace_insn_s, bfun->insn);
      if (insns == 1)
        bfun = bfun->flow.prev;

      if (bfun == NULL)
        return 0;

      steps += 1;
    }

  while (steps < stride)
    {
      const struct btrace_function *prev;

      prev = bfun->flow.prev;
      if (prev == NULL)
        break;

      bfun = prev;
      steps += 1;
    }

  it->function = bfun;
  return steps;
}

/* See btrace.h.  */

int
btrace_call_cmp (const struct btrace_call_iterator *lhs,
                 const struct btrace_call_iterator *rhs)
{
  unsigned int lnum, rnum;

  lnum = btrace_call_number (lhs);
  rnum = btrace_call_number (rhs);

  return (int) (lnum - rnum);
}

/* See btrace.h.  */

int
btrace_find_call_by_number (struct btrace_call_iterator *it,
                            const struct btrace_thread_info *btinfo,
                            unsigned int number)
{
  const struct btrace_function *bfun;

  for (bfun = btinfo->end; bfun != NULL; bfun = bfun->flow.prev)
    {
      unsigned int bnum;

      bnum = bfun->number;
      if (number == bnum)
        {
          it->btinfo = btinfo;
          it->function = bfun;
          return 1;
        }

      /* Functions are ordered and numbered consecutively.  We could bail out
         earlier.  On the other hand, it is very unlikely that we search for
         a nonexistent function.  */
  }

  return 0;
}

/* See btrace.h.  */

void
btrace_set_insn_history (struct btrace_thread_info *btinfo,
                         const struct btrace_insn_iterator *begin,
                         const struct btrace_insn_iterator *end)
{
  if (btinfo->insn_history == NULL)
    btinfo->insn_history = XCNEW (struct btrace_insn_history);

  btinfo->insn_history->begin = *begin;
  btinfo->insn_history->end = *end;
}

/* See btrace.h.  */

void
btrace_set_call_history (struct btrace_thread_info *btinfo,
                         const struct btrace_call_iterator *begin,
                         const struct btrace_call_iterator *end)
{
  gdb_assert (begin->btinfo == end->btinfo);

  if (btinfo->call_history == NULL)
    btinfo->call_history = XCNEW (struct btrace_call_history);

  btinfo->call_history->begin = *begin;
  btinfo->call_history->end = *end;
}

/* See btrace.h.  */

int
btrace_is_replaying (struct thread_info *tp)
{
  return tp->btrace.replay != NULL;
}

/* See btrace.h.  */

int
btrace_is_empty (struct thread_info *tp)
{
  struct btrace_insn_iterator begin, end;
  struct btrace_thread_info *btinfo;

  btinfo = &tp->btrace;

  if (btinfo->begin == NULL)
    return 1;

  btrace_insn_begin (&begin, btinfo);
  btrace_insn_end (&end, btinfo);

  return btrace_insn_cmp (&begin, &end) == 0;
}

/* Forward the cleanup request.  */

static void
do_btrace_data_cleanup (void *arg)
{
  btrace_data_fini ((struct btrace_data *) arg);
}

/* See btrace.h.  */

struct cleanup *
make_cleanup_btrace_data (struct btrace_data *data)
{
  return make_cleanup (do_btrace_data_cleanup, data);
}

#if defined (HAVE_LIBIPT)

/* Print a single packet.  */

static void
pt_print_packet (const struct pt_packet *packet)
{
  switch (packet->type)
    {
    default:
      printf_unfiltered (("[??: %x]"), packet->type);
      break;

    case ppt_psb:
      printf_unfiltered (("psb"));
      break;

    case ppt_psbend:
      printf_unfiltered (("psbend"));
      break;

    case ppt_pad:
      printf_unfiltered (("pad"));
      break;

    case ppt_tip:
      printf_unfiltered (("tip %u: 0x%" PRIx64 ""),
                         packet->payload.ip.ipc,
                         packet->payload.ip.ip);
      break;

    case ppt_tip_pge:
      printf_unfiltered (("tip.pge %u: 0x%" PRIx64 ""),
                         packet->payload.ip.ipc,
                         packet->payload.ip.ip);
      break;

    case ppt_tip_pgd:
      printf_unfiltered (("tip.pgd %u: 0x%" PRIx64 ""),
                         packet->payload.ip.ipc,
                         packet->payload.ip.ip);
      break;

    case ppt_fup:
      printf_unfiltered (("fup %u: 0x%" PRIx64 ""),
                         packet->payload.ip.ipc,
                         packet->payload.ip.ip);
      break;

    case ppt_tnt_8:
      printf_unfiltered (("tnt-8 %u: 0x%" PRIx64 ""),
                         packet->payload.tnt.bit_size,
                         packet->payload.tnt.payload);
      break;

    case ppt_tnt_64:
      printf_unfiltered (("tnt-64 %u: 0x%" PRIx64 ""),
                         packet->payload.tnt.bit_size,
                         packet->payload.tnt.payload);
      break;

    case ppt_pip:
      printf_unfiltered (("pip %" PRIx64 "%s"), packet->payload.pip.cr3,
                         packet->payload.pip.nr ? (" nr") : (""));
      break;

    case ppt_tsc:
      printf_unfiltered (("tsc %" PRIx64 ""), packet->payload.tsc.tsc);
      break;

    case ppt_cbr:
      printf_unfiltered (("cbr %u"), packet->payload.cbr.ratio);
      break;

    case ppt_mode:
      switch (packet->payload.mode.leaf)
        {
        default:
          printf_unfiltered (("mode %u"), packet->payload.mode.leaf);
          break;

        case pt_mol_exec:
          printf_unfiltered (("mode.exec%s%s"),
                             packet->payload.mode.bits.exec.csl
                             ? (" cs.l") : (""),
                             packet->payload.mode.bits.exec.csd
                             ? (" cs.d") : (""));
          break;

        case pt_mol_tsx:
          printf_unfiltered (("mode.tsx%s%s"),
                             packet->payload.mode.bits.tsx.intx
                             ? (" intx") : (""),
                             packet->payload.mode.bits.tsx.abrt
                             ? (" abrt") : (""));
          break;
        }
      break;

    case ppt_ovf:
      printf_unfiltered (("ovf"));
      break;

    case ppt_stop:
      printf_unfiltered (("stop"));
      break;

    case ppt_vmcs:
      printf_unfiltered (("vmcs %" PRIx64 ""), packet->payload.vmcs.base);
      break;

    case ppt_tma:
      printf_unfiltered (("tma %x %x"), packet->payload.tma.ctc,
                         packet->payload.tma.fc);
      break;

    case ppt_mtc:
      printf_unfiltered (("mtc %x"), packet->payload.mtc.ctc);
      break;

    case ppt_cyc:
      printf_unfiltered (("cyc %" PRIx64 ""), packet->payload.cyc.value);
      break;

    case ppt_mnt:
      printf_unfiltered (("mnt %" PRIx64 ""), packet->payload.mnt.payload);
      break;
    }
}

/* Decode packets into MAINT using DECODER.  */

static void
btrace_maint_decode_pt (struct btrace_maint_info *maint,
                        struct pt_packet_decoder *decoder)
{
  int errcode;

  for (;;)
    {
      struct btrace_pt_packet packet;

      errcode = pt_pkt_sync_forward (decoder);
      if (errcode < 0)
        break;

      for (;;)
        {
          pt_pkt_get_offset (decoder, &packet.offset);

          errcode = pt_pkt_next (decoder, &packet.packet,
                                 sizeof(packet.packet));
          if (errcode < 0)
            break;

          if (maint_btrace_pt_skip_pad == 0 || packet.packet.type != ppt_pad)
            {
              packet.errcode = pt_errcode (errcode);
              VEC_safe_push (btrace_pt_packet_s, maint->variant.pt.packets,
                             &packet);
            }
        }

      if (errcode == -pte_eos)
        break;

      packet.errcode = pt_errcode (errcode);
      VEC_safe_push (btrace_pt_packet_s, maint->variant.pt.packets,
                     &packet);

      warning (_("Error at trace offset 0x%" PRIx64 ": %s."),
               packet.offset, pt_errstr (packet.errcode));
    }

  if (errcode != -pte_eos)
    warning (_("Failed to synchronize onto the Intel Processor Trace "
               "stream: %s."), pt_errstr (pt_errcode (errcode)));
}

/* Update the packet history in BTINFO.  */

static void
btrace_maint_update_pt_packets (struct btrace_thread_info *btinfo)
{
  volatile struct gdb_exception except;
  struct pt_packet_decoder *decoder;
  struct btrace_data_pt *pt;
  struct pt_config config;
  int errcode;

  pt = &btinfo->data.variant.pt;

  /* Nothing to do if there is no trace.  */
  if (pt->size == 0)
    return;

  memset (&config, 0, sizeof(config));

  config.size = sizeof (config);
  config.begin = pt->data;
  config.end = pt->data + pt->size;

  config.cpu.vendor = pt_translate_cpu_vendor (pt->config.cpu.vendor);
  config.cpu.family = pt->config.cpu.family;
  config.cpu.model = pt->config.cpu.model;
  config.cpu.stepping = pt->config.cpu.stepping;

  errcode = pt_cpu_errata (&config.errata, &config.cpu);
  if (errcode < 0)
    error (_("Failed to configure the Intel Processor Trace decoder: %s."),
           pt_errstr (pt_errcode (errcode)));

  decoder = pt_pkt_alloc_decoder (&config);
  if (decoder == NULL)
    error (_("Failed to allocate the Intel Processor Trace decoder."));

  TRY
    {
      btrace_maint_decode_pt (&btinfo->maint, decoder);
    }
  CATCH (except, RETURN_MASK_ALL)
    {
      pt_pkt_free_decoder (decoder);

      if (except.reason < 0)
        throw_exception (except);
    }
  END_CATCH

  pt_pkt_free_decoder (decoder);
}

#endif /* !defined (HAVE_LIBIPT)  */

/* Update the packet maintenance information for BTINFO and store the
   low and high bounds into BEGIN and END, respectively.
   Store the current iterator state into FROM and TO.  */

static void
btrace_maint_update_packets (struct btrace_thread_info *btinfo,
                             unsigned int *begin, unsigned int *end,
                             unsigned int *from, unsigned int *to)
{
  switch (btinfo->data.format)
    {
    default:
      *begin = 0;
      *end = 0;
      *from = 0;
      *to = 0;
      break;

    case BTRACE_FORMAT_BTS:
      /* Nothing to do - we operate directly on BTINFO->DATA.  */
      *begin = 0;
      *end = VEC_length (btrace_block_s, btinfo->data.variant.bts.blocks);
      *from = btinfo->maint.variant.bts.packet_history.begin;
      *to = btinfo->maint.variant.bts.packet_history.end;
      break;

#if defined (HAVE_LIBIPT)
    case BTRACE_FORMAT_PT:
      if (VEC_empty (btrace_pt_packet_s, btinfo->maint.variant.pt.packets))
        btrace_maint_update_pt_packets (btinfo);

      *begin = 0;
      *end = VEC_length (btrace_pt_packet_s, btinfo->maint.variant.pt.packets);
      *from = btinfo->maint.variant.pt.packet_history.begin;
      *to = btinfo->maint.variant.pt.packet_history.end;
      break;
#endif /* defined (HAVE_LIBIPT)  */
    }
}

/* Print packets in BTINFO from BEGIN (inclusive) until END (exclusive) and
   update the current iterator position.  */

static void
btrace_maint_print_packets (struct btrace_thread_info *btinfo,
                            unsigned int begin, unsigned int end)
{
  switch (btinfo->data.format)
    {
    default:
      break;

    case BTRACE_FORMAT_BTS:
      {
        VEC (btrace_block_s) *blocks;
        unsigned int blk;

        blocks = btinfo->data.variant.bts.blocks;
        for (blk = begin; blk < end; ++blk)
          {
            const btrace_block_s *block;

            block = VEC_index (btrace_block_s, blocks, blk);

            printf_unfiltered ("%u\tbegin: %s, end: %s\n", blk,
                               core_addr_to_string_nz (block->begin),
                               core_addr_to_string_nz (block->end));
          }

        btinfo->maint.variant.bts.packet_history.begin = begin;
        btinfo->maint.variant.bts.packet_history.end = end;
      }
      break;

#if defined (HAVE_LIBIPT)
    case BTRACE_FORMAT_PT:
      {
        VEC (btrace_pt_packet_s) *packets;
        unsigned int pkt;

        packets = btinfo->maint.variant.pt.packets;
        for (pkt = begin; pkt < end; ++pkt)
          {
            const struct btrace_pt_packet *packet;

            packet = VEC_index (btrace_pt_packet_s, packets, pkt);

            printf_unfiltered ("%u\t", pkt);
            printf_unfiltered ("0x%" PRIx64 "\t", packet->offset);

            if (packet->errcode == pte_ok)
              pt_print_packet (&packet->packet);
            else
              printf_unfiltered ("[error: %s]", pt_errstr (packet->errcode));

            printf_unfiltered ("\n");
          }

        btinfo->maint.variant.pt.packet_history.begin = begin;
        btinfo->maint.variant.pt.packet_history.end = end;
      }
      break;
#endif /* defined (HAVE_LIBIPT)  */
    }
}

/* Read a number from an argument string.  */

static unsigned int
get_uint (char **arg)
{
  char *begin, *end, *pos;
  unsigned long number;

  begin = *arg;
  pos = skip_spaces (begin);

  if (!isdigit (*pos))
    error (_("Expected positive number, got: %s."), pos);

  number = strtoul (pos, &end, 10);
  if (number > UINT_MAX)
    error (_("Number too big."));

  *arg += (end - begin);

  return (unsigned int) number;
}

/* Read a context size from an argument string.  */

static int
get_context_size (char **arg)
{
  char *pos;
  int number;

  pos = skip_spaces (*arg);

  if (!isdigit (*pos))
    error (_("Expected positive number, got: %s."), pos);

  return strtol (pos, arg, 10);
}

/* Complain about junk at the end of an argument string.  */

static void
no_chunk (char *arg)
{
  if (*arg != 0)
    error (_("Junk after argument: %s."), arg);
}

/* The "maintenance btrace packet-history" command.  */

static void
maint_btrace_packet_history_cmd (char *arg, int from_tty)
{
  struct btrace_thread_info *btinfo;
  struct thread_info *tp;
  unsigned int size, begin, end, from, to;

  tp = find_thread_ptid (inferior_ptid);
  if (tp == NULL)
    error (_("No thread."));

  size = 10;
  btinfo = &tp->btrace;

  btrace_maint_update_packets (btinfo, &begin, &end, &from, &to);
  if (begin == end)
    {
      printf_unfiltered (_("No trace.\n"));
      return;
    }

  if (arg == NULL || *arg == 0 || strcmp (arg, "+") == 0)
    {
      from = to;

      if (end - from < size)
        size = end - from;
      to = from + size;
    }
  else if (strcmp (arg, "-") == 0)
    {
      to = from;

      if (to - begin < size)
        size = to - begin;
      from = to - size;
    }
  else
    {
      from = get_uint (&arg);
      if (end <= from)
        error (_("'%u' is out of range."), from);

      arg = skip_spaces (arg);
      if (*arg == ',')
        {
          arg = skip_spaces (++arg);

          if (*arg == '+')
            {
              arg += 1;
              size = get_context_size (&arg);

              no_chunk (arg);

              if (end - from < size)
                size = end - from;
              to = from + size;
            }
          else if (*arg == '-')
            {
              arg += 1;
              size = get_context_size (&arg);

              no_chunk (arg);

              /* Include the packet given as first argument.  */
              from += 1;
              to = from;

              if (to - begin < size)
                size = to - begin;
              from = to - size;
            }
          else
            {
              to = get_uint (&arg);

              /* Include the packet at the second argument and silently
                 truncate the range.  */
              if (to < end)
                to += 1;
              else
                to = end;

              no_chunk (arg);
            }
        }
      else
        {
          no_chunk (arg);

          if (end - from < size)
            size = end - from;
          to = from + size;
        }

      dont_repeat ();
    }

  btrace_maint_print_packets (btinfo, from, to);
}

/* The "maintenance btrace clear-packet-history" command.  */

static void
maint_btrace_clear_packet_history_cmd (char *args, int from_tty)
{
  struct btrace_thread_info *btinfo;
  struct thread_info *tp;

  if (args != NULL && *args != 0)
    error (_("Invalid argument."));

  tp = find_thread_ptid (inferior_ptid);
  if (tp == NULL)
    error (_("No thread."));

  btinfo = &tp->btrace;

  /* Must clear the maint data before - it depends on BTINFO->DATA.  */
  btrace_maint_clear (btinfo);
  btrace_data_clear (&btinfo->data);
}

/* The "maintenance btrace clear" command.  */

static void
maint_btrace_clear_cmd (char *args, int from_tty)
{
  struct btrace_thread_info *btinfo;
  struct thread_info *tp;

  if (args != NULL && *args != 0)
    error (_("Invalid argument."));

  tp = find_thread_ptid (inferior_ptid);
  if (tp == NULL)
    error (_("No thread."));

  btrace_clear (tp);
}

/* The "maintenance btrace" command.  */

static void
maint_btrace_cmd (char *args, int from_tty)
{
  help_list (maint_btrace_cmdlist, "maintenance btrace ", all_commands,
             gdb_stdout);
}

/* The "maintenance set btrace" command.  */

static void
maint_btrace_set_cmd (char *args, int from_tty)
{
  help_list (maint_btrace_set_cmdlist, "maintenance set btrace ", all_commands,
             gdb_stdout);
}

/* The "maintenance show btrace" command.  */

static void
maint_btrace_show_cmd (char *args, int from_tty)
{
  help_list (maint_btrace_show_cmdlist, "maintenance show btrace ",
             all_commands, gdb_stdout);
}

/* The "maintenance set btrace pt" command.  */

static void
maint_btrace_pt_set_cmd (char *args, int from_tty)
{
  help_list (maint_btrace_pt_set_cmdlist, "maintenance set btrace pt ",
             all_commands, gdb_stdout);
}

/* The "maintenance show btrace pt" command.  */

static void
maint_btrace_pt_show_cmd (char *args, int from_tty)
{
  help_list (maint_btrace_pt_show_cmdlist, "maintenance show btrace pt ",
             all_commands, gdb_stdout);
}

/* The "maintenance info btrace" command.  */

static void
maint_info_btrace_cmd (char *args, int from_tty)
{
  struct btrace_thread_info *btinfo;
  struct thread_info *tp;
  const struct btrace_config *conf;

  if (args != NULL && *args != 0)
    error (_("Invalid argument."));

  tp = find_thread_ptid (inferior_ptid);
  if (tp == NULL)
    error (_("No thread."));

  btinfo = &tp->btrace;

  conf = btrace_conf (btinfo);
  if (conf == NULL)
    error (_("No btrace configuration."));

  printf_unfiltered (_("Format: %s.\n"),
                     btrace_format_string (conf->format));

  switch (conf->format)
    {
    default:
      break;

    case BTRACE_FORMAT_BTS:
      printf_unfiltered (_("Number of packets: %u.\n"),
                         VEC_length (btrace_block_s,
                                     btinfo->data.variant.bts.blocks));
      break;

#if defined (HAVE_LIBIPT)
    case BTRACE_FORMAT_PT:
      {
        struct pt_version version;

        version = pt_library_version ();
        printf_unfiltered (_("Version: %u.%u.%u%s.\n"), version.major,
                           version.minor, version.build,
                           version.ext != NULL ? version.ext : "");

        btrace_maint_update_pt_packets (btinfo);
        printf_unfiltered (_("Number of packets: %u.\n"),
                           VEC_length (btrace_pt_packet_s,
                                       btinfo->maint.variant.pt.packets));
      }
      break;
#endif /* defined (HAVE_LIBIPT)  */
    }
}

/* The "maint show btrace pt skip-pad" show value function. */

static void
show_maint_btrace_pt_skip_pad  (struct ui_file *file, int from_tty,
                                  struct cmd_list_element *c,
                                  const char *value)
{
  fprintf_filtered (file, _("Skip PAD packets is %s.\n"), value);
}


/* Initialize btrace maintenance commands.  */

void _initialize_btrace (void);
void
_initialize_btrace (void)
{
  add_cmd ("btrace", class_maintenance, maint_info_btrace_cmd,
           _("Info about branch tracing data."), &maintenanceinfolist);

  add_prefix_cmd ("btrace", class_maintenance, maint_btrace_cmd,
                  _("Branch tracing maintenance commands."),
                  &maint_btrace_cmdlist, "maintenance btrace ",
                  0, &maintenancelist);

  add_prefix_cmd ("btrace", class_maintenance, maint_btrace_set_cmd, _("\
Set branch tracing specific variables."),
                  &maint_btrace_set_cmdlist, "maintenance set btrace ",
                  0, &maintenance_set_cmdlist);

  add_prefix_cmd ("pt", class_maintenance, maint_btrace_pt_set_cmd, _("\
Set Intel Processor Trace specific variables."),
                  &maint_btrace_pt_set_cmdlist, "maintenance set btrace pt ",
                  0, &maint_btrace_set_cmdlist);

  add_prefix_cmd ("btrace", class_maintenance, maint_btrace_show_cmd, _("\
Show branch tracing specific variables."),
                  &maint_btrace_show_cmdlist, "maintenance show btrace ",
                  0, &maintenance_show_cmdlist);

  add_prefix_cmd ("pt", class_maintenance, maint_btrace_pt_show_cmd, _("\
Show Intel Processor Trace specific variables."),
                  &maint_btrace_pt_show_cmdlist, "maintenance show btrace pt ",
                  0, &maint_btrace_show_cmdlist);

  add_setshow_boolean_cmd ("skip-pad", class_maintenance,
                           &maint_btrace_pt_skip_pad, _("\
Set whether PAD packets should be skipped in the btrace packet history."), _("\
Show whether PAD packets should be skipped in the btrace packet history."),_("\
When enabled, PAD packets are ignored in the btrace packet history."),
                           NULL, show_maint_btrace_pt_skip_pad,
                           &maint_btrace_pt_set_cmdlist,
                           &maint_btrace_pt_show_cmdlist);

  add_cmd ("packet-history", class_maintenance, maint_btrace_packet_history_cmd,
           _("Print the raw branch tracing data.\n\
With no argument, print ten more packets after the previous ten-line print.\n\
With '-' as argument print ten packets before a previous ten-line print.\n\
One argument specifies the starting packet of a ten-line print.\n\
Two arguments with comma between specify starting and ending packets to \
print.\n\
Preceded with '+'/'-' the second argument specifies the distance from the \
first.\n"),
           &maint_btrace_cmdlist);

  add_cmd ("clear-packet-history", class_maintenance,
           maint_btrace_clear_packet_history_cmd,
           _("Clears the branch tracing packet history.\n\
Discards the raw branch tracing data but not the execution history data.\n\
"),
           &maint_btrace_cmdlist);

  add_cmd ("clear", class_maintenance, maint_btrace_clear_cmd,
           _("Clears the branch tracing data.\n\
Discards the raw branch tracing data and the execution history data.\n\
The next 'record' command will fetch the branch tracing data anew.\n\
"),
           &maint_btrace_cmdlist);

}