gdb/x86-linux-nat.c

   1 /* Native-dependent code for GNU/Linux x86 (i386 and x86-64).
   2
   3    Copyright (C) 1999-2017 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "inferior.h"
  22 #include "elf/common.h"
  23 #include "gdb_proc_service.h"
  24 #include "nat/gdb_ptrace.h"
  25 #include <sys/user.h>
  26 #include <sys/procfs.h>
  27 #include <sys/uio.h>
  28
  29 #include "x86-nat.h"
  30 #include "linux-nat.h"
  31 #ifndef __x86_64__
  32 #include "i386-linux-nat.h"
  33 #endif
  34 #include "x86-linux-nat.h"
  35 #include "i386-linux-tdep.h"
  36 #ifdef __x86_64__
  37 #include "amd64-linux-tdep.h"
  38 #endif
  39 #include "x86-xstate.h"
  40 #include "nat/linux-btrace.h"
  41 #include "nat/linux-nat.h"
  42 #include "nat/x86-linux.h"
  43 #include "nat/x86-linux-dregs.h"
  44 #include "nat/linux-ptrace.h"
  45
  46 /* linux_nat_new_fork hook.   */
  47
  48 static void
  49 x86_linux_new_fork (struct lwp_info *parent, pid_t child_pid)
  50 {
  51   pid_t parent_pid;
  52   struct x86_debug_reg_state *parent_state;
  53   struct x86_debug_reg_state *child_state;
  54
  55   /* NULL means no watchpoint has ever been set in the parent.  In
  56      that case, there's nothing to do.  */
  57   if (parent->arch_private == NULL)
  58     return;
  59
  60   /* Linux kernel before 2.6.33 commit
  61      72f674d203cd230426437cdcf7dd6f681dad8b0d
  62      will inherit hardware debug registers from parent
  63      on fork/vfork/clone.  Newer Linux kernels create such tasks with
  64      zeroed debug registers.
  65
  66      GDB core assumes the child inherits the watchpoints/hw
  67      breakpoints of the parent, and will remove them all from the
  68      forked off process.  Copy the debug registers mirrors into the
  69      new process so that all breakpoints and watchpoints can be
  70      removed together.  The debug registers mirror will become zeroed
  71      in the end before detaching the forked off process, thus making
  72      this compatible with older Linux kernels too.  */
  73
  74   parent_pid = ptid_get_pid (parent->ptid);
  75   parent_state = x86_debug_reg_state (parent_pid);
  76   child_state = x86_debug_reg_state (child_pid);
  77   *child_state = *parent_state;
  78 }
  79 \f
  80
  81 static void (*super_post_startup_inferior) (struct target_ops *self,
  82                                             ptid_t ptid);
  83
  84 static void
  85 x86_linux_child_post_startup_inferior (struct target_ops *self, ptid_t ptid)
  86 {
  87   x86_cleanup_dregs ();
  88   super_post_startup_inferior (self, ptid);
  89 }
  90
  91 #ifdef __x86_64__
  92 /* Value of CS segment register:
  93      64bit process: 0x33
  94      32bit process: 0x23  */
  95 #define AMD64_LINUX_USER64_CS 0x33
  96
  97 /* Value of DS segment register:
  98      LP64 process: 0x0
  99      X32 process: 0x2b  */
 100 #define AMD64_LINUX_X32_DS 0x2b
 101 #endif
 102
 103 /* Get Linux/x86 target description from running target.  */
 104
 105 static const struct target_desc *
 106 x86_linux_read_description (struct target_ops *ops)
 107 {
 108   int tid;
 109   int is_64bit = 0;
 110 #ifdef __x86_64__
 111   int is_x32;
 112 #endif
 113   static uint64_t xcr0;
 114   uint64_t xcr0_features_bits;
 115
 116   /* GNU/Linux LWP ID's are process ID's.  */
 117   tid = ptid_get_lwp (inferior_ptid);
 118   if (tid == 0)
 119     tid = ptid_get_pid (inferior_ptid); /* Not a threaded program.  */
 120
 121 #ifdef __x86_64__
 122   {
 123     unsigned long cs;
 124     unsigned long ds;
 125
 126     /* Get CS register.  */
 127     errno = 0;
 128     cs = ptrace (PTRACE_PEEKUSER, tid,
 129                  offsetof (struct user_regs_struct, cs), 0);
 130     if (errno != 0)
 131       perror_with_name (_("Couldn't get CS register"));
 132
 133     is_64bit = cs == AMD64_LINUX_USER64_CS;
 134
 135     /* Get DS register.  */
 136     errno = 0;
 137     ds = ptrace (PTRACE_PEEKUSER, tid,
 138                  offsetof (struct user_regs_struct, ds), 0);
 139     if (errno != 0)
 140       perror_with_name (_("Couldn't get DS register"));
 141
 142     is_x32 = ds == AMD64_LINUX_X32_DS;
 143
 144     if (sizeof (void *) == 4 && is_64bit && !is_x32)
 145       error (_("Can't debug 64-bit process with 32-bit GDB"));
 146   }
 147 #elif HAVE_PTRACE_GETFPXREGS
 148   if (have_ptrace_getfpxregs == -1)
 149     {
 150       elf_fpxregset_t fpxregs;
 151
 152       if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 153         {
 154           have_ptrace_getfpxregs = 0;
 155           have_ptrace_getregset = TRIBOOL_FALSE;
 156           return i386_linux_read_description (X86_XSTATE_X87_MASK);
 157         }
 158     }
 159 #endif
 160
 161   if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
 162     {
 163       uint64_t xstateregs[(X86_XSTATE_SSE_SIZE / sizeof (uint64_t))];
 164       struct iovec iov;
 165
 166       iov.iov_base = xstateregs;
 167       iov.iov_len = sizeof (xstateregs);
 168
 169       /* Check if PTRACE_GETREGSET works.  */
 170       if (ptrace (PTRACE_GETREGSET, tid,
 171                   (unsigned int) NT_X86_XSTATE, &iov) < 0)
 172         have_ptrace_getregset = TRIBOOL_FALSE;
 173       else
 174         {
 175           have_ptrace_getregset = TRIBOOL_TRUE;
 176
 177           /* Get XCR0 from XSAVE extended state.  */
 178           xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
 179                              / sizeof (uint64_t))];
 180         }
 181     }
 182
 183   /* Check the native XCR0 only if PTRACE_GETREGSET is available.  If
 184      PTRACE_GETREGSET is not available then set xcr0_features_bits to
 185      zero so that the "no-features" descriptions are returned by the
 186      switches below.  */
 187   if (have_ptrace_getregset == TRIBOOL_TRUE)
 188     xcr0_features_bits = xcr0 & X86_XSTATE_ALL_MASK;
 189   else
 190     xcr0_features_bits = 0;
 191
 192   if (is_64bit)
 193     {
 194 #ifdef __x86_64__
 195       return amd64_linux_read_description (xcr0_features_bits, is_x32);
 196 #endif
 197     }
 198   else
 199     {
 200       const struct target_desc * tdesc
 201         = i386_linux_read_description (xcr0_features_bits);
 202
 203       if (tdesc == NULL)
 204         tdesc = i386_linux_read_description (X86_XSTATE_SSE_MASK);
 205
 206       return tdesc;
 207     }
 208
 209   gdb_assert_not_reached ("failed to return tdesc");
 210 }
 211 \f
 212
 213 /* Enable branch tracing.  */
 214
 215 static struct btrace_target_info *
 216 x86_linux_enable_btrace (struct target_ops *self, ptid_t ptid,
 217                          const struct btrace_config *conf)
 218 {
 219   struct btrace_target_info *tinfo;
 220
 221   errno = 0;
 222   tinfo = linux_enable_btrace (ptid, conf);
 223
 224   if (tinfo == NULL)
 225     error (_("Could not enable branch tracing for %s: %s."),
 226            target_pid_to_str (ptid), safe_strerror (errno));
 227
 228   return tinfo;
 229 }
 230
 231 /* Disable branch tracing.  */
 232
 233 static void
 234 x86_linux_disable_btrace (struct target_ops *self,
 235                           struct btrace_target_info *tinfo)
 236 {
 237   enum btrace_error errcode = linux_disable_btrace (tinfo);
 238
 239   if (errcode != BTRACE_ERR_NONE)
 240     error (_("Could not disable branch tracing."));
 241 }
 242
 243 /* Teardown branch tracing.  */
 244
 245 static void
 246 x86_linux_teardown_btrace (struct target_ops *self,
 247                            struct btrace_target_info *tinfo)
 248 {
 249   /* Ignore errors.  */
 250   linux_disable_btrace (tinfo);
 251 }
 252
 253 static enum btrace_error
 254 x86_linux_read_btrace (struct target_ops *self,
 255                        struct btrace_data *data,
 256                        struct btrace_target_info *btinfo,
 257                        enum btrace_read_type type)
 258 {
 259   return linux_read_btrace (data, btinfo, type);
 260 }
 261
 262 /* See to_btrace_conf in target.h.  */
 263
 264 static const struct btrace_config *
 265 x86_linux_btrace_conf (struct target_ops *self,
 266                        const struct btrace_target_info *btinfo)
 267 {
 268   return linux_btrace_conf (btinfo);
 269 }
 270
 271 \f
 272
 273 /* Helper for ps_get_thread_area.  Sets BASE_ADDR to a pointer to
 274    the thread local storage (or its descriptor) and returns PS_OK
 275    on success.  Returns PS_ERR on failure.  */
 276
 277 ps_err_e
 278 x86_linux_get_thread_area (pid_t pid, void *addr, unsigned int *base_addr)
 279 {
 280   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 281      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 282      4 byte integers in size: `entry_number', `base_addr', `limit',
 283      and a bunch of status bits.
 284
 285      The values returned by this ptrace call should be part of the
 286      regcache buffer, and ps_get_thread_area should channel its
 287      request through the regcache.  That way remote targets could
 288      provide the value using the remote protocol and not this direct
 289      call.
 290
 291      Is this function needed?  I'm guessing that the `base' is the
 292      address of a descriptor that libthread_db uses to find the
 293      thread local address base that GDB needs.  Perhaps that
 294      descriptor is defined by the ABI.  Anyway, given that
 295      libthread_db calls this function without prompting (gdb
 296      requesting tls base) I guess it needs info in there anyway.  */
 297   unsigned int desc[4];
 298
 299   /* This code assumes that "int" is 32 bits and that
 300      GET_THREAD_AREA returns no more than 4 int values.  */
 301   gdb_assert (sizeof (int) == 4);
 302
 303 #ifndef PTRACE_GET_THREAD_AREA
 304 #define PTRACE_GET_THREAD_AREA 25
 305 #endif
 306
 307   if (ptrace (PTRACE_GET_THREAD_AREA, pid, addr, &desc) < 0)
 308     return PS_ERR;
 309
 310   *base_addr = desc[1];
 311   return PS_OK;
 312 }
 313 \f
 314
 315 /* Create an x86 GNU/Linux target.  */
 316
 317 struct target_ops *
 318 x86_linux_create_target (void)
 319 {
 320   /* Fill in the generic GNU/Linux methods.  */
 321   struct target_ops *t = linux_target ();
 322
 323   /* Initialize the debug register function vectors.  */
 324   x86_use_watchpoints (t);
 325   x86_dr_low.set_control = x86_linux_dr_set_control;
 326   x86_dr_low.set_addr = x86_linux_dr_set_addr;
 327   x86_dr_low.get_addr = x86_linux_dr_get_addr;
 328   x86_dr_low.get_status = x86_linux_dr_get_status;
 329   x86_dr_low.get_control = x86_linux_dr_get_control;
 330   x86_set_debug_register_length (sizeof (void *));
 331
 332   /* Override the GNU/Linux inferior startup hook.  */
 333   super_post_startup_inferior = t->to_post_startup_inferior;
 334   t->to_post_startup_inferior = x86_linux_child_post_startup_inferior;
 335
 336   /* Add the description reader.  */
 337   t->to_read_description = x86_linux_read_description;
 338
 339   /* Add btrace methods.  */
 340   t->to_supports_btrace = linux_supports_btrace;
 341   t->to_enable_btrace = x86_linux_enable_btrace;
 342   t->to_disable_btrace = x86_linux_disable_btrace;
 343   t->to_teardown_btrace = x86_linux_teardown_btrace;
 344   t->to_read_btrace = x86_linux_read_btrace;
 345   t->to_btrace_conf = x86_linux_btrace_conf;
 346
 347   return t;
 348 }
 349
 350 /* Add an x86 GNU/Linux target.  */
 351
 352 void
 353 x86_linux_add_target (struct target_ops *t)
 354 {
 355   linux_nat_add_target (t);
 356   linux_nat_set_new_thread (t, x86_linux_new_thread);
 357   linux_nat_set_delete_thread (t, x86_linux_delete_thread);
 358   linux_nat_set_new_fork (t, x86_linux_new_fork);
 359   linux_nat_set_forget_process (t, x86_forget_process);
 360   linux_nat_set_prepare_to_resume (t, x86_linux_prepare_to_resume);
 361 }