gdb/amd64-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2020 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 "frame.h"
  22 #include "frame-unwind.h"
  23 #include "gdbcore.h"
  24 #include "symtab.h"
  25 #include "objfiles.h"
  26 #include "osabi.h"
  27 #include "regcache.h"
  28 #include "regset.h"
  29 #include "target.h"
  30 #include "trad-frame.h"
  31
  32 #include "obsd-tdep.h"
  33 #include "amd64-tdep.h"
  34 #include "i387-tdep.h"
  35 #include "gdbsupport/x86-xstate.h"
  36 #include "solib-svr4.h"
  37 #include "bsd-uthread.h"
  38
  39 /* Support for signal handlers.  */
  40
  41 /* Default page size.  */
  42 static const int amd64obsd_page_size = 4096;
  43
  44 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
  45    routine.  */
  46
  47 static int
  48 amd64obsd_sigtramp_p (struct frame_info *this_frame)
  49 {
  50   CORE_ADDR pc = get_frame_pc (this_frame);
  51   CORE_ADDR start_pc = (pc & ~(amd64obsd_page_size - 1));
  52   const gdb_byte osigreturn[] =
  53   {
  54     0x48, 0xc7, 0xc0,
  55     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  56     0xcd, 0x80                  /* int $0x80 */
  57   };
  58   const gdb_byte sigreturn[] =
  59   {
  60     0x48, 0xc7, 0xc0,
  61     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  62     0x0f, 0x05                  /* syscall */
  63   };
  64   size_t buflen = (sizeof sigreturn) + 1;
  65   gdb_byte *buf;
  66   const char *name;
  67
  68   /* If the function has a valid symbol name, it isn't a
  69      trampoline.  */
  70   find_pc_partial_function (pc, &name, NULL, NULL);
  71   if (name != NULL)
  72     return 0;
  73
  74   /* If the function lives in a valid section (even without a starting
  75      point) it isn't a trampoline.  */
  76   if (find_pc_section (pc) != NULL)
  77     return 0;
  78
  79   /* If we can't read the instructions at START_PC, return zero.  */
  80   buf = (gdb_byte *) alloca ((sizeof sigreturn) + 1);
  81   if (!safe_frame_unwind_memory (this_frame, start_pc + 6, buf, buflen))
  82     return 0;
  83
  84   /* Check for sigreturn(2).  Depending on how the assembler encoded
  85      the `movq %rsp, %rdi' instruction, the code starts at offset 6 or
  86      7.  OpenBSD 5.0 and later use the `syscall' instruction.  Older
  87      versions use `int $0x80'.  Check for both.  */
  88   if (memcmp (buf, sigreturn, sizeof sigreturn)
  89       && memcmp (buf + 1, sigreturn, sizeof sigreturn)
  90       && memcmp (buf, osigreturn, sizeof osigreturn)
  91       && memcmp (buf + 1, osigreturn, sizeof osigreturn))
  92     return 0;
  93
  94   return 1;
  95 }
  96
  97 /* Assuming THIS_FRAME is for a BSD sigtramp routine, return the
  98    address of the associated sigcontext structure.  */
  99
 100 static CORE_ADDR
 101 amd64obsd_sigcontext_addr (struct frame_info *this_frame)
 102 {
 103   CORE_ADDR pc = get_frame_pc (this_frame);
 104   ULONGEST offset = (pc & (amd64obsd_page_size - 1));
 105
 106   /* The %rsp register points at `struct sigcontext' upon entry of a
 107      signal trampoline.  The relevant part of the trampoline is
 108
 109         call    *%rax
 110         movq    %rsp, %rdi
 111         pushq   %rdi
 112         movq    $SYS_sigreturn,%rax
 113         int     $0x80
 114
 115      (see /usr/src/sys/arch/amd64/amd64/locore.S).  The `pushq'
 116      instruction clobbers %rsp, but its value is saved in `%rdi'.  */
 117
 118   if (offset > 5)
 119     return get_frame_register_unsigned (this_frame, AMD64_RDI_REGNUM);
 120   else
 121     return get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 122 }
 123 \f
 124 /* OpenBSD 3.5 or later.  */
 125
 126 /* Mapping between the general-purpose registers in `struct reg'
 127    format and GDB's register cache layout.  */
 128
 129 /* From <machine/reg.h>.  */
 130 int amd64obsd_r_reg_offset[] =
 131 {
 132   14 * 8,                       /* %rax */
 133   13 * 8,                       /* %rbx */
 134   3 * 8,                        /* %rcx */
 135   2 * 8,                        /* %rdx */
 136   1 * 8,                        /* %rsi */
 137   0 * 8,                        /* %rdi */
 138   12 * 8,                       /* %rbp */
 139   15 * 8,                       /* %rsp */
 140   4 * 8,                        /* %r8 ..  */
 141   5 * 8,
 142   6 * 8,
 143   7 * 8,
 144   8 * 8,
 145   9 * 8,
 146   10 * 8,
 147   11 * 8,                       /* ... %r15 */
 148   16 * 8,                       /* %rip */
 149   17 * 8,                       /* %eflags */
 150   18 * 8,                       /* %cs */
 151   19 * 8,                       /* %ss */
 152   20 * 8,                       /* %ds */
 153   21 * 8,                       /* %es */
 154   22 * 8,                       /* %fs */
 155   23 * 8                        /* %gs */
 156 };
 157
 158 /* From <machine/signal.h>.  */
 159 static int amd64obsd_sc_reg_offset[] =
 160 {
 161   14 * 8,                       /* %rax */
 162   13 * 8,                       /* %rbx */
 163   3 * 8,                        /* %rcx */
 164   2 * 8,                        /* %rdx */
 165   1 * 8,                        /* %rsi */
 166   0 * 8,                        /* %rdi */
 167   12 * 8,                       /* %rbp */
 168   24 * 8,                       /* %rsp */
 169   4 * 8,                        /* %r8 ...  */
 170   5 * 8,
 171   6 * 8,
 172   7 * 8,
 173   8 * 8,
 174   9 * 8,
 175   10 * 8,
 176   11 * 8,                       /* ... %r15 */
 177   21 * 8,                       /* %rip */
 178   23 * 8,                       /* %eflags */
 179   22 * 8,                       /* %cs */
 180   25 * 8,                       /* %ss */
 181   18 * 8,                       /* %ds */
 182   17 * 8,                       /* %es */
 183   16 * 8,                       /* %fs */
 184   15 * 8                        /* %gs */
 185 };
 186
 187 /* From /usr/src/lib/libpthread/arch/amd64/uthread_machdep.c.  */
 188 static int amd64obsd_uthread_reg_offset[] =
 189 {
 190   19 * 8,                       /* %rax */
 191   16 * 8,                       /* %rbx */
 192   18 * 8,                       /* %rcx */
 193   17 * 8,                       /* %rdx */
 194   14 * 8,                       /* %rsi */
 195   13 * 8,                       /* %rdi */
 196   15 * 8,                       /* %rbp */
 197   -1,                           /* %rsp */
 198   12 * 8,                       /* %r8 ...  */
 199   11 * 8,
 200   10 * 8,
 201   9 * 8,
 202   8 * 8,
 203   7 * 8,
 204   6 * 8,
 205   5 * 8,                        /* ... %r15 */
 206   20 * 8,                       /* %rip */
 207   4 * 8,                        /* %eflags */
 208   21 * 8,                       /* %cs */
 209   -1,                           /* %ss */
 210   3 * 8,                        /* %ds */
 211   2 * 8,                        /* %es */
 212   1 * 8,                        /* %fs */
 213   0 * 8                         /* %gs */
 214 };
 215
 216 /* Offset within the thread structure where we can find the saved
 217    stack pointer (%esp).  */
 218 #define AMD64OBSD_UTHREAD_RSP_OFFSET    400
 219
 220 static void
 221 amd64obsd_supply_uthread (struct regcache *regcache,
 222                           int regnum, CORE_ADDR addr)
 223 {
 224   struct gdbarch *gdbarch = regcache->arch ();
 225   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 226   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 227   CORE_ADDR sp = 0;
 228   gdb_byte buf[8];
 229   int i;
 230
 231   gdb_assert (regnum >= -1);
 232
 233   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 234     {
 235       int offset;
 236
 237       /* Fetch stack pointer from thread structure.  */
 238       sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 239
 240       /* Adjust the stack pointer such that it looks as if we just
 241          returned from _thread_machdep_switch.  */
 242       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 243       store_unsigned_integer (buf, 8, byte_order, sp + offset);
 244       regcache->raw_supply (AMD64_RSP_REGNUM, buf);
 245     }
 246
 247   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 248     {
 249       if (amd64obsd_uthread_reg_offset[i] != -1
 250           && (regnum == -1 || regnum == i))
 251         {
 252           /* Fetch stack pointer from thread structure (if we didn't
 253              do so already).  */
 254           if (sp == 0)
 255             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 256
 257           /* Read the saved register from the stack frame.  */
 258           read_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 259           regcache->raw_supply (i, buf);
 260         }
 261     }
 262 }
 263
 264 static void
 265 amd64obsd_collect_uthread (const struct regcache *regcache,
 266                            int regnum, CORE_ADDR addr)
 267 {
 268   struct gdbarch *gdbarch = regcache->arch ();
 269   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 270   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 271   CORE_ADDR sp = 0;
 272   gdb_byte buf[8];
 273   int i;
 274
 275   gdb_assert (regnum >= -1);
 276
 277   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 278     {
 279       int offset;
 280
 281       /* Calculate the stack pointer (frame pointer) that will be
 282          stored into the thread structure.  */
 283       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 284       regcache->raw_collect (AMD64_RSP_REGNUM, buf);
 285       sp = extract_unsigned_integer (buf, 8, byte_order) - offset;
 286
 287       /* Store the stack pointer.  */
 288       write_memory_unsigned_integer (sp_addr, 8, byte_order, sp);
 289
 290       /* The stack pointer was (potentially) modified.  Make sure we
 291          build a proper stack frame.  */
 292       regnum = -1;
 293     }
 294
 295   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 296     {
 297       if (amd64obsd_uthread_reg_offset[i] != -1
 298           && (regnum == -1 || regnum == i))
 299         {
 300           /* Fetch stack pointer from thread structure (if we didn't
 301              calculate it already).  */
 302           if (sp == 0)
 303             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 304
 305           /* Write the register into the stack frame.  */
 306           regcache->raw_collect (i, buf);
 307           write_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 308         }
 309     }
 310 }
 311 /* Kernel debugging support.  */
 312
 313 /* From <machine/frame.h>.  Easy since `struct trapframe' matches
 314    `struct sigcontext'.  */
 315 #define amd64obsd_tf_reg_offset amd64obsd_sc_reg_offset
 316
 317 static struct trad_frame_cache *
 318 amd64obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
 319 {
 320   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 321   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 322   struct trad_frame_cache *cache;
 323   CORE_ADDR func, sp, addr;
 324   ULONGEST cs;
 325   const char *name;
 326   int i;
 327
 328   if (*this_cache)
 329     return (struct trad_frame_cache *) *this_cache;
 330
 331   cache = trad_frame_cache_zalloc (this_frame);
 332   *this_cache = cache;
 333
 334   func = get_frame_func (this_frame);
 335   sp = get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 336
 337   find_pc_partial_function (func, &name, NULL, NULL);
 338   if (name && startswith (name, "Xintr"))
 339     addr = sp + 8;              /* It's an interrupt frame.  */
 340   else
 341     addr = sp;
 342
 343   for (i = 0; i < ARRAY_SIZE (amd64obsd_tf_reg_offset); i++)
 344     if (amd64obsd_tf_reg_offset[i] != -1)
 345       trad_frame_set_reg_addr (cache, i, addr + amd64obsd_tf_reg_offset[i]);
 346
 347   /* Read %cs from trap frame.  */
 348   addr += amd64obsd_tf_reg_offset[AMD64_CS_REGNUM];
 349   cs = read_memory_unsigned_integer (addr, 8, byte_order);
 350   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 351     {
 352       /* Trap from user space; terminate backtrace.  */
 353       trad_frame_set_id (cache, outer_frame_id);
 354     }
 355   else
 356     {
 357       /* Construct the frame ID using the function start.  */
 358       trad_frame_set_id (cache, frame_id_build (sp + 16, func));
 359     }
 360
 361   return cache;
 362 }
 363
 364 static void
 365 amd64obsd_trapframe_this_id (struct frame_info *this_frame,
 366                              void **this_cache, struct frame_id *this_id)
 367 {
 368   struct trad_frame_cache *cache =
 369     amd64obsd_trapframe_cache (this_frame, this_cache);
 370
 371   trad_frame_get_id (cache, this_id);
 372 }
 373
 374 static struct value *
 375 amd64obsd_trapframe_prev_register (struct frame_info *this_frame,
 376                                    void **this_cache, int regnum)
 377 {
 378   struct trad_frame_cache *cache =
 379     amd64obsd_trapframe_cache (this_frame, this_cache);
 380
 381   return trad_frame_get_register (cache, this_frame, regnum);
 382 }
 383
 384 static int
 385 amd64obsd_trapframe_sniffer (const struct frame_unwind *self,
 386                              struct frame_info *this_frame,
 387                              void **this_prologue_cache)
 388 {
 389   ULONGEST cs;
 390   const char *name;
 391
 392   /* Check Current Privilege Level and bail out if we're not executing
 393      in kernel space.  */
 394   cs = get_frame_register_unsigned (this_frame, AMD64_CS_REGNUM);
 395   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 396     return 0;
 397
 398   find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
 399   return (name && ((strcmp (name, "calltrap") == 0)
 400                    || (strcmp (name, "osyscall1") == 0)
 401                    || (strcmp (name, "Xsyscall") == 0)
 402                    || (startswith (name, "Xintr"))));
 403 }
 404
 405 static const struct frame_unwind amd64obsd_trapframe_unwind = {
 406   /* FIXME: kettenis/20051219: This really is more like an interrupt
 407      frame, but SIGTRAMP_FRAME would print <signal handler called>,
 408      which really is not what we want here.  */
 409   NORMAL_FRAME,
 410   default_frame_unwind_stop_reason,
 411   amd64obsd_trapframe_this_id,
 412   amd64obsd_trapframe_prev_register,
 413   NULL,
 414   amd64obsd_trapframe_sniffer
 415 };
 416 \f
 417
 418 static void
 419 amd64obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 420 {
 421   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 422
 423   amd64_init_abi (info, gdbarch,
 424                   amd64_target_description (X86_XSTATE_SSE_MASK, true));
 425   obsd_init_abi (info, gdbarch);
 426
 427   /* Initialize general-purpose register set details.  */
 428   tdep->gregset_reg_offset = amd64obsd_r_reg_offset;
 429   tdep->gregset_num_regs = ARRAY_SIZE (amd64obsd_r_reg_offset);
 430   tdep->sizeof_gregset = 24 * 8;
 431
 432   tdep->jb_pc_offset = 7 * 8;
 433
 434   tdep->sigtramp_p = amd64obsd_sigtramp_p;
 435   tdep->sigcontext_addr = amd64obsd_sigcontext_addr;
 436   tdep->sc_reg_offset = amd64obsd_sc_reg_offset;
 437   tdep->sc_num_regs = ARRAY_SIZE (amd64obsd_sc_reg_offset);
 438
 439   /* OpenBSD provides a user-level threads implementation.  */
 440   bsd_uthread_set_supply_uthread (gdbarch, amd64obsd_supply_uthread);
 441   bsd_uthread_set_collect_uthread (gdbarch, amd64obsd_collect_uthread);
 442
 443   /* OpenBSD uses SVR4-style shared libraries.  */
 444   set_solib_svr4_fetch_link_map_offsets
 445     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 446
 447   /* Unwind kernel trap frames correctly.  */
 448   frame_unwind_prepend_unwinder (gdbarch, &amd64obsd_trapframe_unwind);
 449 }
 450
 451 void _initialize_amd64obsd_tdep ();
 452 void
 453 _initialize_amd64obsd_tdep ()
 454 {
 455   /* The OpenBSD/amd64 native dependent code makes this assumption.  */
 456   gdb_assert (ARRAY_SIZE (amd64obsd_r_reg_offset) == AMD64_NUM_GREGS);
 457
 458   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
 459                           GDB_OSABI_OPENBSD, amd64obsd_init_abi);
 460 }