gdb/amd64-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2024 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 "frame.h"
  21 #include "frame-unwind.h"
  22 #include "gdbcore.h"
  23 #include "symtab.h"
  24 #include "objfiles.h"
  25 #include "osabi.h"
  26 #include "regcache.h"
  27 #include "regset.h"
  28 #include "target.h"
  29 #include "trad-frame.h"
  30
  31 #include "obsd-tdep.h"
  32 #include "amd64-tdep.h"
  33 #include "i387-tdep.h"
  34 #include "gdbsupport/x86-xstate.h"
  35 #include "solib-svr4.h"
  36 #include "bsd-uthread.h"
  37
  38 /* Support for signal handlers.  */
  39
  40 /* Default page size.  */
  41 static const int amd64obsd_page_size = 4096;
  42
  43 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
  44    routine.  */
  45
  46 static int
  47 amd64obsd_sigtramp_p (const frame_info_ptr &this_frame)
  48 {
  49   CORE_ADDR pc = get_frame_pc (this_frame);
  50   CORE_ADDR start_pc = (pc & ~(amd64obsd_page_size - 1));
  51   const gdb_byte osigreturn[] =
  52   {
  53     0x48, 0xc7, 0xc0,
  54     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  55     0xcd, 0x80                  /* int $0x80 */
  56   };
  57   const gdb_byte sigreturn[] =
  58   {
  59     0x48, 0xc7, 0xc0,
  60     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  61     0x0f, 0x05                  /* syscall */
  62   };
  63   size_t buflen = (sizeof sigreturn) + 1;
  64   gdb_byte *buf;
  65   const char *name;
  66
  67   /* If the function has a valid symbol name, it isn't a
  68      trampoline.  */
  69   find_pc_partial_function (pc, &name, NULL, NULL);
  70   if (name != NULL)
  71     return 0;
  72
  73   /* If the function lives in a valid section (even without a starting
  74      point) it isn't a trampoline.  */
  75   if (find_pc_section (pc) != NULL)
  76     return 0;
  77
  78   /* If we can't read the instructions at START_PC, return zero.  */
  79   buf = (gdb_byte *) alloca ((sizeof sigreturn) + 1);
  80   if (!safe_frame_unwind_memory (this_frame, start_pc + 6, {buf, buflen}))
  81     return 0;
  82
  83   /* Check for sigreturn(2).  Depending on how the assembler encoded
  84      the `movq %rsp, %rdi' instruction, the code starts at offset 6 or
  85      7.  OpenBSD 5.0 and later use the `syscall' instruction.  Older
  86      versions use `int $0x80'.  Check for both.  */
  87   if (memcmp (buf, sigreturn, sizeof sigreturn)
  88       && memcmp (buf + 1, sigreturn, sizeof sigreturn)
  89       && memcmp (buf, osigreturn, sizeof osigreturn)
  90       && memcmp (buf + 1, osigreturn, sizeof osigreturn))
  91     return 0;
  92
  93   return 1;
  94 }
  95
  96 /* Assuming THIS_FRAME is for a BSD sigtramp routine, return the
  97    address of the associated sigcontext structure.  */
  98
  99 static CORE_ADDR
 100 amd64obsd_sigcontext_addr (const frame_info_ptr &this_frame)
 101 {
 102   CORE_ADDR pc = get_frame_pc (this_frame);
 103   ULONGEST offset = (pc & (amd64obsd_page_size - 1));
 104
 105   /* The %rsp register points at `struct sigcontext' upon entry of a
 106      signal trampoline.  The relevant part of the trampoline is
 107
 108         call    *%rax
 109         movq    %rsp, %rdi
 110         pushq   %rdi
 111         movq    $SYS_sigreturn,%rax
 112         int     $0x80
 113
 114      (see /usr/src/sys/arch/amd64/amd64/locore.S).  The `pushq'
 115      instruction clobbers %rsp, but its value is saved in `%rdi'.  */
 116
 117   if (offset > 5)
 118     return get_frame_register_unsigned (this_frame, AMD64_RDI_REGNUM);
 119   else
 120     return get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 121 }
 122 \f
 123 /* OpenBSD 3.5 or later.  */
 124
 125 /* Mapping between the general-purpose registers in `struct reg'
 126    format and GDB's register cache layout.  */
 127
 128 /* From <machine/reg.h>.  */
 129 int amd64obsd_r_reg_offset[] =
 130 {
 131   14 * 8,                       /* %rax */
 132   13 * 8,                       /* %rbx */
 133   3 * 8,                        /* %rcx */
 134   2 * 8,                        /* %rdx */
 135   1 * 8,                        /* %rsi */
 136   0 * 8,                        /* %rdi */
 137   12 * 8,                       /* %rbp */
 138   15 * 8,                       /* %rsp */
 139   4 * 8,                        /* %r8 ..  */
 140   5 * 8,
 141   6 * 8,
 142   7 * 8,
 143   8 * 8,
 144   9 * 8,
 145   10 * 8,
 146   11 * 8,                       /* ... %r15 */
 147   16 * 8,                       /* %rip */
 148   17 * 8,                       /* %eflags */
 149   18 * 8,                       /* %cs */
 150   19 * 8,                       /* %ss */
 151   20 * 8,                       /* %ds */
 152   21 * 8,                       /* %es */
 153   22 * 8,                       /* %fs */
 154   23 * 8                        /* %gs */
 155 };
 156
 157 /* From <machine/signal.h>.  */
 158 static int amd64obsd_sc_reg_offset[] =
 159 {
 160   14 * 8,                       /* %rax */
 161   13 * 8,                       /* %rbx */
 162   3 * 8,                        /* %rcx */
 163   2 * 8,                        /* %rdx */
 164   1 * 8,                        /* %rsi */
 165   0 * 8,                        /* %rdi */
 166   12 * 8,                       /* %rbp */
 167   24 * 8,                       /* %rsp */
 168   4 * 8,                        /* %r8 ...  */
 169   5 * 8,
 170   6 * 8,
 171   7 * 8,
 172   8 * 8,
 173   9 * 8,
 174   10 * 8,
 175   11 * 8,                       /* ... %r15 */
 176   21 * 8,                       /* %rip */
 177   23 * 8,                       /* %eflags */
 178   22 * 8,                       /* %cs */
 179   25 * 8,                       /* %ss */
 180   18 * 8,                       /* %ds */
 181   17 * 8,                       /* %es */
 182   16 * 8,                       /* %fs */
 183   15 * 8                        /* %gs */
 184 };
 185
 186 /* From /usr/src/lib/libpthread/arch/amd64/uthread_machdep.c.  */
 187 static int amd64obsd_uthread_reg_offset[] =
 188 {
 189   19 * 8,                       /* %rax */
 190   16 * 8,                       /* %rbx */
 191   18 * 8,                       /* %rcx */
 192   17 * 8,                       /* %rdx */
 193   14 * 8,                       /* %rsi */
 194   13 * 8,                       /* %rdi */
 195   15 * 8,                       /* %rbp */
 196   -1,                           /* %rsp */
 197   12 * 8,                       /* %r8 ...  */
 198   11 * 8,
 199   10 * 8,
 200   9 * 8,
 201   8 * 8,
 202   7 * 8,
 203   6 * 8,
 204   5 * 8,                        /* ... %r15 */
 205   20 * 8,                       /* %rip */
 206   4 * 8,                        /* %eflags */
 207   21 * 8,                       /* %cs */
 208   -1,                           /* %ss */
 209   3 * 8,                        /* %ds */
 210   2 * 8,                        /* %es */
 211   1 * 8,                        /* %fs */
 212   0 * 8                         /* %gs */
 213 };
 214
 215 /* Offset within the thread structure where we can find the saved
 216    stack pointer (%esp).  */
 217 #define AMD64OBSD_UTHREAD_RSP_OFFSET    400
 218
 219 static void
 220 amd64obsd_supply_uthread (struct regcache *regcache,
 221                           int regnum, CORE_ADDR addr)
 222 {
 223   struct gdbarch *gdbarch = regcache->arch ();
 224   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 225   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 226   CORE_ADDR sp = 0;
 227   gdb_byte buf[8];
 228   int i;
 229
 230   gdb_assert (regnum >= -1);
 231
 232   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 233     {
 234       int offset;
 235
 236       /* Fetch stack pointer from thread structure.  */
 237       sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 238
 239       /* Adjust the stack pointer such that it looks as if we just
 240          returned from _thread_machdep_switch.  */
 241       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 242       store_unsigned_integer (buf, 8, byte_order, sp + offset);
 243       regcache->raw_supply (AMD64_RSP_REGNUM, buf);
 244     }
 245
 246   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 247     {
 248       if (amd64obsd_uthread_reg_offset[i] != -1
 249           && (regnum == -1 || regnum == i))
 250         {
 251           /* Fetch stack pointer from thread structure (if we didn't
 252              do so already).  */
 253           if (sp == 0)
 254             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 255
 256           /* Read the saved register from the stack frame.  */
 257           read_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 258           regcache->raw_supply (i, buf);
 259         }
 260     }
 261 }
 262
 263 static void
 264 amd64obsd_collect_uthread (const struct regcache *regcache,
 265                            int regnum, CORE_ADDR addr)
 266 {
 267   struct gdbarch *gdbarch = regcache->arch ();
 268   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 269   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 270   CORE_ADDR sp = 0;
 271   gdb_byte buf[8];
 272   int i;
 273
 274   gdb_assert (regnum >= -1);
 275
 276   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 277     {
 278       int offset;
 279
 280       /* Calculate the stack pointer (frame pointer) that will be
 281          stored into the thread structure.  */
 282       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 283       regcache->raw_collect (AMD64_RSP_REGNUM, buf);
 284       sp = extract_unsigned_integer (buf, 8, byte_order) - offset;
 285
 286       /* Store the stack pointer.  */
 287       write_memory_unsigned_integer (sp_addr, 8, byte_order, sp);
 288
 289       /* The stack pointer was (potentially) modified.  Make sure we
 290          build a proper stack frame.  */
 291       regnum = -1;
 292     }
 293
 294   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 295     {
 296       if (amd64obsd_uthread_reg_offset[i] != -1
 297           && (regnum == -1 || regnum == i))
 298         {
 299           /* Fetch stack pointer from thread structure (if we didn't
 300              calculate it already).  */
 301           if (sp == 0)
 302             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 303
 304           /* Write the register into the stack frame.  */
 305           regcache->raw_collect (i, buf);
 306           write_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 307         }
 308     }
 309 }
 310 /* Kernel debugging support.  */
 311
 312 /* From <machine/frame.h>.  Easy since `struct trapframe' matches
 313    `struct sigcontext'.  */
 314 #define amd64obsd_tf_reg_offset amd64obsd_sc_reg_offset
 315
 316 static struct trad_frame_cache *
 317 amd64obsd_trapframe_cache (const frame_info_ptr &this_frame, void **this_cache)
 318 {
 319   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 320   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 321   struct trad_frame_cache *cache;
 322   CORE_ADDR func, sp, addr;
 323   ULONGEST cs;
 324   const char *name;
 325   int i;
 326
 327   if (*this_cache)
 328     return (struct trad_frame_cache *) *this_cache;
 329
 330   cache = trad_frame_cache_zalloc (this_frame);
 331   *this_cache = cache;
 332
 333   func = get_frame_func (this_frame);
 334   sp = get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 335
 336   find_pc_partial_function (func, &name, NULL, NULL);
 337   if (name && startswith (name, "Xintr"))
 338     addr = sp + 8;              /* It's an interrupt frame.  */
 339   else
 340     addr = sp;
 341
 342   for (i = 0; i < ARRAY_SIZE (amd64obsd_tf_reg_offset); i++)
 343     if (amd64obsd_tf_reg_offset[i] != -1)
 344       trad_frame_set_reg_addr (cache, i, addr + amd64obsd_tf_reg_offset[i]);
 345
 346   /* Read %cs from trap frame.  */
 347   addr += amd64obsd_tf_reg_offset[AMD64_CS_REGNUM];
 348   cs = read_memory_unsigned_integer (addr, 8, byte_order);
 349   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 350     {
 351       /* Trap from user space; terminate backtrace.  */
 352       trad_frame_set_id (cache, outer_frame_id);
 353     }
 354   else
 355     {
 356       /* Construct the frame ID using the function start.  */
 357       trad_frame_set_id (cache, frame_id_build (sp + 16, func));
 358     }
 359
 360   return cache;
 361 }
 362
 363 static void
 364 amd64obsd_trapframe_this_id (const frame_info_ptr &this_frame,
 365                              void **this_cache, struct frame_id *this_id)
 366 {
 367   struct trad_frame_cache *cache =
 368     amd64obsd_trapframe_cache (this_frame, this_cache);
 369
 370   trad_frame_get_id (cache, this_id);
 371 }
 372
 373 static struct value *
 374 amd64obsd_trapframe_prev_register (const frame_info_ptr &this_frame,
 375                                    void **this_cache, int regnum)
 376 {
 377   struct trad_frame_cache *cache =
 378     amd64obsd_trapframe_cache (this_frame, this_cache);
 379
 380   return trad_frame_get_register (cache, this_frame, regnum);
 381 }
 382
 383 static int
 384 amd64obsd_trapframe_sniffer (const struct frame_unwind *self,
 385                              const frame_info_ptr &this_frame,
 386                              void **this_prologue_cache)
 387 {
 388   ULONGEST cs;
 389   const char *name;
 390
 391   /* Check Current Privilege Level and bail out if we're not executing
 392      in kernel space.  */
 393   cs = get_frame_register_unsigned (this_frame, AMD64_CS_REGNUM);
 394   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 395     return 0;
 396
 397   find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
 398   return (name && ((strcmp (name, "calltrap") == 0)
 399                    || (strcmp (name, "osyscall1") == 0)
 400                    || (strcmp (name, "Xsyscall") == 0)
 401                    || (startswith (name, "Xintr"))));
 402 }
 403
 404 static const struct frame_unwind amd64obsd_trapframe_unwind =
 405 {
 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   "amd64 openbsd trap",
 410   NORMAL_FRAME,
 411   default_frame_unwind_stop_reason,
 412   amd64obsd_trapframe_this_id,
 413   amd64obsd_trapframe_prev_register,
 414   NULL,
 415   amd64obsd_trapframe_sniffer
 416 };
 417 \f
 418
 419 static void
 420 amd64obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 421 {
 422   i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (gdbarch);
 423
 424   amd64_init_abi (info, gdbarch,
 425                   amd64_target_description (X86_XSTATE_SSE_MASK, true));
 426   obsd_init_abi (info, gdbarch);
 427
 428   /* Initialize general-purpose register set details.  */
 429   tdep->gregset_reg_offset = amd64obsd_r_reg_offset;
 430   tdep->gregset_num_regs = ARRAY_SIZE (amd64obsd_r_reg_offset);
 431   tdep->sizeof_gregset = 24 * 8;
 432
 433   tdep->jb_pc_offset = 7 * 8;
 434
 435   tdep->sigtramp_p = amd64obsd_sigtramp_p;
 436   tdep->sigcontext_addr = amd64obsd_sigcontext_addr;
 437   tdep->sc_reg_offset = amd64obsd_sc_reg_offset;
 438   tdep->sc_num_regs = ARRAY_SIZE (amd64obsd_sc_reg_offset);
 439
 440   /* OpenBSD provides a user-level threads implementation.  */
 441   bsd_uthread_set_supply_uthread (gdbarch, amd64obsd_supply_uthread);
 442   bsd_uthread_set_collect_uthread (gdbarch, amd64obsd_collect_uthread);
 443
 444   /* OpenBSD uses SVR4-style shared libraries.  */
 445   set_solib_svr4_fetch_link_map_offsets
 446     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 447
 448   /* Unwind kernel trap frames correctly.  */
 449   frame_unwind_prepend_unwinder (gdbarch, &amd64obsd_trapframe_unwind);
 450 }
 451
 452 void _initialize_amd64obsd_tdep ();
 453 void
 454 _initialize_amd64obsd_tdep ()
 455 {
 456   /* The OpenBSD/amd64 native dependent code makes this assumption.  */
 457   gdb_assert (ARRAY_SIZE (amd64obsd_r_reg_offset) == AMD64_NUM_GREGS);
 458
 459   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
 460                           GDB_OSABI_OPENBSD, amd64obsd_init_abi);
 461 }