gdb/amd64-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2019 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
  22 /* Local non-gdb includes.  */
  23 #include "amd64-tdep.h"
  24 #include "bsd-uthread.h"
  25 #include "common/x86-xstate.h"
  26 #include "frame-unwind.h"
  27 #include "frame.h"
  28 #include "gdbcore.h"
  29 #include "i387-tdep.h"
  30 #include "objfiles.h"
  31 #include "obsd-tdep.h"
  32 #include "osabi.h"
  33 #include "regcache.h"
  34 #include "regset.h"
  35 #include "solib-svr4.h"
  36 #include "symtab.h"
  37 #include "target.h"
  38 #include "trad-frame.h"
  39
  40 /* Support for signal handlers.  */
  41
  42 /* Default page size.  */
  43 static const int amd64obsd_page_size = 4096;
  44
  45 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
  46    routine.  */
  47
  48 static int
  49 amd64obsd_sigtramp_p (struct frame_info *this_frame)
  50 {
  51   CORE_ADDR pc = get_frame_pc (this_frame);
  52   CORE_ADDR start_pc = (pc & ~(amd64obsd_page_size - 1));
  53   const gdb_byte osigreturn[] =
  54   {
  55     0x48, 0xc7, 0xc0,
  56     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  57     0xcd, 0x80                  /* int $0x80 */
  58   };
  59   const gdb_byte sigreturn[] =
  60   {
  61     0x48, 0xc7, 0xc0,
  62     0x67, 0x00, 0x00, 0x00,     /* movq $SYS_sigreturn, %rax */
  63     0x0f, 0x05                  /* syscall */
  64   };
  65   size_t buflen = (sizeof sigreturn) + 1;
  66   gdb_byte *buf;
  67   const char *name;
  68
  69   /* If the function has a valid symbol name, it isn't a
  70      trampoline.  */
  71   find_pc_partial_function (pc, &name, NULL, NULL);
  72   if (name != NULL)
  73     return 0;
  74
  75   /* If the function lives in a valid section (even without a starting
  76      point) it isn't a trampoline.  */
  77   if (find_pc_section (pc) != NULL)
  78     return 0;
  79
  80   /* If we can't read the instructions at START_PC, return zero.  */
  81   buf = (gdb_byte *) alloca ((sizeof sigreturn) + 1);
  82   if (!safe_frame_unwind_memory (this_frame, start_pc + 6, buf, buflen))
  83     return 0;
  84
  85   /* Check for sigreturn(2).  Depending on how the assembler encoded
  86      the `movq %rsp, %rdi' instruction, the code starts at offset 6 or
  87      7.  OpenBSD 5.0 and later use the `syscall' instruction.  Older
  88      versions use `int $0x80'.  Check for both.  */
  89   if (memcmp (buf, sigreturn, sizeof sigreturn)
  90       && memcmp (buf + 1, sigreturn, sizeof sigreturn)
  91       && memcmp (buf, osigreturn, sizeof osigreturn)
  92       && memcmp (buf + 1, osigreturn, sizeof osigreturn))
  93     return 0;
  94
  95   return 1;
  96 }
  97
  98 /* Assuming THIS_FRAME is for a BSD sigtramp routine, return the
  99    address of the associated sigcontext structure.  */
 100
 101 static CORE_ADDR
 102 amd64obsd_sigcontext_addr (struct frame_info *this_frame)
 103 {
 104   CORE_ADDR pc = get_frame_pc (this_frame);
 105   ULONGEST offset = (pc & (amd64obsd_page_size - 1));
 106
 107   /* The %rsp register points at `struct sigcontext' upon entry of a
 108      signal trampoline.  The relevant part of the trampoline is
 109
 110         call    *%rax
 111         movq    %rsp, %rdi
 112         pushq   %rdi
 113         movq    $SYS_sigreturn,%rax
 114         int     $0x80
 115
 116      (see /usr/src/sys/arch/amd64/amd64/locore.S).  The `pushq'
 117      instruction clobbers %rsp, but its value is saved in `%rdi'.  */
 118
 119   if (offset > 5)
 120     return get_frame_register_unsigned (this_frame, AMD64_RDI_REGNUM);
 121   else
 122     return get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 123 }
 124 \f
 125 /* OpenBSD 3.5 or later.  */
 126
 127 /* Mapping between the general-purpose registers in `struct reg'
 128    format and GDB's register cache layout.  */
 129
 130 /* From <machine/reg.h>.  */
 131 int amd64obsd_r_reg_offset[] =
 132 {
 133   14 * 8,                       /* %rax */
 134   13 * 8,                       /* %rbx */
 135   3 * 8,                        /* %rcx */
 136   2 * 8,                        /* %rdx */
 137   1 * 8,                        /* %rsi */
 138   0 * 8,                        /* %rdi */
 139   12 * 8,                       /* %rbp */
 140   15 * 8,                       /* %rsp */
 141   4 * 8,                        /* %r8 ..  */
 142   5 * 8,
 143   6 * 8,
 144   7 * 8,
 145   8 * 8,
 146   9 * 8,
 147   10 * 8,
 148   11 * 8,                       /* ... %r15 */
 149   16 * 8,                       /* %rip */
 150   17 * 8,                       /* %eflags */
 151   18 * 8,                       /* %cs */
 152   19 * 8,                       /* %ss */
 153   20 * 8,                       /* %ds */
 154   21 * 8,                       /* %es */
 155   22 * 8,                       /* %fs */
 156   23 * 8                        /* %gs */
 157 };
 158
 159 /* From <machine/signal.h>.  */
 160 static int amd64obsd_sc_reg_offset[] =
 161 {
 162   14 * 8,                       /* %rax */
 163   13 * 8,                       /* %rbx */
 164   3 * 8,                        /* %rcx */
 165   2 * 8,                        /* %rdx */
 166   1 * 8,                        /* %rsi */
 167   0 * 8,                        /* %rdi */
 168   12 * 8,                       /* %rbp */
 169   24 * 8,                       /* %rsp */
 170   4 * 8,                        /* %r8 ...  */
 171   5 * 8,
 172   6 * 8,
 173   7 * 8,
 174   8 * 8,
 175   9 * 8,
 176   10 * 8,
 177   11 * 8,                       /* ... %r15 */
 178   21 * 8,                       /* %rip */
 179   23 * 8,                       /* %eflags */
 180   22 * 8,                       /* %cs */
 181   25 * 8,                       /* %ss */
 182   18 * 8,                       /* %ds */
 183   17 * 8,                       /* %es */
 184   16 * 8,                       /* %fs */
 185   15 * 8                        /* %gs */
 186 };
 187
 188 /* From /usr/src/lib/libpthread/arch/amd64/uthread_machdep.c.  */
 189 static int amd64obsd_uthread_reg_offset[] =
 190 {
 191   19 * 8,                       /* %rax */
 192   16 * 8,                       /* %rbx */
 193   18 * 8,                       /* %rcx */
 194   17 * 8,                       /* %rdx */
 195   14 * 8,                       /* %rsi */
 196   13 * 8,                       /* %rdi */
 197   15 * 8,                       /* %rbp */
 198   -1,                           /* %rsp */
 199   12 * 8,                       /* %r8 ...  */
 200   11 * 8,
 201   10 * 8,
 202   9 * 8,
 203   8 * 8,
 204   7 * 8,
 205   6 * 8,
 206   5 * 8,                        /* ... %r15 */
 207   20 * 8,                       /* %rip */
 208   4 * 8,                        /* %eflags */
 209   21 * 8,                       /* %cs */
 210   -1,                           /* %ss */
 211   3 * 8,                        /* %ds */
 212   2 * 8,                        /* %es */
 213   1 * 8,                        /* %fs */
 214   0 * 8                         /* %gs */
 215 };
 216
 217 /* Offset within the thread structure where we can find the saved
 218    stack pointer (%esp).  */
 219 #define AMD64OBSD_UTHREAD_RSP_OFFSET    400
 220
 221 static void
 222 amd64obsd_supply_uthread (struct regcache *regcache,
 223                           int regnum, CORE_ADDR addr)
 224 {
 225   struct gdbarch *gdbarch = regcache->arch ();
 226   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 227   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 228   CORE_ADDR sp = 0;
 229   gdb_byte buf[8];
 230   int i;
 231
 232   gdb_assert (regnum >= -1);
 233
 234   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 235     {
 236       int offset;
 237
 238       /* Fetch stack pointer from thread structure.  */
 239       sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 240
 241       /* Adjust the stack pointer such that it looks as if we just
 242          returned from _thread_machdep_switch.  */
 243       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 244       store_unsigned_integer (buf, 8, byte_order, sp + offset);
 245       regcache->raw_supply (AMD64_RSP_REGNUM, buf);
 246     }
 247
 248   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 249     {
 250       if (amd64obsd_uthread_reg_offset[i] != -1
 251           && (regnum == -1 || regnum == i))
 252         {
 253           /* Fetch stack pointer from thread structure (if we didn't
 254              do so already).  */
 255           if (sp == 0)
 256             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 257
 258           /* Read the saved register from the stack frame.  */
 259           read_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 260           regcache->raw_supply (i, buf);
 261         }
 262     }
 263 }
 264
 265 static void
 266 amd64obsd_collect_uthread (const struct regcache *regcache,
 267                            int regnum, CORE_ADDR addr)
 268 {
 269   struct gdbarch *gdbarch = regcache->arch ();
 270   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 271   CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
 272   CORE_ADDR sp = 0;
 273   gdb_byte buf[8];
 274   int i;
 275
 276   gdb_assert (regnum >= -1);
 277
 278   if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
 279     {
 280       int offset;
 281
 282       /* Calculate the stack pointer (frame pointer) that will be
 283          stored into the thread structure.  */
 284       offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
 285       regcache->raw_collect (AMD64_RSP_REGNUM, buf);
 286       sp = extract_unsigned_integer (buf, 8, byte_order) - offset;
 287
 288       /* Store the stack pointer.  */
 289       write_memory_unsigned_integer (sp_addr, 8, byte_order, sp);
 290
 291       /* The stack pointer was (potentially) modified.  Make sure we
 292          build a proper stack frame.  */
 293       regnum = -1;
 294     }
 295
 296   for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
 297     {
 298       if (amd64obsd_uthread_reg_offset[i] != -1
 299           && (regnum == -1 || regnum == i))
 300         {
 301           /* Fetch stack pointer from thread structure (if we didn't
 302              calculate it already).  */
 303           if (sp == 0)
 304             sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
 305
 306           /* Write the register into the stack frame.  */
 307           regcache->raw_collect (i, buf);
 308           write_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
 309         }
 310     }
 311 }
 312 /* Kernel debugging support.  */
 313
 314 /* From <machine/frame.h>.  Easy since `struct trapframe' matches
 315    `struct sigcontext'.  */
 316 #define amd64obsd_tf_reg_offset amd64obsd_sc_reg_offset
 317
 318 static struct trad_frame_cache *
 319 amd64obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
 320 {
 321   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 322   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 323   struct trad_frame_cache *cache;
 324   CORE_ADDR func, sp, addr;
 325   ULONGEST cs;
 326   const char *name;
 327   int i;
 328
 329   if (*this_cache)
 330     return (struct trad_frame_cache *) *this_cache;
 331
 332   cache = trad_frame_cache_zalloc (this_frame);
 333   *this_cache = cache;
 334
 335   func = get_frame_func (this_frame);
 336   sp = get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
 337
 338   find_pc_partial_function (func, &name, NULL, NULL);
 339   if (name && startswith (name, "Xintr"))
 340     addr = sp + 8;              /* It's an interrupt frame.  */
 341   else
 342     addr = sp;
 343
 344   for (i = 0; i < ARRAY_SIZE (amd64obsd_tf_reg_offset); i++)
 345     if (amd64obsd_tf_reg_offset[i] != -1)
 346       trad_frame_set_reg_addr (cache, i, addr + amd64obsd_tf_reg_offset[i]);
 347
 348   /* Read %cs from trap frame.  */
 349   addr += amd64obsd_tf_reg_offset[AMD64_CS_REGNUM];
 350   cs = read_memory_unsigned_integer (addr, 8, byte_order);
 351   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 352     {
 353       /* Trap from user space; terminate backtrace.  */
 354       trad_frame_set_id (cache, outer_frame_id);
 355     }
 356   else
 357     {
 358       /* Construct the frame ID using the function start.  */
 359       trad_frame_set_id (cache, frame_id_build (sp + 16, func));
 360     }
 361
 362   return cache;
 363 }
 364
 365 static void
 366 amd64obsd_trapframe_this_id (struct frame_info *this_frame,
 367                              void **this_cache, struct frame_id *this_id)
 368 {
 369   struct trad_frame_cache *cache =
 370     amd64obsd_trapframe_cache (this_frame, this_cache);
 371
 372   trad_frame_get_id (cache, this_id);
 373 }
 374
 375 static struct value *
 376 amd64obsd_trapframe_prev_register (struct frame_info *this_frame,
 377                                    void **this_cache, int regnum)
 378 {
 379   struct trad_frame_cache *cache =
 380     amd64obsd_trapframe_cache (this_frame, this_cache);
 381
 382   return trad_frame_get_register (cache, this_frame, regnum);
 383 }
 384
 385 static int
 386 amd64obsd_trapframe_sniffer (const struct frame_unwind *self,
 387                              struct frame_info *this_frame,
 388                              void **this_prologue_cache)
 389 {
 390   ULONGEST cs;
 391   const char *name;
 392
 393   /* Check Current Privilege Level and bail out if we're not executing
 394      in kernel space.  */
 395   cs = get_frame_register_unsigned (this_frame, AMD64_CS_REGNUM);
 396   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 397     return 0;
 398
 399   find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
 400   return (name && ((strcmp (name, "calltrap") == 0)
 401                    || (strcmp (name, "osyscall1") == 0)
 402                    || (strcmp (name, "Xsyscall") == 0)
 403                    || (startswith (name, "Xintr"))));
 404 }
 405
 406 static const struct frame_unwind amd64obsd_trapframe_unwind = {
 407   /* FIXME: kettenis/20051219: This really is more like an interrupt
 408      frame, but SIGTRAMP_FRAME would print <signal handler called>,
 409      which really is not what we want here.  */
 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   struct gdbarch_tdep *tdep = 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
 453 _initialize_amd64obsd_tdep (void)
 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 }