gdb/i386obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/i386.
   2
   3    Copyright (C) 1988-1989, 1991-1992, 1994, 1996, 2000-2012 Free
   4    Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "arch-utils.h"
  23 #include "frame.h"
  24 #include "frame-unwind.h"
  25 #include "gdbcore.h"
  26 #include "regcache.h"
  27 #include "regset.h"
  28 #include "symtab.h"
  29 #include "objfiles.h"
  30 #include "osabi.h"
  31 #include "target.h"
  32 #include "trad-frame.h"
  33
  34 #include "gdb_assert.h"
  35 #include "gdb_string.h"
  36
  37 #include "i386-tdep.h"
  38 #include "i387-tdep.h"
  39 #include "solib-svr4.h"
  40 #include "bsd-uthread.h"
  41
  42 /* Support for signal handlers.  */
  43
  44 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  45    in virtual memory.  The randomness makes it somewhat tricky to
  46    detect it, but fortunately we can rely on the fact that the start
  47    of the sigtramp routine is page-aligned.  We recognize the
  48    trampoline by looking for the code that invokes the sigreturn
  49    system call.  The offset where we can find that code varies from
  50    release to release.
  51
  52    By the way, the mapping mentioned above is read-only, so you cannot
  53    place a breakpoint in the signal trampoline.  */
  54
  55 /* Default page size.  */
  56 static const int i386obsd_page_size = 4096;
  57
  58 /* Offset for sigreturn(2).  */
  59 static const int i386obsd_sigreturn_offset[] = {
  60   0x0a,                         /* OpenBSD 3.2 */
  61   0x14,                         /* OpenBSD 3.6 */
  62   0x3a,                         /* OpenBSD 3.8 */
  63   -1
  64 };
  65
  66 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
  67    routine.  */
  68
  69 static int
  70 i386obsd_sigtramp_p (struct frame_info *this_frame)
  71 {
  72   CORE_ADDR pc = get_frame_pc (this_frame);
  73   CORE_ADDR start_pc = (pc & ~(i386obsd_page_size - 1));
  74   /* The call sequence invoking sigreturn(2).  */
  75   const gdb_byte sigreturn[] =
  76   {
  77     0xb8,
  78     0x67, 0x00, 0x00, 0x00,     /* movl $SYS_sigreturn, %eax */
  79     0xcd, 0x80                  /* int $0x80 */
  80   };
  81   size_t buflen = sizeof sigreturn;
  82   const int *offset;
  83   gdb_byte *buf;
  84   const char *name;
  85
  86   /* If the function has a valid symbol name, it isn't a
  87      trampoline.  */
  88   find_pc_partial_function (pc, &name, NULL, NULL);
  89   if (name != NULL)
  90     return 0;
  91
  92   /* If the function lives in a valid section (even without a starting
  93      point) it isn't a trampoline.  */
  94   if (find_pc_section (pc) != NULL)
  95     return 0;
  96
  97   /* Allocate buffer.  */
  98   buf = alloca (buflen);
  99
 100   /* Loop over all offsets.  */
 101   for (offset = i386obsd_sigreturn_offset; *offset != -1; offset++)
 102     {
 103       /* If we can't read the instructions, return zero.  */
 104       if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,
 105                                      buf, buflen))
 106         return 0;
 107
 108       /* Check for sigreturn(2).  */
 109       if (memcmp (buf, sigreturn, buflen) == 0)
 110         return 1;
 111     }
 112
 113   return 0;
 114 }
 115 \f
 116 /* Mapping between the general-purpose registers in `struct reg'
 117    format and GDB's register cache layout.  */
 118
 119 /* From <machine/reg.h>.  */
 120 static int i386obsd_r_reg_offset[] =
 121 {
 122   0 * 4,                        /* %eax */
 123   1 * 4,                        /* %ecx */
 124   2 * 4,                        /* %edx */
 125   3 * 4,                        /* %ebx */
 126   4 * 4,                        /* %esp */
 127   5 * 4,                        /* %ebp */
 128   6 * 4,                        /* %esi */
 129   7 * 4,                        /* %edi */
 130   8 * 4,                        /* %eip */
 131   9 * 4,                        /* %eflags */
 132   10 * 4,                       /* %cs */
 133   11 * 4,                       /* %ss */
 134   12 * 4,                       /* %ds */
 135   13 * 4,                       /* %es */
 136   14 * 4,                       /* %fs */
 137   15 * 4                        /* %gs */
 138 };
 139
 140 static void
 141 i386obsd_aout_supply_regset (const struct regset *regset,
 142                              struct regcache *regcache, int regnum,
 143                              const void *regs, size_t len)
 144 {
 145   const struct gdbarch_tdep *tdep = gdbarch_tdep (regset->arch);
 146   const gdb_byte *gregs = regs;
 147
 148   gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
 149
 150   i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);
 151   i387_supply_fsave (regcache, regnum, gregs + tdep->sizeof_gregset);
 152 }
 153
 154 static const struct regset *
 155 i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,
 156                                         const char *sect_name,
 157                                         size_t sect_size)
 158 {
 159   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 160
 161   /* OpenBSD a.out core dumps don't use seperate register sets for the
 162      general-purpose and floating-point registers.  */
 163
 164   if (strcmp (sect_name, ".reg") == 0
 165       && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)
 166     {
 167       if (tdep->gregset == NULL)
 168         tdep->gregset =
 169           regset_alloc (gdbarch, i386obsd_aout_supply_regset, NULL);
 170       return tdep->gregset;
 171     }
 172
 173   return NULL;
 174 }
 175 \f
 176
 177 /* Sigtramp routine location for OpenBSD 3.1 and earlier releases.  */
 178 CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
 179 CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
 180
 181 /* From <machine/signal.h>.  */
 182 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
 183 {
 184   10 * 4,                       /* %eax */
 185   9 * 4,                        /* %ecx */
 186   8 * 4,                        /* %edx */
 187   7 * 4,                        /* %ebx */
 188   14 * 4,                       /* %esp */
 189   6 * 4,                        /* %ebp */
 190   5 * 4,                        /* %esi */
 191   4 * 4,                        /* %edi */
 192   11 * 4,                       /* %eip */
 193   13 * 4,                       /* %eflags */
 194   12 * 4,                       /* %cs */
 195   15 * 4,                       /* %ss */
 196   3 * 4,                        /* %ds */
 197   2 * 4,                        /* %es */
 198   1 * 4,                        /* %fs */
 199   0 * 4                         /* %gs */
 200 };
 201
 202 /* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c.  */
 203 static int i386obsd_uthread_reg_offset[] =
 204 {
 205   11 * 4,                       /* %eax */
 206   10 * 4,                       /* %ecx */
 207   9 * 4,                        /* %edx */
 208   8 * 4,                        /* %ebx */
 209   -1,                           /* %esp */
 210   6 * 4,                        /* %ebp */
 211   5 * 4,                        /* %esi */
 212   4 * 4,                        /* %edi */
 213   12 * 4,                       /* %eip */
 214   -1,                           /* %eflags */
 215   13 * 4,                       /* %cs */
 216   -1,                           /* %ss */
 217   3 * 4,                        /* %ds */
 218   2 * 4,                        /* %es */
 219   1 * 4,                        /* %fs */
 220   0 * 4                         /* %gs */
 221 };
 222
 223 /* Offset within the thread structure where we can find the saved
 224    stack pointer (%esp).  */
 225 #define I386OBSD_UTHREAD_ESP_OFFSET     176
 226
 227 static void
 228 i386obsd_supply_uthread (struct regcache *regcache,
 229                          int regnum, CORE_ADDR addr)
 230 {
 231   struct gdbarch *gdbarch = get_regcache_arch (regcache);
 232   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 233   CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
 234   CORE_ADDR sp = 0;
 235   gdb_byte buf[4];
 236   int i;
 237
 238   gdb_assert (regnum >= -1);
 239
 240   if (regnum == -1 || regnum == I386_ESP_REGNUM)
 241     {
 242       int offset;
 243
 244       /* Fetch stack pointer from thread structure.  */
 245       sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
 246
 247       /* Adjust the stack pointer such that it looks as if we just
 248          returned from _thread_machdep_switch.  */
 249       offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
 250       store_unsigned_integer (buf, 4, byte_order, sp + offset);
 251       regcache_raw_supply (regcache, I386_ESP_REGNUM, buf);
 252     }
 253
 254   for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
 255     {
 256       if (i386obsd_uthread_reg_offset[i] != -1
 257           && (regnum == -1 || regnum == i))
 258         {
 259           /* Fetch stack pointer from thread structure (if we didn't
 260              do so already).  */
 261           if (sp == 0)
 262             sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
 263
 264           /* Read the saved register from the stack frame.  */
 265           read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
 266           regcache_raw_supply (regcache, i, buf);
 267         }
 268     }
 269 }
 270
 271 static void
 272 i386obsd_collect_uthread (const struct regcache *regcache,
 273                           int regnum, CORE_ADDR addr)
 274 {
 275   struct gdbarch *gdbarch = get_regcache_arch (regcache);
 276   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 277   CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
 278   CORE_ADDR sp = 0;
 279   gdb_byte buf[4];
 280   int i;
 281
 282   gdb_assert (regnum >= -1);
 283
 284   if (regnum == -1 || regnum == I386_ESP_REGNUM)
 285     {
 286       int offset;
 287
 288       /* Calculate the stack pointer (frame pointer) that will be
 289          stored into the thread structure.  */
 290       offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
 291       regcache_raw_collect (regcache, I386_ESP_REGNUM, buf);
 292       sp = extract_unsigned_integer (buf, 4, byte_order) - offset;
 293
 294       /* Store the stack pointer.  */
 295       write_memory_unsigned_integer (sp_addr, 4, byte_order, sp);
 296
 297       /* The stack pointer was (potentially) modified.  Make sure we
 298          build a proper stack frame.  */
 299       regnum = -1;
 300     }
 301
 302   for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
 303     {
 304       if (i386obsd_uthread_reg_offset[i] != -1
 305           && (regnum == -1 || regnum == i))
 306         {
 307           /* Fetch stack pointer from thread structure (if we didn't
 308              calculate it already).  */
 309           if (sp == 0)
 310             sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
 311
 312           /* Write the register into the stack frame.  */
 313           regcache_raw_collect (regcache, i, buf);
 314           write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
 315         }
 316     }
 317 }
 318 \f
 319 /* Kernel debugging support.  */
 320
 321 /* From <machine/frame.h>.  Note that %esp and %ess are only saved in
 322    a trap frame when entering the kernel from user space.  */
 323 static int i386obsd_tf_reg_offset[] =
 324 {
 325   10 * 4,                       /* %eax */
 326   9 * 4,                        /* %ecx */
 327   8 * 4,                        /* %edx */
 328   7 * 4,                        /* %ebx */
 329   -1,                           /* %esp */
 330   6 * 4,                        /* %ebp */
 331   5 * 4,                        /* %esi */
 332   4 * 4,                        /* %edi */
 333   13 * 4,                       /* %eip */
 334   15 * 4,                       /* %eflags */
 335   14 * 4,                       /* %cs */
 336   -1,                           /* %ss */
 337   3 * 4,                        /* %ds */
 338   2 * 4,                        /* %es */
 339   0 * 4,                        /* %fs */
 340   1 * 4                         /* %gs */
 341 };
 342
 343 static struct trad_frame_cache *
 344 i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
 345 {
 346   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 347   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 348   struct trad_frame_cache *cache;
 349   CORE_ADDR func, sp, addr;
 350   ULONGEST cs;
 351   const char *name;
 352   int i;
 353
 354   if (*this_cache)
 355     return *this_cache;
 356
 357   cache = trad_frame_cache_zalloc (this_frame);
 358   *this_cache = cache;
 359
 360   func = get_frame_func (this_frame);
 361   sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);
 362
 363   find_pc_partial_function (func, &name, NULL, NULL);
 364   if (name && strncmp (name, "Xintr", 5) == 0)
 365     addr = sp + 8;              /* It's an interrupt frame.  */
 366   else
 367     addr = sp;
 368
 369   for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)
 370     if (i386obsd_tf_reg_offset[i] != -1)
 371       trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]);
 372
 373   /* Read %cs from trap frame.  */
 374   addr += i386obsd_tf_reg_offset[I386_CS_REGNUM];
 375   cs = read_memory_unsigned_integer (addr, 4, byte_order);
 376   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 377     {
 378       /* Trap from user space; terminate backtrace.  */
 379       trad_frame_set_id (cache, outer_frame_id);
 380     }
 381   else
 382     {
 383       /* Construct the frame ID using the function start.  */
 384       trad_frame_set_id (cache, frame_id_build (sp + 8, func));
 385     }
 386
 387   return cache;
 388 }
 389
 390 static void
 391 i386obsd_trapframe_this_id (struct frame_info *this_frame,
 392                             void **this_cache, struct frame_id *this_id)
 393 {
 394   struct trad_frame_cache *cache =
 395     i386obsd_trapframe_cache (this_frame, this_cache);
 396
 397   trad_frame_get_id (cache, this_id);
 398 }
 399
 400 static struct value *
 401 i386obsd_trapframe_prev_register (struct frame_info *this_frame,
 402                                   void **this_cache, int regnum)
 403 {
 404   struct trad_frame_cache *cache =
 405     i386obsd_trapframe_cache (this_frame, this_cache);
 406
 407   return trad_frame_get_register (cache, this_frame, regnum);
 408 }
 409
 410 static int
 411 i386obsd_trapframe_sniffer (const struct frame_unwind *self,
 412                             struct frame_info *this_frame,
 413                             void **this_prologue_cache)
 414 {
 415   ULONGEST cs;
 416   const char *name;
 417
 418   /* Check Current Privilege Level and bail out if we're not executing
 419      in kernel space.  */
 420   cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM);
 421   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 422     return 0;
 423
 424   find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
 425   return (name && (strcmp (name, "calltrap") == 0
 426                    || strcmp (name, "syscall1") == 0
 427                    || strncmp (name, "Xintr", 5) == 0
 428                    || strncmp (name, "Xsoft", 5) == 0));
 429 }
 430
 431 static const struct frame_unwind i386obsd_trapframe_unwind = {
 432   /* FIXME: kettenis/20051219: This really is more like an interrupt
 433      frame, but SIGTRAMP_FRAME would print <signal handler called>,
 434      which really is not what we want here.  */
 435   NORMAL_FRAME,
 436   default_frame_unwind_stop_reason,
 437   i386obsd_trapframe_this_id,
 438   i386obsd_trapframe_prev_register,
 439   NULL,
 440   i386obsd_trapframe_sniffer
 441 };
 442 \f
 443
 444 static void
 445 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 446 {
 447   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 448
 449   /* Obviously OpenBSD is BSD-based.  */
 450   i386bsd_init_abi (info, gdbarch);
 451
 452   /* OpenBSD has a different `struct reg'.  */
 453   tdep->gregset_reg_offset = i386obsd_r_reg_offset;
 454   tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
 455   tdep->sizeof_gregset = 16 * 4;
 456
 457   /* OpenBSD uses -freg-struct-return by default.  */
 458   tdep->struct_return = reg_struct_return;
 459
 460   /* OpenBSD uses a different memory layout.  */
 461   tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
 462   tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
 463   tdep->sigtramp_p = i386obsd_sigtramp_p;
 464
 465   /* OpenBSD has a `struct sigcontext' that's different from the
 466      original 4.3 BSD.  */
 467   tdep->sc_reg_offset = i386obsd_sc_reg_offset;
 468   tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
 469
 470   /* OpenBSD provides a user-level threads implementation.  */
 471   bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread);
 472   bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread);
 473
 474   /* Unwind kernel trap frames correctly.  */
 475   frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);
 476 }
 477
 478 /* OpenBSD a.out.  */
 479
 480 static void
 481 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 482 {
 483   i386obsd_init_abi (info, gdbarch);
 484
 485   /* OpenBSD a.out has a single register set.  */
 486   set_gdbarch_regset_from_core_section
 487     (gdbarch, i386obsd_aout_regset_from_core_section);
 488 }
 489
 490 /* OpenBSD ELF.  */
 491
 492 static void
 493 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 494 {
 495   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 496
 497   /* It's still OpenBSD.  */
 498   i386obsd_init_abi (info, gdbarch);
 499
 500   /* But ELF-based.  */
 501   i386_elf_init_abi (info, gdbarch);
 502
 503   /* OpenBSD ELF uses SVR4-style shared libraries.  */
 504   set_solib_svr4_fetch_link_map_offsets
 505     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 506 }
 507 \f
 508
 509 /* Provide a prototype to silence -Wmissing-prototypes.  */
 510 void _initialize_i386obsd_tdep (void);
 511
 512 void
 513 _initialize_i386obsd_tdep (void)
 514 {
 515   /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are
 516      indistingushable from NetBSD/i386 a.out binaries, building a GDB
 517      that should support both these targets will probably not work as
 518      expected.  */
 519 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 520
 521   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,
 522                           i386obsd_aout_init_abi);
 523   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,
 524                           i386obsd_elf_init_abi);
 525 }