gdb/i386obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/i386.
   2
   3    Copyright (C) 1988, 1989, 1991, 1992, 1994, 1996, 2000, 2001, 2002, 2003,
   4    2004, 2005, 2006, 2007 Free 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 the frame preceding NEXT_FRAME corresponds to an
  67    OpenBSD sigtramp routine.  */
  68
  69 static int
  70 i386obsd_sigtramp_p (struct frame_info *next_frame)
  71 {
  72   CORE_ADDR pc = frame_pc_unwind (next_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   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 (next_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   CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
 232   CORE_ADDR sp = 0;
 233   gdb_byte buf[4];
 234   int i;
 235
 236   gdb_assert (regnum >= -1);
 237
 238   if (regnum == -1 || regnum == I386_ESP_REGNUM)
 239     {
 240       int offset;
 241
 242       /* Fetch stack pointer from thread structure.  */
 243       sp = read_memory_unsigned_integer (sp_addr, 4);
 244
 245       /* Adjust the stack pointer such that it looks as if we just
 246          returned from _thread_machdep_switch.  */
 247       offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
 248       store_unsigned_integer (buf, 4, sp + offset);
 249       regcache_raw_supply (regcache, I386_ESP_REGNUM, buf);
 250     }
 251
 252   for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
 253     {
 254       if (i386obsd_uthread_reg_offset[i] != -1
 255           && (regnum == -1 || regnum == i))
 256         {
 257           /* Fetch stack pointer from thread structure (if we didn't
 258              do so already).  */
 259           if (sp == 0)
 260             sp = read_memory_unsigned_integer (sp_addr, 4);
 261
 262           /* Read the saved register from the stack frame.  */
 263           read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
 264           regcache_raw_supply (regcache, i, buf);
 265         }
 266     }
 267 }
 268
 269 static void
 270 i386obsd_collect_uthread (const struct regcache *regcache,
 271                           int regnum, CORE_ADDR addr)
 272 {
 273   CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
 274   CORE_ADDR sp = 0;
 275   gdb_byte buf[4];
 276   int i;
 277
 278   gdb_assert (regnum >= -1);
 279
 280   if (regnum == -1 || regnum == I386_ESP_REGNUM)
 281     {
 282       int offset;
 283
 284       /* Calculate the stack pointer (frame pointer) that will be
 285          stored into the thread structure.  */
 286       offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
 287       regcache_raw_collect (regcache, I386_ESP_REGNUM, buf);
 288       sp = extract_unsigned_integer (buf, 4) - offset;
 289
 290       /* Store the stack pointer.  */
 291       write_memory_unsigned_integer (sp_addr, 4, sp);
 292
 293       /* The stack pointer was (potentially) modified.  Make sure we
 294          build a proper stack frame.  */
 295       regnum = -1;
 296     }
 297
 298   for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
 299     {
 300       if (i386obsd_uthread_reg_offset[i] != -1
 301           && (regnum == -1 || regnum == i))
 302         {
 303           /* Fetch stack pointer from thread structure (if we didn't
 304              calculate it already).  */
 305           if (sp == 0)
 306             sp = read_memory_unsigned_integer (sp_addr, 4);
 307
 308           /* Write the register into the stack frame.  */
 309           regcache_raw_collect (regcache, i, buf);
 310           write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
 311         }
 312     }
 313 }
 314 \f
 315 /* Kernel debugging support.  */
 316
 317 /* From <machine/frame.h>.  Note that %esp and %ess are only saved in
 318    a trap frame when entering the kernel from user space.  */
 319 static int i386obsd_tf_reg_offset[] =
 320 {
 321   10 * 4,                       /* %eax */
 322   9 * 4,                        /* %ecx */
 323   8 * 4,                        /* %edx */
 324   7 * 4,                        /* %ebx */
 325   -1,                           /* %esp */
 326   6 * 4,                        /* %ebp */
 327   5 * 4,                        /* %esi */
 328   4 * 4,                        /* %edi */
 329   13 * 4,                       /* %eip */
 330   15 * 4,                       /* %eflags */
 331   14 * 4,                       /* %cs */
 332   -1,                           /* %ss */
 333   3 * 4,                        /* %ds */
 334   2 * 4,                        /* %es */
 335   0 * 4,                        /* %fs */
 336   1 * 4                         /* %gs */
 337 };
 338
 339 static struct trad_frame_cache *
 340 i386obsd_trapframe_cache(struct frame_info *next_frame, void **this_cache)
 341 {
 342   struct trad_frame_cache *cache;
 343   CORE_ADDR func, sp, addr;
 344   ULONGEST cs;
 345   char *name;
 346   int i;
 347
 348   if (*this_cache)
 349     return *this_cache;
 350
 351   cache = trad_frame_cache_zalloc (next_frame);
 352   *this_cache = cache;
 353
 354   /* NORMAL_FRAME matches the type in i386obsd_trapframe_unwind, but
 355      SIGTRAMP_FRAME might be more appropriate.  */
 356   func = frame_func_unwind (next_frame, NORMAL_FRAME);
 357   sp = frame_unwind_register_unsigned (next_frame, I386_ESP_REGNUM);
 358
 359   find_pc_partial_function (func, &name, NULL, NULL);
 360   if (name && strncmp (name, "Xintr", 5) == 0)
 361     addr = sp + 8;              /* It's an interrupt frame.  */
 362   else
 363     addr = sp;
 364
 365   for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)
 366     if (i386obsd_tf_reg_offset[i] != -1)
 367       trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]);
 368
 369   /* Read %cs from trap frame.  */
 370   addr += i386obsd_tf_reg_offset[I386_CS_REGNUM];
 371   cs = read_memory_unsigned_integer (addr, 4);
 372   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 373     {
 374       /* Trap from user space; terminate backtrace.  */
 375       trad_frame_set_id (cache, null_frame_id);
 376     }
 377   else
 378     {
 379       /* Construct the frame ID using the function start.  */
 380       trad_frame_set_id (cache, frame_id_build (sp + 8, func));
 381     }
 382
 383   return cache;
 384 }
 385
 386 static void
 387 i386obsd_trapframe_this_id (struct frame_info *next_frame,
 388                             void **this_cache, struct frame_id *this_id)
 389 {
 390   struct trad_frame_cache *cache =
 391     i386obsd_trapframe_cache (next_frame, this_cache);
 392
 393   trad_frame_get_id (cache, this_id);
 394 }
 395
 396 static void
 397 i386obsd_trapframe_prev_register (struct frame_info *next_frame,
 398                                   void **this_cache, int regnum,
 399                                   int *optimizedp, enum lval_type *lvalp,
 400                                   CORE_ADDR *addrp, int *realnump,
 401                                   gdb_byte *valuep)
 402 {
 403   struct trad_frame_cache *cache =
 404     i386obsd_trapframe_cache (next_frame, this_cache);
 405
 406   trad_frame_get_register (cache, next_frame, regnum,
 407                            optimizedp, lvalp, addrp, realnump, valuep);
 408 }
 409
 410 static int
 411 i386obsd_trapframe_sniffer (const struct frame_unwind *self,
 412                             struct frame_info *next_frame,
 413                             void **this_prologue_cache)
 414 {
 415   ULONGEST cs;
 416   char *name;
 417
 418   /* Check Current Privilege Level and bail out if we're not executing
 419      in kernel space.  */
 420   cs = frame_unwind_register_unsigned (next_frame, I386_CS_REGNUM);
 421   if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
 422     return 0;
 423
 424   find_pc_partial_function (frame_pc_unwind (next_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   i386obsd_trapframe_this_id,
 437   i386obsd_trapframe_prev_register,
 438   NULL,
 439   i386obsd_trapframe_sniffer
 440 };
 441 \f
 442
 443 static void
 444 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 445 {
 446   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 447
 448   /* Obviously OpenBSD is BSD-based.  */
 449   i386bsd_init_abi (info, gdbarch);
 450
 451   /* OpenBSD has a different `struct reg'.  */
 452   tdep->gregset_reg_offset = i386obsd_r_reg_offset;
 453   tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
 454   tdep->sizeof_gregset = 16 * 4;
 455
 456   /* OpenBSD uses -freg-struct-return by default.  */
 457   tdep->struct_return = reg_struct_return;
 458
 459   /* OpenBSD uses a different memory layout.  */
 460   tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
 461   tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
 462   tdep->sigtramp_p = i386obsd_sigtramp_p;
 463
 464   /* OpenBSD has a `struct sigcontext' that's different from the
 465      original 4.3 BSD.  */
 466   tdep->sc_reg_offset = i386obsd_sc_reg_offset;
 467   tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
 468
 469   /* OpenBSD provides a user-level threads implementation.  */
 470   bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread);
 471   bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread);
 472
 473   /* Unwind kernel trap frames correctly.  */
 474   frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);
 475 }
 476
 477 /* OpenBSD a.out.  */
 478
 479 static void
 480 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 481 {
 482   i386obsd_init_abi (info, gdbarch);
 483
 484   /* OpenBSD a.out has a single register set.  */
 485   set_gdbarch_regset_from_core_section
 486     (gdbarch, i386obsd_aout_regset_from_core_section);
 487 }
 488
 489 /* OpenBSD ELF.  */
 490
 491 static void
 492 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 493 {
 494   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 495
 496   /* It's still OpenBSD.  */
 497   i386obsd_init_abi (info, gdbarch);
 498
 499   /* But ELF-based.  */
 500   i386_elf_init_abi (info, gdbarch);
 501
 502   /* OpenBSD ELF uses SVR4-style shared libraries.  */
 503   set_solib_svr4_fetch_link_map_offsets
 504     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 505 }
 506 \f
 507
 508 /* Provide a prototype to silence -Wmissing-prototypes.  */
 509 void _initialize_i386obsd_tdep (void);
 510
 511 void
 512 _initialize_i386obsd_tdep (void)
 513 {
 514   /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are
 515      indistingushable from NetBSD/i386 a.out binaries, building a GDB
 516      that should support both these targets will probably not work as
 517      expected.  */
 518 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
 519
 520   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,
 521                           i386obsd_aout_init_abi);
 522   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,
 523                           i386obsd_elf_init_abi);
 524 }