| 1 | /* Target-dependent code for OpenBSD/i386. |
| 2 | |
| 3 | Copyright (C) 1988-2020 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 "arch-utils.h" |
| 22 | #include "frame.h" |
| 23 | #include "frame-unwind.h" |
| 24 | #include "gdbcore.h" |
| 25 | #include "regcache.h" |
| 26 | #include "regset.h" |
| 27 | #include "symtab.h" |
| 28 | #include "objfiles.h" |
| 29 | #include "osabi.h" |
| 30 | #include "target.h" |
| 31 | #include "trad-frame.h" |
| 32 | |
| 33 | #include "obsd-tdep.h" |
| 34 | #include "i386-tdep.h" |
| 35 | #include "i387-tdep.h" |
| 36 | #include "solib-svr4.h" |
| 37 | #include "bsd-uthread.h" |
| 38 | |
| 39 | /* Support for signal handlers. */ |
| 40 | |
| 41 | /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page |
| 42 | in virtual memory. The randomness makes it somewhat tricky to |
| 43 | detect it, but fortunately we can rely on the fact that the start |
| 44 | of the sigtramp routine is page-aligned. We recognize the |
| 45 | trampoline by looking for the code that invokes the sigreturn |
| 46 | system call. The offset where we can find that code varies from |
| 47 | release to release. |
| 48 | |
| 49 | By the way, the mapping mentioned above is read-only, so you cannot |
| 50 | place a breakpoint in the signal trampoline. */ |
| 51 | |
| 52 | /* Default page size. */ |
| 53 | static const int i386obsd_page_size = 4096; |
| 54 | |
| 55 | /* Offset for sigreturn(2). */ |
| 56 | static const int i386obsd_sigreturn_offset[] = { |
| 57 | 0x0a, /* OpenBSD 3.2 */ |
| 58 | 0x14, /* OpenBSD 3.6 */ |
| 59 | 0x3a, /* OpenBSD 3.8 */ |
| 60 | -1 |
| 61 | }; |
| 62 | |
| 63 | /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp |
| 64 | routine. */ |
| 65 | |
| 66 | static int |
| 67 | i386obsd_sigtramp_p (struct frame_info *this_frame) |
| 68 | { |
| 69 | CORE_ADDR pc = get_frame_pc (this_frame); |
| 70 | CORE_ADDR start_pc = (pc & ~(i386obsd_page_size - 1)); |
| 71 | /* The call sequence invoking sigreturn(2). */ |
| 72 | const gdb_byte sigreturn[] = |
| 73 | { |
| 74 | 0xb8, |
| 75 | 0x67, 0x00, 0x00, 0x00, /* movl $SYS_sigreturn, %eax */ |
| 76 | 0xcd, 0x80 /* int $0x80 */ |
| 77 | }; |
| 78 | size_t buflen = sizeof sigreturn; |
| 79 | const int *offset; |
| 80 | gdb_byte *buf; |
| 81 | const char *name; |
| 82 | |
| 83 | /* If the function has a valid symbol name, it isn't a |
| 84 | trampoline. */ |
| 85 | find_pc_partial_function (pc, &name, NULL, NULL); |
| 86 | if (name != NULL) |
| 87 | return 0; |
| 88 | |
| 89 | /* If the function lives in a valid section (even without a starting |
| 90 | point) it isn't a trampoline. */ |
| 91 | if (find_pc_section (pc) != NULL) |
| 92 | return 0; |
| 93 | |
| 94 | /* Allocate buffer. */ |
| 95 | buf = (gdb_byte *) alloca (buflen); |
| 96 | |
| 97 | /* Loop over all offsets. */ |
| 98 | for (offset = i386obsd_sigreturn_offset; *offset != -1; offset++) |
| 99 | { |
| 100 | /* If we can't read the instructions, return zero. */ |
| 101 | if (!safe_frame_unwind_memory (this_frame, start_pc + *offset, |
| 102 | buf, buflen)) |
| 103 | return 0; |
| 104 | |
| 105 | /* Check for sigreturn(2). */ |
| 106 | if (memcmp (buf, sigreturn, buflen) == 0) |
| 107 | return 1; |
| 108 | } |
| 109 | |
| 110 | return 0; |
| 111 | } |
| 112 | \f |
| 113 | /* Mapping between the general-purpose registers in `struct reg' |
| 114 | format and GDB's register cache layout. */ |
| 115 | |
| 116 | /* From <machine/reg.h>. */ |
| 117 | static int i386obsd_r_reg_offset[] = |
| 118 | { |
| 119 | 0 * 4, /* %eax */ |
| 120 | 1 * 4, /* %ecx */ |
| 121 | 2 * 4, /* %edx */ |
| 122 | 3 * 4, /* %ebx */ |
| 123 | 4 * 4, /* %esp */ |
| 124 | 5 * 4, /* %ebp */ |
| 125 | 6 * 4, /* %esi */ |
| 126 | 7 * 4, /* %edi */ |
| 127 | 8 * 4, /* %eip */ |
| 128 | 9 * 4, /* %eflags */ |
| 129 | 10 * 4, /* %cs */ |
| 130 | 11 * 4, /* %ss */ |
| 131 | 12 * 4, /* %ds */ |
| 132 | 13 * 4, /* %es */ |
| 133 | 14 * 4, /* %fs */ |
| 134 | 15 * 4 /* %gs */ |
| 135 | }; |
| 136 | |
| 137 | \f |
| 138 | |
| 139 | /* Sigtramp routine location for OpenBSD 3.1 and earlier releases. */ |
| 140 | CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20; |
| 141 | CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0; |
| 142 | |
| 143 | /* From <machine/signal.h>. */ |
| 144 | int i386obsd_sc_reg_offset[I386_NUM_GREGS] = |
| 145 | { |
| 146 | 10 * 4, /* %eax */ |
| 147 | 9 * 4, /* %ecx */ |
| 148 | 8 * 4, /* %edx */ |
| 149 | 7 * 4, /* %ebx */ |
| 150 | 14 * 4, /* %esp */ |
| 151 | 6 * 4, /* %ebp */ |
| 152 | 5 * 4, /* %esi */ |
| 153 | 4 * 4, /* %edi */ |
| 154 | 11 * 4, /* %eip */ |
| 155 | 13 * 4, /* %eflags */ |
| 156 | 12 * 4, /* %cs */ |
| 157 | 15 * 4, /* %ss */ |
| 158 | 3 * 4, /* %ds */ |
| 159 | 2 * 4, /* %es */ |
| 160 | 1 * 4, /* %fs */ |
| 161 | 0 * 4 /* %gs */ |
| 162 | }; |
| 163 | |
| 164 | /* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c. */ |
| 165 | static int i386obsd_uthread_reg_offset[] = |
| 166 | { |
| 167 | 11 * 4, /* %eax */ |
| 168 | 10 * 4, /* %ecx */ |
| 169 | 9 * 4, /* %edx */ |
| 170 | 8 * 4, /* %ebx */ |
| 171 | -1, /* %esp */ |
| 172 | 6 * 4, /* %ebp */ |
| 173 | 5 * 4, /* %esi */ |
| 174 | 4 * 4, /* %edi */ |
| 175 | 12 * 4, /* %eip */ |
| 176 | -1, /* %eflags */ |
| 177 | 13 * 4, /* %cs */ |
| 178 | -1, /* %ss */ |
| 179 | 3 * 4, /* %ds */ |
| 180 | 2 * 4, /* %es */ |
| 181 | 1 * 4, /* %fs */ |
| 182 | 0 * 4 /* %gs */ |
| 183 | }; |
| 184 | |
| 185 | /* Offset within the thread structure where we can find the saved |
| 186 | stack pointer (%esp). */ |
| 187 | #define I386OBSD_UTHREAD_ESP_OFFSET 176 |
| 188 | |
| 189 | static void |
| 190 | i386obsd_supply_uthread (struct regcache *regcache, |
| 191 | int regnum, CORE_ADDR addr) |
| 192 | { |
| 193 | struct gdbarch *gdbarch = regcache->arch (); |
| 194 | enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); |
| 195 | CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET; |
| 196 | CORE_ADDR sp = 0; |
| 197 | gdb_byte buf[4]; |
| 198 | int i; |
| 199 | |
| 200 | gdb_assert (regnum >= -1); |
| 201 | |
| 202 | if (regnum == -1 || regnum == I386_ESP_REGNUM) |
| 203 | { |
| 204 | int offset; |
| 205 | |
| 206 | /* Fetch stack pointer from thread structure. */ |
| 207 | sp = read_memory_unsigned_integer (sp_addr, 4, byte_order); |
| 208 | |
| 209 | /* Adjust the stack pointer such that it looks as if we just |
| 210 | returned from _thread_machdep_switch. */ |
| 211 | offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4; |
| 212 | store_unsigned_integer (buf, 4, byte_order, sp + offset); |
| 213 | regcache->raw_supply (I386_ESP_REGNUM, buf); |
| 214 | } |
| 215 | |
| 216 | for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++) |
| 217 | { |
| 218 | if (i386obsd_uthread_reg_offset[i] != -1 |
| 219 | && (regnum == -1 || regnum == i)) |
| 220 | { |
| 221 | /* Fetch stack pointer from thread structure (if we didn't |
| 222 | do so already). */ |
| 223 | if (sp == 0) |
| 224 | sp = read_memory_unsigned_integer (sp_addr, 4, byte_order); |
| 225 | |
| 226 | /* Read the saved register from the stack frame. */ |
| 227 | read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4); |
| 228 | regcache->raw_supply (i, buf); |
| 229 | } |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | static void |
| 234 | i386obsd_collect_uthread (const struct regcache *regcache, |
| 235 | int regnum, CORE_ADDR addr) |
| 236 | { |
| 237 | struct gdbarch *gdbarch = regcache->arch (); |
| 238 | enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); |
| 239 | CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET; |
| 240 | CORE_ADDR sp = 0; |
| 241 | gdb_byte buf[4]; |
| 242 | int i; |
| 243 | |
| 244 | gdb_assert (regnum >= -1); |
| 245 | |
| 246 | if (regnum == -1 || regnum == I386_ESP_REGNUM) |
| 247 | { |
| 248 | int offset; |
| 249 | |
| 250 | /* Calculate the stack pointer (frame pointer) that will be |
| 251 | stored into the thread structure. */ |
| 252 | offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4; |
| 253 | regcache->raw_collect (I386_ESP_REGNUM, buf); |
| 254 | sp = extract_unsigned_integer (buf, 4, byte_order) - offset; |
| 255 | |
| 256 | /* Store the stack pointer. */ |
| 257 | write_memory_unsigned_integer (sp_addr, 4, byte_order, sp); |
| 258 | |
| 259 | /* The stack pointer was (potentially) modified. Make sure we |
| 260 | build a proper stack frame. */ |
| 261 | regnum = -1; |
| 262 | } |
| 263 | |
| 264 | for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++) |
| 265 | { |
| 266 | if (i386obsd_uthread_reg_offset[i] != -1 |
| 267 | && (regnum == -1 || regnum == i)) |
| 268 | { |
| 269 | /* Fetch stack pointer from thread structure (if we didn't |
| 270 | calculate it already). */ |
| 271 | if (sp == 0) |
| 272 | sp = read_memory_unsigned_integer (sp_addr, 4, byte_order); |
| 273 | |
| 274 | /* Write the register into the stack frame. */ |
| 275 | regcache->raw_collect (i, buf); |
| 276 | write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4); |
| 277 | } |
| 278 | } |
| 279 | } |
| 280 | \f |
| 281 | /* Kernel debugging support. */ |
| 282 | |
| 283 | /* From <machine/frame.h>. Note that %esp and %ess are only saved in |
| 284 | a trap frame when entering the kernel from user space. */ |
| 285 | static int i386obsd_tf_reg_offset[] = |
| 286 | { |
| 287 | 10 * 4, /* %eax */ |
| 288 | 9 * 4, /* %ecx */ |
| 289 | 8 * 4, /* %edx */ |
| 290 | 7 * 4, /* %ebx */ |
| 291 | -1, /* %esp */ |
| 292 | 6 * 4, /* %ebp */ |
| 293 | 5 * 4, /* %esi */ |
| 294 | 4 * 4, /* %edi */ |
| 295 | 13 * 4, /* %eip */ |
| 296 | 15 * 4, /* %eflags */ |
| 297 | 14 * 4, /* %cs */ |
| 298 | -1, /* %ss */ |
| 299 | 3 * 4, /* %ds */ |
| 300 | 2 * 4, /* %es */ |
| 301 | 0 * 4, /* %fs */ |
| 302 | 1 * 4 /* %gs */ |
| 303 | }; |
| 304 | |
| 305 | static struct trad_frame_cache * |
| 306 | i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache) |
| 307 | { |
| 308 | struct gdbarch *gdbarch = get_frame_arch (this_frame); |
| 309 | enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); |
| 310 | struct trad_frame_cache *cache; |
| 311 | CORE_ADDR func, sp, addr; |
| 312 | ULONGEST cs; |
| 313 | const char *name; |
| 314 | int i; |
| 315 | |
| 316 | if (*this_cache) |
| 317 | return (struct trad_frame_cache *) *this_cache; |
| 318 | |
| 319 | cache = trad_frame_cache_zalloc (this_frame); |
| 320 | *this_cache = cache; |
| 321 | |
| 322 | func = get_frame_func (this_frame); |
| 323 | sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM); |
| 324 | |
| 325 | find_pc_partial_function (func, &name, NULL, NULL); |
| 326 | if (name && startswith (name, "Xintr")) |
| 327 | addr = sp + 8; /* It's an interrupt frame. */ |
| 328 | else |
| 329 | addr = sp; |
| 330 | |
| 331 | for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++) |
| 332 | if (i386obsd_tf_reg_offset[i] != -1) |
| 333 | trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]); |
| 334 | |
| 335 | /* Read %cs from trap frame. */ |
| 336 | addr += i386obsd_tf_reg_offset[I386_CS_REGNUM]; |
| 337 | cs = read_memory_unsigned_integer (addr, 4, byte_order); |
| 338 | if ((cs & I386_SEL_RPL) == I386_SEL_UPL) |
| 339 | { |
| 340 | /* Trap from user space; terminate backtrace. */ |
| 341 | trad_frame_set_id (cache, outer_frame_id); |
| 342 | } |
| 343 | else |
| 344 | { |
| 345 | /* Construct the frame ID using the function start. */ |
| 346 | trad_frame_set_id (cache, frame_id_build (sp + 8, func)); |
| 347 | } |
| 348 | |
| 349 | return cache; |
| 350 | } |
| 351 | |
| 352 | static void |
| 353 | i386obsd_trapframe_this_id (struct frame_info *this_frame, |
| 354 | void **this_cache, struct frame_id *this_id) |
| 355 | { |
| 356 | struct trad_frame_cache *cache = |
| 357 | i386obsd_trapframe_cache (this_frame, this_cache); |
| 358 | |
| 359 | trad_frame_get_id (cache, this_id); |
| 360 | } |
| 361 | |
| 362 | static struct value * |
| 363 | i386obsd_trapframe_prev_register (struct frame_info *this_frame, |
| 364 | void **this_cache, int regnum) |
| 365 | { |
| 366 | struct trad_frame_cache *cache = |
| 367 | i386obsd_trapframe_cache (this_frame, this_cache); |
| 368 | |
| 369 | return trad_frame_get_register (cache, this_frame, regnum); |
| 370 | } |
| 371 | |
| 372 | static int |
| 373 | i386obsd_trapframe_sniffer (const struct frame_unwind *self, |
| 374 | struct frame_info *this_frame, |
| 375 | void **this_prologue_cache) |
| 376 | { |
| 377 | ULONGEST cs; |
| 378 | const char *name; |
| 379 | |
| 380 | /* Check Current Privilege Level and bail out if we're not executing |
| 381 | in kernel space. */ |
| 382 | cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM); |
| 383 | if ((cs & I386_SEL_RPL) == I386_SEL_UPL) |
| 384 | return 0; |
| 385 | |
| 386 | find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL); |
| 387 | return (name && (strcmp (name, "calltrap") == 0 |
| 388 | || strcmp (name, "syscall1") == 0 |
| 389 | || startswith (name, "Xintr") |
| 390 | || startswith (name, "Xsoft"))); |
| 391 | } |
| 392 | |
| 393 | static const struct frame_unwind i386obsd_trapframe_unwind = { |
| 394 | /* FIXME: kettenis/20051219: This really is more like an interrupt |
| 395 | frame, but SIGTRAMP_FRAME would print <signal handler called>, |
| 396 | which really is not what we want here. */ |
| 397 | NORMAL_FRAME, |
| 398 | default_frame_unwind_stop_reason, |
| 399 | i386obsd_trapframe_this_id, |
| 400 | i386obsd_trapframe_prev_register, |
| 401 | NULL, |
| 402 | i386obsd_trapframe_sniffer |
| 403 | }; |
| 404 | \f |
| 405 | |
| 406 | static void |
| 407 | i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) |
| 408 | { |
| 409 | struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); |
| 410 | |
| 411 | /* Obviously OpenBSD is BSD-based. */ |
| 412 | i386bsd_init_abi (info, gdbarch); |
| 413 | obsd_init_abi (info, gdbarch); |
| 414 | i386_elf_init_abi (info, gdbarch); |
| 415 | |
| 416 | /* OpenBSD has a different `struct reg'. */ |
| 417 | tdep->gregset_reg_offset = i386obsd_r_reg_offset; |
| 418 | tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset); |
| 419 | tdep->sizeof_gregset = 16 * 4; |
| 420 | |
| 421 | /* OpenBSD uses -freg-struct-return by default. */ |
| 422 | tdep->struct_return = reg_struct_return; |
| 423 | |
| 424 | /* OpenBSD uses a different memory layout. */ |
| 425 | tdep->sigtramp_start = i386obsd_sigtramp_start_addr; |
| 426 | tdep->sigtramp_end = i386obsd_sigtramp_end_addr; |
| 427 | tdep->sigtramp_p = i386obsd_sigtramp_p; |
| 428 | |
| 429 | /* OpenBSD has a `struct sigcontext' that's different from the |
| 430 | original 4.3 BSD. */ |
| 431 | tdep->sc_reg_offset = i386obsd_sc_reg_offset; |
| 432 | tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset); |
| 433 | |
| 434 | /* OpenBSD provides a user-level threads implementation. */ |
| 435 | bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread); |
| 436 | bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread); |
| 437 | |
| 438 | /* Unwind kernel trap frames correctly. */ |
| 439 | frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind); |
| 440 | |
| 441 | /* OpenBSD ELF uses SVR4-style shared libraries. */ |
| 442 | set_solib_svr4_fetch_link_map_offsets |
| 443 | (gdbarch, svr4_ilp32_fetch_link_map_offsets); |
| 444 | } |
| 445 | |
| 446 | void |
| 447 | _initialize_i386obsd_tdep (void) |
| 448 | { |
| 449 | gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD, |
| 450 | i386obsd_init_abi); |
| 451 | } |