1 /* Target-dependent code for OpenBSD/i386.
3 Copyright (C) 1988-2014 Free Software Foundation, Inc.
5 This file is part of GDB.
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.
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.
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/>. */
21 #include "arch-utils.h"
23 #include "frame-unwind.h"
31 #include "trad-frame.h"
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"
39 /* Support for signal handlers. */
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
49 By the way, the mapping mentioned above is read-only, so you cannot
50 place a breakpoint in the signal trampoline. */
52 /* Default page size. */
53 static const int i386obsd_page_size = 4096;
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 */
63 /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
67 i386obsd_sigtramp_p (struct frame_info *this_frame)
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[] =
75 0x67, 0x00, 0x00, 0x00, /* movl $SYS_sigreturn, %eax */
76 0xcd, 0x80 /* int $0x80 */
78 size_t buflen = sizeof sigreturn;
83 /* If the function has a valid symbol name, it isn't a
85 find_pc_partial_function (pc, &name, NULL, NULL);
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)
94 /* Allocate buffer. */
95 buf = alloca (buflen);
97 /* Loop over all offsets. */
98 for (offset = i386obsd_sigreturn_offset; *offset != -1; offset++)
100 /* If we can't read the instructions, return zero. */
101 if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,
105 /* Check for sigreturn(2). */
106 if (memcmp (buf, sigreturn, buflen) == 0)
113 /* Mapping between the general-purpose registers in `struct reg'
114 format and GDB's register cache layout. */
116 /* From <machine/reg.h>. */
117 static int i386obsd_r_reg_offset[] =
138 i386obsd_aout_supply_regset (const struct regset *regset,
139 struct regcache *regcache, int regnum,
140 const void *regs, size_t len)
142 struct gdbarch *gdbarch = get_regcache_arch (regcache);
143 const struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
144 const gdb_byte *gregs = regs;
146 gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);
148 i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);
149 i387_supply_fsave (regcache, regnum, gregs + tdep->sizeof_gregset);
152 static const struct regset i386obsd_aout_gregset =
154 NULL, i386obsd_aout_supply_regset, NULL
157 static const struct regset *
158 i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,
159 const char *sect_name,
162 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
164 /* OpenBSD a.out core dumps don't use seperate register sets for the
165 general-purpose and floating-point registers. */
167 if (strcmp (sect_name, ".reg") == 0
168 && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)
169 return &i386obsd_aout_gregset;
175 /* Sigtramp routine location for OpenBSD 3.1 and earlier releases. */
176 CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
177 CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
179 /* From <machine/signal.h>. */
180 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
191 13 * 4, /* %eflags */
200 /* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c. */
201 static int i386obsd_uthread_reg_offset[] =
221 /* Offset within the thread structure where we can find the saved
222 stack pointer (%esp). */
223 #define I386OBSD_UTHREAD_ESP_OFFSET 176
226 i386obsd_supply_uthread (struct regcache *regcache,
227 int regnum, CORE_ADDR addr)
229 struct gdbarch *gdbarch = get_regcache_arch (regcache);
230 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
231 CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
236 gdb_assert (regnum >= -1);
238 if (regnum == -1 || regnum == I386_ESP_REGNUM)
242 /* Fetch stack pointer from thread structure. */
243 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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, byte_order, sp + offset);
249 regcache_raw_supply (regcache, I386_ESP_REGNUM, buf);
252 for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
254 if (i386obsd_uthread_reg_offset[i] != -1
255 && (regnum == -1 || regnum == i))
257 /* Fetch stack pointer from thread structure (if we didn't
260 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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);
270 i386obsd_collect_uthread (const struct regcache *regcache,
271 int regnum, CORE_ADDR addr)
273 struct gdbarch *gdbarch = get_regcache_arch (regcache);
274 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
275 CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
280 gdb_assert (regnum >= -1);
282 if (regnum == -1 || regnum == I386_ESP_REGNUM)
286 /* Calculate the stack pointer (frame pointer) that will be
287 stored into the thread structure. */
288 offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
289 regcache_raw_collect (regcache, I386_ESP_REGNUM, buf);
290 sp = extract_unsigned_integer (buf, 4, byte_order) - offset;
292 /* Store the stack pointer. */
293 write_memory_unsigned_integer (sp_addr, 4, byte_order, sp);
295 /* The stack pointer was (potentially) modified. Make sure we
296 build a proper stack frame. */
300 for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
302 if (i386obsd_uthread_reg_offset[i] != -1
303 && (regnum == -1 || regnum == i))
305 /* Fetch stack pointer from thread structure (if we didn't
306 calculate it already). */
308 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
310 /* Write the register into the stack frame. */
311 regcache_raw_collect (regcache, i, buf);
312 write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
317 /* Kernel debugging support. */
319 /* From <machine/frame.h>. Note that %esp and %ess are only saved in
320 a trap frame when entering the kernel from user space. */
321 static int i386obsd_tf_reg_offset[] =
332 15 * 4, /* %eflags */
341 static struct trad_frame_cache *
342 i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
344 struct gdbarch *gdbarch = get_frame_arch (this_frame);
345 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
346 struct trad_frame_cache *cache;
347 CORE_ADDR func, sp, addr;
355 cache = trad_frame_cache_zalloc (this_frame);
358 func = get_frame_func (this_frame);
359 sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);
361 find_pc_partial_function (func, &name, NULL, NULL);
362 if (name && strncmp (name, "Xintr", 5) == 0)
363 addr = sp + 8; /* It's an interrupt frame. */
367 for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)
368 if (i386obsd_tf_reg_offset[i] != -1)
369 trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]);
371 /* Read %cs from trap frame. */
372 addr += i386obsd_tf_reg_offset[I386_CS_REGNUM];
373 cs = read_memory_unsigned_integer (addr, 4, byte_order);
374 if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
376 /* Trap from user space; terminate backtrace. */
377 trad_frame_set_id (cache, outer_frame_id);
381 /* Construct the frame ID using the function start. */
382 trad_frame_set_id (cache, frame_id_build (sp + 8, func));
389 i386obsd_trapframe_this_id (struct frame_info *this_frame,
390 void **this_cache, struct frame_id *this_id)
392 struct trad_frame_cache *cache =
393 i386obsd_trapframe_cache (this_frame, this_cache);
395 trad_frame_get_id (cache, this_id);
398 static struct value *
399 i386obsd_trapframe_prev_register (struct frame_info *this_frame,
400 void **this_cache, int regnum)
402 struct trad_frame_cache *cache =
403 i386obsd_trapframe_cache (this_frame, this_cache);
405 return trad_frame_get_register (cache, this_frame, regnum);
409 i386obsd_trapframe_sniffer (const struct frame_unwind *self,
410 struct frame_info *this_frame,
411 void **this_prologue_cache)
416 /* Check Current Privilege Level and bail out if we're not executing
418 cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM);
419 if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
422 find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
423 return (name && (strcmp (name, "calltrap") == 0
424 || strcmp (name, "syscall1") == 0
425 || strncmp (name, "Xintr", 5) == 0
426 || strncmp (name, "Xsoft", 5) == 0));
429 static const struct frame_unwind i386obsd_trapframe_unwind = {
430 /* FIXME: kettenis/20051219: This really is more like an interrupt
431 frame, but SIGTRAMP_FRAME would print <signal handler called>,
432 which really is not what we want here. */
434 default_frame_unwind_stop_reason,
435 i386obsd_trapframe_this_id,
436 i386obsd_trapframe_prev_register,
438 i386obsd_trapframe_sniffer
443 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
445 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
447 /* Obviously OpenBSD is BSD-based. */
448 i386bsd_init_abi (info, gdbarch);
449 obsd_init_abi (info, gdbarch);
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;
456 /* OpenBSD uses -freg-struct-return by default. */
457 tdep->struct_return = reg_struct_return;
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;
464 /* OpenBSD has a `struct sigcontext' that's different from the
466 tdep->sc_reg_offset = i386obsd_sc_reg_offset;
467 tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
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);
473 /* Unwind kernel trap frames correctly. */
474 frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);
480 i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
482 i386obsd_init_abi (info, gdbarch);
484 /* OpenBSD a.out has a single register set. */
485 set_gdbarch_regset_from_core_section
486 (gdbarch, i386obsd_aout_regset_from_core_section);
492 i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
494 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
496 /* It's still OpenBSD. */
497 i386obsd_init_abi (info, gdbarch);
500 i386_elf_init_abi (info, gdbarch);
502 /* OpenBSD ELF uses SVR4-style shared libraries. */
503 set_solib_svr4_fetch_link_map_offsets
504 (gdbarch, svr4_ilp32_fetch_link_map_offsets);
508 /* Provide a prototype to silence -Wmissing-prototypes. */
509 void _initialize_i386obsd_tdep (void);
512 _initialize_i386obsd_tdep (void)
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
518 #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT
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);