1 /* Target-dependent code for OpenBSD/i386.
3 Copyright (C) 1988-2016 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 = (gdb_byte *) 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[] =
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;
143 /* From <machine/signal.h>. */
144 int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
155 13 * 4, /* %eflags */
164 /* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c. */
165 static int i386obsd_uthread_reg_offset[] =
185 /* Offset within the thread structure where we can find the saved
186 stack pointer (%esp). */
187 #define I386OBSD_UTHREAD_ESP_OFFSET 176
190 i386obsd_supply_uthread (struct regcache *regcache,
191 int regnum, CORE_ADDR addr)
193 struct gdbarch *gdbarch = get_regcache_arch (regcache);
194 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
195 CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
200 gdb_assert (regnum >= -1);
202 if (regnum == -1 || regnum == I386_ESP_REGNUM)
206 /* Fetch stack pointer from thread structure. */
207 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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 (regcache, I386_ESP_REGNUM, buf);
216 for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
218 if (i386obsd_uthread_reg_offset[i] != -1
219 && (regnum == -1 || regnum == i))
221 /* Fetch stack pointer from thread structure (if we didn't
224 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
226 /* Read the saved register from the stack frame. */
227 read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
228 regcache_raw_supply (regcache, i, buf);
234 i386obsd_collect_uthread (const struct regcache *regcache,
235 int regnum, CORE_ADDR addr)
237 struct gdbarch *gdbarch = get_regcache_arch (regcache);
238 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
239 CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
244 gdb_assert (regnum >= -1);
246 if (regnum == -1 || regnum == I386_ESP_REGNUM)
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 (regcache, I386_ESP_REGNUM, buf);
254 sp = extract_unsigned_integer (buf, 4, byte_order) - offset;
256 /* Store the stack pointer. */
257 write_memory_unsigned_integer (sp_addr, 4, byte_order, sp);
259 /* The stack pointer was (potentially) modified. Make sure we
260 build a proper stack frame. */
264 for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
266 if (i386obsd_uthread_reg_offset[i] != -1
267 && (regnum == -1 || regnum == i))
269 /* Fetch stack pointer from thread structure (if we didn't
270 calculate it already). */
272 sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
274 /* Write the register into the stack frame. */
275 regcache_raw_collect (regcache, i, buf);
276 write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
281 /* Kernel debugging support. */
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[] =
296 15 * 4, /* %eflags */
305 static struct trad_frame_cache *
306 i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
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;
317 return (struct trad_frame_cache *) *this_cache;
319 cache = trad_frame_cache_zalloc (this_frame);
322 func = get_frame_func (this_frame);
323 sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);
325 find_pc_partial_function (func, &name, NULL, NULL);
326 if (name && startswith (name, "Xintr"))
327 addr = sp + 8; /* It's an interrupt frame. */
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]);
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)
340 /* Trap from user space; terminate backtrace. */
341 trad_frame_set_id (cache, outer_frame_id);
345 /* Construct the frame ID using the function start. */
346 trad_frame_set_id (cache, frame_id_build (sp + 8, func));
353 i386obsd_trapframe_this_id (struct frame_info *this_frame,
354 void **this_cache, struct frame_id *this_id)
356 struct trad_frame_cache *cache =
357 i386obsd_trapframe_cache (this_frame, this_cache);
359 trad_frame_get_id (cache, this_id);
362 static struct value *
363 i386obsd_trapframe_prev_register (struct frame_info *this_frame,
364 void **this_cache, int regnum)
366 struct trad_frame_cache *cache =
367 i386obsd_trapframe_cache (this_frame, this_cache);
369 return trad_frame_get_register (cache, this_frame, regnum);
373 i386obsd_trapframe_sniffer (const struct frame_unwind *self,
374 struct frame_info *this_frame,
375 void **this_prologue_cache)
380 /* Check Current Privilege Level and bail out if we're not executing
382 cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM);
383 if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
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")));
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. */
398 default_frame_unwind_stop_reason,
399 i386obsd_trapframe_this_id,
400 i386obsd_trapframe_prev_register,
402 i386obsd_trapframe_sniffer
407 i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
409 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
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);
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;
421 /* OpenBSD uses -freg-struct-return by default. */
422 tdep->struct_return = reg_struct_return;
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;
429 /* OpenBSD has a `struct sigcontext' that's different from the
431 tdep->sc_reg_offset = i386obsd_sc_reg_offset;
432 tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
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);
438 /* Unwind kernel trap frames correctly. */
439 frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);
441 /* OpenBSD ELF uses SVR4-style shared libraries. */
442 set_solib_svr4_fetch_link_map_offsets
443 (gdbarch, svr4_ilp32_fetch_link_map_offsets);
447 /* Provide a prototype to silence -Wmissing-prototypes. */
448 void _initialize_i386obsd_tdep (void);
451 _initialize_i386obsd_tdep (void)
453 gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD,