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ca557f44 AC |
1 | /* Target-dependent code for GNU/Linux running on i386's, for GDB. |
2 | ||
4be87837 | 3 | Copyright 2000, 2001, 2002, 2003 Free Software Foundation, Inc. |
e7ee86a9 JB |
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 2 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, write to the Free Software | |
19 | Foundation, Inc., 59 Temple Place - Suite 330, | |
20 | Boston, MA 02111-1307, USA. */ | |
21 | ||
22 | #include "defs.h" | |
23 | #include "gdbcore.h" | |
24 | #include "frame.h" | |
25 | #include "value.h" | |
4e052eda | 26 | #include "regcache.h" |
6441c4a0 | 27 | #include "inferior.h" |
0670c0aa | 28 | #include "osabi.h" |
38c968cf | 29 | #include "reggroups.h" |
0670c0aa | 30 | #include "solib-svr4.h" |
e7ee86a9 | 31 | |
0670c0aa | 32 | #include "gdb_string.h" |
4be87837 | 33 | |
8201327c MK |
34 | #include "i386-tdep.h" |
35 | #include "i386-linux-tdep.h" | |
0670c0aa | 36 | #include "glibc-tdep.h" |
8201327c | 37 | |
6441c4a0 MK |
38 | /* Return the name of register REG. */ |
39 | ||
16775908 | 40 | static const char * |
6441c4a0 MK |
41 | i386_linux_register_name (int reg) |
42 | { | |
43 | /* Deal with the extra "orig_eax" pseudo register. */ | |
44 | if (reg == I386_LINUX_ORIG_EAX_REGNUM) | |
45 | return "orig_eax"; | |
46 | ||
47 | return i386_register_name (reg); | |
48 | } | |
38c968cf AC |
49 | |
50 | /* Return non-zero, when the register is in the corresponding register | |
51 | group. Put the LINUX_ORIG_EAX register in the system group. */ | |
52 | static int | |
53 | i386_linux_register_reggroup_p (struct gdbarch *gdbarch, int regnum, | |
54 | struct reggroup *group) | |
55 | { | |
56 | if (regnum == I386_LINUX_ORIG_EAX_REGNUM) | |
57 | return (group == system_reggroup | |
58 | || group == save_reggroup | |
59 | || group == restore_reggroup); | |
60 | return i386_register_reggroup_p (gdbarch, regnum, group); | |
61 | } | |
62 | ||
e7ee86a9 JB |
63 | \f |
64 | /* Recognizing signal handler frames. */ | |
65 | ||
ca557f44 | 66 | /* GNU/Linux has two flavors of signals. Normal signal handlers, and |
e7ee86a9 JB |
67 | "realtime" (RT) signals. The RT signals can provide additional |
68 | information to the signal handler if the SA_SIGINFO flag is set | |
69 | when establishing a signal handler using `sigaction'. It is not | |
ca557f44 AC |
70 | unlikely that future versions of GNU/Linux will support SA_SIGINFO |
71 | for normal signals too. */ | |
e7ee86a9 JB |
72 | |
73 | /* When the i386 Linux kernel calls a signal handler and the | |
74 | SA_RESTORER flag isn't set, the return address points to a bit of | |
75 | code on the stack. This function returns whether the PC appears to | |
76 | be within this bit of code. | |
77 | ||
78 | The instruction sequence for normal signals is | |
79 | pop %eax | |
acd5c798 | 80 | mov $0x77, %eax |
e7ee86a9 JB |
81 | int $0x80 |
82 | or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80. | |
83 | ||
84 | Checking for the code sequence should be somewhat reliable, because | |
85 | the effect is to call the system call sigreturn. This is unlikely | |
86 | to occur anywhere other than a signal trampoline. | |
87 | ||
88 | It kind of sucks that we have to read memory from the process in | |
89 | order to identify a signal trampoline, but there doesn't seem to be | |
d7bd68ca | 90 | any other way. The PC_IN_SIGTRAMP macro in tm-linux.h arranges to |
e7ee86a9 JB |
91 | only call us if no function name could be identified, which should |
92 | be the case since the code is on the stack. | |
93 | ||
94 | Detection of signal trampolines for handlers that set the | |
95 | SA_RESTORER flag is in general not possible. Unfortunately this is | |
96 | what the GNU C Library has been doing for quite some time now. | |
97 | However, as of version 2.1.2, the GNU C Library uses signal | |
98 | trampolines (named __restore and __restore_rt) that are identical | |
99 | to the ones used by the kernel. Therefore, these trampolines are | |
100 | supported too. */ | |
101 | ||
acd5c798 MK |
102 | #define LINUX_SIGTRAMP_INSN0 0x58 /* pop %eax */ |
103 | #define LINUX_SIGTRAMP_OFFSET0 0 | |
104 | #define LINUX_SIGTRAMP_INSN1 0xb8 /* mov $NNNN, %eax */ | |
105 | #define LINUX_SIGTRAMP_OFFSET1 1 | |
106 | #define LINUX_SIGTRAMP_INSN2 0xcd /* int */ | |
107 | #define LINUX_SIGTRAMP_OFFSET2 6 | |
e7ee86a9 JB |
108 | |
109 | static const unsigned char linux_sigtramp_code[] = | |
110 | { | |
111 | LINUX_SIGTRAMP_INSN0, /* pop %eax */ | |
acd5c798 | 112 | LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77, %eax */ |
e7ee86a9 JB |
113 | LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */ |
114 | }; | |
115 | ||
116 | #define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code) | |
117 | ||
118 | /* If PC is in a sigtramp routine, return the address of the start of | |
119 | the routine. Otherwise, return 0. */ | |
120 | ||
121 | static CORE_ADDR | |
122 | i386_linux_sigtramp_start (CORE_ADDR pc) | |
123 | { | |
124 | unsigned char buf[LINUX_SIGTRAMP_LEN]; | |
125 | ||
126 | /* We only recognize a signal trampoline if PC is at the start of | |
127 | one of the three instructions. We optimize for finding the PC at | |
128 | the start, as will be the case when the trampoline is not the | |
129 | first frame on the stack. We assume that in the case where the | |
130 | PC is not at the start of the instruction sequence, there will be | |
131 | a few trailing readable bytes on the stack. */ | |
132 | ||
133 | if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) | |
134 | return 0; | |
135 | ||
136 | if (buf[0] != LINUX_SIGTRAMP_INSN0) | |
137 | { | |
138 | int adjust; | |
139 | ||
140 | switch (buf[0]) | |
141 | { | |
142 | case LINUX_SIGTRAMP_INSN1: | |
143 | adjust = LINUX_SIGTRAMP_OFFSET1; | |
144 | break; | |
145 | case LINUX_SIGTRAMP_INSN2: | |
146 | adjust = LINUX_SIGTRAMP_OFFSET2; | |
147 | break; | |
148 | default: | |
149 | return 0; | |
150 | } | |
151 | ||
152 | pc -= adjust; | |
153 | ||
154 | if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) | |
155 | return 0; | |
156 | } | |
157 | ||
158 | if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0) | |
159 | return 0; | |
160 | ||
161 | return pc; | |
162 | } | |
163 | ||
164 | /* This function does the same for RT signals. Here the instruction | |
165 | sequence is | |
acd5c798 | 166 | mov $0xad, %eax |
e7ee86a9 JB |
167 | int $0x80 |
168 | or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80. | |
169 | ||
170 | The effect is to call the system call rt_sigreturn. */ | |
171 | ||
acd5c798 MK |
172 | #define LINUX_RT_SIGTRAMP_INSN0 0xb8 /* mov $NNNN, %eax */ |
173 | #define LINUX_RT_SIGTRAMP_OFFSET0 0 | |
174 | #define LINUX_RT_SIGTRAMP_INSN1 0xcd /* int */ | |
175 | #define LINUX_RT_SIGTRAMP_OFFSET1 5 | |
e7ee86a9 JB |
176 | |
177 | static const unsigned char linux_rt_sigtramp_code[] = | |
178 | { | |
acd5c798 | 179 | LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad, %eax */ |
e7ee86a9 JB |
180 | LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */ |
181 | }; | |
182 | ||
183 | #define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code) | |
184 | ||
185 | /* If PC is in a RT sigtramp routine, return the address of the start | |
186 | of the routine. Otherwise, return 0. */ | |
187 | ||
188 | static CORE_ADDR | |
189 | i386_linux_rt_sigtramp_start (CORE_ADDR pc) | |
190 | { | |
191 | unsigned char buf[LINUX_RT_SIGTRAMP_LEN]; | |
192 | ||
193 | /* We only recognize a signal trampoline if PC is at the start of | |
194 | one of the two instructions. We optimize for finding the PC at | |
195 | the start, as will be the case when the trampoline is not the | |
196 | first frame on the stack. We assume that in the case where the | |
197 | PC is not at the start of the instruction sequence, there will be | |
198 | a few trailing readable bytes on the stack. */ | |
199 | ||
200 | if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) | |
201 | return 0; | |
202 | ||
203 | if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) | |
204 | { | |
205 | if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) | |
206 | return 0; | |
207 | ||
208 | pc -= LINUX_RT_SIGTRAMP_OFFSET1; | |
209 | ||
210 | if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) | |
211 | return 0; | |
212 | } | |
213 | ||
214 | if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) | |
215 | return 0; | |
216 | ||
217 | return pc; | |
218 | } | |
219 | ||
ca557f44 | 220 | /* Return whether PC is in a GNU/Linux sigtramp routine. */ |
e7ee86a9 | 221 | |
8201327c MK |
222 | static int |
223 | i386_linux_pc_in_sigtramp (CORE_ADDR pc, char *name) | |
e7ee86a9 | 224 | { |
ef17e74b DJ |
225 | /* If we have NAME, we can optimize the search. The trampolines are |
226 | named __restore and __restore_rt. However, they aren't dynamically | |
227 | exported from the shared C library, so the trampoline may appear to | |
228 | be part of the preceding function. This should always be sigaction, | |
229 | __sigaction, or __libc_sigaction (all aliases to the same function). */ | |
230 | if (name == NULL || strstr (name, "sigaction") != NULL) | |
231 | return (i386_linux_sigtramp_start (pc) != 0 | |
232 | || i386_linux_rt_sigtramp_start (pc) != 0); | |
233 | ||
234 | return (strcmp ("__restore", name) == 0 | |
235 | || strcmp ("__restore_rt", name) == 0); | |
e7ee86a9 JB |
236 | } |
237 | ||
acd5c798 MK |
238 | /* Offset to struct sigcontext in ucontext, from <asm/ucontext.h>. */ |
239 | #define I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET 20 | |
240 | ||
241 | /* Assuming NEXT_FRAME is a frame following a GNU/Linux sigtramp | |
242 | routine, return the address of the associated sigcontext structure. */ | |
e7ee86a9 | 243 | |
b7d15bf7 | 244 | static CORE_ADDR |
acd5c798 | 245 | i386_linux_sigcontext_addr (struct frame_info *next_frame) |
e7ee86a9 JB |
246 | { |
247 | CORE_ADDR pc; | |
acd5c798 MK |
248 | CORE_ADDR sp; |
249 | char buf[4]; | |
250 | ||
c7f16359 | 251 | frame_unwind_register (next_frame, I386_ESP_REGNUM, buf); |
acd5c798 | 252 | sp = extract_unsigned_integer (buf, 4); |
e7ee86a9 | 253 | |
acd5c798 | 254 | pc = i386_linux_sigtramp_start (frame_pc_unwind (next_frame)); |
e7ee86a9 JB |
255 | if (pc) |
256 | { | |
acd5c798 MK |
257 | /* The sigcontext structure lives on the stack, right after |
258 | the signum argument. We determine the address of the | |
259 | sigcontext structure by looking at the frame's stack | |
260 | pointer. Keep in mind that the first instruction of the | |
261 | sigtramp code is "pop %eax". If the PC is after this | |
262 | instruction, adjust the returned value accordingly. */ | |
263 | if (pc == frame_pc_unwind (next_frame)) | |
e7ee86a9 JB |
264 | return sp + 4; |
265 | return sp; | |
266 | } | |
267 | ||
acd5c798 | 268 | pc = i386_linux_rt_sigtramp_start (frame_pc_unwind (next_frame)); |
e7ee86a9 JB |
269 | if (pc) |
270 | { | |
acd5c798 MK |
271 | CORE_ADDR ucontext_addr; |
272 | ||
273 | /* The sigcontext structure is part of the user context. A | |
274 | pointer to the user context is passed as the third argument | |
275 | to the signal handler. */ | |
276 | read_memory (sp + 8, buf, 4); | |
9fbfb822 | 277 | ucontext_addr = extract_unsigned_integer (buf, 4); |
acd5c798 | 278 | return ucontext_addr + I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET; |
e7ee86a9 JB |
279 | } |
280 | ||
281 | error ("Couldn't recognize signal trampoline."); | |
282 | return 0; | |
283 | } | |
284 | ||
6441c4a0 MK |
285 | /* Set the program counter for process PTID to PC. */ |
286 | ||
8201327c | 287 | static void |
6441c4a0 MK |
288 | i386_linux_write_pc (CORE_ADDR pc, ptid_t ptid) |
289 | { | |
c7f16359 | 290 | write_register_pid (I386_EIP_REGNUM, pc, ptid); |
6441c4a0 MK |
291 | |
292 | /* We must be careful with modifying the program counter. If we | |
293 | just interrupted a system call, the kernel might try to restart | |
294 | it when we resume the inferior. On restarting the system call, | |
295 | the kernel will try backing up the program counter even though it | |
296 | no longer points at the system call. This typically results in a | |
297 | SIGSEGV or SIGILL. We can prevent this by writing `-1' in the | |
298 | "orig_eax" pseudo-register. | |
299 | ||
300 | Note that "orig_eax" is saved when setting up a dummy call frame. | |
301 | This means that it is properly restored when that frame is | |
302 | popped, and that the interrupted system call will be restarted | |
303 | when we resume the inferior on return from a function call from | |
304 | within GDB. In all other cases the system call will not be | |
305 | restarted. */ | |
306 | write_register_pid (I386_LINUX_ORIG_EAX_REGNUM, -1, ptid); | |
307 | } | |
308 | \f | |
305d65ca | 309 | /* Fetch (and possibly build) an appropriate link_map_offsets |
ca557f44 | 310 | structure for native GNU/Linux x86 targets using the struct offsets |
305d65ca | 311 | defined in link.h (but without actual reference to that file). |
1a8629c7 | 312 | |
ca557f44 AC |
313 | This makes it possible to access GNU/Linux x86 shared libraries |
314 | from a GDB that was not built on an GNU/Linux x86 host (for cross | |
315 | debugging). */ | |
1a8629c7 | 316 | |
8201327c | 317 | static struct link_map_offsets * |
1a8629c7 MS |
318 | i386_linux_svr4_fetch_link_map_offsets (void) |
319 | { | |
320 | static struct link_map_offsets lmo; | |
305d65ca | 321 | static struct link_map_offsets *lmp = NULL; |
1a8629c7 | 322 | |
305d65ca | 323 | if (lmp == NULL) |
1a8629c7 MS |
324 | { |
325 | lmp = &lmo; | |
326 | ||
305d65ca MK |
327 | lmo.r_debug_size = 8; /* The actual size is 20 bytes, but |
328 | this is all we need. */ | |
1a8629c7 MS |
329 | lmo.r_map_offset = 4; |
330 | lmo.r_map_size = 4; | |
331 | ||
305d65ca MK |
332 | lmo.link_map_size = 20; /* The actual size is 552 bytes, but |
333 | this is all we need. */ | |
1a8629c7 MS |
334 | lmo.l_addr_offset = 0; |
335 | lmo.l_addr_size = 4; | |
336 | ||
337 | lmo.l_name_offset = 4; | |
338 | lmo.l_name_size = 4; | |
339 | ||
340 | lmo.l_next_offset = 12; | |
341 | lmo.l_next_size = 4; | |
342 | ||
343 | lmo.l_prev_offset = 16; | |
344 | lmo.l_prev_size = 4; | |
345 | } | |
346 | ||
305d65ca | 347 | return lmp; |
1a8629c7 | 348 | } |
8201327c MK |
349 | \f |
350 | ||
e9f1aad5 MK |
351 | /* The register sets used in GNU/Linux ELF core-dumps are identical to |
352 | the register sets in `struct user' that are used for a.out | |
353 | core-dumps. These are also used by ptrace(2). The corresponding | |
354 | types are `elf_gregset_t' for the general-purpose registers (with | |
355 | `elf_greg_t' the type of a single GP register) and `elf_fpregset_t' | |
356 | for the floating-point registers. | |
357 | ||
358 | Those types used to be available under the names `gregset_t' and | |
359 | `fpregset_t' too, and GDB used those names in the past. But those | |
360 | names are now used for the register sets used in the `mcontext_t' | |
361 | type, which have a different size and layout. */ | |
362 | ||
363 | /* Mapping between the general-purpose registers in `struct user' | |
364 | format and GDB's register cache layout. */ | |
365 | ||
366 | /* From <sys/reg.h>. */ | |
367 | static int i386_linux_gregset_reg_offset[] = | |
368 | { | |
369 | 6 * 4, /* %eax */ | |
370 | 1 * 4, /* %ecx */ | |
371 | 2 * 4, /* %edx */ | |
372 | 0 * 4, /* %ebx */ | |
373 | 15 * 4, /* %esp */ | |
374 | 5 * 4, /* %ebp */ | |
375 | 3 * 4, /* %esi */ | |
376 | 4 * 4, /* %edi */ | |
377 | 12 * 4, /* %eip */ | |
378 | 14 * 4, /* %eflags */ | |
379 | 13 * 4, /* %cs */ | |
380 | 16 * 4, /* %ss */ | |
381 | 7 * 4, /* %ds */ | |
382 | 8 * 4, /* %es */ | |
383 | 9 * 4, /* %fs */ | |
384 | 10 * 4, /* %gs */ | |
385 | -1, -1, -1, -1, -1, -1, -1, -1, | |
386 | -1, -1, -1, -1, -1, -1, -1, -1, | |
387 | -1, -1, -1, -1, -1, -1, -1, -1, | |
388 | -1, | |
389 | 11 * 4 /* "orig_eax" */ | |
390 | }; | |
391 | ||
392 | /* Mapping between the general-purpose registers in `struct | |
393 | sigcontext' format and GDB's register cache layout. */ | |
394 | ||
a3386186 | 395 | /* From <asm/sigcontext.h>. */ |
bb489b3c | 396 | static int i386_linux_sc_reg_offset[] = |
a3386186 MK |
397 | { |
398 | 11 * 4, /* %eax */ | |
399 | 10 * 4, /* %ecx */ | |
400 | 9 * 4, /* %edx */ | |
401 | 8 * 4, /* %ebx */ | |
402 | 7 * 4, /* %esp */ | |
403 | 6 * 4, /* %ebp */ | |
404 | 5 * 4, /* %esi */ | |
405 | 4 * 4, /* %edi */ | |
406 | 14 * 4, /* %eip */ | |
407 | 16 * 4, /* %eflags */ | |
408 | 15 * 4, /* %cs */ | |
409 | 18 * 4, /* %ss */ | |
410 | 3 * 4, /* %ds */ | |
411 | 2 * 4, /* %es */ | |
412 | 1 * 4, /* %fs */ | |
413 | 0 * 4 /* %gs */ | |
414 | }; | |
415 | ||
8201327c MK |
416 | static void |
417 | i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) | |
418 | { | |
419 | struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); | |
420 | ||
421 | /* GNU/Linux uses ELF. */ | |
422 | i386_elf_init_abi (info, gdbarch); | |
423 | ||
8201327c MK |
424 | /* Since we have the extra "orig_eax" register on GNU/Linux, we have |
425 | to adjust a few things. */ | |
426 | ||
427 | set_gdbarch_write_pc (gdbarch, i386_linux_write_pc); | |
bb489b3c | 428 | set_gdbarch_num_regs (gdbarch, I386_LINUX_NUM_REGS); |
8201327c | 429 | set_gdbarch_register_name (gdbarch, i386_linux_register_name); |
38c968cf | 430 | set_gdbarch_register_reggroup_p (gdbarch, i386_linux_register_reggroup_p); |
8201327c | 431 | |
e9f1aad5 MK |
432 | tdep->gregset_reg_offset = i386_linux_gregset_reg_offset; |
433 | tdep->gregset_num_regs = ARRAY_SIZE (i386_linux_gregset_reg_offset); | |
434 | tdep->sizeof_gregset = 17 * 4; | |
435 | ||
8201327c MK |
436 | tdep->jb_pc_offset = 20; /* From <bits/setjmp.h>. */ |
437 | ||
b7d15bf7 | 438 | tdep->sigcontext_addr = i386_linux_sigcontext_addr; |
a3386186 | 439 | tdep->sc_reg_offset = i386_linux_sc_reg_offset; |
bb489b3c | 440 | tdep->sc_num_regs = ARRAY_SIZE (i386_linux_sc_reg_offset); |
8201327c | 441 | |
b7d15bf7 MK |
442 | /* When the i386 Linux kernel calls a signal handler, the return |
443 | address points to a bit of code on the stack. This function is | |
444 | used to identify this bit of code as a signal trampoline in order | |
445 | to support backtracing through calls to signal handlers. */ | |
8201327c | 446 | set_gdbarch_pc_in_sigtramp (gdbarch, i386_linux_pc_in_sigtramp); |
8201327c | 447 | |
bb41a796 | 448 | set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver); |
8201327c MK |
449 | set_solib_svr4_fetch_link_map_offsets (gdbarch, |
450 | i386_linux_svr4_fetch_link_map_offsets); | |
451 | } | |
452 | ||
453 | /* Provide a prototype to silence -Wmissing-prototypes. */ | |
454 | extern void _initialize_i386_linux_tdep (void); | |
455 | ||
456 | void | |
457 | _initialize_i386_linux_tdep (void) | |
458 | { | |
05816f70 | 459 | gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_LINUX, |
8201327c MK |
460 | i386_linux_init_abi); |
461 | } |