1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
|
/* Intel 386 target-dependent stuff.
Copyright (C) 1988, 1989, 1991 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <stdio.h>
#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "gdbcore.h"
/* helper functions for tm-i386.h */
/* stdio style buffering to minimize calls to ptrace */
static CORE_ADDR codestream_next_addr;
static CORE_ADDR codestream_addr;
static unsigned char codestream_buf[sizeof (int)];
static int codestream_off;
static int codestream_cnt;
#define codestream_tell() (codestream_addr + codestream_off)
#define codestream_peek() (codestream_cnt == 0 ? \
codestream_fill(1): codestream_buf[codestream_off])
#define codestream_get() (codestream_cnt-- == 0 ? \
codestream_fill(0) : codestream_buf[codestream_off++])
static unsigned char
codestream_fill (peek_flag)
{
codestream_addr = codestream_next_addr;
codestream_next_addr += sizeof (int);
codestream_off = 0;
codestream_cnt = sizeof (int);
read_memory (codestream_addr,
(unsigned char *)codestream_buf,
sizeof (int));
if (peek_flag)
return (codestream_peek());
else
return (codestream_get());
}
static void
codestream_seek (place)
{
codestream_next_addr = place & -sizeof (int);
codestream_cnt = 0;
codestream_fill (1);
while (codestream_tell() != place)
codestream_get ();
}
static void
codestream_read (buf, count)
unsigned char *buf;
{
unsigned char *p;
int i;
p = buf;
for (i = 0; i < count; i++)
*p++ = codestream_get ();
}
/* next instruction is a jump, move to target */
static
i386_follow_jump ()
{
int long_delta;
short short_delta;
char byte_delta;
int data16;
int pos;
pos = codestream_tell ();
data16 = 0;
if (codestream_peek () == 0x66)
{
codestream_get ();
data16 = 1;
}
switch (codestream_get ())
{
case 0xe9:
/* relative jump: if data16 == 0, disp32, else disp16 */
if (data16)
{
codestream_read ((unsigned char *)&short_delta, 2);
/* include size of jmp inst (including the 0x66 prefix). */
pos += short_delta + 4;
}
else
{
codestream_read ((unsigned char *)&long_delta, 4);
pos += long_delta + 5;
}
break;
case 0xeb:
/* relative jump, disp8 (ignore data16) */
codestream_read ((unsigned char *)&byte_delta, 1);
pos += byte_delta + 2;
break;
}
codestream_seek (pos);
}
/*
* find & return amound a local space allocated, and advance codestream to
* first register push (if any)
*
* if entry sequence doesn't make sense, return -1, and leave
* codestream pointer random
*/
static long
i386_get_frame_setup (pc)
{
unsigned char op;
codestream_seek (pc);
i386_follow_jump ();
op = codestream_get ();
if (op == 0x58) /* popl %eax */
{
/*
* this function must start with
*
* popl %eax 0x58
* xchgl %eax, (%esp) 0x87 0x04 0x24
* or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00
*
* (the system 5 compiler puts out the second xchg
* inst, and the assembler doesn't try to optimize it,
* so the 'sib' form gets generated)
*
* this sequence is used to get the address of the return
* buffer for a function that returns a structure
*/
int pos;
unsigned char buf[4];
static unsigned char proto1[3] = { 0x87,0x04,0x24 };
static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 };
pos = codestream_tell ();
codestream_read (buf, 4);
if (bcmp (buf, proto1, 3) == 0)
pos += 3;
else if (bcmp (buf, proto2, 4) == 0)
pos += 4;
codestream_seek (pos);
op = codestream_get (); /* update next opcode */
}
if (op == 0x55) /* pushl %ebp */
{
/* check for movl %esp, %ebp - can be written two ways */
switch (codestream_get ())
{
case 0x8b:
if (codestream_get () != 0xec)
return (-1);
break;
case 0x89:
if (codestream_get () != 0xe5)
return (-1);
break;
default:
return (-1);
}
/* check for stack adjustment
*
* subl $XXX, %esp
*
* note: you can't subtract a 16 bit immediate
* from a 32 bit reg, so we don't have to worry
* about a data16 prefix
*/
op = codestream_peek ();
if (op == 0x83)
{
/* subl with 8 bit immed */
codestream_get ();
if (codestream_get () != 0xec)
/* Some instruction starting with 0x83 other than subl. */
{
codestream_seek (codestream_tell () - 2);
return 0;
}
/* subl with signed byte immediate
* (though it wouldn't make sense to be negative)
*/
return (codestream_get());
}
else if (op == 0x81)
{
/* subl with 32 bit immed */
int locals;
codestream_get();
if (codestream_get () != 0xec)
/* Some instruction starting with 0x81 other than subl. */
{
codestream_seek (codestream_tell () - 2);
return 0;
}
/* subl with 32 bit immediate */
codestream_read ((unsigned char *)&locals, 4);
SWAP_TARGET_AND_HOST (&locals, 4);
return (locals);
}
else
{
return (0);
}
}
else if (op == 0xc8)
{
/* enter instruction: arg is 16 bit unsigned immed */
unsigned short slocals;
codestream_read ((unsigned char *)&slocals, 2);
SWAP_TARGET_AND_HOST (&slocals, 2);
codestream_get (); /* flush final byte of enter instruction */
return (slocals);
}
return (-1);
}
/* Return number of args passed to a frame.
Can return -1, meaning no way to tell. */
/* on the 386, the instruction following the call could be:
* popl %ecx - one arg
* addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits
* anything else - zero args
*/
int
i386_frame_num_args (fi)
struct frame_info fi;
{
int retpc;
unsigned char op;
struct frame_info *pfi;
int frameless;
FRAMELESS_FUNCTION_INVOCATION (fi, frameless);
if (frameless)
/* In the absence of a frame pointer, GDB doesn't get correct values
for nameless arguments. Return -1, so it doesn't print any
nameless arguments. */
return -1;
pfi = get_prev_frame_info ((fi));
if (pfi == 0)
{
/* Note: this can happen if we are looking at the frame for
main, because FRAME_CHAIN_VALID won't let us go into
start. If we have debugging symbols, that's not really
a big deal; it just means it will only show as many arguments
to main as are declared. */
return -1;
}
else
{
retpc = pfi->pc;
op = read_memory_integer (retpc, 1);
if (op == 0x59)
/* pop %ecx */
return 1;
else if (op == 0x83)
{
op = read_memory_integer (retpc+1, 1);
if (op == 0xc4)
/* addl $<signed imm 8 bits>, %esp */
return (read_memory_integer (retpc+2,1)&0xff)/4;
else
return 0;
}
else if (op == 0x81)
{ /* add with 32 bit immediate */
op = read_memory_integer (retpc+1, 1);
if (op == 0xc4)
/* addl $<imm 32>, %esp */
return read_memory_integer (retpc+2, 4) / 4;
else
return 0;
}
else
{
return 0;
}
}
}
/*
* parse the first few instructions of the function to see
* what registers were stored.
*
* We handle these cases:
*
* The startup sequence can be at the start of the function,
* or the function can start with a branch to startup code at the end.
*
* %ebp can be set up with either the 'enter' instruction, or
* 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful,
* but was once used in the sys5 compiler)
*
* Local space is allocated just below the saved %ebp by either the
* 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has
* a 16 bit unsigned argument for space to allocate, and the
* 'addl' instruction could have either a signed byte, or
* 32 bit immediate.
*
* Next, the registers used by this function are pushed. In
* the sys5 compiler they will always be in the order: %edi, %esi, %ebx
* (and sometimes a harmless bug causes it to also save but not restore %eax);
* however, the code below is willing to see the pushes in any order,
* and will handle up to 8 of them.
*
* If the setup sequence is at the end of the function, then the
* next instruction will be a branch back to the start.
*/
i386_frame_find_saved_regs (fip, fsrp)
struct frame_info *fip;
struct frame_saved_regs *fsrp;
{
long locals;
unsigned char *p;
unsigned char op;
CORE_ADDR dummy_bottom;
CORE_ADDR adr;
int i;
bzero (fsrp, sizeof *fsrp);
/* if frame is the end of a dummy, compute where the
* beginning would be
*/
dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH;
/* check if the PC is in the stack, in a dummy frame */
if (dummy_bottom <= fip->pc && fip->pc <= fip->frame)
{
/* all regs were saved by push_call_dummy () */
adr = fip->frame;
for (i = 0; i < NUM_REGS; i++)
{
adr -= REGISTER_RAW_SIZE (i);
fsrp->regs[i] = adr;
}
return;
}
locals = i386_get_frame_setup (get_pc_function_start (fip->pc));
if (locals >= 0)
{
adr = fip->frame - 4 - locals;
for (i = 0; i < 8; i++)
{
op = codestream_get ();
if (op < 0x50 || op > 0x57)
break;
fsrp->regs[op - 0x50] = adr;
adr -= 4;
}
}
fsrp->regs[PC_REGNUM] = fip->frame + 4;
fsrp->regs[FP_REGNUM] = fip->frame;
}
/* return pc of first real instruction */
i386_skip_prologue (pc)
{
unsigned char op;
int i;
if (i386_get_frame_setup (pc) < 0)
return (pc);
/* found valid frame setup - codestream now points to
* start of push instructions for saving registers
*/
/* skip over register saves */
for (i = 0; i < 8; i++)
{
op = codestream_peek ();
/* break if not pushl inst */
if (op < 0x50 || op > 0x57)
break;
codestream_get ();
}
i386_follow_jump ();
return (codestream_tell ());
}
i386_push_dummy_frame ()
{
CORE_ADDR sp = read_register (SP_REGNUM);
int regnum;
char regbuf[MAX_REGISTER_RAW_SIZE];
sp = push_word (sp, read_register (PC_REGNUM));
sp = push_word (sp, read_register (FP_REGNUM));
write_register (FP_REGNUM, sp);
for (regnum = 0; regnum < NUM_REGS; regnum++)
{
read_register_gen (regnum, regbuf);
sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum));
}
write_register (SP_REGNUM, sp);
}
i386_pop_frame ()
{
FRAME frame = get_current_frame ();
CORE_ADDR fp;
int regnum;
struct frame_saved_regs fsr;
struct frame_info *fi;
char regbuf[MAX_REGISTER_RAW_SIZE];
fi = get_frame_info (frame);
fp = fi->frame;
get_frame_saved_regs (fi, &fsr);
for (regnum = 0; regnum < NUM_REGS; regnum++)
{
CORE_ADDR adr;
adr = fsr.regs[regnum];
if (adr)
{
read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum));
write_register_bytes (REGISTER_BYTE (regnum), regbuf,
REGISTER_RAW_SIZE (regnum));
}
}
write_register (FP_REGNUM, read_memory_integer (fp, 4));
write_register (PC_REGNUM, read_memory_integer (fp + 4, 4));
write_register (SP_REGNUM, fp + 8);
flush_cached_frames ();
set_current_frame ( create_new_frame (read_register (FP_REGNUM),
read_pc ()));
}
|