1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26
27 /*
28 * The Sun Studio and GCC (patched for opensolaris/illumos) compilers
29 * implement a argument saving scheme on amd64 via the -Wu,save-args or
30 * options. When the option is specified, INTEGER type function arguments
31 * passed via registers will be saved on the stack immediately after %rbp, and
32 * will not be modified through out the life of the routine.
33 *
34 * +--------+
35 * %rbp --> | %rbp |
36 * +--------+
37 * -0x8(%rbp) | %rdi |
38 * +--------+
39 * -0x10(%rbp) | %rsi |
40 * +--------+
41 * -0x18(%rbp) | %rdx |
42 * +--------+
43 * -0x20(%rbp) | %rcx |
44 * +--------+
45 * -0x28(%rbp) | %r8 |
46 * +--------+
47 * -0x30(%rbp) | %r9 |
48 * +--------+
49 *
50 *
51 * For example, for the following function,
52 *
53 * void
54 * foo(int a1, int a2, int a3, int a4, int a5, int a6, int a7)
55 * {
56 * ...
57 * }
58 *
59 * Disassembled code will look something like the following:
60 *
61 * pushq %rbp
62 * movq %rsp, %rbp
63 * subq $imm8, %rsp **
64 * movq %rdi, -0x8(%rbp)
65 * movq %rsi, -0x10(%rbp)
66 * movq %rdx, -0x18(%rbp)
67 * movq %rcx, -0x20(%rbp)
68 * movq %r8, -0x28(%rbp)
69 * movq %r9, -0x30(%rbp)
70 * ...
71 * or
72 * pushq %rbp
73 * movq %rsp, %rbp
74 * subq $imm8, %rsp **
75 * movq %r9, -0x30(%rbp)
76 * movq %r8, -0x28(%rbp)
77 * movq %rcx, -0x20(%rbp)
78 * movq %rdx, -0x18(%rbp)
79 * movq %rsi, -0x10(%rbp)
80 * movq %rdi, -0x8(%rbp)
81 * ...
82 * or
83 * pushq %rbp
84 * movq %rsp, %rbp
85 * pushq %rdi
86 * pushq %rsi
87 * pushq %rdx
88 * pushq %rcx
89 * pushq %r8
90 * pushq %r9
91 *
92 * **: The space being reserved is in addition to what the current
93 * function prolog already reserves.
94 *
95 * We loop through the first SAVEARGS_INSN_SEQ_LEN bytes of the function
96 * looking for each argument saving instruction we would expect to see.
97 *
98 * If there are odd number of arguments to a function, additional space is
99 * reserved on the stack to maintain 16-byte alignment. For example,
100 *
101 * argc == 0: no argument saving.
102 * argc == 3: save 3, but space for 4 is reserved
103 * argc == 7: save 6.
104 */
105
106 #include <sys/sysmacros.h>
107 #include <sys/types.h>
108 #include <libdisasm.h>
109 #include <string.h>
110
111 #include <saveargs.h>
112
113 /*
114 * Size of the instruction sequence arrays. It should correspond to
115 * the maximum number of arguments passed via registers.
116 */
117 #define INSTR_ARRAY_SIZE 6
118
119 #define INSTR1(ins, off) (ins[(off)])
120 #define INSTR2(ins, off) (ins[(off)] + (ins[(off) + 1] << 8))
121 #define INSTR3(ins, off) \
122 (ins[(off)] + (ins[(off) + 1] << 8) + (ins[(off + 2)] << 16))
123 #define INSTR4(ins, off) \
124 (ins[(off)] + (ins[(off) + 1] << 8) + (ins[(off + 2)] << 16) + \
125 (ins[(off) + 3] << 24))
126
127 /*
128 * Sun Studio 10 patch implementation saves %rdi first;
129 * GCC 3.4.3 Sun branch implementation saves them in reverse order.
130 */
131 static const uint32_t save_instr[INSTR_ARRAY_SIZE] = {
132 0xf87d8948, /* movq %rdi, -0x8(%rbp) */
133 0xf0758948, /* movq %rsi, -0x10(%rbp) */
134 0xe8558948, /* movq %rdx, -0x18(%rbp) */
135 0xe04d8948, /* movq %rcx, -0x20(%rbp) */
136 0xd845894c, /* movq %r8, -0x28(%rbp) */
137 0xd04d894c /* movq %r9, -0x30(%rbp) */
138 };
139
140 static const uint16_t save_instr_push[] = {
141 0x57, /* pushq %rdi */
142 0x56, /* pushq %rsi */
143 0x52, /* pushq %rdx */
144 0x51, /* pushq %rcx */
145 0x5041, /* pushq %r8 */
146 0x5141 /* pushq %r9 */
147 };
148
149 /*
150 * If the return type of a function is a structure greater than 16 bytes in
151 * size, %rdi will contain the address to which it should be stored, and
152 * arguments will begin at %rsi. Studio will push all of the normal argument
153 * registers anyway, GCC will start pushing at %rsi, so we need a separate
154 * pattern.
155 */
156 static const uint32_t save_instr_sr[INSTR_ARRAY_SIZE-1] = {
157 0xf8758948, /* movq %rsi,-0x8(%rbp) */
158 0xf0558948, /* movq %rdx,-0x10(%rbp) */
159 0xe84d8948, /* movq %rcx,-0x18(%rbp) */
160 0xe045894c, /* movq %r8,-0x20(%rbp) */
161 0xd84d894c /* movq %r9,-0x28(%rbp) */
162 };
163
164 static const uint8_t save_fp_pushes[] = {
165 0x55, /* pushq %rbp */
166 0xcc /* int $0x3 */
167 };
168 #define NUM_FP_PUSHES (sizeof (save_fp_pushes) / sizeof (save_fp_pushes[0]))
169
170 static const uint32_t save_fp_movs[] = {
171 0x00e58948, /* movq %rsp,%rbp, encoding 1 */
172 0x00ec8b48, /* movq %rsp,%rbp, encoding 2 */
173 };
174 #define NUM_FP_MOVS (sizeof (save_fp_movs) / sizeof (save_fp_movs[0]))
175
176 typedef struct {
177 uint8_t *data;
178 size_t size;
179 } text_t;
180
181 static int
182 do_read(void *data, uint64_t addr, void *buf, size_t len)
183 {
184 text_t *t = data;
185
186 if (addr >= t->size)
187 return (-1);
188
189 len = MIN(len, t->size - addr);
190
191 (void) memcpy(buf, (char *)t->data + addr, len);
192
193 return (len);
194 }
195
196 /* ARGSUSED */
197 int
198 do_lookup(void *data, uint64_t addr, char *buf, size_t buflen, uint64_t *start,
199 size_t *symlen)
200 {
201 /* We don't actually need lookup info */
202 return (-1);
203 }
204
205 static int
206 instr_size(dis_handle_t *dhp, uint8_t *ins, unsigned int i, size_t size)
207 {
208 text_t t;
209
210 t.data = ins;
211 t.size = size;
212
213 dis_set_data(dhp, &t);
214 return (dis_instrlen(dhp, i));
215 }
216
217 static boolean_t
218 has_saved_fp(dis_handle_t *dhp, uint8_t *ins, int size)
219 {
220 int i, j;
221 uint32_t n;
222 boolean_t found_push = B_FALSE;
223 ssize_t sz = 0;
224
225 for (i = 0; i < size; i += sz) {
226 if ((sz = instr_size(dhp, ins, i, size)) < 1)
227 return (B_FALSE);
228
229 if (found_push == B_FALSE) {
230 if (sz != 1)
231 continue;
232
233 n = INSTR1(ins, i);
234 for (j = 0; j <= NUM_FP_PUSHES; j++)
235 if (save_fp_pushes[j] == n) {
236 found_push = B_TRUE;
237 break;
238 }
239 } else {
240 if (sz != 3)
241 continue;
242 n = INSTR3(ins, i);
243 for (j = 0; j <= NUM_FP_MOVS; j++)
244 if (save_fp_movs[j] == n)
245 return (B_TRUE);
246 }
247 }
248
249 return (B_FALSE);
250 }
251
252 int
253 saveargs_has_args(uint8_t *ins, size_t size, uint_t argc, int start_index)
254 {
255 int i, j;
256 uint32_t n;
257 uint8_t found = 0;
258 ssize_t sz = 0;
259 dis_handle_t *dhp = NULL;
260 int ret = SAVEARGS_NO_ARGS;
261
262 argc = MIN((start_index + argc), INSTR_ARRAY_SIZE);
263
264 if ((dhp = dis_handle_create(DIS_X86_SIZE64, NULL, do_lookup,
265 do_read)) == NULL)
266 return (SAVEARGS_NO_ARGS);
267
268 if (!has_saved_fp(dhp, ins, size)) {
269 dis_handle_destroy(dhp);
270 return (SAVEARGS_NO_ARGS);
271 }
272
273 /*
274 * For each possible style of argument saving, walk the insn stream as
275 * we've been given it, and set bit N in 'found' if we find the
276 * instruction saving the Nth argument.
277 */
278
279 /*
280 * Compare against regular implementation
281 */
282 found = 0;
283 for (i = 0; i < size; i += sz) {
284 sz = instr_size(dhp, ins, i, size);
285
286 if (sz < 1)
287 break;
288 else if (sz != 4)
289 continue;
290
291 n = INSTR4(ins, i);
292
293 for (j = 0; j < argc; j++) {
294 if (n == save_instr[j]) {
295 found |= (1 << j);
296
297 if (found == ((1 << argc) - 1)) {
298 ret = start_index ?
299 SAVEARGS_STRUCT_ARGS :
300 SAVEARGS_TRAD_ARGS;
301 goto done;
302 }
303
304 break;
305 }
306 }
307 }
308
309 /*
310 * Compare against GCC push-based implementation
311 */
312 found = 0;
313 for (i = 0; i < size; i += sz) {
314 if ((sz = instr_size(dhp, ins, i, size)) < 1)
315 break;
316
317 for (j = start_index; j < argc; j++) {
318 if (sz == 2) /* Two byte */
319 n = INSTR2(ins, i);
320 else if (sz == 1)
321 n = INSTR1(ins, i);
322 else
323 continue;
324
325 if (n == save_instr_push[j]) {
326 found |= (1 << (j - start_index));
327
328 if (found ==
329 ((1 << (argc - start_index)) - 1)) {
330 ret = SAVEARGS_TRAD_ARGS;
331 goto done;
332 }
333
334 break;
335 }
336 }
337 }
338
339 /*
340 * Look for a GCC-style returned structure.
341 */
342 found = 0;
343 if (start_index != 0) {
344 for (i = 0; i < size; i += sz) {
345 sz = instr_size(dhp, ins, i, size);
346
347 if (sz < 1)
348 break;
349 else if (sz != 4)
350 continue;
351
352 n = INSTR4(ins, i);
353
354 /* argc is inclusive of start_index, allow for that */
355 for (j = 0; j < (argc - start_index); j++) {
356 if (n == save_instr_sr[j]) {
357 found |= (1 << j);
358
359 if (found ==
360 ((1 << (argc - start_index)) - 1)) {
361 ret = SAVEARGS_TRAD_ARGS;
362 goto done;
363 }
364
365 break;
366 }
367 }
368 }
369 }
370
371 done:
372 dis_handle_destroy(dhp);
373 return (ret);
374 }