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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * recordmcount.c: construct a table of the locations of calls to 'mcount'
4 * so that ftrace can find them quickly.
5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
6 *
7 * Restructured to fit Linux format, as well as other updates:
8 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
9 */
10
11/*
12 * Strategy: alter the .o file in-place.
13 *
14 * Append a new STRTAB that has the new section names, followed by a new array
15 * ElfXX_Shdr[] that has the new section headers, followed by the section
16 * contents for __mcount_loc and its relocations. The old shstrtab strings,
17 * and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple
18 * kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader)
19 * will ignore the garbage regions, because they are not designated by the
20 * new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage,
21 * then use "ld -r" to create a new file that omits the garbage.]
22 */
23
24#include <sys/types.h>
25#include <sys/mman.h>
26#include <sys/stat.h>
27#include <getopt.h>
28#include <elf.h>
29#include <fcntl.h>
30#include <stdio.h>
31#include <stdlib.h>
32#include <string.h>
33#include <unistd.h>
34
35#ifndef EM_AARCH64
36#define EM_AARCH64 183
37#define R_AARCH64_NONE 0
38#define R_AARCH64_ABS64 257
39#endif
40
41#ifndef EM_LOONGARCH
42#define EM_LOONGARCH 258
43#define R_LARCH_32 1
44#define R_LARCH_64 2
45#define R_LARCH_MARK_LA 20
46#define R_LARCH_SOP_PUSH_PLT_PCREL 29
47#endif
48
49#define R_ARM_PC24 1
50#define R_ARM_THM_CALL 10
51#define R_ARM_CALL 28
52
53#define R_AARCH64_CALL26 283
54
55static int fd_map; /* File descriptor for file being modified. */
56static int mmap_failed; /* Boolean flag. */
57static char gpfx; /* prefix for global symbol name (sometimes '_') */
58static struct stat sb; /* Remember .st_size, etc. */
59static const char *altmcount; /* alternate mcount symbol name */
60static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
61static void *file_map; /* pointer of the mapped file */
62static void *file_end; /* pointer to the end of the mapped file */
63static int file_updated; /* flag to state file was changed */
64static void *file_ptr; /* current file pointer location */
65
66static void *file_append; /* added to the end of the file */
67static size_t file_append_size; /* how much is added to end of file */
68
69/* Per-file resource cleanup when multiple files. */
70static void file_append_cleanup(void)
71{
72 free(file_append);
73 file_append = NULL;
74 file_append_size = 0;
75 file_updated = 0;
76}
77
78static void mmap_cleanup(void)
79{
80 if (!mmap_failed)
81 munmap(file_map, sb.st_size);
82 else
83 free(file_map);
84 file_map = NULL;
85}
86
87/* ulseek, uwrite, ...: Check return value for errors. */
88
89static off_t ulseek(off_t const offset, int const whence)
90{
91 switch (whence) {
92 case SEEK_SET:
93 file_ptr = file_map + offset;
94 break;
95 case SEEK_CUR:
96 file_ptr += offset;
97 break;
98 case SEEK_END:
99 file_ptr = file_map + (sb.st_size - offset);
100 break;
101 }
102 if (file_ptr < file_map) {
103 fprintf(stderr, "lseek: seek before file\n");
104 return -1;
105 }
106 return file_ptr - file_map;
107}
108
109static ssize_t uwrite(void const *const buf, size_t const count)
110{
111 size_t cnt = count;
112 off_t idx = 0;
113
114 file_updated = 1;
115
116 if (file_ptr + count >= file_end) {
117 off_t aoffset = (file_ptr + count) - file_end;
118
119 if (aoffset > file_append_size) {
120 file_append = realloc(file_append, aoffset);
121 file_append_size = aoffset;
122 }
123 if (!file_append) {
124 perror("write");
125 file_append_cleanup();
126 mmap_cleanup();
127 return -1;
128 }
129 if (file_ptr < file_end) {
130 cnt = file_end - file_ptr;
131 } else {
132 cnt = 0;
133 idx = aoffset - count;
134 }
135 }
136
137 if (cnt)
138 memcpy(file_ptr, buf, cnt);
139
140 if (cnt < count)
141 memcpy(file_append + idx, buf + cnt, count - cnt);
142
143 file_ptr += count;
144 return count;
145}
146
147static void * umalloc(size_t size)
148{
149 void *const addr = malloc(size);
150 if (addr == 0) {
151 fprintf(stderr, "malloc failed: %zu bytes\n", size);
152 file_append_cleanup();
153 mmap_cleanup();
154 return NULL;
155 }
156 return addr;
157}
158
159/*
160 * Get the whole file as a programming convenience in order to avoid
161 * malloc+lseek+read+free of many pieces. If successful, then mmap
162 * avoids copying unused pieces; else just read the whole file.
163 * Open for both read and write; new info will be appended to the file.
164 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
165 * do not propagate to the file until an explicit overwrite at the last.
166 * This preserves most aspects of consistency (all except .st_size)
167 * for simultaneous readers of the file while we are appending to it.
168 * However, multiple writers still are bad. We choose not to use
169 * locking because it is expensive and the use case of kernel build
170 * makes multiple writers unlikely.
171 */
172static void *mmap_file(char const *fname)
173{
174 /* Avoid problems if early cleanup() */
175 fd_map = -1;
176 mmap_failed = 1;
177 file_map = NULL;
178 file_ptr = NULL;
179 file_updated = 0;
180 sb.st_size = 0;
181
182 fd_map = open(fname, O_RDONLY);
183 if (fd_map < 0) {
184 perror(fname);
185 return NULL;
186 }
187 if (fstat(fd_map, &sb) < 0) {
188 perror(fname);
189 goto out;
190 }
191 if (!S_ISREG(sb.st_mode)) {
192 fprintf(stderr, "not a regular file: %s\n", fname);
193 goto out;
194 }
195 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
196 fd_map, 0);
197 if (file_map == MAP_FAILED) {
198 mmap_failed = 1;
199 file_map = umalloc(sb.st_size);
200 if (!file_map) {
201 perror(fname);
202 goto out;
203 }
204 if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
205 perror(fname);
206 free(file_map);
207 file_map = NULL;
208 goto out;
209 }
210 } else
211 mmap_failed = 0;
212out:
213 close(fd_map);
214 fd_map = -1;
215
216 file_end = file_map + sb.st_size;
217
218 return file_map;
219}
220
221
222static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
223static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
224static unsigned char *ideal_nop;
225
226static char rel_type_nop;
227
228static int (*make_nop)(void *map, size_t const offset);
229
230static int make_nop_x86(void *map, size_t const offset)
231{
232 uint32_t *ptr;
233 unsigned char *op;
234
235 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
236 ptr = map + offset;
237 if (*ptr != 0)
238 return -1;
239
240 op = map + offset - 1;
241 if (*op != 0xe8)
242 return -1;
243
244 /* convert to nop */
245 if (ulseek(offset - 1, SEEK_SET) < 0)
246 return -1;
247 if (uwrite(ideal_nop, 5) < 0)
248 return -1;
249 return 0;
250}
251
252static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
253static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
254static unsigned char *ideal_nop4_arm;
255
256static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
257static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
258static unsigned char *bl_mcount_arm;
259
260static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
261static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
262static unsigned char *push_arm;
263
264static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
265static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
266static unsigned char *ideal_nop2_thumb;
267
268static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
269static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
270static unsigned char *push_bl_mcount_thumb;
271
272static int make_nop_arm(void *map, size_t const offset)
273{
274 char *ptr;
275 int cnt = 1;
276 int nop_size;
277 size_t off = offset;
278
279 ptr = map + offset;
280 if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
281 if (memcmp(ptr - 4, push_arm, 4) == 0) {
282 off -= 4;
283 cnt = 2;
284 }
285 ideal_nop = ideal_nop4_arm;
286 nop_size = 4;
287 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
288 cnt = 3;
289 nop_size = 2;
290 off -= 2;
291 ideal_nop = ideal_nop2_thumb;
292 } else
293 return -1;
294
295 /* Convert to nop */
296 if (ulseek(off, SEEK_SET) < 0)
297 return -1;
298
299 do {
300 if (uwrite(ideal_nop, nop_size) < 0)
301 return -1;
302 } while (--cnt > 0);
303
304 return 0;
305}
306
307static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
308static int make_nop_arm64(void *map, size_t const offset)
309{
310 uint32_t *ptr;
311
312 ptr = map + offset;
313 /* bl <_mcount> is 0x94000000 before relocation */
314 if (*ptr != 0x94000000)
315 return -1;
316
317 /* Convert to nop */
318 if (ulseek(offset, SEEK_SET) < 0)
319 return -1;
320 if (uwrite(ideal_nop, 4) < 0)
321 return -1;
322 return 0;
323}
324
325static int write_file(const char *fname)
326{
327 char tmp_file[strlen(fname) + 4];
328 size_t n;
329
330 if (!file_updated)
331 return 0;
332
333 sprintf(tmp_file, "%s.rc", fname);
334
335 /*
336 * After reading the entire file into memory, delete it
337 * and write it back, to prevent weird side effects of modifying
338 * an object file in place.
339 */
340 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
341 if (fd_map < 0) {
342 perror(fname);
343 return -1;
344 }
345 n = write(fd_map, file_map, sb.st_size);
346 if (n != sb.st_size) {
347 perror("write");
348 close(fd_map);
349 return -1;
350 }
351 if (file_append_size) {
352 n = write(fd_map, file_append, file_append_size);
353 if (n != file_append_size) {
354 perror("write");
355 close(fd_map);
356 return -1;
357 }
358 }
359 close(fd_map);
360 if (rename(tmp_file, fname) < 0) {
361 perror(fname);
362 return -1;
363 }
364 return 0;
365}
366
367/* w8rev, w8nat, ...: Handle endianness. */
368
369static uint64_t w8rev(uint64_t const x)
370{
371 return ((0xff & (x >> (0 * 8))) << (7 * 8))
372 | ((0xff & (x >> (1 * 8))) << (6 * 8))
373 | ((0xff & (x >> (2 * 8))) << (5 * 8))
374 | ((0xff & (x >> (3 * 8))) << (4 * 8))
375 | ((0xff & (x >> (4 * 8))) << (3 * 8))
376 | ((0xff & (x >> (5 * 8))) << (2 * 8))
377 | ((0xff & (x >> (6 * 8))) << (1 * 8))
378 | ((0xff & (x >> (7 * 8))) << (0 * 8));
379}
380
381static uint32_t w4rev(uint32_t const x)
382{
383 return ((0xff & (x >> (0 * 8))) << (3 * 8))
384 | ((0xff & (x >> (1 * 8))) << (2 * 8))
385 | ((0xff & (x >> (2 * 8))) << (1 * 8))
386 | ((0xff & (x >> (3 * 8))) << (0 * 8));
387}
388
389static uint32_t w2rev(uint16_t const x)
390{
391 return ((0xff & (x >> (0 * 8))) << (1 * 8))
392 | ((0xff & (x >> (1 * 8))) << (0 * 8));
393}
394
395static uint64_t w8nat(uint64_t const x)
396{
397 return x;
398}
399
400static uint32_t w4nat(uint32_t const x)
401{
402 return x;
403}
404
405static uint32_t w2nat(uint16_t const x)
406{
407 return x;
408}
409
410static uint64_t (*w8)(uint64_t);
411static uint32_t (*w)(uint32_t);
412static uint32_t (*w2)(uint16_t);
413
414/* Names of the sections that could contain calls to mcount. */
415static int is_mcounted_section_name(char const *const txtname)
416{
417 return strncmp(".text", txtname, 5) == 0 ||
418 strcmp(".init.text", txtname) == 0 ||
419 strcmp(".ref.text", txtname) == 0 ||
420 strcmp(".sched.text", txtname) == 0 ||
421 strcmp(".spinlock.text", txtname) == 0 ||
422 strcmp(".irqentry.text", txtname) == 0 ||
423 strcmp(".softirqentry.text", txtname) == 0 ||
424 strcmp(".kprobes.text", txtname) == 0 ||
425 strcmp(".cpuidle.text", txtname) == 0;
426}
427
428static char const *already_has_rel_mcount = "success"; /* our work here is done! */
429
430/* 32 bit and 64 bit are very similar */
431#include "recordmcount.h"
432#define RECORD_MCOUNT_64
433#include "recordmcount.h"
434
435static int arm_is_fake_mcount(Elf32_Rel const *rp)
436{
437 switch (ELF32_R_TYPE(w(rp->r_info))) {
438 case R_ARM_THM_CALL:
439 case R_ARM_CALL:
440 case R_ARM_PC24:
441 return 0;
442 }
443
444 return 1;
445}
446
447static int arm64_is_fake_mcount(Elf64_Rel const *rp)
448{
449 return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
450}
451
452static int LARCH32_is_fake_mcount(Elf32_Rel const *rp)
453{
454 switch (ELF64_R_TYPE(w(rp->r_info))) {
455 case R_LARCH_MARK_LA:
456 case R_LARCH_SOP_PUSH_PLT_PCREL:
457 return 0;
458 }
459
460 return 1;
461}
462
463static int LARCH64_is_fake_mcount(Elf64_Rel const *rp)
464{
465 switch (ELF64_R_TYPE(w(rp->r_info))) {
466 case R_LARCH_MARK_LA:
467 case R_LARCH_SOP_PUSH_PLT_PCREL:
468 return 0;
469 }
470
471 return 1;
472}
473
474/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
475 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
476 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
477 * to imply the order of the members; the spec does not say so.
478 * typedef unsigned char Elf64_Byte;
479 * fails on MIPS64 because their <elf.h> already has it!
480 */
481
482typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
483
484union mips_r_info {
485 Elf64_Xword r_info;
486 struct {
487 Elf64_Word r_sym; /* Symbol index. */
488 myElf64_Byte r_ssym; /* Special symbol. */
489 myElf64_Byte r_type3; /* Third relocation. */
490 myElf64_Byte r_type2; /* Second relocation. */
491 myElf64_Byte r_type; /* First relocation. */
492 } r_mips;
493};
494
495static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
496{
497 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
498}
499
500static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
501{
502 rp->r_info = ((union mips_r_info){
503 .r_mips = { .r_sym = w(sym), .r_type = type }
504 }).r_info;
505}
506
507static int do_file(char const *const fname)
508{
509 unsigned int reltype = 0;
510 Elf32_Ehdr *ehdr;
511 int rc = -1;
512
513 ehdr = mmap_file(fname);
514 if (!ehdr)
515 goto out;
516
517 w = w4nat;
518 w2 = w2nat;
519 w8 = w8nat;
520 switch (ehdr->e_ident[EI_DATA]) {
521 static unsigned int const endian = 1;
522 default:
523 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
524 ehdr->e_ident[EI_DATA], fname);
525 goto out;
526 case ELFDATA2LSB:
527 if (*(unsigned char const *)&endian != 1) {
528 /* main() is big endian, file.o is little endian. */
529 w = w4rev;
530 w2 = w2rev;
531 w8 = w8rev;
532 }
533 ideal_nop4_arm = ideal_nop4_arm_le;
534 bl_mcount_arm = bl_mcount_arm_le;
535 push_arm = push_arm_le;
536 ideal_nop2_thumb = ideal_nop2_thumb_le;
537 push_bl_mcount_thumb = push_bl_mcount_thumb_le;
538 break;
539 case ELFDATA2MSB:
540 if (*(unsigned char const *)&endian != 0) {
541 /* main() is little endian, file.o is big endian. */
542 w = w4rev;
543 w2 = w2rev;
544 w8 = w8rev;
545 }
546 ideal_nop4_arm = ideal_nop4_arm_be;
547 bl_mcount_arm = bl_mcount_arm_be;
548 push_arm = push_arm_be;
549 ideal_nop2_thumb = ideal_nop2_thumb_be;
550 push_bl_mcount_thumb = push_bl_mcount_thumb_be;
551 break;
552 } /* end switch */
553 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 ||
554 w2(ehdr->e_type) != ET_REL ||
555 ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
556 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
557 goto out;
558 }
559
560 gpfx = '_';
561 switch (w2(ehdr->e_machine)) {
562 default:
563 fprintf(stderr, "unrecognized e_machine %u %s\n",
564 w2(ehdr->e_machine), fname);
565 goto out;
566 case EM_386:
567 reltype = R_386_32;
568 rel_type_nop = R_386_NONE;
569 make_nop = make_nop_x86;
570 ideal_nop = ideal_nop5_x86_32;
571 mcount_adjust_32 = -1;
572 gpfx = 0;
573 break;
574 case EM_ARM:
575 reltype = R_ARM_ABS32;
576 altmcount = "__gnu_mcount_nc";
577 make_nop = make_nop_arm;
578 rel_type_nop = R_ARM_NONE;
579 is_fake_mcount32 = arm_is_fake_mcount;
580 gpfx = 0;
581 break;
582 case EM_AARCH64:
583 reltype = R_AARCH64_ABS64;
584 make_nop = make_nop_arm64;
585 rel_type_nop = R_AARCH64_NONE;
586 ideal_nop = ideal_nop4_arm64;
587 is_fake_mcount64 = arm64_is_fake_mcount;
588 break;
589 case EM_IA_64: reltype = R_IA64_IMM64; break;
590 case EM_MIPS: /* reltype: e_class */ break;
591 case EM_LOONGARCH: /* reltype: e_class */ break;
592 case EM_PPC: reltype = R_PPC_ADDR32; break;
593 case EM_PPC64: reltype = R_PPC64_ADDR64; break;
594 case EM_S390: /* reltype: e_class */ break;
595 case EM_SH: reltype = R_SH_DIR32; gpfx = 0; break;
596 case EM_SPARCV9: reltype = R_SPARC_64; break;
597 case EM_X86_64:
598 make_nop = make_nop_x86;
599 ideal_nop = ideal_nop5_x86_64;
600 reltype = R_X86_64_64;
601 rel_type_nop = R_X86_64_NONE;
602 mcount_adjust_64 = -1;
603 gpfx = 0;
604 break;
605 } /* end switch */
606
607 switch (ehdr->e_ident[EI_CLASS]) {
608 default:
609 fprintf(stderr, "unrecognized ELF class %d %s\n",
610 ehdr->e_ident[EI_CLASS], fname);
611 goto out;
612 case ELFCLASS32:
613 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
614 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
615 fprintf(stderr,
616 "unrecognized ET_REL file: %s\n", fname);
617 goto out;
618 }
619 if (w2(ehdr->e_machine) == EM_MIPS) {
620 reltype = R_MIPS_32;
621 is_fake_mcount32 = MIPS32_is_fake_mcount;
622 }
623 if (w2(ehdr->e_machine) == EM_LOONGARCH) {
624 reltype = R_LARCH_32;
625 is_fake_mcount32 = LARCH32_is_fake_mcount;
626 }
627 if (do32(ehdr, fname, reltype) < 0)
628 goto out;
629 break;
630 case ELFCLASS64: {
631 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
632 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
633 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
634 fprintf(stderr,
635 "unrecognized ET_REL file: %s\n", fname);
636 goto out;
637 }
638 if (w2(ghdr->e_machine) == EM_S390) {
639 reltype = R_390_64;
640 mcount_adjust_64 = -14;
641 }
642 if (w2(ghdr->e_machine) == EM_MIPS) {
643 reltype = R_MIPS_64;
644 Elf64_r_sym = MIPS64_r_sym;
645 Elf64_r_info = MIPS64_r_info;
646 is_fake_mcount64 = MIPS64_is_fake_mcount;
647 }
648 if (w2(ghdr->e_machine) == EM_LOONGARCH) {
649 reltype = R_LARCH_64;
650 is_fake_mcount64 = LARCH64_is_fake_mcount;
651 }
652 if (do64(ghdr, fname, reltype) < 0)
653 goto out;
654 break;
655 }
656 } /* end switch */
657
658 rc = write_file(fname);
659out:
660 file_append_cleanup();
661 mmap_cleanup();
662 return rc;
663}
664
665int main(int argc, char *argv[])
666{
667 const char ftrace[] = "/ftrace.o";
668 int ftrace_size = sizeof(ftrace) - 1;
669 int n_error = 0; /* gcc-4.3.0 false positive complaint */
670 int c;
671 int i;
672
673 while ((c = getopt(argc, argv, "w")) >= 0) {
674 switch (c) {
675 case 'w':
676 warn_on_notrace_sect = 1;
677 break;
678 default:
679 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
680 return 0;
681 }
682 }
683
684 if ((argc - optind) < 1) {
685 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
686 return 0;
687 }
688
689 /* Process each file in turn, allowing deep failure. */
690 for (i = optind; i < argc; i++) {
691 char *file = argv[i];
692 int len;
693
694 /*
695 * The file kernel/trace/ftrace.o references the mcount
696 * function but does not call it. Since ftrace.o should
697 * not be traced anyway, we just skip it.
698 */
699 len = strlen(file);
700 if (len >= ftrace_size &&
701 strcmp(file + (len - ftrace_size), ftrace) == 0)
702 continue;
703
704 if (do_file(file)) {
705 fprintf(stderr, "%s: failed\n", file);
706 ++n_error;
707 }
708 }
709 return !!n_error;
710}
1/*
2 * recordmcount.c: construct a table of the locations of calls to 'mcount'
3 * so that ftrace can find them quickly.
4 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
5 * Licensed under the GNU General Public License, version 2 (GPLv2).
6 *
7 * Restructured to fit Linux format, as well as other updates:
8 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
9 */
10
11/*
12 * Strategy: alter the .o file in-place.
13 *
14 * Append a new STRTAB that has the new section names, followed by a new array
15 * ElfXX_Shdr[] that has the new section headers, followed by the section
16 * contents for __mcount_loc and its relocations. The old shstrtab strings,
17 * and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple
18 * kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader)
19 * will ignore the garbage regions, because they are not designated by the
20 * new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage,
21 * then use "ld -r" to create a new file that omits the garbage.]
22 */
23
24#include <sys/types.h>
25#include <sys/mman.h>
26#include <sys/stat.h>
27#include <getopt.h>
28#include <elf.h>
29#include <fcntl.h>
30#include <setjmp.h>
31#include <stdio.h>
32#include <stdlib.h>
33#include <string.h>
34#include <unistd.h>
35
36#ifndef EM_METAG
37/* Remove this when these make it to the standard system elf.h. */
38#define EM_METAG 174
39#define R_METAG_ADDR32 2
40#define R_METAG_NONE 3
41#endif
42
43#ifndef EM_AARCH64
44#define EM_AARCH64 183
45#define R_AARCH64_NONE 0
46#define R_AARCH64_ABS64 257
47#endif
48
49static int fd_map; /* File descriptor for file being modified. */
50static int mmap_failed; /* Boolean flag. */
51static char gpfx; /* prefix for global symbol name (sometimes '_') */
52static struct stat sb; /* Remember .st_size, etc. */
53static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
54static const char *altmcount; /* alternate mcount symbol name */
55static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
56static void *file_map; /* pointer of the mapped file */
57static void *file_end; /* pointer to the end of the mapped file */
58static int file_updated; /* flag to state file was changed */
59static void *file_ptr; /* current file pointer location */
60static void *file_append; /* added to the end of the file */
61static size_t file_append_size; /* how much is added to end of file */
62
63/* setjmp() return values */
64enum {
65 SJ_SETJMP = 0, /* hardwired first return */
66 SJ_FAIL,
67 SJ_SUCCEED
68};
69
70/* Per-file resource cleanup when multiple files. */
71static void
72cleanup(void)
73{
74 if (!mmap_failed)
75 munmap(file_map, sb.st_size);
76 else
77 free(file_map);
78 file_map = NULL;
79 free(file_append);
80 file_append = NULL;
81 file_append_size = 0;
82 file_updated = 0;
83}
84
85static void __attribute__((noreturn))
86fail_file(void)
87{
88 cleanup();
89 longjmp(jmpenv, SJ_FAIL);
90}
91
92static void __attribute__((noreturn))
93succeed_file(void)
94{
95 cleanup();
96 longjmp(jmpenv, SJ_SUCCEED);
97}
98
99/* ulseek, uread, ...: Check return value for errors. */
100
101static off_t
102ulseek(int const fd, off_t const offset, int const whence)
103{
104 switch (whence) {
105 case SEEK_SET:
106 file_ptr = file_map + offset;
107 break;
108 case SEEK_CUR:
109 file_ptr += offset;
110 break;
111 case SEEK_END:
112 file_ptr = file_map + (sb.st_size - offset);
113 break;
114 }
115 if (file_ptr < file_map) {
116 fprintf(stderr, "lseek: seek before file\n");
117 fail_file();
118 }
119 return file_ptr - file_map;
120}
121
122static size_t
123uread(int const fd, void *const buf, size_t const count)
124{
125 size_t const n = read(fd, buf, count);
126 if (n != count) {
127 perror("read");
128 fail_file();
129 }
130 return n;
131}
132
133static size_t
134uwrite(int const fd, void const *const buf, size_t const count)
135{
136 size_t cnt = count;
137 off_t idx = 0;
138
139 file_updated = 1;
140
141 if (file_ptr + count >= file_end) {
142 off_t aoffset = (file_ptr + count) - file_end;
143
144 if (aoffset > file_append_size) {
145 file_append = realloc(file_append, aoffset);
146 file_append_size = aoffset;
147 }
148 if (!file_append) {
149 perror("write");
150 fail_file();
151 }
152 if (file_ptr < file_end) {
153 cnt = file_end - file_ptr;
154 } else {
155 cnt = 0;
156 idx = aoffset - count;
157 }
158 }
159
160 if (cnt)
161 memcpy(file_ptr, buf, cnt);
162
163 if (cnt < count)
164 memcpy(file_append + idx, buf + cnt, count - cnt);
165
166 file_ptr += count;
167 return count;
168}
169
170static void *
171umalloc(size_t size)
172{
173 void *const addr = malloc(size);
174 if (addr == 0) {
175 fprintf(stderr, "malloc failed: %zu bytes\n", size);
176 fail_file();
177 }
178 return addr;
179}
180
181static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
182static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
183static unsigned char *ideal_nop;
184
185static char rel_type_nop;
186
187static int (*make_nop)(void *map, size_t const offset);
188
189static int make_nop_x86(void *map, size_t const offset)
190{
191 uint32_t *ptr;
192 unsigned char *op;
193
194 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
195 ptr = map + offset;
196 if (*ptr != 0)
197 return -1;
198
199 op = map + offset - 1;
200 if (*op != 0xe8)
201 return -1;
202
203 /* convert to nop */
204 ulseek(fd_map, offset - 1, SEEK_SET);
205 uwrite(fd_map, ideal_nop, 5);
206 return 0;
207}
208
209static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
210static int make_nop_arm64(void *map, size_t const offset)
211{
212 uint32_t *ptr;
213
214 ptr = map + offset;
215 /* bl <_mcount> is 0x94000000 before relocation */
216 if (*ptr != 0x94000000)
217 return -1;
218
219 /* Convert to nop */
220 ulseek(fd_map, offset, SEEK_SET);
221 uwrite(fd_map, ideal_nop, 4);
222 return 0;
223}
224
225/*
226 * Get the whole file as a programming convenience in order to avoid
227 * malloc+lseek+read+free of many pieces. If successful, then mmap
228 * avoids copying unused pieces; else just read the whole file.
229 * Open for both read and write; new info will be appended to the file.
230 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
231 * do not propagate to the file until an explicit overwrite at the last.
232 * This preserves most aspects of consistency (all except .st_size)
233 * for simultaneous readers of the file while we are appending to it.
234 * However, multiple writers still are bad. We choose not to use
235 * locking because it is expensive and the use case of kernel build
236 * makes multiple writers unlikely.
237 */
238static void *mmap_file(char const *fname)
239{
240 fd_map = open(fname, O_RDONLY);
241 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
242 perror(fname);
243 fail_file();
244 }
245 if (!S_ISREG(sb.st_mode)) {
246 fprintf(stderr, "not a regular file: %s\n", fname);
247 fail_file();
248 }
249 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
250 fd_map, 0);
251 mmap_failed = 0;
252 if (file_map == MAP_FAILED) {
253 mmap_failed = 1;
254 file_map = umalloc(sb.st_size);
255 uread(fd_map, file_map, sb.st_size);
256 }
257 close(fd_map);
258
259 file_end = file_map + sb.st_size;
260
261 return file_map;
262}
263
264static void write_file(const char *fname)
265{
266 char tmp_file[strlen(fname) + 4];
267 size_t n;
268
269 if (!file_updated)
270 return;
271
272 sprintf(tmp_file, "%s.rc", fname);
273
274 /*
275 * After reading the entire file into memory, delete it
276 * and write it back, to prevent weird side effects of modifying
277 * an object file in place.
278 */
279 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
280 if (fd_map < 0) {
281 perror(fname);
282 fail_file();
283 }
284 n = write(fd_map, file_map, sb.st_size);
285 if (n != sb.st_size) {
286 perror("write");
287 fail_file();
288 }
289 if (file_append_size) {
290 n = write(fd_map, file_append, file_append_size);
291 if (n != file_append_size) {
292 perror("write");
293 fail_file();
294 }
295 }
296 close(fd_map);
297 if (rename(tmp_file, fname) < 0) {
298 perror(fname);
299 fail_file();
300 }
301}
302
303/* w8rev, w8nat, ...: Handle endianness. */
304
305static uint64_t w8rev(uint64_t const x)
306{
307 return ((0xff & (x >> (0 * 8))) << (7 * 8))
308 | ((0xff & (x >> (1 * 8))) << (6 * 8))
309 | ((0xff & (x >> (2 * 8))) << (5 * 8))
310 | ((0xff & (x >> (3 * 8))) << (4 * 8))
311 | ((0xff & (x >> (4 * 8))) << (3 * 8))
312 | ((0xff & (x >> (5 * 8))) << (2 * 8))
313 | ((0xff & (x >> (6 * 8))) << (1 * 8))
314 | ((0xff & (x >> (7 * 8))) << (0 * 8));
315}
316
317static uint32_t w4rev(uint32_t const x)
318{
319 return ((0xff & (x >> (0 * 8))) << (3 * 8))
320 | ((0xff & (x >> (1 * 8))) << (2 * 8))
321 | ((0xff & (x >> (2 * 8))) << (1 * 8))
322 | ((0xff & (x >> (3 * 8))) << (0 * 8));
323}
324
325static uint32_t w2rev(uint16_t const x)
326{
327 return ((0xff & (x >> (0 * 8))) << (1 * 8))
328 | ((0xff & (x >> (1 * 8))) << (0 * 8));
329}
330
331static uint64_t w8nat(uint64_t const x)
332{
333 return x;
334}
335
336static uint32_t w4nat(uint32_t const x)
337{
338 return x;
339}
340
341static uint32_t w2nat(uint16_t const x)
342{
343 return x;
344}
345
346static uint64_t (*w8)(uint64_t);
347static uint32_t (*w)(uint32_t);
348static uint32_t (*w2)(uint16_t);
349
350/* Names of the sections that could contain calls to mcount. */
351static int
352is_mcounted_section_name(char const *const txtname)
353{
354 return strcmp(".text", txtname) == 0 ||
355 strcmp(".ref.text", txtname) == 0 ||
356 strcmp(".sched.text", txtname) == 0 ||
357 strcmp(".spinlock.text", txtname) == 0 ||
358 strcmp(".irqentry.text", txtname) == 0 ||
359 strcmp(".kprobes.text", txtname) == 0 ||
360 strcmp(".text.unlikely", txtname) == 0;
361}
362
363/* 32 bit and 64 bit are very similar */
364#include "recordmcount.h"
365#define RECORD_MCOUNT_64
366#include "recordmcount.h"
367
368/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
369 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
370 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
371 * to imply the order of the members; the spec does not say so.
372 * typedef unsigned char Elf64_Byte;
373 * fails on MIPS64 because their <elf.h> already has it!
374 */
375
376typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
377
378union mips_r_info {
379 Elf64_Xword r_info;
380 struct {
381 Elf64_Word r_sym; /* Symbol index. */
382 myElf64_Byte r_ssym; /* Special symbol. */
383 myElf64_Byte r_type3; /* Third relocation. */
384 myElf64_Byte r_type2; /* Second relocation. */
385 myElf64_Byte r_type; /* First relocation. */
386 } r_mips;
387};
388
389static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
390{
391 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
392}
393
394static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
395{
396 rp->r_info = ((union mips_r_info){
397 .r_mips = { .r_sym = w(sym), .r_type = type }
398 }).r_info;
399}
400
401static void
402do_file(char const *const fname)
403{
404 Elf32_Ehdr *const ehdr = mmap_file(fname);
405 unsigned int reltype = 0;
406
407 w = w4nat;
408 w2 = w2nat;
409 w8 = w8nat;
410 switch (ehdr->e_ident[EI_DATA]) {
411 static unsigned int const endian = 1;
412 default:
413 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
414 ehdr->e_ident[EI_DATA], fname);
415 fail_file();
416 break;
417 case ELFDATA2LSB:
418 if (*(unsigned char const *)&endian != 1) {
419 /* main() is big endian, file.o is little endian. */
420 w = w4rev;
421 w2 = w2rev;
422 w8 = w8rev;
423 }
424 break;
425 case ELFDATA2MSB:
426 if (*(unsigned char const *)&endian != 0) {
427 /* main() is little endian, file.o is big endian. */
428 w = w4rev;
429 w2 = w2rev;
430 w8 = w8rev;
431 }
432 break;
433 } /* end switch */
434 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
435 || w2(ehdr->e_type) != ET_REL
436 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
437 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
438 fail_file();
439 }
440
441 gpfx = 0;
442 switch (w2(ehdr->e_machine)) {
443 default:
444 fprintf(stderr, "unrecognized e_machine %d %s\n",
445 w2(ehdr->e_machine), fname);
446 fail_file();
447 break;
448 case EM_386:
449 reltype = R_386_32;
450 rel_type_nop = R_386_NONE;
451 make_nop = make_nop_x86;
452 ideal_nop = ideal_nop5_x86_32;
453 mcount_adjust_32 = -1;
454 break;
455 case EM_ARM: reltype = R_ARM_ABS32;
456 altmcount = "__gnu_mcount_nc";
457 break;
458 case EM_AARCH64:
459 reltype = R_AARCH64_ABS64;
460 make_nop = make_nop_arm64;
461 rel_type_nop = R_AARCH64_NONE;
462 ideal_nop = ideal_nop4_arm64;
463 gpfx = '_';
464 break;
465 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
466 case EM_METAG: reltype = R_METAG_ADDR32;
467 altmcount = "_mcount_wrapper";
468 rel_type_nop = R_METAG_NONE;
469 /* We happen to have the same requirement as MIPS */
470 is_fake_mcount32 = MIPS32_is_fake_mcount;
471 break;
472 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
473 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
474 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
475 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
476 case EM_SH: reltype = R_SH_DIR32; break;
477 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
478 case EM_X86_64:
479 make_nop = make_nop_x86;
480 ideal_nop = ideal_nop5_x86_64;
481 reltype = R_X86_64_64;
482 rel_type_nop = R_X86_64_NONE;
483 mcount_adjust_64 = -1;
484 break;
485 } /* end switch */
486
487 switch (ehdr->e_ident[EI_CLASS]) {
488 default:
489 fprintf(stderr, "unrecognized ELF class %d %s\n",
490 ehdr->e_ident[EI_CLASS], fname);
491 fail_file();
492 break;
493 case ELFCLASS32:
494 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
495 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
496 fprintf(stderr,
497 "unrecognized ET_REL file: %s\n", fname);
498 fail_file();
499 }
500 if (w2(ehdr->e_machine) == EM_MIPS) {
501 reltype = R_MIPS_32;
502 is_fake_mcount32 = MIPS32_is_fake_mcount;
503 }
504 do32(ehdr, fname, reltype);
505 break;
506 case ELFCLASS64: {
507 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
508 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
509 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
510 fprintf(stderr,
511 "unrecognized ET_REL file: %s\n", fname);
512 fail_file();
513 }
514 if (w2(ghdr->e_machine) == EM_S390) {
515 reltype = R_390_64;
516 mcount_adjust_64 = -14;
517 }
518 if (w2(ghdr->e_machine) == EM_MIPS) {
519 reltype = R_MIPS_64;
520 Elf64_r_sym = MIPS64_r_sym;
521 Elf64_r_info = MIPS64_r_info;
522 is_fake_mcount64 = MIPS64_is_fake_mcount;
523 }
524 do64(ghdr, fname, reltype);
525 break;
526 }
527 } /* end switch */
528
529 write_file(fname);
530 cleanup();
531}
532
533int
534main(int argc, char *argv[])
535{
536 const char ftrace[] = "/ftrace.o";
537 int ftrace_size = sizeof(ftrace) - 1;
538 int n_error = 0; /* gcc-4.3.0 false positive complaint */
539 int c;
540 int i;
541
542 while ((c = getopt(argc, argv, "w")) >= 0) {
543 switch (c) {
544 case 'w':
545 warn_on_notrace_sect = 1;
546 break;
547 default:
548 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
549 return 0;
550 }
551 }
552
553 if ((argc - optind) < 1) {
554 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
555 return 0;
556 }
557
558 /* Process each file in turn, allowing deep failure. */
559 for (i = optind; i < argc; i++) {
560 char *file = argv[i];
561 int const sjval = setjmp(jmpenv);
562 int len;
563
564 /*
565 * The file kernel/trace/ftrace.o references the mcount
566 * function but does not call it. Since ftrace.o should
567 * not be traced anyway, we just skip it.
568 */
569 len = strlen(file);
570 if (len >= ftrace_size &&
571 strcmp(file + (len - ftrace_size), ftrace) == 0)
572 continue;
573
574 switch (sjval) {
575 default:
576 fprintf(stderr, "internal error: %s\n", file);
577 exit(1);
578 break;
579 case SJ_SETJMP: /* normal sequence */
580 /* Avoid problems if early cleanup() */
581 fd_map = -1;
582 mmap_failed = 1;
583 file_map = NULL;
584 file_ptr = NULL;
585 file_updated = 0;
586 do_file(file);
587 break;
588 case SJ_FAIL: /* error in do_file or below */
589 fprintf(stderr, "%s: failed\n", file);
590 ++n_error;
591 break;
592 case SJ_SUCCEED: /* premature success */
593 /* do nothing */
594 break;
595 } /* end switch */
596 }
597 return !!n_error;
598}