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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#define R_ARM_PC24 1
42#define R_ARM_THM_CALL 10
43#define R_ARM_CALL 28
44
45#define R_AARCH64_CALL26 283
46
47static int fd_map; /* File descriptor for file being modified. */
48static int mmap_failed; /* Boolean flag. */
49static char gpfx; /* prefix for global symbol name (sometimes '_') */
50static struct stat sb; /* Remember .st_size, etc. */
51static const char *altmcount; /* alternate mcount symbol name */
52static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
53static void *file_map; /* pointer of the mapped file */
54static void *file_end; /* pointer to the end of the mapped file */
55static int file_updated; /* flag to state file was changed */
56static void *file_ptr; /* current file pointer location */
57
58static void *file_append; /* added to the end of the file */
59static size_t file_append_size; /* how much is added to end of file */
60
61/* Per-file resource cleanup when multiple files. */
62static void file_append_cleanup(void)
63{
64 free(file_append);
65 file_append = NULL;
66 file_append_size = 0;
67 file_updated = 0;
68}
69
70static void mmap_cleanup(void)
71{
72 if (!mmap_failed)
73 munmap(file_map, sb.st_size);
74 else
75 free(file_map);
76 file_map = NULL;
77}
78
79/* ulseek, uwrite, ...: Check return value for errors. */
80
81static off_t ulseek(off_t const offset, int const whence)
82{
83 switch (whence) {
84 case SEEK_SET:
85 file_ptr = file_map + offset;
86 break;
87 case SEEK_CUR:
88 file_ptr += offset;
89 break;
90 case SEEK_END:
91 file_ptr = file_map + (sb.st_size - offset);
92 break;
93 }
94 if (file_ptr < file_map) {
95 fprintf(stderr, "lseek: seek before file\n");
96 return -1;
97 }
98 return file_ptr - file_map;
99}
100
101static ssize_t uwrite(void const *const buf, size_t const count)
102{
103 size_t cnt = count;
104 off_t idx = 0;
105
106 file_updated = 1;
107
108 if (file_ptr + count >= file_end) {
109 off_t aoffset = (file_ptr + count) - file_end;
110
111 if (aoffset > file_append_size) {
112 file_append = realloc(file_append, aoffset);
113 file_append_size = aoffset;
114 }
115 if (!file_append) {
116 perror("write");
117 file_append_cleanup();
118 mmap_cleanup();
119 return -1;
120 }
121 if (file_ptr < file_end) {
122 cnt = file_end - file_ptr;
123 } else {
124 cnt = 0;
125 idx = aoffset - count;
126 }
127 }
128
129 if (cnt)
130 memcpy(file_ptr, buf, cnt);
131
132 if (cnt < count)
133 memcpy(file_append + idx, buf + cnt, count - cnt);
134
135 file_ptr += count;
136 return count;
137}
138
139static void * umalloc(size_t size)
140{
141 void *const addr = malloc(size);
142 if (addr == 0) {
143 fprintf(stderr, "malloc failed: %zu bytes\n", size);
144 file_append_cleanup();
145 mmap_cleanup();
146 return NULL;
147 }
148 return addr;
149}
150
151/*
152 * Get the whole file as a programming convenience in order to avoid
153 * malloc+lseek+read+free of many pieces. If successful, then mmap
154 * avoids copying unused pieces; else just read the whole file.
155 * Open for both read and write; new info will be appended to the file.
156 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
157 * do not propagate to the file until an explicit overwrite at the last.
158 * This preserves most aspects of consistency (all except .st_size)
159 * for simultaneous readers of the file while we are appending to it.
160 * However, multiple writers still are bad. We choose not to use
161 * locking because it is expensive and the use case of kernel build
162 * makes multiple writers unlikely.
163 */
164static void *mmap_file(char const *fname)
165{
166 /* Avoid problems if early cleanup() */
167 fd_map = -1;
168 mmap_failed = 1;
169 file_map = NULL;
170 file_ptr = NULL;
171 file_updated = 0;
172 sb.st_size = 0;
173
174 fd_map = open(fname, O_RDONLY);
175 if (fd_map < 0) {
176 perror(fname);
177 return NULL;
178 }
179 if (fstat(fd_map, &sb) < 0) {
180 perror(fname);
181 goto out;
182 }
183 if (!S_ISREG(sb.st_mode)) {
184 fprintf(stderr, "not a regular file: %s\n", fname);
185 goto out;
186 }
187 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
188 fd_map, 0);
189 if (file_map == MAP_FAILED) {
190 mmap_failed = 1;
191 file_map = umalloc(sb.st_size);
192 if (!file_map) {
193 perror(fname);
194 goto out;
195 }
196 if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
197 perror(fname);
198 free(file_map);
199 file_map = NULL;
200 goto out;
201 }
202 } else
203 mmap_failed = 0;
204out:
205 close(fd_map);
206 fd_map = -1;
207
208 file_end = file_map + sb.st_size;
209
210 return file_map;
211}
212
213
214static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
215static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
216static unsigned char *ideal_nop;
217
218static char rel_type_nop;
219
220static int (*make_nop)(void *map, size_t const offset);
221
222static int make_nop_x86(void *map, size_t const offset)
223{
224 uint32_t *ptr;
225 unsigned char *op;
226
227 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
228 ptr = map + offset;
229 if (*ptr != 0)
230 return -1;
231
232 op = map + offset - 1;
233 if (*op != 0xe8)
234 return -1;
235
236 /* convert to nop */
237 if (ulseek(offset - 1, SEEK_SET) < 0)
238 return -1;
239 if (uwrite(ideal_nop, 5) < 0)
240 return -1;
241 return 0;
242}
243
244static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
245static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
246static unsigned char *ideal_nop4_arm;
247
248static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
249static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
250static unsigned char *bl_mcount_arm;
251
252static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
253static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
254static unsigned char *push_arm;
255
256static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
257static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
258static unsigned char *ideal_nop2_thumb;
259
260static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
261static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
262static unsigned char *push_bl_mcount_thumb;
263
264static int make_nop_arm(void *map, size_t const offset)
265{
266 char *ptr;
267 int cnt = 1;
268 int nop_size;
269 size_t off = offset;
270
271 ptr = map + offset;
272 if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
273 if (memcmp(ptr - 4, push_arm, 4) == 0) {
274 off -= 4;
275 cnt = 2;
276 }
277 ideal_nop = ideal_nop4_arm;
278 nop_size = 4;
279 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
280 cnt = 3;
281 nop_size = 2;
282 off -= 2;
283 ideal_nop = ideal_nop2_thumb;
284 } else
285 return -1;
286
287 /* Convert to nop */
288 if (ulseek(off, SEEK_SET) < 0)
289 return -1;
290
291 do {
292 if (uwrite(ideal_nop, nop_size) < 0)
293 return -1;
294 } while (--cnt > 0);
295
296 return 0;
297}
298
299static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
300static int make_nop_arm64(void *map, size_t const offset)
301{
302 uint32_t *ptr;
303
304 ptr = map + offset;
305 /* bl <_mcount> is 0x94000000 before relocation */
306 if (*ptr != 0x94000000)
307 return -1;
308
309 /* Convert to nop */
310 if (ulseek(offset, SEEK_SET) < 0)
311 return -1;
312 if (uwrite(ideal_nop, 4) < 0)
313 return -1;
314 return 0;
315}
316
317static int write_file(const char *fname)
318{
319 char tmp_file[strlen(fname) + 4];
320 size_t n;
321
322 if (!file_updated)
323 return 0;
324
325 sprintf(tmp_file, "%s.rc", fname);
326
327 /*
328 * After reading the entire file into memory, delete it
329 * and write it back, to prevent weird side effects of modifying
330 * an object file in place.
331 */
332 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
333 if (fd_map < 0) {
334 perror(fname);
335 return -1;
336 }
337 n = write(fd_map, file_map, sb.st_size);
338 if (n != sb.st_size) {
339 perror("write");
340 close(fd_map);
341 return -1;
342 }
343 if (file_append_size) {
344 n = write(fd_map, file_append, file_append_size);
345 if (n != file_append_size) {
346 perror("write");
347 close(fd_map);
348 return -1;
349 }
350 }
351 close(fd_map);
352 if (rename(tmp_file, fname) < 0) {
353 perror(fname);
354 return -1;
355 }
356 return 0;
357}
358
359/* w8rev, w8nat, ...: Handle endianness. */
360
361static uint64_t w8rev(uint64_t const x)
362{
363 return ((0xff & (x >> (0 * 8))) << (7 * 8))
364 | ((0xff & (x >> (1 * 8))) << (6 * 8))
365 | ((0xff & (x >> (2 * 8))) << (5 * 8))
366 | ((0xff & (x >> (3 * 8))) << (4 * 8))
367 | ((0xff & (x >> (4 * 8))) << (3 * 8))
368 | ((0xff & (x >> (5 * 8))) << (2 * 8))
369 | ((0xff & (x >> (6 * 8))) << (1 * 8))
370 | ((0xff & (x >> (7 * 8))) << (0 * 8));
371}
372
373static uint32_t w4rev(uint32_t const x)
374{
375 return ((0xff & (x >> (0 * 8))) << (3 * 8))
376 | ((0xff & (x >> (1 * 8))) << (2 * 8))
377 | ((0xff & (x >> (2 * 8))) << (1 * 8))
378 | ((0xff & (x >> (3 * 8))) << (0 * 8));
379}
380
381static uint32_t w2rev(uint16_t const x)
382{
383 return ((0xff & (x >> (0 * 8))) << (1 * 8))
384 | ((0xff & (x >> (1 * 8))) << (0 * 8));
385}
386
387static uint64_t w8nat(uint64_t const x)
388{
389 return x;
390}
391
392static uint32_t w4nat(uint32_t const x)
393{
394 return x;
395}
396
397static uint32_t w2nat(uint16_t const x)
398{
399 return x;
400}
401
402static uint64_t (*w8)(uint64_t);
403static uint32_t (*w)(uint32_t);
404static uint32_t (*w2)(uint16_t);
405
406/* Names of the sections that could contain calls to mcount. */
407static int is_mcounted_section_name(char const *const txtname)
408{
409 return strncmp(".text", txtname, 5) == 0 ||
410 strcmp(".init.text", txtname) == 0 ||
411 strcmp(".ref.text", txtname) == 0 ||
412 strcmp(".sched.text", txtname) == 0 ||
413 strcmp(".spinlock.text", txtname) == 0 ||
414 strcmp(".irqentry.text", txtname) == 0 ||
415 strcmp(".softirqentry.text", txtname) == 0 ||
416 strcmp(".kprobes.text", txtname) == 0 ||
417 strcmp(".cpuidle.text", txtname) == 0;
418}
419
420static char const *already_has_rel_mcount = "success"; /* our work here is done! */
421
422/* 32 bit and 64 bit are very similar */
423#include "recordmcount.h"
424#define RECORD_MCOUNT_64
425#include "recordmcount.h"
426
427static int arm_is_fake_mcount(Elf32_Rel const *rp)
428{
429 switch (ELF32_R_TYPE(w(rp->r_info))) {
430 case R_ARM_THM_CALL:
431 case R_ARM_CALL:
432 case R_ARM_PC24:
433 return 0;
434 }
435
436 return 1;
437}
438
439static int arm64_is_fake_mcount(Elf64_Rel const *rp)
440{
441 return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
442}
443
444/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
445 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
446 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
447 * to imply the order of the members; the spec does not say so.
448 * typedef unsigned char Elf64_Byte;
449 * fails on MIPS64 because their <elf.h> already has it!
450 */
451
452typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
453
454union mips_r_info {
455 Elf64_Xword r_info;
456 struct {
457 Elf64_Word r_sym; /* Symbol index. */
458 myElf64_Byte r_ssym; /* Special symbol. */
459 myElf64_Byte r_type3; /* Third relocation. */
460 myElf64_Byte r_type2; /* Second relocation. */
461 myElf64_Byte r_type; /* First relocation. */
462 } r_mips;
463};
464
465static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
466{
467 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
468}
469
470static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
471{
472 rp->r_info = ((union mips_r_info){
473 .r_mips = { .r_sym = w(sym), .r_type = type }
474 }).r_info;
475}
476
477static int do_file(char const *const fname)
478{
479 unsigned int reltype = 0;
480 Elf32_Ehdr *ehdr;
481 int rc = -1;
482
483 ehdr = mmap_file(fname);
484 if (!ehdr)
485 goto out;
486
487 w = w4nat;
488 w2 = w2nat;
489 w8 = w8nat;
490 switch (ehdr->e_ident[EI_DATA]) {
491 static unsigned int const endian = 1;
492 default:
493 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
494 ehdr->e_ident[EI_DATA], fname);
495 goto out;
496 case ELFDATA2LSB:
497 if (*(unsigned char const *)&endian != 1) {
498 /* main() is big endian, file.o is little endian. */
499 w = w4rev;
500 w2 = w2rev;
501 w8 = w8rev;
502 }
503 ideal_nop4_arm = ideal_nop4_arm_le;
504 bl_mcount_arm = bl_mcount_arm_le;
505 push_arm = push_arm_le;
506 ideal_nop2_thumb = ideal_nop2_thumb_le;
507 push_bl_mcount_thumb = push_bl_mcount_thumb_le;
508 break;
509 case ELFDATA2MSB:
510 if (*(unsigned char const *)&endian != 0) {
511 /* main() is little endian, file.o is big endian. */
512 w = w4rev;
513 w2 = w2rev;
514 w8 = w8rev;
515 }
516 ideal_nop4_arm = ideal_nop4_arm_be;
517 bl_mcount_arm = bl_mcount_arm_be;
518 push_arm = push_arm_be;
519 ideal_nop2_thumb = ideal_nop2_thumb_be;
520 push_bl_mcount_thumb = push_bl_mcount_thumb_be;
521 break;
522 } /* end switch */
523 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 ||
524 w2(ehdr->e_type) != ET_REL ||
525 ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
526 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
527 goto out;
528 }
529
530 gpfx = '_';
531 switch (w2(ehdr->e_machine)) {
532 default:
533 fprintf(stderr, "unrecognized e_machine %u %s\n",
534 w2(ehdr->e_machine), fname);
535 goto out;
536 case EM_386:
537 reltype = R_386_32;
538 rel_type_nop = R_386_NONE;
539 make_nop = make_nop_x86;
540 ideal_nop = ideal_nop5_x86_32;
541 mcount_adjust_32 = -1;
542 gpfx = 0;
543 break;
544 case EM_ARM:
545 reltype = R_ARM_ABS32;
546 altmcount = "__gnu_mcount_nc";
547 make_nop = make_nop_arm;
548 rel_type_nop = R_ARM_NONE;
549 is_fake_mcount32 = arm_is_fake_mcount;
550 gpfx = 0;
551 break;
552 case EM_AARCH64:
553 reltype = R_AARCH64_ABS64;
554 make_nop = make_nop_arm64;
555 rel_type_nop = R_AARCH64_NONE;
556 ideal_nop = ideal_nop4_arm64;
557 is_fake_mcount64 = arm64_is_fake_mcount;
558 break;
559 case EM_IA_64: reltype = R_IA64_IMM64; break;
560 case EM_MIPS: /* reltype: e_class */ break;
561 case EM_PPC: reltype = R_PPC_ADDR32; break;
562 case EM_PPC64: reltype = R_PPC64_ADDR64; break;
563 case EM_S390: /* reltype: e_class */ break;
564 case EM_SH: reltype = R_SH_DIR32; gpfx = 0; break;
565 case EM_SPARCV9: reltype = R_SPARC_64; break;
566 case EM_X86_64:
567 make_nop = make_nop_x86;
568 ideal_nop = ideal_nop5_x86_64;
569 reltype = R_X86_64_64;
570 rel_type_nop = R_X86_64_NONE;
571 mcount_adjust_64 = -1;
572 gpfx = 0;
573 break;
574 } /* end switch */
575
576 switch (ehdr->e_ident[EI_CLASS]) {
577 default:
578 fprintf(stderr, "unrecognized ELF class %d %s\n",
579 ehdr->e_ident[EI_CLASS], fname);
580 goto out;
581 case ELFCLASS32:
582 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
583 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
584 fprintf(stderr,
585 "unrecognized ET_REL file: %s\n", fname);
586 goto out;
587 }
588 if (w2(ehdr->e_machine) == EM_MIPS) {
589 reltype = R_MIPS_32;
590 is_fake_mcount32 = MIPS32_is_fake_mcount;
591 }
592 if (do32(ehdr, fname, reltype) < 0)
593 goto out;
594 break;
595 case ELFCLASS64: {
596 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
597 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
598 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
599 fprintf(stderr,
600 "unrecognized ET_REL file: %s\n", fname);
601 goto out;
602 }
603 if (w2(ghdr->e_machine) == EM_S390) {
604 reltype = R_390_64;
605 mcount_adjust_64 = -14;
606 }
607 if (w2(ghdr->e_machine) == EM_MIPS) {
608 reltype = R_MIPS_64;
609 Elf64_r_sym = MIPS64_r_sym;
610 Elf64_r_info = MIPS64_r_info;
611 is_fake_mcount64 = MIPS64_is_fake_mcount;
612 }
613 if (do64(ghdr, fname, reltype) < 0)
614 goto out;
615 break;
616 }
617 } /* end switch */
618
619 rc = write_file(fname);
620out:
621 file_append_cleanup();
622 mmap_cleanup();
623 return rc;
624}
625
626int main(int argc, char *argv[])
627{
628 const char ftrace[] = "/ftrace.o";
629 int ftrace_size = sizeof(ftrace) - 1;
630 int n_error = 0; /* gcc-4.3.0 false positive complaint */
631 int c;
632 int i;
633
634 while ((c = getopt(argc, argv, "w")) >= 0) {
635 switch (c) {
636 case 'w':
637 warn_on_notrace_sect = 1;
638 break;
639 default:
640 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
641 return 0;
642 }
643 }
644
645 if ((argc - optind) < 1) {
646 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
647 return 0;
648 }
649
650 /* Process each file in turn, allowing deep failure. */
651 for (i = optind; i < argc; i++) {
652 char *file = argv[i];
653 int len;
654
655 /*
656 * The file kernel/trace/ftrace.o references the mcount
657 * function but does not call it. Since ftrace.o should
658 * not be traced anyway, we just skip it.
659 */
660 len = strlen(file);
661 if (len >= ftrace_size &&
662 strcmp(file + (len - ftrace_size), ftrace) == 0)
663 continue;
664
665 if (do_file(file)) {
666 fprintf(stderr, "%s: failed\n", file);
667 ++n_error;
668 }
669 }
670 return !!n_error;
671}
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
36static int fd_map; /* File descriptor for file being modified. */
37static int mmap_failed; /* Boolean flag. */
38static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
39static char gpfx; /* prefix for global symbol name (sometimes '_') */
40static struct stat sb; /* Remember .st_size, etc. */
41static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
42static const char *altmcount; /* alternate mcount symbol name */
43static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
44
45/* setjmp() return values */
46enum {
47 SJ_SETJMP = 0, /* hardwired first return */
48 SJ_FAIL,
49 SJ_SUCCEED
50};
51
52/* Per-file resource cleanup when multiple files. */
53static void
54cleanup(void)
55{
56 if (!mmap_failed)
57 munmap(ehdr_curr, sb.st_size);
58 else
59 free(ehdr_curr);
60 close(fd_map);
61}
62
63static void __attribute__((noreturn))
64fail_file(void)
65{
66 cleanup();
67 longjmp(jmpenv, SJ_FAIL);
68}
69
70static void __attribute__((noreturn))
71succeed_file(void)
72{
73 cleanup();
74 longjmp(jmpenv, SJ_SUCCEED);
75}
76
77/* ulseek, uread, ...: Check return value for errors. */
78
79static off_t
80ulseek(int const fd, off_t const offset, int const whence)
81{
82 off_t const w = lseek(fd, offset, whence);
83 if (w == (off_t)-1) {
84 perror("lseek");
85 fail_file();
86 }
87 return w;
88}
89
90static size_t
91uread(int const fd, void *const buf, size_t const count)
92{
93 size_t const n = read(fd, buf, count);
94 if (n != count) {
95 perror("read");
96 fail_file();
97 }
98 return n;
99}
100
101static size_t
102uwrite(int const fd, void const *const buf, size_t const count)
103{
104 size_t const n = write(fd, buf, count);
105 if (n != count) {
106 perror("write");
107 fail_file();
108 }
109 return n;
110}
111
112static void *
113umalloc(size_t size)
114{
115 void *const addr = malloc(size);
116 if (addr == 0) {
117 fprintf(stderr, "malloc failed: %zu bytes\n", size);
118 fail_file();
119 }
120 return addr;
121}
122
123static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
124static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
125static unsigned char *ideal_nop;
126
127static char rel_type_nop;
128
129static int (*make_nop)(void *map, size_t const offset);
130
131static int make_nop_x86(void *map, size_t const offset)
132{
133 uint32_t *ptr;
134 unsigned char *op;
135
136 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
137 ptr = map + offset;
138 if (*ptr != 0)
139 return -1;
140
141 op = map + offset - 1;
142 if (*op != 0xe8)
143 return -1;
144
145 /* convert to nop */
146 ulseek(fd_map, offset - 1, SEEK_SET);
147 uwrite(fd_map, ideal_nop, 5);
148 return 0;
149}
150
151/*
152 * Get the whole file as a programming convenience in order to avoid
153 * malloc+lseek+read+free of many pieces. If successful, then mmap
154 * avoids copying unused pieces; else just read the whole file.
155 * Open for both read and write; new info will be appended to the file.
156 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
157 * do not propagate to the file until an explicit overwrite at the last.
158 * This preserves most aspects of consistency (all except .st_size)
159 * for simultaneous readers of the file while we are appending to it.
160 * However, multiple writers still are bad. We choose not to use
161 * locking because it is expensive and the use case of kernel build
162 * makes multiple writers unlikely.
163 */
164static void *mmap_file(char const *fname)
165{
166 void *addr;
167
168 fd_map = open(fname, O_RDWR);
169 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
170 perror(fname);
171 fail_file();
172 }
173 if (!S_ISREG(sb.st_mode)) {
174 fprintf(stderr, "not a regular file: %s\n", fname);
175 fail_file();
176 }
177 addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
178 fd_map, 0);
179 mmap_failed = 0;
180 if (addr == MAP_FAILED) {
181 mmap_failed = 1;
182 addr = umalloc(sb.st_size);
183 uread(fd_map, addr, sb.st_size);
184 }
185 return addr;
186}
187
188/* w8rev, w8nat, ...: Handle endianness. */
189
190static uint64_t w8rev(uint64_t const x)
191{
192 return ((0xff & (x >> (0 * 8))) << (7 * 8))
193 | ((0xff & (x >> (1 * 8))) << (6 * 8))
194 | ((0xff & (x >> (2 * 8))) << (5 * 8))
195 | ((0xff & (x >> (3 * 8))) << (4 * 8))
196 | ((0xff & (x >> (4 * 8))) << (3 * 8))
197 | ((0xff & (x >> (5 * 8))) << (2 * 8))
198 | ((0xff & (x >> (6 * 8))) << (1 * 8))
199 | ((0xff & (x >> (7 * 8))) << (0 * 8));
200}
201
202static uint32_t w4rev(uint32_t const x)
203{
204 return ((0xff & (x >> (0 * 8))) << (3 * 8))
205 | ((0xff & (x >> (1 * 8))) << (2 * 8))
206 | ((0xff & (x >> (2 * 8))) << (1 * 8))
207 | ((0xff & (x >> (3 * 8))) << (0 * 8));
208}
209
210static uint32_t w2rev(uint16_t const x)
211{
212 return ((0xff & (x >> (0 * 8))) << (1 * 8))
213 | ((0xff & (x >> (1 * 8))) << (0 * 8));
214}
215
216static uint64_t w8nat(uint64_t const x)
217{
218 return x;
219}
220
221static uint32_t w4nat(uint32_t const x)
222{
223 return x;
224}
225
226static uint32_t w2nat(uint16_t const x)
227{
228 return x;
229}
230
231static uint64_t (*w8)(uint64_t);
232static uint32_t (*w)(uint32_t);
233static uint32_t (*w2)(uint16_t);
234
235/* Names of the sections that could contain calls to mcount. */
236static int
237is_mcounted_section_name(char const *const txtname)
238{
239 return strcmp(".text", txtname) == 0 ||
240 strcmp(".ref.text", txtname) == 0 ||
241 strcmp(".sched.text", txtname) == 0 ||
242 strcmp(".spinlock.text", txtname) == 0 ||
243 strcmp(".irqentry.text", txtname) == 0 ||
244 strcmp(".kprobes.text", txtname) == 0 ||
245 strcmp(".text.unlikely", txtname) == 0;
246}
247
248/* 32 bit and 64 bit are very similar */
249#include "recordmcount.h"
250#define RECORD_MCOUNT_64
251#include "recordmcount.h"
252
253/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
254 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
255 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
256 * to imply the order of the members; the spec does not say so.
257 * typedef unsigned char Elf64_Byte;
258 * fails on MIPS64 because their <elf.h> already has it!
259 */
260
261typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
262
263union mips_r_info {
264 Elf64_Xword r_info;
265 struct {
266 Elf64_Word r_sym; /* Symbol index. */
267 myElf64_Byte r_ssym; /* Special symbol. */
268 myElf64_Byte r_type3; /* Third relocation. */
269 myElf64_Byte r_type2; /* Second relocation. */
270 myElf64_Byte r_type; /* First relocation. */
271 } r_mips;
272};
273
274static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
275{
276 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
277}
278
279static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
280{
281 rp->r_info = ((union mips_r_info){
282 .r_mips = { .r_sym = w(sym), .r_type = type }
283 }).r_info;
284}
285
286static void
287do_file(char const *const fname)
288{
289 Elf32_Ehdr *const ehdr = mmap_file(fname);
290 unsigned int reltype = 0;
291
292 ehdr_curr = ehdr;
293 w = w4nat;
294 w2 = w2nat;
295 w8 = w8nat;
296 switch (ehdr->e_ident[EI_DATA]) {
297 static unsigned int const endian = 1;
298 default:
299 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
300 ehdr->e_ident[EI_DATA], fname);
301 fail_file();
302 break;
303 case ELFDATA2LSB:
304 if (*(unsigned char const *)&endian != 1) {
305 /* main() is big endian, file.o is little endian. */
306 w = w4rev;
307 w2 = w2rev;
308 w8 = w8rev;
309 }
310 break;
311 case ELFDATA2MSB:
312 if (*(unsigned char const *)&endian != 0) {
313 /* main() is little endian, file.o is big endian. */
314 w = w4rev;
315 w2 = w2rev;
316 w8 = w8rev;
317 }
318 break;
319 } /* end switch */
320 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
321 || w2(ehdr->e_type) != ET_REL
322 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
323 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
324 fail_file();
325 }
326
327 gpfx = 0;
328 switch (w2(ehdr->e_machine)) {
329 default:
330 fprintf(stderr, "unrecognized e_machine %d %s\n",
331 w2(ehdr->e_machine), fname);
332 fail_file();
333 break;
334 case EM_386:
335 reltype = R_386_32;
336 make_nop = make_nop_x86;
337 ideal_nop = ideal_nop5_x86_32;
338 mcount_adjust_32 = -1;
339 break;
340 case EM_ARM: reltype = R_ARM_ABS32;
341 altmcount = "__gnu_mcount_nc";
342 break;
343 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
344 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
345 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
346 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
347 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
348 case EM_SH: reltype = R_SH_DIR32; break;
349 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
350 case EM_X86_64:
351 make_nop = make_nop_x86;
352 ideal_nop = ideal_nop5_x86_64;
353 reltype = R_X86_64_64;
354 mcount_adjust_64 = -1;
355 break;
356 } /* end switch */
357
358 switch (ehdr->e_ident[EI_CLASS]) {
359 default:
360 fprintf(stderr, "unrecognized ELF class %d %s\n",
361 ehdr->e_ident[EI_CLASS], fname);
362 fail_file();
363 break;
364 case ELFCLASS32:
365 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
366 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
367 fprintf(stderr,
368 "unrecognized ET_REL file: %s\n", fname);
369 fail_file();
370 }
371 if (w2(ehdr->e_machine) == EM_S390) {
372 reltype = R_390_32;
373 mcount_adjust_32 = -4;
374 }
375 if (w2(ehdr->e_machine) == EM_MIPS) {
376 reltype = R_MIPS_32;
377 is_fake_mcount32 = MIPS32_is_fake_mcount;
378 }
379 do32(ehdr, fname, reltype);
380 break;
381 case ELFCLASS64: {
382 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
383 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
384 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
385 fprintf(stderr,
386 "unrecognized ET_REL file: %s\n", fname);
387 fail_file();
388 }
389 if (w2(ghdr->e_machine) == EM_S390) {
390 reltype = R_390_64;
391 mcount_adjust_64 = -8;
392 }
393 if (w2(ghdr->e_machine) == EM_MIPS) {
394 reltype = R_MIPS_64;
395 Elf64_r_sym = MIPS64_r_sym;
396 Elf64_r_info = MIPS64_r_info;
397 is_fake_mcount64 = MIPS64_is_fake_mcount;
398 }
399 do64(ghdr, fname, reltype);
400 break;
401 }
402 } /* end switch */
403
404 cleanup();
405}
406
407int
408main(int argc, char *argv[])
409{
410 const char ftrace[] = "/ftrace.o";
411 int ftrace_size = sizeof(ftrace) - 1;
412 int n_error = 0; /* gcc-4.3.0 false positive complaint */
413 int c;
414 int i;
415
416 while ((c = getopt(argc, argv, "w")) >= 0) {
417 switch (c) {
418 case 'w':
419 warn_on_notrace_sect = 1;
420 break;
421 default:
422 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
423 return 0;
424 }
425 }
426
427 if ((argc - optind) < 1) {
428 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
429 return 0;
430 }
431
432 /* Process each file in turn, allowing deep failure. */
433 for (i = optind; i < argc; i++) {
434 char *file = argv[i];
435 int const sjval = setjmp(jmpenv);
436 int len;
437
438 /*
439 * The file kernel/trace/ftrace.o references the mcount
440 * function but does not call it. Since ftrace.o should
441 * not be traced anyway, we just skip it.
442 */
443 len = strlen(file);
444 if (len >= ftrace_size &&
445 strcmp(file + (len - ftrace_size), ftrace) == 0)
446 continue;
447
448 switch (sjval) {
449 default:
450 fprintf(stderr, "internal error: %s\n", file);
451 exit(1);
452 break;
453 case SJ_SETJMP: /* normal sequence */
454 /* Avoid problems if early cleanup() */
455 fd_map = -1;
456 ehdr_curr = NULL;
457 mmap_failed = 1;
458 do_file(file);
459 break;
460 case SJ_FAIL: /* error in do_file or below */
461 ++n_error;
462 break;
463 case SJ_SUCCEED: /* premature success */
464 /* do nothing */
465 break;
466 } /* end switch */
467 }
468 return !!n_error;
469}
470
471