1 // SPDX-License-Identifier: GPL-2.0-only
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.
7 * Restructured to fit Linux format, as well as other updates:
8 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
12 * Strategy: alter the .o file in-place.
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.]
24 #include <sys/types.h>
36 #define EM_AARCH64 183
37 #define R_AARCH64_NONE 0
38 #define R_AARCH64_ABS64 257
41 static int fd_map; /* File descriptor for file being modified. */
42 static int mmap_failed; /* Boolean flag. */
43 static char gpfx; /* prefix for global symbol name (sometimes '_') */
44 static struct stat sb; /* Remember .st_size, etc. */
45 static const char *altmcount; /* alternate mcount symbol name */
46 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
47 static void *file_map; /* pointer of the mapped file */
48 static void *file_end; /* pointer to the end of the mapped file */
49 static int file_updated; /* flag to state file was changed */
50 static void *file_ptr; /* current file pointer location */
51 static void *file_append; /* added to the end of the file */
52 static size_t file_append_size; /* how much is added to end of file */
54 /* Per-file resource cleanup when multiple files. */
55 static void cleanup(void)
58 munmap(file_map, sb.st_size);
68 /* ulseek, uwrite, ...: Check return value for errors. */
70 static off_t ulseek(off_t const offset, int const whence)
74 file_ptr = file_map + offset;
80 file_ptr = file_map + (sb.st_size - offset);
83 if (file_ptr < file_map) {
84 fprintf(stderr, "lseek: seek before file\n");
87 return file_ptr - file_map;
90 static ssize_t uwrite(void const *const buf, size_t const count)
97 if (file_ptr + count >= file_end) {
98 off_t aoffset = (file_ptr + count) - file_end;
100 if (aoffset > file_append_size) {
101 file_append = realloc(file_append, aoffset);
102 file_append_size = aoffset;
109 if (file_ptr < file_end) {
110 cnt = file_end - file_ptr;
113 idx = aoffset - count;
118 memcpy(file_ptr, buf, cnt);
121 memcpy(file_append + idx, buf + cnt, count - cnt);
127 static void * umalloc(size_t size)
129 void *const addr = malloc(size);
131 fprintf(stderr, "malloc failed: %zu bytes\n", size);
138 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
139 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
140 static unsigned char *ideal_nop;
142 static char rel_type_nop;
144 static int (*make_nop)(void *map, size_t const offset);
146 static int make_nop_x86(void *map, size_t const offset)
151 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
156 op = map + offset - 1;
161 if (ulseek(offset - 1, SEEK_SET) < 0)
163 if (uwrite(ideal_nop, 5) < 0)
168 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
169 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
170 static unsigned char *ideal_nop4_arm;
172 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
173 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
174 static unsigned char *bl_mcount_arm;
176 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
177 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
178 static unsigned char *push_arm;
180 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
181 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
182 static unsigned char *ideal_nop2_thumb;
184 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
185 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
186 static unsigned char *push_bl_mcount_thumb;
188 static int make_nop_arm(void *map, size_t const offset)
196 if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
197 if (memcmp(ptr - 4, push_arm, 4) == 0) {
201 ideal_nop = ideal_nop4_arm;
203 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
207 ideal_nop = ideal_nop2_thumb;
212 if (ulseek(off, SEEK_SET) < 0)
216 if (uwrite(ideal_nop, nop_size) < 0)
223 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
224 static int make_nop_arm64(void *map, size_t const offset)
229 /* bl <_mcount> is 0x94000000 before relocation */
230 if (*ptr != 0x94000000)
234 if (ulseek(offset, SEEK_SET) < 0)
236 if (uwrite(ideal_nop, 4) < 0)
242 * Get the whole file as a programming convenience in order to avoid
243 * malloc+lseek+read+free of many pieces. If successful, then mmap
244 * avoids copying unused pieces; else just read the whole file.
245 * Open for both read and write; new info will be appended to the file.
246 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
247 * do not propagate to the file until an explicit overwrite at the last.
248 * This preserves most aspects of consistency (all except .st_size)
249 * for simultaneous readers of the file while we are appending to it.
250 * However, multiple writers still are bad. We choose not to use
251 * locking because it is expensive and the use case of kernel build
252 * makes multiple writers unlikely.
254 static void *mmap_file(char const *fname)
258 fd_map = open(fname, O_RDONLY);
264 if (fstat(fd_map, &sb) < 0) {
269 if (!S_ISREG(sb.st_mode)) {
270 fprintf(stderr, "not a regular file: %s\n", fname);
274 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
277 if (file_map == MAP_FAILED) {
279 file_map = umalloc(sb.st_size);
284 if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
294 file_end = file_map + sb.st_size;
299 static int write_file(const char *fname)
301 char tmp_file[strlen(fname) + 4];
307 sprintf(tmp_file, "%s.rc", fname);
310 * After reading the entire file into memory, delete it
311 * and write it back, to prevent weird side effects of modifying
312 * an object file in place.
314 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
320 n = write(fd_map, file_map, sb.st_size);
321 if (n != sb.st_size) {
327 if (file_append_size) {
328 n = write(fd_map, file_append, file_append_size);
329 if (n != file_append_size) {
337 if (rename(tmp_file, fname) < 0) {
345 /* w8rev, w8nat, ...: Handle endianness. */
347 static uint64_t w8rev(uint64_t const x)
349 return ((0xff & (x >> (0 * 8))) << (7 * 8))
350 | ((0xff & (x >> (1 * 8))) << (6 * 8))
351 | ((0xff & (x >> (2 * 8))) << (5 * 8))
352 | ((0xff & (x >> (3 * 8))) << (4 * 8))
353 | ((0xff & (x >> (4 * 8))) << (3 * 8))
354 | ((0xff & (x >> (5 * 8))) << (2 * 8))
355 | ((0xff & (x >> (6 * 8))) << (1 * 8))
356 | ((0xff & (x >> (7 * 8))) << (0 * 8));
359 static uint32_t w4rev(uint32_t const x)
361 return ((0xff & (x >> (0 * 8))) << (3 * 8))
362 | ((0xff & (x >> (1 * 8))) << (2 * 8))
363 | ((0xff & (x >> (2 * 8))) << (1 * 8))
364 | ((0xff & (x >> (3 * 8))) << (0 * 8));
367 static uint32_t w2rev(uint16_t const x)
369 return ((0xff & (x >> (0 * 8))) << (1 * 8))
370 | ((0xff & (x >> (1 * 8))) << (0 * 8));
373 static uint64_t w8nat(uint64_t const x)
378 static uint32_t w4nat(uint32_t const x)
383 static uint32_t w2nat(uint16_t const x)
388 static uint64_t (*w8)(uint64_t);
389 static uint32_t (*w)(uint32_t);
390 static uint32_t (*w2)(uint16_t);
392 /* Names of the sections that could contain calls to mcount. */
393 static int is_mcounted_section_name(char const *const txtname)
395 return strncmp(".text", txtname, 5) == 0 ||
396 strcmp(".init.text", txtname) == 0 ||
397 strcmp(".ref.text", txtname) == 0 ||
398 strcmp(".sched.text", txtname) == 0 ||
399 strcmp(".spinlock.text", txtname) == 0 ||
400 strcmp(".irqentry.text", txtname) == 0 ||
401 strcmp(".softirqentry.text", txtname) == 0 ||
402 strcmp(".kprobes.text", txtname) == 0 ||
403 strcmp(".cpuidle.text", txtname) == 0;
406 static char const *already_has_rel_mcount = "success"; /* our work here is done! */
408 /* 32 bit and 64 bit are very similar */
409 #include "recordmcount.h"
410 #define RECORD_MCOUNT_64
411 #include "recordmcount.h"
413 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
414 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
415 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
416 * to imply the order of the members; the spec does not say so.
417 * typedef unsigned char Elf64_Byte;
418 * fails on MIPS64 because their <elf.h> already has it!
421 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
426 Elf64_Word r_sym; /* Symbol index. */
427 myElf64_Byte r_ssym; /* Special symbol. */
428 myElf64_Byte r_type3; /* Third relocation. */
429 myElf64_Byte r_type2; /* Second relocation. */
430 myElf64_Byte r_type; /* First relocation. */
434 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
436 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
439 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
441 rp->r_info = ((union mips_r_info){
442 .r_mips = { .r_sym = w(sym), .r_type = type }
446 static int do_file(char const *const fname)
448 Elf32_Ehdr *const ehdr = mmap_file(fname);
449 unsigned int reltype = 0;
458 switch (ehdr->e_ident[EI_DATA]) {
459 static unsigned int const endian = 1;
461 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
462 ehdr->e_ident[EI_DATA], fname);
466 if (*(unsigned char const *)&endian != 1) {
467 /* main() is big endian, file.o is little endian. */
472 ideal_nop4_arm = ideal_nop4_arm_le;
473 bl_mcount_arm = bl_mcount_arm_le;
474 push_arm = push_arm_le;
475 ideal_nop2_thumb = ideal_nop2_thumb_le;
476 push_bl_mcount_thumb = push_bl_mcount_thumb_le;
479 if (*(unsigned char const *)&endian != 0) {
480 /* main() is little endian, file.o is big endian. */
485 ideal_nop4_arm = ideal_nop4_arm_be;
486 bl_mcount_arm = bl_mcount_arm_be;
487 push_arm = push_arm_be;
488 ideal_nop2_thumb = ideal_nop2_thumb_be;
489 push_bl_mcount_thumb = push_bl_mcount_thumb_be;
492 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
493 || w2(ehdr->e_type) != ET_REL
494 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
495 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
501 switch (w2(ehdr->e_machine)) {
503 fprintf(stderr, "unrecognized e_machine %u %s\n",
504 w2(ehdr->e_machine), fname);
509 rel_type_nop = R_386_NONE;
510 make_nop = make_nop_x86;
511 ideal_nop = ideal_nop5_x86_32;
512 mcount_adjust_32 = -1;
514 case EM_ARM: reltype = R_ARM_ABS32;
515 altmcount = "__gnu_mcount_nc";
516 make_nop = make_nop_arm;
517 rel_type_nop = R_ARM_NONE;
520 reltype = R_AARCH64_ABS64;
521 make_nop = make_nop_arm64;
522 rel_type_nop = R_AARCH64_NONE;
523 ideal_nop = ideal_nop4_arm64;
526 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
527 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
528 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
529 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
530 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
531 case EM_SH: reltype = R_SH_DIR32; break;
532 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
534 make_nop = make_nop_x86;
535 ideal_nop = ideal_nop5_x86_64;
536 reltype = R_X86_64_64;
537 rel_type_nop = R_X86_64_NONE;
538 mcount_adjust_64 = -1;
542 switch (ehdr->e_ident[EI_CLASS]) {
544 fprintf(stderr, "unrecognized ELF class %d %s\n",
545 ehdr->e_ident[EI_CLASS], fname);
549 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
550 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
552 "unrecognized ET_REL file: %s\n", fname);
556 if (w2(ehdr->e_machine) == EM_MIPS) {
558 is_fake_mcount32 = MIPS32_is_fake_mcount;
560 if (do32(ehdr, fname, reltype) < 0)
564 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
565 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
566 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
568 "unrecognized ET_REL file: %s\n", fname);
572 if (w2(ghdr->e_machine) == EM_S390) {
574 mcount_adjust_64 = -14;
576 if (w2(ghdr->e_machine) == EM_MIPS) {
578 Elf64_r_sym = MIPS64_r_sym;
579 Elf64_r_info = MIPS64_r_info;
580 is_fake_mcount64 = MIPS64_is_fake_mcount;
582 if (do64(ghdr, fname, reltype) < 0)
588 rc = write_file(fname);
594 int main(int argc, char *argv[])
596 const char ftrace[] = "/ftrace.o";
597 int ftrace_size = sizeof(ftrace) - 1;
598 int n_error = 0; /* gcc-4.3.0 false positive complaint */
602 while ((c = getopt(argc, argv, "w")) >= 0) {
605 warn_on_notrace_sect = 1;
608 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
613 if ((argc - optind) < 1) {
614 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
618 /* Process each file in turn, allowing deep failure. */
619 for (i = optind; i < argc; i++) {
620 char *file = argv[i];
624 * The file kernel/trace/ftrace.o references the mcount
625 * function but does not call it. Since ftrace.o should
626 * not be traced anyway, we just skip it.
629 if (len >= ftrace_size &&
630 strcmp(file + (len - ftrace_size), ftrace) == 0)
633 /* Avoid problems if early cleanup() */
640 fprintf(stderr, "%s: failed\n", file);