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
42 #define EM_LOONGARCH 258
45 #define R_LARCH_MARK_LA 20
46 #define R_LARCH_SOP_PUSH_PLT_PCREL 29
50 #define R_ARM_THM_CALL 10
53 #define R_AARCH64_CALL26 283
55 static int fd_map; /* File descriptor for file being modified. */
56 static int mmap_failed; /* Boolean flag. */
57 static char gpfx; /* prefix for global symbol name (sometimes '_') */
58 static struct stat sb; /* Remember .st_size, etc. */
59 static const char *altmcount; /* alternate mcount symbol name */
60 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
61 static void *file_map; /* pointer of the mapped file */
62 static void *file_end; /* pointer to the end of the mapped file */
63 static int file_updated; /* flag to state file was changed */
64 static void *file_ptr; /* current file pointer location */
66 static void *file_append; /* added to the end of the file */
67 static size_t file_append_size; /* how much is added to end of file */
69 /* Per-file resource cleanup when multiple files. */
70 static void file_append_cleanup(void)
78 static void mmap_cleanup(void)
81 munmap(file_map, sb.st_size);
87 /* ulseek, uwrite, ...: Check return value for errors. */
89 static off_t ulseek(off_t const offset, int const whence)
93 file_ptr = file_map + offset;
99 file_ptr = file_map + (sb.st_size - offset);
102 if (file_ptr < file_map) {
103 fprintf(stderr, "lseek: seek before file\n");
106 return file_ptr - file_map;
109 static ssize_t uwrite(void const *const buf, size_t const count)
116 if (file_ptr + count >= file_end) {
117 off_t aoffset = (file_ptr + count) - file_end;
119 if (aoffset > file_append_size) {
120 file_append = realloc(file_append, aoffset);
121 file_append_size = aoffset;
125 file_append_cleanup();
129 if (file_ptr < file_end) {
130 cnt = file_end - file_ptr;
133 idx = aoffset - count;
138 memcpy(file_ptr, buf, cnt);
141 memcpy(file_append + idx, buf + cnt, count - cnt);
147 static void * umalloc(size_t size)
149 void *const addr = malloc(size);
151 fprintf(stderr, "malloc failed: %zu bytes\n", size);
152 file_append_cleanup();
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.
172 static void *mmap_file(char const *fname)
174 /* Avoid problems if early cleanup() */
182 fd_map = open(fname, O_RDONLY);
187 if (fstat(fd_map, &sb) < 0) {
191 if (!S_ISREG(sb.st_mode)) {
192 fprintf(stderr, "not a regular file: %s\n", fname);
195 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
197 if (file_map == MAP_FAILED) {
199 file_map = umalloc(sb.st_size);
204 if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
216 file_end = file_map + sb.st_size;
222 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
223 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
224 static unsigned char *ideal_nop;
226 static char rel_type_nop;
228 static int (*make_nop)(void *map, size_t const offset);
230 static int make_nop_x86(void *map, size_t const offset)
235 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
240 op = map + offset - 1;
245 if (ulseek(offset - 1, SEEK_SET) < 0)
247 if (uwrite(ideal_nop, 5) < 0)
252 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
253 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
254 static unsigned char *ideal_nop4_arm;
256 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
257 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
258 static unsigned char *bl_mcount_arm;
260 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
261 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
262 static unsigned char *push_arm;
264 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
265 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
266 static unsigned char *ideal_nop2_thumb;
268 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
269 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
270 static unsigned char *push_bl_mcount_thumb;
272 static int make_nop_arm(void *map, size_t const offset)
280 if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
281 if (memcmp(ptr - 4, push_arm, 4) == 0) {
285 ideal_nop = ideal_nop4_arm;
287 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
291 ideal_nop = ideal_nop2_thumb;
296 if (ulseek(off, SEEK_SET) < 0)
300 if (uwrite(ideal_nop, nop_size) < 0)
307 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
308 static int make_nop_arm64(void *map, size_t const offset)
313 /* bl <_mcount> is 0x94000000 before relocation */
314 if (*ptr != 0x94000000)
318 if (ulseek(offset, SEEK_SET) < 0)
320 if (uwrite(ideal_nop, 4) < 0)
325 static int write_file(const char *fname)
327 char tmp_file[strlen(fname) + 4];
333 sprintf(tmp_file, "%s.rc", fname);
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.
340 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
345 n = write(fd_map, file_map, sb.st_size);
346 if (n != sb.st_size) {
351 if (file_append_size) {
352 n = write(fd_map, file_append, file_append_size);
353 if (n != file_append_size) {
360 if (rename(tmp_file, fname) < 0) {
367 /* w8rev, w8nat, ...: Handle endianness. */
369 static uint64_t w8rev(uint64_t const x)
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));
381 static uint32_t w4rev(uint32_t const x)
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));
389 static uint32_t w2rev(uint16_t const x)
391 return ((0xff & (x >> (0 * 8))) << (1 * 8))
392 | ((0xff & (x >> (1 * 8))) << (0 * 8));
395 static uint64_t w8nat(uint64_t const x)
400 static uint32_t w4nat(uint32_t const x)
405 static uint32_t w2nat(uint16_t const x)
410 static uint64_t (*w8)(uint64_t);
411 static uint32_t (*w)(uint32_t);
412 static uint32_t (*w2)(uint16_t);
414 /* Names of the sections that could contain calls to mcount. */
415 static int is_mcounted_section_name(char const *const txtname)
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;
428 static char const *already_has_rel_mcount = "success"; /* our work here is done! */
430 /* 32 bit and 64 bit are very similar */
431 #include "recordmcount.h"
432 #define RECORD_MCOUNT_64
433 #include "recordmcount.h"
435 static int arm_is_fake_mcount(Elf32_Rel const *rp)
437 switch (ELF32_R_TYPE(w(rp->r_info))) {
447 static int arm64_is_fake_mcount(Elf64_Rel const *rp)
449 return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
452 static int LARCH32_is_fake_mcount(Elf32_Rel const *rp)
454 switch (ELF64_R_TYPE(w(rp->r_info))) {
455 case R_LARCH_MARK_LA:
456 case R_LARCH_SOP_PUSH_PLT_PCREL:
463 static int LARCH64_is_fake_mcount(Elf64_Rel const *rp)
465 switch (ELF64_R_TYPE(w(rp->r_info))) {
466 case R_LARCH_MARK_LA:
467 case R_LARCH_SOP_PUSH_PLT_PCREL:
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!
482 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
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. */
495 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
497 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
500 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
502 rp->r_info = ((union mips_r_info){
503 .r_mips = { .r_sym = w(sym), .r_type = type }
507 static int do_file(char const *const fname)
509 unsigned int reltype = 0;
513 ehdr = mmap_file(fname);
520 switch (ehdr->e_ident[EI_DATA]) {
521 static unsigned int const endian = 1;
523 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
524 ehdr->e_ident[EI_DATA], fname);
527 if (*(unsigned char const *)&endian != 1) {
528 /* main() is big endian, file.o is little endian. */
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;
540 if (*(unsigned char const *)&endian != 0) {
541 /* main() is little endian, file.o is big endian. */
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;
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);
561 switch (w2(ehdr->e_machine)) {
563 fprintf(stderr, "unrecognized e_machine %u %s\n",
564 w2(ehdr->e_machine), fname);
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;
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;
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;
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;
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;
607 switch (ehdr->e_ident[EI_CLASS]) {
609 fprintf(stderr, "unrecognized ELF class %d %s\n",
610 ehdr->e_ident[EI_CLASS], fname);
613 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
614 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
616 "unrecognized ET_REL file: %s\n", fname);
619 if (w2(ehdr->e_machine) == EM_MIPS) {
621 is_fake_mcount32 = MIPS32_is_fake_mcount;
623 if (w2(ehdr->e_machine) == EM_LOONGARCH) {
624 reltype = R_LARCH_32;
625 is_fake_mcount32 = LARCH32_is_fake_mcount;
627 if (do32(ehdr, fname, reltype) < 0)
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)) {
635 "unrecognized ET_REL file: %s\n", fname);
638 if (w2(ghdr->e_machine) == EM_S390) {
640 mcount_adjust_64 = -14;
642 if (w2(ghdr->e_machine) == EM_MIPS) {
644 Elf64_r_sym = MIPS64_r_sym;
645 Elf64_r_info = MIPS64_r_info;
646 is_fake_mcount64 = MIPS64_is_fake_mcount;
648 if (w2(ghdr->e_machine) == EM_LOONGARCH) {
649 reltype = R_LARCH_64;
650 is_fake_mcount64 = LARCH64_is_fake_mcount;
652 if (do64(ghdr, fname, reltype) < 0)
658 rc = write_file(fname);
660 file_append_cleanup();
665 int main(int argc, char *argv[])
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 */
673 while ((c = getopt(argc, argv, "w")) >= 0) {
676 warn_on_notrace_sect = 1;
679 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
684 if ((argc - optind) < 1) {
685 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
689 /* Process each file in turn, allowing deep failure. */
690 for (i = optind; i < argc; i++) {
691 char *file = argv[i];
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.
700 if (len >= ftrace_size &&
701 strcmp(file + (len - ftrace_size), ftrace) == 0)
705 fprintf(stderr, "%s: failed\n", file);