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).
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>
37 * glibc synced up and added the metag number but didn't add the relocations.
38 * Work around this in a crude manner for now.
43 #ifndef R_METAG_ADDR32
44 #define R_METAG_ADDR32 2
47 #define R_METAG_NONE 3
51 #define EM_AARCH64 183
52 #define R_AARCH64_NONE 0
53 #define R_AARCH64_ABS64 257
57 #define R_ARM_THM_CALL 10
60 static int fd_map; /* File descriptor for file being modified. */
61 static int mmap_failed; /* Boolean flag. */
62 static char gpfx; /* prefix for global symbol name (sometimes '_') */
63 static struct stat sb; /* Remember .st_size, etc. */
64 static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
65 static const char *altmcount; /* alternate mcount symbol name */
66 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
67 static void *file_map; /* pointer of the mapped file */
68 static void *file_end; /* pointer to the end of the mapped file */
69 static int file_updated; /* flag to state file was changed */
70 static void *file_ptr; /* current file pointer location */
71 static void *file_append; /* added to the end of the file */
72 static size_t file_append_size; /* how much is added to end of file */
74 /* setjmp() return values */
76 SJ_SETJMP = 0, /* hardwired first return */
81 /* Per-file resource cleanup when multiple files. */
86 munmap(file_map, sb.st_size);
96 static void __attribute__((noreturn))
100 longjmp(jmpenv, SJ_FAIL);
103 static void __attribute__((noreturn))
107 longjmp(jmpenv, SJ_SUCCEED);
110 /* ulseek, uread, ...: Check return value for errors. */
113 ulseek(int const fd, off_t const offset, int const whence)
117 file_ptr = file_map + offset;
123 file_ptr = file_map + (sb.st_size - offset);
126 if (file_ptr < file_map) {
127 fprintf(stderr, "lseek: seek before file\n");
130 return file_ptr - file_map;
134 uread(int const fd, void *const buf, size_t const count)
136 size_t const n = read(fd, buf, count);
145 uwrite(int const fd, void const *const buf, size_t const count)
153 if (file_ptr + count >= file_end) {
154 off_t aoffset = (file_ptr + count) - file_end;
156 if (aoffset > file_append_size) {
157 p = realloc(file_append, aoffset);
161 file_append_size = aoffset;
167 if (file_ptr < file_end) {
168 cnt = file_end - file_ptr;
171 idx = aoffset - count;
176 memcpy(file_ptr, buf, cnt);
179 memcpy(file_append + idx, buf + cnt, count - cnt);
188 void *const addr = malloc(size);
190 fprintf(stderr, "malloc failed: %zu bytes\n", size);
196 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
197 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
198 static unsigned char *ideal_nop;
200 static char rel_type_nop;
202 static int (*make_nop)(void *map, size_t const offset);
204 static int make_nop_x86(void *map, size_t const offset)
209 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
214 op = map + offset - 1;
219 ulseek(fd_map, offset - 1, SEEK_SET);
220 uwrite(fd_map, ideal_nop, 5);
224 static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
225 static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
226 static unsigned char *ideal_nop4_arm;
228 static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
229 static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
230 static unsigned char *bl_mcount_arm;
232 static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
233 static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
234 static unsigned char *push_arm;
236 static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
237 static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
238 static unsigned char *ideal_nop2_thumb;
240 static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
241 static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
242 static unsigned char *push_bl_mcount_thumb;
244 static int make_nop_arm(void *map, size_t const offset)
252 if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
253 if (memcmp(ptr - 4, push_arm, 4) == 0) {
257 ideal_nop = ideal_nop4_arm;
259 } else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
263 ideal_nop = ideal_nop2_thumb;
268 ulseek(fd_map, off, SEEK_SET);
271 uwrite(fd_map, ideal_nop, nop_size);
277 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
278 static int make_nop_arm64(void *map, size_t const offset)
283 /* bl <_mcount> is 0x94000000 before relocation */
284 if (*ptr != 0x94000000)
288 ulseek(fd_map, offset, SEEK_SET);
289 uwrite(fd_map, ideal_nop, 4);
294 * Get the whole file as a programming convenience in order to avoid
295 * malloc+lseek+read+free of many pieces. If successful, then mmap
296 * avoids copying unused pieces; else just read the whole file.
297 * Open for both read and write; new info will be appended to the file.
298 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
299 * do not propagate to the file until an explicit overwrite at the last.
300 * This preserves most aspects of consistency (all except .st_size)
301 * for simultaneous readers of the file while we are appending to it.
302 * However, multiple writers still are bad. We choose not to use
303 * locking because it is expensive and the use case of kernel build
304 * makes multiple writers unlikely.
306 static void *mmap_file(char const *fname)
308 fd_map = open(fname, O_RDONLY);
309 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
313 if (!S_ISREG(sb.st_mode)) {
314 fprintf(stderr, "not a regular file: %s\n", fname);
317 file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
320 if (file_map == MAP_FAILED) {
322 file_map = umalloc(sb.st_size);
323 uread(fd_map, file_map, sb.st_size);
327 file_end = file_map + sb.st_size;
332 static void write_file(const char *fname)
334 char tmp_file[strlen(fname) + 4];
340 sprintf(tmp_file, "%s.rc", fname);
343 * After reading the entire file into memory, delete it
344 * and write it back, to prevent weird side effects of modifying
345 * an object file in place.
347 fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
352 n = write(fd_map, file_map, sb.st_size);
353 if (n != sb.st_size) {
357 if (file_append_size) {
358 n = write(fd_map, file_append, file_append_size);
359 if (n != file_append_size) {
365 if (rename(tmp_file, fname) < 0) {
371 /* w8rev, w8nat, ...: Handle endianness. */
373 static uint64_t w8rev(uint64_t const x)
375 return ((0xff & (x >> (0 * 8))) << (7 * 8))
376 | ((0xff & (x >> (1 * 8))) << (6 * 8))
377 | ((0xff & (x >> (2 * 8))) << (5 * 8))
378 | ((0xff & (x >> (3 * 8))) << (4 * 8))
379 | ((0xff & (x >> (4 * 8))) << (3 * 8))
380 | ((0xff & (x >> (5 * 8))) << (2 * 8))
381 | ((0xff & (x >> (6 * 8))) << (1 * 8))
382 | ((0xff & (x >> (7 * 8))) << (0 * 8));
385 static uint32_t w4rev(uint32_t const x)
387 return ((0xff & (x >> (0 * 8))) << (3 * 8))
388 | ((0xff & (x >> (1 * 8))) << (2 * 8))
389 | ((0xff & (x >> (2 * 8))) << (1 * 8))
390 | ((0xff & (x >> (3 * 8))) << (0 * 8));
393 static uint32_t w2rev(uint16_t const x)
395 return ((0xff & (x >> (0 * 8))) << (1 * 8))
396 | ((0xff & (x >> (1 * 8))) << (0 * 8));
399 static uint64_t w8nat(uint64_t const x)
404 static uint32_t w4nat(uint32_t const x)
409 static uint32_t w2nat(uint16_t const x)
414 static uint64_t (*w8)(uint64_t);
415 static uint32_t (*w)(uint32_t);
416 static uint32_t (*w2)(uint16_t);
418 /* Names of the sections that could contain calls to mcount. */
420 is_mcounted_section_name(char const *const txtname)
422 return strncmp(".text", txtname, 5) == 0 ||
423 strcmp(".init.text", txtname) == 0 ||
424 strcmp(".ref.text", txtname) == 0 ||
425 strcmp(".sched.text", txtname) == 0 ||
426 strcmp(".spinlock.text", txtname) == 0 ||
427 strcmp(".irqentry.text", txtname) == 0 ||
428 strcmp(".softirqentry.text", txtname) == 0 ||
429 strcmp(".kprobes.text", txtname) == 0 ||
430 strcmp(".cpuidle.text", txtname) == 0 ||
431 strcmp(".text.unlikely", txtname) == 0;
434 /* 32 bit and 64 bit are very similar */
435 #include "recordmcount.h"
436 #define RECORD_MCOUNT_64
437 #include "recordmcount.h"
439 static int arm_is_fake_mcount(Elf32_Rel const *rp)
441 switch (ELF32_R_TYPE(w(rp->r_info))) {
451 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
452 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
453 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
454 * to imply the order of the members; the spec does not say so.
455 * typedef unsigned char Elf64_Byte;
456 * fails on MIPS64 because their <elf.h> already has it!
459 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
464 Elf64_Word r_sym; /* Symbol index. */
465 myElf64_Byte r_ssym; /* Special symbol. */
466 myElf64_Byte r_type3; /* Third relocation. */
467 myElf64_Byte r_type2; /* Second relocation. */
468 myElf64_Byte r_type; /* First relocation. */
472 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
474 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
477 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
479 rp->r_info = ((union mips_r_info){
480 .r_mips = { .r_sym = w(sym), .r_type = type }
485 do_file(char const *const fname)
487 Elf32_Ehdr *const ehdr = mmap_file(fname);
488 unsigned int reltype = 0;
493 switch (ehdr->e_ident[EI_DATA]) {
494 static unsigned int const endian = 1;
496 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
497 ehdr->e_ident[EI_DATA], fname);
501 if (*(unsigned char const *)&endian != 1) {
502 /* main() is big endian, file.o is little endian. */
507 ideal_nop4_arm = ideal_nop4_arm_le;
508 bl_mcount_arm = bl_mcount_arm_le;
509 push_arm = push_arm_le;
510 ideal_nop2_thumb = ideal_nop2_thumb_le;
511 push_bl_mcount_thumb = push_bl_mcount_thumb_le;
514 if (*(unsigned char const *)&endian != 0) {
515 /* main() is little endian, file.o is big endian. */
520 ideal_nop4_arm = ideal_nop4_arm_be;
521 bl_mcount_arm = bl_mcount_arm_be;
522 push_arm = push_arm_be;
523 ideal_nop2_thumb = ideal_nop2_thumb_be;
524 push_bl_mcount_thumb = push_bl_mcount_thumb_be;
527 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
528 || w2(ehdr->e_type) != ET_REL
529 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
530 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
535 switch (w2(ehdr->e_machine)) {
537 fprintf(stderr, "unrecognized e_machine %d %s\n",
538 w2(ehdr->e_machine), fname);
543 rel_type_nop = R_386_NONE;
544 make_nop = make_nop_x86;
545 ideal_nop = ideal_nop5_x86_32;
546 mcount_adjust_32 = -1;
548 case EM_ARM: reltype = R_ARM_ABS32;
549 altmcount = "__gnu_mcount_nc";
550 make_nop = make_nop_arm;
551 rel_type_nop = R_ARM_NONE;
552 is_fake_mcount32 = arm_is_fake_mcount;
555 reltype = R_AARCH64_ABS64;
556 make_nop = make_nop_arm64;
557 rel_type_nop = R_AARCH64_NONE;
558 ideal_nop = ideal_nop4_arm64;
561 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
562 case EM_METAG: reltype = R_METAG_ADDR32;
563 altmcount = "_mcount_wrapper";
564 rel_type_nop = R_METAG_NONE;
565 /* We happen to have the same requirement as MIPS */
566 is_fake_mcount32 = MIPS32_is_fake_mcount;
568 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
569 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
570 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
571 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
572 case EM_SH: reltype = R_SH_DIR32; break;
573 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
575 make_nop = make_nop_x86;
576 ideal_nop = ideal_nop5_x86_64;
577 reltype = R_X86_64_64;
578 rel_type_nop = R_X86_64_NONE;
579 mcount_adjust_64 = -1;
583 switch (ehdr->e_ident[EI_CLASS]) {
585 fprintf(stderr, "unrecognized ELF class %d %s\n",
586 ehdr->e_ident[EI_CLASS], fname);
590 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
591 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
593 "unrecognized ET_REL file: %s\n", fname);
596 if (w2(ehdr->e_machine) == EM_MIPS) {
598 is_fake_mcount32 = MIPS32_is_fake_mcount;
600 do32(ehdr, fname, reltype);
603 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
604 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
605 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
607 "unrecognized ET_REL file: %s\n", fname);
610 if (w2(ghdr->e_machine) == EM_S390) {
612 mcount_adjust_64 = -14;
614 if (w2(ghdr->e_machine) == EM_MIPS) {
616 Elf64_r_sym = MIPS64_r_sym;
617 Elf64_r_info = MIPS64_r_info;
618 is_fake_mcount64 = MIPS64_is_fake_mcount;
620 do64(ghdr, fname, reltype);
630 main(int argc, char *argv[])
632 const char ftrace[] = "/ftrace.o";
633 int ftrace_size = sizeof(ftrace) - 1;
634 int n_error = 0; /* gcc-4.3.0 false positive complaint */
638 while ((c = getopt(argc, argv, "w")) >= 0) {
641 warn_on_notrace_sect = 1;
644 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
649 if ((argc - optind) < 1) {
650 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
654 /* Process each file in turn, allowing deep failure. */
655 for (i = optind; i < argc; i++) {
656 char *file = argv[i];
657 int const sjval = setjmp(jmpenv);
661 * The file kernel/trace/ftrace.o references the mcount
662 * function but does not call it. Since ftrace.o should
663 * not be traced anyway, we just skip it.
666 if (len >= ftrace_size &&
667 strcmp(file + (len - ftrace_size), ftrace) == 0)
672 fprintf(stderr, "internal error: %s\n", file);
675 case SJ_SETJMP: /* normal sequence */
676 /* Avoid problems if early cleanup() */
684 case SJ_FAIL: /* error in do_file or below */
685 fprintf(stderr, "%s: failed\n", file);
688 case SJ_SUCCEED: /* premature success */