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 /* Remove this when these make it to the standard system elf.h. */
39 #define R_METAG_ADDR32 2
40 #define R_METAG_NONE 3
44 #define EM_AARCH64 183
45 #define R_AARCH64_NONE 0
46 #define R_AARCH64_ABS64 257
49 static int fd_map; /* File descriptor for file being modified. */
50 static int mmap_failed; /* Boolean flag. */
51 static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
52 static char gpfx; /* prefix for global symbol name (sometimes '_') */
53 static struct stat sb; /* Remember .st_size, etc. */
54 static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
55 static const char *altmcount; /* alternate mcount symbol name */
56 static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
58 /* setjmp() return values */
60 SJ_SETJMP = 0, /* hardwired first return */
65 /* Per-file resource cleanup when multiple files. */
70 munmap(ehdr_curr, sb.st_size);
76 static void __attribute__((noreturn))
80 longjmp(jmpenv, SJ_FAIL);
83 static void __attribute__((noreturn))
87 longjmp(jmpenv, SJ_SUCCEED);
90 /* ulseek, uread, ...: Check return value for errors. */
93 ulseek(int const fd, off_t const offset, int const whence)
95 off_t const w = lseek(fd, offset, whence);
104 uread(int const fd, void *const buf, size_t const count)
106 size_t const n = read(fd, buf, count);
115 uwrite(int const fd, void const *const buf, size_t const count)
117 size_t const n = write(fd, buf, count);
128 void *const addr = malloc(size);
130 fprintf(stderr, "malloc failed: %zu bytes\n", size);
136 static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
137 static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
138 static unsigned char *ideal_nop;
140 static char rel_type_nop;
142 static int (*make_nop)(void *map, size_t const offset);
144 static int make_nop_x86(void *map, size_t const offset)
149 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
154 op = map + offset - 1;
159 ulseek(fd_map, offset - 1, SEEK_SET);
160 uwrite(fd_map, ideal_nop, 5);
164 static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
165 static int make_nop_arm64(void *map, size_t const offset)
170 /* bl <_mcount> is 0x94000000 before relocation */
171 if (*ptr != 0x94000000)
175 ulseek(fd_map, offset, SEEK_SET);
176 uwrite(fd_map, ideal_nop, 4);
181 * Get the whole file as a programming convenience in order to avoid
182 * malloc+lseek+read+free of many pieces. If successful, then mmap
183 * avoids copying unused pieces; else just read the whole file.
184 * Open for both read and write; new info will be appended to the file.
185 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
186 * do not propagate to the file until an explicit overwrite at the last.
187 * This preserves most aspects of consistency (all except .st_size)
188 * for simultaneous readers of the file while we are appending to it.
189 * However, multiple writers still are bad. We choose not to use
190 * locking because it is expensive and the use case of kernel build
191 * makes multiple writers unlikely.
193 static void *mmap_file(char const *fname)
197 fd_map = open(fname, O_RDWR);
198 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
202 if (!S_ISREG(sb.st_mode)) {
203 fprintf(stderr, "not a regular file: %s\n", fname);
206 addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
209 if (addr == MAP_FAILED) {
211 addr = umalloc(sb.st_size);
212 uread(fd_map, addr, sb.st_size);
217 /* w8rev, w8nat, ...: Handle endianness. */
219 static uint64_t w8rev(uint64_t const x)
221 return ((0xff & (x >> (0 * 8))) << (7 * 8))
222 | ((0xff & (x >> (1 * 8))) << (6 * 8))
223 | ((0xff & (x >> (2 * 8))) << (5 * 8))
224 | ((0xff & (x >> (3 * 8))) << (4 * 8))
225 | ((0xff & (x >> (4 * 8))) << (3 * 8))
226 | ((0xff & (x >> (5 * 8))) << (2 * 8))
227 | ((0xff & (x >> (6 * 8))) << (1 * 8))
228 | ((0xff & (x >> (7 * 8))) << (0 * 8));
231 static uint32_t w4rev(uint32_t const x)
233 return ((0xff & (x >> (0 * 8))) << (3 * 8))
234 | ((0xff & (x >> (1 * 8))) << (2 * 8))
235 | ((0xff & (x >> (2 * 8))) << (1 * 8))
236 | ((0xff & (x >> (3 * 8))) << (0 * 8));
239 static uint32_t w2rev(uint16_t const x)
241 return ((0xff & (x >> (0 * 8))) << (1 * 8))
242 | ((0xff & (x >> (1 * 8))) << (0 * 8));
245 static uint64_t w8nat(uint64_t const x)
250 static uint32_t w4nat(uint32_t const x)
255 static uint32_t w2nat(uint16_t const x)
260 static uint64_t (*w8)(uint64_t);
261 static uint32_t (*w)(uint32_t);
262 static uint32_t (*w2)(uint16_t);
264 /* Names of the sections that could contain calls to mcount. */
266 is_mcounted_section_name(char const *const txtname)
268 return strcmp(".text", txtname) == 0 ||
269 strcmp(".ref.text", txtname) == 0 ||
270 strcmp(".sched.text", txtname) == 0 ||
271 strcmp(".spinlock.text", txtname) == 0 ||
272 strcmp(".irqentry.text", txtname) == 0 ||
273 strcmp(".kprobes.text", txtname) == 0 ||
274 strcmp(".text.unlikely", txtname) == 0;
277 /* 32 bit and 64 bit are very similar */
278 #include "recordmcount.h"
279 #define RECORD_MCOUNT_64
280 #include "recordmcount.h"
282 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
283 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
284 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
285 * to imply the order of the members; the spec does not say so.
286 * typedef unsigned char Elf64_Byte;
287 * fails on MIPS64 because their <elf.h> already has it!
290 typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
295 Elf64_Word r_sym; /* Symbol index. */
296 myElf64_Byte r_ssym; /* Special symbol. */
297 myElf64_Byte r_type3; /* Third relocation. */
298 myElf64_Byte r_type2; /* Second relocation. */
299 myElf64_Byte r_type; /* First relocation. */
303 static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
305 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
308 static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
310 rp->r_info = ((union mips_r_info){
311 .r_mips = { .r_sym = w(sym), .r_type = type }
316 do_file(char const *const fname)
318 Elf32_Ehdr *const ehdr = mmap_file(fname);
319 unsigned int reltype = 0;
325 switch (ehdr->e_ident[EI_DATA]) {
326 static unsigned int const endian = 1;
328 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
329 ehdr->e_ident[EI_DATA], fname);
333 if (*(unsigned char const *)&endian != 1) {
334 /* main() is big endian, file.o is little endian. */
341 if (*(unsigned char const *)&endian != 0) {
342 /* main() is little endian, file.o is big endian. */
349 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
350 || w2(ehdr->e_type) != ET_REL
351 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
352 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
357 switch (w2(ehdr->e_machine)) {
359 fprintf(stderr, "unrecognized e_machine %d %s\n",
360 w2(ehdr->e_machine), fname);
365 rel_type_nop = R_386_NONE;
366 make_nop = make_nop_x86;
367 ideal_nop = ideal_nop5_x86_32;
368 mcount_adjust_32 = -1;
370 case EM_ARM: reltype = R_ARM_ABS32;
371 altmcount = "__gnu_mcount_nc";
374 reltype = R_AARCH64_ABS64;
375 make_nop = make_nop_arm64;
376 rel_type_nop = R_AARCH64_NONE;
377 ideal_nop = ideal_nop4_arm64;
380 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
381 case EM_METAG: reltype = R_METAG_ADDR32;
382 altmcount = "_mcount_wrapper";
383 rel_type_nop = R_METAG_NONE;
384 /* We happen to have the same requirement as MIPS */
385 is_fake_mcount32 = MIPS32_is_fake_mcount;
387 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
388 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
389 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
390 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
391 case EM_SH: reltype = R_SH_DIR32; break;
392 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
394 make_nop = make_nop_x86;
395 ideal_nop = ideal_nop5_x86_64;
396 reltype = R_X86_64_64;
397 rel_type_nop = R_X86_64_NONE;
398 mcount_adjust_64 = -1;
402 switch (ehdr->e_ident[EI_CLASS]) {
404 fprintf(stderr, "unrecognized ELF class %d %s\n",
405 ehdr->e_ident[EI_CLASS], fname);
409 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
410 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
412 "unrecognized ET_REL file: %s\n", fname);
415 if (w2(ehdr->e_machine) == EM_MIPS) {
417 is_fake_mcount32 = MIPS32_is_fake_mcount;
419 do32(ehdr, fname, reltype);
422 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
423 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
424 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
426 "unrecognized ET_REL file: %s\n", fname);
429 if (w2(ghdr->e_machine) == EM_S390) {
431 mcount_adjust_64 = -14;
433 if (w2(ghdr->e_machine) == EM_MIPS) {
435 Elf64_r_sym = MIPS64_r_sym;
436 Elf64_r_info = MIPS64_r_info;
437 is_fake_mcount64 = MIPS64_is_fake_mcount;
439 do64(ghdr, fname, reltype);
448 main(int argc, char *argv[])
450 const char ftrace[] = "/ftrace.o";
451 int ftrace_size = sizeof(ftrace) - 1;
452 int n_error = 0; /* gcc-4.3.0 false positive complaint */
456 while ((c = getopt(argc, argv, "w")) >= 0) {
459 warn_on_notrace_sect = 1;
462 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
467 if ((argc - optind) < 1) {
468 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
472 /* Process each file in turn, allowing deep failure. */
473 for (i = optind; i < argc; i++) {
474 char *file = argv[i];
475 int const sjval = setjmp(jmpenv);
479 * The file kernel/trace/ftrace.o references the mcount
480 * function but does not call it. Since ftrace.o should
481 * not be traced anyway, we just skip it.
484 if (len >= ftrace_size &&
485 strcmp(file + (len - ftrace_size), ftrace) == 0)
490 fprintf(stderr, "internal error: %s\n", file);
493 case SJ_SETJMP: /* normal sequence */
494 /* Avoid problems if early cleanup() */
500 case SJ_FAIL: /* error in do_file or below */
503 case SJ_SUCCEED: /* premature success */