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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 | ||
36 | #ifndef EM_METAG | |
37 | /* Remove this when these make it to the standard system elf.h. */ | |
38 | #define EM_METAG 174 | |
39 | #define R_METAG_ADDR32 2 | |
40 | #define R_METAG_NONE 3 | |
41 | #endif | |
42 | ||
43 | #ifndef EM_AARCH64 | |
44 | #define EM_AARCH64 183 | |
45 | #define R_AARCH64_ABS64 257 | |
46 | #endif | |
47 | ||
48 | static int fd_map; /* File descriptor for file being modified. */ | |
49 | static int mmap_failed; /* Boolean flag. */ | |
50 | static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */ | |
51 | static char gpfx; /* prefix for global symbol name (sometimes '_') */ | |
52 | static struct stat sb; /* Remember .st_size, etc. */ | |
53 | static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ | |
54 | static const char *altmcount; /* alternate mcount symbol name */ | |
55 | static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */ | |
56 | ||
57 | /* setjmp() return values */ | |
58 | enum { | |
59 | SJ_SETJMP = 0, /* hardwired first return */ | |
60 | SJ_FAIL, | |
61 | SJ_SUCCEED | |
62 | }; | |
63 | ||
64 | /* Per-file resource cleanup when multiple files. */ | |
65 | static void | |
66 | cleanup(void) | |
67 | { | |
68 | if (!mmap_failed) | |
69 | munmap(ehdr_curr, sb.st_size); | |
70 | else | |
71 | free(ehdr_curr); | |
72 | close(fd_map); | |
73 | } | |
74 | ||
75 | static void __attribute__((noreturn)) | |
76 | fail_file(void) | |
77 | { | |
78 | cleanup(); | |
79 | longjmp(jmpenv, SJ_FAIL); | |
80 | } | |
81 | ||
82 | static void __attribute__((noreturn)) | |
83 | succeed_file(void) | |
84 | { | |
85 | cleanup(); | |
86 | longjmp(jmpenv, SJ_SUCCEED); | |
87 | } | |
88 | ||
89 | /* ulseek, uread, ...: Check return value for errors. */ | |
90 | ||
91 | static off_t | |
92 | ulseek(int const fd, off_t const offset, int const whence) | |
93 | { | |
94 | off_t const w = lseek(fd, offset, whence); | |
95 | if (w == (off_t)-1) { | |
96 | perror("lseek"); | |
97 | fail_file(); | |
98 | } | |
99 | return w; | |
100 | } | |
101 | ||
102 | static size_t | |
103 | uread(int const fd, void *const buf, size_t const count) | |
104 | { | |
105 | size_t const n = read(fd, buf, count); | |
106 | if (n != count) { | |
107 | perror("read"); | |
108 | fail_file(); | |
109 | } | |
110 | return n; | |
111 | } | |
112 | ||
113 | static size_t | |
114 | uwrite(int const fd, void const *const buf, size_t const count) | |
115 | { | |
116 | size_t const n = write(fd, buf, count); | |
117 | if (n != count) { | |
118 | perror("write"); | |
119 | fail_file(); | |
120 | } | |
121 | return n; | |
122 | } | |
123 | ||
124 | static void * | |
125 | umalloc(size_t size) | |
126 | { | |
127 | void *const addr = malloc(size); | |
128 | if (addr == 0) { | |
129 | fprintf(stderr, "malloc failed: %zu bytes\n", size); | |
130 | fail_file(); | |
131 | } | |
132 | return addr; | |
133 | } | |
134 | ||
135 | static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; | |
136 | static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; | |
137 | static unsigned char *ideal_nop; | |
138 | ||
139 | static char rel_type_nop; | |
140 | ||
141 | static int (*make_nop)(void *map, size_t const offset); | |
142 | ||
143 | static int make_nop_x86(void *map, size_t const offset) | |
144 | { | |
145 | uint32_t *ptr; | |
146 | unsigned char *op; | |
147 | ||
148 | /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ | |
149 | ptr = map + offset; | |
150 | if (*ptr != 0) | |
151 | return -1; | |
152 | ||
153 | op = map + offset - 1; | |
154 | if (*op != 0xe8) | |
155 | return -1; | |
156 | ||
157 | /* convert to nop */ | |
158 | ulseek(fd_map, offset - 1, SEEK_SET); | |
159 | uwrite(fd_map, ideal_nop, 5); | |
160 | return 0; | |
161 | } | |
162 | ||
163 | /* | |
164 | * Get the whole file as a programming convenience in order to avoid | |
165 | * malloc+lseek+read+free of many pieces. If successful, then mmap | |
166 | * avoids copying unused pieces; else just read the whole file. | |
167 | * Open for both read and write; new info will be appended to the file. | |
168 | * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr | |
169 | * do not propagate to the file until an explicit overwrite at the last. | |
170 | * This preserves most aspects of consistency (all except .st_size) | |
171 | * for simultaneous readers of the file while we are appending to it. | |
172 | * However, multiple writers still are bad. We choose not to use | |
173 | * locking because it is expensive and the use case of kernel build | |
174 | * makes multiple writers unlikely. | |
175 | */ | |
176 | static void *mmap_file(char const *fname) | |
177 | { | |
178 | void *addr; | |
179 | ||
180 | fd_map = open(fname, O_RDWR); | |
181 | if (fd_map < 0 || fstat(fd_map, &sb) < 0) { | |
182 | perror(fname); | |
183 | fail_file(); | |
184 | } | |
185 | if (!S_ISREG(sb.st_mode)) { | |
186 | fprintf(stderr, "not a regular file: %s\n", fname); | |
187 | fail_file(); | |
188 | } | |
189 | addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, | |
190 | fd_map, 0); | |
191 | mmap_failed = 0; | |
192 | if (addr == MAP_FAILED) { | |
193 | mmap_failed = 1; | |
194 | addr = umalloc(sb.st_size); | |
195 | uread(fd_map, addr, sb.st_size); | |
196 | } | |
197 | return addr; | |
198 | } | |
199 | ||
200 | /* w8rev, w8nat, ...: Handle endianness. */ | |
201 | ||
202 | static uint64_t w8rev(uint64_t const x) | |
203 | { | |
204 | return ((0xff & (x >> (0 * 8))) << (7 * 8)) | |
205 | | ((0xff & (x >> (1 * 8))) << (6 * 8)) | |
206 | | ((0xff & (x >> (2 * 8))) << (5 * 8)) | |
207 | | ((0xff & (x >> (3 * 8))) << (4 * 8)) | |
208 | | ((0xff & (x >> (4 * 8))) << (3 * 8)) | |
209 | | ((0xff & (x >> (5 * 8))) << (2 * 8)) | |
210 | | ((0xff & (x >> (6 * 8))) << (1 * 8)) | |
211 | | ((0xff & (x >> (7 * 8))) << (0 * 8)); | |
212 | } | |
213 | ||
214 | static uint32_t w4rev(uint32_t const x) | |
215 | { | |
216 | return ((0xff & (x >> (0 * 8))) << (3 * 8)) | |
217 | | ((0xff & (x >> (1 * 8))) << (2 * 8)) | |
218 | | ((0xff & (x >> (2 * 8))) << (1 * 8)) | |
219 | | ((0xff & (x >> (3 * 8))) << (0 * 8)); | |
220 | } | |
221 | ||
222 | static uint32_t w2rev(uint16_t const x) | |
223 | { | |
224 | return ((0xff & (x >> (0 * 8))) << (1 * 8)) | |
225 | | ((0xff & (x >> (1 * 8))) << (0 * 8)); | |
226 | } | |
227 | ||
228 | static uint64_t w8nat(uint64_t const x) | |
229 | { | |
230 | return x; | |
231 | } | |
232 | ||
233 | static uint32_t w4nat(uint32_t const x) | |
234 | { | |
235 | return x; | |
236 | } | |
237 | ||
238 | static uint32_t w2nat(uint16_t const x) | |
239 | { | |
240 | return x; | |
241 | } | |
242 | ||
243 | static uint64_t (*w8)(uint64_t); | |
244 | static uint32_t (*w)(uint32_t); | |
245 | static uint32_t (*w2)(uint16_t); | |
246 | ||
247 | /* Names of the sections that could contain calls to mcount. */ | |
248 | static int | |
249 | is_mcounted_section_name(char const *const txtname) | |
250 | { | |
251 | return strcmp(".text", txtname) == 0 || | |
252 | strcmp(".ref.text", txtname) == 0 || | |
253 | strcmp(".sched.text", txtname) == 0 || | |
254 | strcmp(".spinlock.text", txtname) == 0 || | |
255 | strcmp(".irqentry.text", txtname) == 0 || | |
256 | strcmp(".kprobes.text", txtname) == 0 || | |
257 | strcmp(".text.unlikely", txtname) == 0; | |
258 | } | |
259 | ||
260 | /* 32 bit and 64 bit are very similar */ | |
261 | #include "recordmcount.h" | |
262 | #define RECORD_MCOUNT_64 | |
263 | #include "recordmcount.h" | |
264 | ||
265 | /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. | |
266 | * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf | |
267 | * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] | |
268 | * to imply the order of the members; the spec does not say so. | |
269 | * typedef unsigned char Elf64_Byte; | |
270 | * fails on MIPS64 because their <elf.h> already has it! | |
271 | */ | |
272 | ||
273 | typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ | |
274 | ||
275 | union mips_r_info { | |
276 | Elf64_Xword r_info; | |
277 | struct { | |
278 | Elf64_Word r_sym; /* Symbol index. */ | |
279 | myElf64_Byte r_ssym; /* Special symbol. */ | |
280 | myElf64_Byte r_type3; /* Third relocation. */ | |
281 | myElf64_Byte r_type2; /* Second relocation. */ | |
282 | myElf64_Byte r_type; /* First relocation. */ | |
283 | } r_mips; | |
284 | }; | |
285 | ||
286 | static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) | |
287 | { | |
288 | return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); | |
289 | } | |
290 | ||
291 | static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) | |
292 | { | |
293 | rp->r_info = ((union mips_r_info){ | |
294 | .r_mips = { .r_sym = w(sym), .r_type = type } | |
295 | }).r_info; | |
296 | } | |
297 | ||
298 | static void | |
299 | do_file(char const *const fname) | |
300 | { | |
301 | Elf32_Ehdr *const ehdr = mmap_file(fname); | |
302 | unsigned int reltype = 0; | |
303 | ||
304 | ehdr_curr = ehdr; | |
305 | w = w4nat; | |
306 | w2 = w2nat; | |
307 | w8 = w8nat; | |
308 | switch (ehdr->e_ident[EI_DATA]) { | |
309 | static unsigned int const endian = 1; | |
310 | default: | |
311 | fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", | |
312 | ehdr->e_ident[EI_DATA], fname); | |
313 | fail_file(); | |
314 | break; | |
315 | case ELFDATA2LSB: | |
316 | if (*(unsigned char const *)&endian != 1) { | |
317 | /* main() is big endian, file.o is little endian. */ | |
318 | w = w4rev; | |
319 | w2 = w2rev; | |
320 | w8 = w8rev; | |
321 | } | |
322 | break; | |
323 | case ELFDATA2MSB: | |
324 | if (*(unsigned char const *)&endian != 0) { | |
325 | /* main() is little endian, file.o is big endian. */ | |
326 | w = w4rev; | |
327 | w2 = w2rev; | |
328 | w8 = w8rev; | |
329 | } | |
330 | break; | |
331 | } /* end switch */ | |
332 | if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 | |
333 | || w2(ehdr->e_type) != ET_REL | |
334 | || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { | |
335 | fprintf(stderr, "unrecognized ET_REL file %s\n", fname); | |
336 | fail_file(); | |
337 | } | |
338 | ||
339 | gpfx = 0; | |
340 | switch (w2(ehdr->e_machine)) { | |
341 | default: | |
342 | fprintf(stderr, "unrecognized e_machine %d %s\n", | |
343 | w2(ehdr->e_machine), fname); | |
344 | fail_file(); | |
345 | break; | |
346 | case EM_386: | |
347 | reltype = R_386_32; | |
348 | make_nop = make_nop_x86; | |
349 | ideal_nop = ideal_nop5_x86_32; | |
350 | mcount_adjust_32 = -1; | |
351 | break; | |
352 | case EM_ARM: reltype = R_ARM_ABS32; | |
353 | altmcount = "__gnu_mcount_nc"; | |
354 | break; | |
355 | case EM_AARCH64: | |
356 | reltype = R_AARCH64_ABS64; gpfx = '_'; break; | |
357 | case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; | |
358 | case EM_METAG: reltype = R_METAG_ADDR32; | |
359 | altmcount = "_mcount_wrapper"; | |
360 | rel_type_nop = R_METAG_NONE; | |
361 | /* We happen to have the same requirement as MIPS */ | |
362 | is_fake_mcount32 = MIPS32_is_fake_mcount; | |
363 | break; | |
364 | case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; | |
365 | case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; | |
366 | case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; | |
367 | case EM_S390: /* reltype: e_class */ gpfx = '_'; break; | |
368 | case EM_SH: reltype = R_SH_DIR32; break; | |
369 | case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; | |
370 | case EM_X86_64: | |
371 | make_nop = make_nop_x86; | |
372 | ideal_nop = ideal_nop5_x86_64; | |
373 | reltype = R_X86_64_64; | |
374 | mcount_adjust_64 = -1; | |
375 | break; | |
376 | } /* end switch */ | |
377 | ||
378 | switch (ehdr->e_ident[EI_CLASS]) { | |
379 | default: | |
380 | fprintf(stderr, "unrecognized ELF class %d %s\n", | |
381 | ehdr->e_ident[EI_CLASS], fname); | |
382 | fail_file(); | |
383 | break; | |
384 | case ELFCLASS32: | |
385 | if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) | |
386 | || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { | |
387 | fprintf(stderr, | |
388 | "unrecognized ET_REL file: %s\n", fname); | |
389 | fail_file(); | |
390 | } | |
391 | if (w2(ehdr->e_machine) == EM_MIPS) { | |
392 | reltype = R_MIPS_32; | |
393 | is_fake_mcount32 = MIPS32_is_fake_mcount; | |
394 | } | |
395 | do32(ehdr, fname, reltype); | |
396 | break; | |
397 | case ELFCLASS64: { | |
398 | Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; | |
399 | if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) | |
400 | || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { | |
401 | fprintf(stderr, | |
402 | "unrecognized ET_REL file: %s\n", fname); | |
403 | fail_file(); | |
404 | } | |
405 | if (w2(ghdr->e_machine) == EM_S390) { | |
406 | reltype = R_390_64; | |
407 | mcount_adjust_64 = -8; | |
408 | } | |
409 | if (w2(ghdr->e_machine) == EM_MIPS) { | |
410 | reltype = R_MIPS_64; | |
411 | Elf64_r_sym = MIPS64_r_sym; | |
412 | Elf64_r_info = MIPS64_r_info; | |
413 | is_fake_mcount64 = MIPS64_is_fake_mcount; | |
414 | } | |
415 | do64(ghdr, fname, reltype); | |
416 | break; | |
417 | } | |
418 | } /* end switch */ | |
419 | ||
420 | cleanup(); | |
421 | } | |
422 | ||
423 | int | |
424 | main(int argc, char *argv[]) | |
425 | { | |
426 | const char ftrace[] = "/ftrace.o"; | |
427 | int ftrace_size = sizeof(ftrace) - 1; | |
428 | int n_error = 0; /* gcc-4.3.0 false positive complaint */ | |
429 | int c; | |
430 | int i; | |
431 | ||
432 | while ((c = getopt(argc, argv, "w")) >= 0) { | |
433 | switch (c) { | |
434 | case 'w': | |
435 | warn_on_notrace_sect = 1; | |
436 | break; | |
437 | default: | |
438 | fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); | |
439 | return 0; | |
440 | } | |
441 | } | |
442 | ||
443 | if ((argc - optind) < 1) { | |
444 | fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); | |
445 | return 0; | |
446 | } | |
447 | ||
448 | /* Process each file in turn, allowing deep failure. */ | |
449 | for (i = optind; i < argc; i++) { | |
450 | char *file = argv[i]; | |
451 | int const sjval = setjmp(jmpenv); | |
452 | int len; | |
453 | ||
454 | /* | |
455 | * The file kernel/trace/ftrace.o references the mcount | |
456 | * function but does not call it. Since ftrace.o should | |
457 | * not be traced anyway, we just skip it. | |
458 | */ | |
459 | len = strlen(file); | |
460 | if (len >= ftrace_size && | |
461 | strcmp(file + (len - ftrace_size), ftrace) == 0) | |
462 | continue; | |
463 | ||
464 | switch (sjval) { | |
465 | default: | |
466 | fprintf(stderr, "internal error: %s\n", file); | |
467 | exit(1); | |
468 | break; | |
469 | case SJ_SETJMP: /* normal sequence */ | |
470 | /* Avoid problems if early cleanup() */ | |
471 | fd_map = -1; | |
472 | ehdr_curr = NULL; | |
473 | mmap_failed = 1; | |
474 | do_file(file); | |
475 | break; | |
476 | case SJ_FAIL: /* error in do_file or below */ | |
477 | ++n_error; | |
478 | break; | |
479 | case SJ_SUCCEED: /* premature success */ | |
480 | /* do nothing */ | |
481 | break; | |
482 | } /* end switch */ | |
483 | } | |
484 | return !!n_error; | |
485 | } |