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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 | static int fd_map; /* File descriptor for file being modified. */ |
37 | static int mmap_failed; /* Boolean flag. */ |
38 | static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */ |
39 | static char gpfx; /* prefix for global symbol name (sometimes '_') */ |
40 | static struct stat sb; /* Remember .st_size, etc. */ |
41 | static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ |
42 | static const char *altmcount; /* alternate mcount symbol name */ |
43 | static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */ |
44 | |
45 | /* setjmp() return values */ |
46 | enum { |
47 | SJ_SETJMP = 0, /* hardwired first return */ |
48 | SJ_FAIL, |
49 | SJ_SUCCEED |
50 | }; |
51 | |
52 | /* Per-file resource cleanup when multiple files. */ |
53 | static void |
54 | cleanup(void) |
55 | { |
56 | if (!mmap_failed) |
57 | munmap(ehdr_curr, sb.st_size); |
58 | else |
59 | free(ehdr_curr); |
60 | close(fd_map); |
61 | } |
62 | |
63 | static void __attribute__((noreturn)) |
64 | fail_file(void) |
65 | { |
66 | cleanup(); |
67 | longjmp(jmpenv, SJ_FAIL); |
68 | } |
69 | |
70 | static void __attribute__((noreturn)) |
71 | succeed_file(void) |
72 | { |
73 | cleanup(); |
74 | longjmp(jmpenv, SJ_SUCCEED); |
75 | } |
76 | |
77 | /* ulseek, uread, ...: Check return value for errors. */ |
78 | |
79 | static off_t |
80 | ulseek(int const fd, off_t const offset, int const whence) |
81 | { |
82 | off_t const w = lseek(fd, offset, whence); |
83 | if (w == (off_t)-1) { |
84 | perror("lseek"); |
85 | fail_file(); |
86 | } |
87 | return w; |
88 | } |
89 | |
90 | static size_t |
91 | uread(int const fd, void *const buf, size_t const count) |
92 | { |
93 | size_t const n = read(fd, buf, count); |
94 | if (n != count) { |
95 | perror("read"); |
96 | fail_file(); |
97 | } |
98 | return n; |
99 | } |
100 | |
101 | static size_t |
102 | uwrite(int const fd, void const *const buf, size_t const count) |
103 | { |
104 | size_t const n = write(fd, buf, count); |
105 | if (n != count) { |
106 | perror("write"); |
107 | fail_file(); |
108 | } |
109 | return n; |
110 | } |
111 | |
112 | static void * |
113 | umalloc(size_t size) |
114 | { |
115 | void *const addr = malloc(size); |
116 | if (addr == 0) { |
117 | fprintf(stderr, "malloc failed: %zu bytes\n", size); |
118 | fail_file(); |
119 | } |
120 | return addr; |
121 | } |
122 | |
123 | static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; |
124 | static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; |
125 | static unsigned char *ideal_nop; |
126 | |
127 | static char rel_type_nop; |
128 | |
129 | static int (*make_nop)(void *map, size_t const offset); |
130 | |
131 | static int make_nop_x86(void *map, size_t const offset) |
132 | { |
133 | uint32_t *ptr; |
134 | unsigned char *op; |
135 | |
136 | /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ |
137 | ptr = map + offset; |
138 | if (*ptr != 0) |
139 | return -1; |
140 | |
141 | op = map + offset - 1; |
142 | if (*op != 0xe8) |
143 | return -1; |
144 | |
145 | /* convert to nop */ |
146 | ulseek(fd_map, offset - 1, SEEK_SET); |
147 | uwrite(fd_map, ideal_nop, 5); |
148 | return 0; |
149 | } |
150 | |
151 | /* |
152 | * Get the whole file as a programming convenience in order to avoid |
153 | * malloc+lseek+read+free of many pieces. If successful, then mmap |
154 | * avoids copying unused pieces; else just read the whole file. |
155 | * Open for both read and write; new info will be appended to the file. |
156 | * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr |
157 | * do not propagate to the file until an explicit overwrite at the last. |
158 | * This preserves most aspects of consistency (all except .st_size) |
159 | * for simultaneous readers of the file while we are appending to it. |
160 | * However, multiple writers still are bad. We choose not to use |
161 | * locking because it is expensive and the use case of kernel build |
162 | * makes multiple writers unlikely. |
163 | */ |
164 | static void *mmap_file(char const *fname) |
165 | { |
166 | void *addr; |
167 | |
168 | fd_map = open(fname, O_RDWR); |
169 | if (fd_map < 0 || fstat(fd_map, &sb) < 0) { |
170 | perror(fname); |
171 | fail_file(); |
172 | } |
173 | if (!S_ISREG(sb.st_mode)) { |
174 | fprintf(stderr, "not a regular file: %s\n", fname); |
175 | fail_file(); |
176 | } |
177 | addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, |
178 | fd_map, 0); |
179 | mmap_failed = 0; |
180 | if (addr == MAP_FAILED) { |
181 | mmap_failed = 1; |
182 | addr = umalloc(sb.st_size); |
183 | uread(fd_map, addr, sb.st_size); |
184 | } |
185 | return addr; |
186 | } |
187 | |
188 | /* w8rev, w8nat, ...: Handle endianness. */ |
189 | |
190 | static uint64_t w8rev(uint64_t const x) |
191 | { |
192 | return ((0xff & (x >> (0 * 8))) << (7 * 8)) |
193 | | ((0xff & (x >> (1 * 8))) << (6 * 8)) |
194 | | ((0xff & (x >> (2 * 8))) << (5 * 8)) |
195 | | ((0xff & (x >> (3 * 8))) << (4 * 8)) |
196 | | ((0xff & (x >> (4 * 8))) << (3 * 8)) |
197 | | ((0xff & (x >> (5 * 8))) << (2 * 8)) |
198 | | ((0xff & (x >> (6 * 8))) << (1 * 8)) |
199 | | ((0xff & (x >> (7 * 8))) << (0 * 8)); |
200 | } |
201 | |
202 | static uint32_t w4rev(uint32_t const x) |
203 | { |
204 | return ((0xff & (x >> (0 * 8))) << (3 * 8)) |
205 | | ((0xff & (x >> (1 * 8))) << (2 * 8)) |
206 | | ((0xff & (x >> (2 * 8))) << (1 * 8)) |
207 | | ((0xff & (x >> (3 * 8))) << (0 * 8)); |
208 | } |
209 | |
210 | static uint32_t w2rev(uint16_t const x) |
211 | { |
212 | return ((0xff & (x >> (0 * 8))) << (1 * 8)) |
213 | | ((0xff & (x >> (1 * 8))) << (0 * 8)); |
214 | } |
215 | |
216 | static uint64_t w8nat(uint64_t const x) |
217 | { |
218 | return x; |
219 | } |
220 | |
221 | static uint32_t w4nat(uint32_t const x) |
222 | { |
223 | return x; |
224 | } |
225 | |
226 | static uint32_t w2nat(uint16_t const x) |
227 | { |
228 | return x; |
229 | } |
230 | |
231 | static uint64_t (*w8)(uint64_t); |
232 | static uint32_t (*w)(uint32_t); |
233 | static uint32_t (*w2)(uint16_t); |
234 | |
235 | /* Names of the sections that could contain calls to mcount. */ |
236 | static int |
237 | is_mcounted_section_name(char const *const txtname) |
238 | { |
239 | return strcmp(".text", txtname) == 0 || |
240 | strcmp(".ref.text", txtname) == 0 || |
241 | strcmp(".sched.text", txtname) == 0 || |
242 | strcmp(".spinlock.text", txtname) == 0 || |
243 | strcmp(".irqentry.text", txtname) == 0 || |
244 | strcmp(".kprobes.text", txtname) == 0 || |
245 | strcmp(".text.unlikely", txtname) == 0; |
246 | } |
247 | |
248 | /* 32 bit and 64 bit are very similar */ |
249 | #include "recordmcount.h" |
250 | #define RECORD_MCOUNT_64 |
251 | #include "recordmcount.h" |
252 | |
253 | /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. |
254 | * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf |
255 | * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] |
256 | * to imply the order of the members; the spec does not say so. |
257 | * typedef unsigned char Elf64_Byte; |
258 | * fails on MIPS64 because their <elf.h> already has it! |
259 | */ |
260 | |
261 | typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ |
262 | |
263 | union mips_r_info { |
264 | Elf64_Xword r_info; |
265 | struct { |
266 | Elf64_Word r_sym; /* Symbol index. */ |
267 | myElf64_Byte r_ssym; /* Special symbol. */ |
268 | myElf64_Byte r_type3; /* Third relocation. */ |
269 | myElf64_Byte r_type2; /* Second relocation. */ |
270 | myElf64_Byte r_type; /* First relocation. */ |
271 | } r_mips; |
272 | }; |
273 | |
274 | static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) |
275 | { |
276 | return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); |
277 | } |
278 | |
279 | static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) |
280 | { |
281 | rp->r_info = ((union mips_r_info){ |
282 | .r_mips = { .r_sym = w(sym), .r_type = type } |
283 | }).r_info; |
284 | } |
285 | |
286 | static void |
287 | do_file(char const *const fname) |
288 | { |
289 | Elf32_Ehdr *const ehdr = mmap_file(fname); |
290 | unsigned int reltype = 0; |
291 | |
292 | ehdr_curr = ehdr; |
293 | w = w4nat; |
294 | w2 = w2nat; |
295 | w8 = w8nat; |
296 | switch (ehdr->e_ident[EI_DATA]) { |
297 | static unsigned int const endian = 1; |
298 | default: |
299 | fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", |
300 | ehdr->e_ident[EI_DATA], fname); |
301 | fail_file(); |
302 | break; |
303 | case ELFDATA2LSB: |
304 | if (*(unsigned char const *)&endian != 1) { |
305 | /* main() is big endian, file.o is little endian. */ |
306 | w = w4rev; |
307 | w2 = w2rev; |
308 | w8 = w8rev; |
309 | } |
310 | break; |
311 | case ELFDATA2MSB: |
312 | if (*(unsigned char const *)&endian != 0) { |
313 | /* main() is little endian, file.o is big endian. */ |
314 | w = w4rev; |
315 | w2 = w2rev; |
316 | w8 = w8rev; |
317 | } |
318 | break; |
319 | } /* end switch */ |
320 | if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 |
321 | || w2(ehdr->e_type) != ET_REL |
322 | || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { |
323 | fprintf(stderr, "unrecognized ET_REL file %s\n", fname); |
324 | fail_file(); |
325 | } |
326 | |
327 | gpfx = 0; |
328 | switch (w2(ehdr->e_machine)) { |
329 | default: |
330 | fprintf(stderr, "unrecognized e_machine %d %s\n", |
331 | w2(ehdr->e_machine), fname); |
332 | fail_file(); |
333 | break; |
334 | case EM_386: |
335 | reltype = R_386_32; |
336 | make_nop = make_nop_x86; |
337 | ideal_nop = ideal_nop5_x86_32; |
338 | mcount_adjust_32 = -1; |
339 | break; |
340 | case EM_ARM: reltype = R_ARM_ABS32; |
341 | altmcount = "__gnu_mcount_nc"; |
342 | break; |
343 | case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; |
344 | case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; |
345 | case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; |
346 | case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; |
347 | case EM_S390: /* reltype: e_class */ gpfx = '_'; break; |
348 | case EM_SH: reltype = R_SH_DIR32; break; |
349 | case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; |
350 | case EM_X86_64: |
351 | make_nop = make_nop_x86; |
352 | ideal_nop = ideal_nop5_x86_64; |
353 | reltype = R_X86_64_64; |
354 | mcount_adjust_64 = -1; |
355 | break; |
356 | } /* end switch */ |
357 | |
358 | switch (ehdr->e_ident[EI_CLASS]) { |
359 | default: |
360 | fprintf(stderr, "unrecognized ELF class %d %s\n", |
361 | ehdr->e_ident[EI_CLASS], fname); |
362 | fail_file(); |
363 | break; |
364 | case ELFCLASS32: |
365 | if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) |
366 | || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { |
367 | fprintf(stderr, |
368 | "unrecognized ET_REL file: %s\n", fname); |
369 | fail_file(); |
370 | } |
371 | if (w2(ehdr->e_machine) == EM_S390) { |
372 | reltype = R_390_32; |
373 | mcount_adjust_32 = -4; |
374 | } |
375 | if (w2(ehdr->e_machine) == EM_MIPS) { |
376 | reltype = R_MIPS_32; |
377 | is_fake_mcount32 = MIPS32_is_fake_mcount; |
378 | } |
379 | do32(ehdr, fname, reltype); |
380 | break; |
381 | case ELFCLASS64: { |
382 | Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; |
383 | if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) |
384 | || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { |
385 | fprintf(stderr, |
386 | "unrecognized ET_REL file: %s\n", fname); |
387 | fail_file(); |
388 | } |
389 | if (w2(ghdr->e_machine) == EM_S390) { |
390 | reltype = R_390_64; |
391 | mcount_adjust_64 = -8; |
392 | } |
393 | if (w2(ghdr->e_machine) == EM_MIPS) { |
394 | reltype = R_MIPS_64; |
395 | Elf64_r_sym = MIPS64_r_sym; |
396 | Elf64_r_info = MIPS64_r_info; |
397 | is_fake_mcount64 = MIPS64_is_fake_mcount; |
398 | } |
399 | do64(ghdr, fname, reltype); |
400 | break; |
401 | } |
402 | } /* end switch */ |
403 | |
404 | cleanup(); |
405 | } |
406 | |
407 | int |
408 | main(int argc, char *argv[]) |
409 | { |
410 | const char ftrace[] = "/ftrace.o"; |
411 | int ftrace_size = sizeof(ftrace) - 1; |
412 | int n_error = 0; /* gcc-4.3.0 false positive complaint */ |
413 | int c; |
414 | int i; |
415 | |
416 | while ((c = getopt(argc, argv, "w")) >= 0) { |
417 | switch (c) { |
418 | case 'w': |
419 | warn_on_notrace_sect = 1; |
420 | break; |
421 | default: |
422 | fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); |
423 | return 0; |
424 | } |
425 | } |
426 | |
427 | if ((argc - optind) < 1) { |
428 | fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); |
429 | return 0; |
430 | } |
431 | |
432 | /* Process each file in turn, allowing deep failure. */ |
433 | for (i = optind; i < argc; i++) { |
434 | char *file = argv[i]; |
435 | int const sjval = setjmp(jmpenv); |
436 | int len; |
437 | |
438 | /* |
439 | * The file kernel/trace/ftrace.o references the mcount |
440 | * function but does not call it. Since ftrace.o should |
441 | * not be traced anyway, we just skip it. |
442 | */ |
443 | len = strlen(file); |
444 | if (len >= ftrace_size && |
445 | strcmp(file + (len - ftrace_size), ftrace) == 0) |
446 | continue; |
447 | |
448 | switch (sjval) { |
449 | default: |
450 | fprintf(stderr, "internal error: %s\n", file); |
451 | exit(1); |
452 | break; |
453 | case SJ_SETJMP: /* normal sequence */ |
454 | /* Avoid problems if early cleanup() */ |
455 | fd_map = -1; |
456 | ehdr_curr = NULL; |
457 | mmap_failed = 1; |
458 | do_file(file); |
459 | break; |
460 | case SJ_FAIL: /* error in do_file or below */ |
461 | ++n_error; |
462 | break; |
463 | case SJ_SUCCEED: /* premature success */ |
464 | /* do nothing */ |
465 | break; |
466 | } /* end switch */ |
467 | } |
468 | return !!n_error; |
469 | } |
470 | |
471 | |
472 |
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