Commit | Line | Data |
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81d3858d JR |
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 <elf.h> | |
28 | #include <fcntl.h> | |
29 | #include <setjmp.h> | |
30 | #include <stdio.h> | |
31 | #include <stdlib.h> | |
32 | #include <string.h> | |
33 | #include <unistd.h> | |
34 | ||
35 | static int fd_map; /* File descriptor for file being modified. */ | |
36 | static int mmap_failed; /* Boolean flag. */ | |
37 | static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */ | |
38 | static char gpfx; /* prefix for global symbol name (sometimes '_') */ | |
39 | static struct stat sb; /* Remember .st_size, etc. */ | |
40 | static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ | |
ed60453f | 41 | static const char *altmcount; /* alternate mcount symbol name */ |
81d3858d JR |
42 | |
43 | /* setjmp() return values */ | |
44 | enum { | |
45 | SJ_SETJMP = 0, /* hardwired first return */ | |
46 | SJ_FAIL, | |
47 | SJ_SUCCEED | |
48 | }; | |
49 | ||
50 | /* Per-file resource cleanup when multiple files. */ | |
51 | static void | |
52 | cleanup(void) | |
53 | { | |
54 | if (!mmap_failed) | |
55 | munmap(ehdr_curr, sb.st_size); | |
56 | else | |
57 | free(ehdr_curr); | |
58 | close(fd_map); | |
59 | } | |
60 | ||
61 | static void __attribute__((noreturn)) | |
62 | fail_file(void) | |
63 | { | |
64 | cleanup(); | |
65 | longjmp(jmpenv, SJ_FAIL); | |
66 | } | |
67 | ||
68 | static void __attribute__((noreturn)) | |
69 | succeed_file(void) | |
70 | { | |
71 | cleanup(); | |
72 | longjmp(jmpenv, SJ_SUCCEED); | |
73 | } | |
74 | ||
75 | /* ulseek, uread, ...: Check return value for errors. */ | |
76 | ||
77 | static off_t | |
78 | ulseek(int const fd, off_t const offset, int const whence) | |
79 | { | |
80 | off_t const w = lseek(fd, offset, whence); | |
dd5477ff | 81 | if (w == (off_t)-1) { |
81d3858d JR |
82 | perror("lseek"); |
83 | fail_file(); | |
84 | } | |
85 | return w; | |
86 | } | |
87 | ||
88 | static size_t | |
89 | uread(int const fd, void *const buf, size_t const count) | |
90 | { | |
91 | size_t const n = read(fd, buf, count); | |
92 | if (n != count) { | |
93 | perror("read"); | |
94 | fail_file(); | |
95 | } | |
96 | return n; | |
97 | } | |
98 | ||
99 | static size_t | |
100 | uwrite(int const fd, void const *const buf, size_t const count) | |
101 | { | |
102 | size_t const n = write(fd, buf, count); | |
103 | if (n != count) { | |
104 | perror("write"); | |
105 | fail_file(); | |
106 | } | |
107 | return n; | |
108 | } | |
109 | ||
110 | static void * | |
111 | umalloc(size_t size) | |
112 | { | |
113 | void *const addr = malloc(size); | |
dd5477ff | 114 | if (addr == 0) { |
81d3858d JR |
115 | fprintf(stderr, "malloc failed: %zu bytes\n", size); |
116 | fail_file(); | |
117 | } | |
118 | return addr; | |
119 | } | |
120 | ||
ffd618fa SR |
121 | static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; |
122 | static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; | |
123 | static unsigned char *ideal_nop; | |
124 | ||
125 | static char rel_type_nop; | |
126 | ||
127 | static int (*make_nop)(void *map, size_t const offset); | |
128 | ||
129 | static int make_nop_x86(void *map, size_t const offset) | |
130 | { | |
131 | uint32_t *ptr; | |
132 | unsigned char *op; | |
133 | ||
134 | /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ | |
135 | ptr = map + offset; | |
136 | if (*ptr != 0) | |
137 | return -1; | |
138 | ||
139 | op = map + offset - 1; | |
140 | if (*op != 0xe8) | |
141 | return -1; | |
142 | ||
143 | /* convert to nop */ | |
144 | ulseek(fd_map, offset - 1, SEEK_SET); | |
145 | uwrite(fd_map, ideal_nop, 5); | |
146 | return 0; | |
147 | } | |
148 | ||
81d3858d JR |
149 | /* |
150 | * Get the whole file as a programming convenience in order to avoid | |
151 | * malloc+lseek+read+free of many pieces. If successful, then mmap | |
152 | * avoids copying unused pieces; else just read the whole file. | |
153 | * Open for both read and write; new info will be appended to the file. | |
154 | * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr | |
155 | * do not propagate to the file until an explicit overwrite at the last. | |
156 | * This preserves most aspects of consistency (all except .st_size) | |
157 | * for simultaneous readers of the file while we are appending to it. | |
158 | * However, multiple writers still are bad. We choose not to use | |
159 | * locking because it is expensive and the use case of kernel build | |
160 | * makes multiple writers unlikely. | |
161 | */ | |
162 | static void *mmap_file(char const *fname) | |
163 | { | |
164 | void *addr; | |
165 | ||
166 | fd_map = open(fname, O_RDWR); | |
dd5477ff | 167 | if (fd_map < 0 || fstat(fd_map, &sb) < 0) { |
81d3858d JR |
168 | perror(fname); |
169 | fail_file(); | |
170 | } | |
171 | if (!S_ISREG(sb.st_mode)) { | |
172 | fprintf(stderr, "not a regular file: %s\n", fname); | |
173 | fail_file(); | |
174 | } | |
175 | addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, | |
176 | fd_map, 0); | |
177 | mmap_failed = 0; | |
dd5477ff | 178 | if (addr == MAP_FAILED) { |
81d3858d JR |
179 | mmap_failed = 1; |
180 | addr = umalloc(sb.st_size); | |
181 | uread(fd_map, addr, sb.st_size); | |
182 | } | |
183 | return addr; | |
184 | } | |
185 | ||
186 | /* w8rev, w8nat, ...: Handle endianness. */ | |
187 | ||
188 | static uint64_t w8rev(uint64_t const x) | |
189 | { | |
190 | return ((0xff & (x >> (0 * 8))) << (7 * 8)) | |
191 | | ((0xff & (x >> (1 * 8))) << (6 * 8)) | |
192 | | ((0xff & (x >> (2 * 8))) << (5 * 8)) | |
193 | | ((0xff & (x >> (3 * 8))) << (4 * 8)) | |
194 | | ((0xff & (x >> (4 * 8))) << (3 * 8)) | |
195 | | ((0xff & (x >> (5 * 8))) << (2 * 8)) | |
196 | | ((0xff & (x >> (6 * 8))) << (1 * 8)) | |
197 | | ((0xff & (x >> (7 * 8))) << (0 * 8)); | |
198 | } | |
199 | ||
200 | static uint32_t w4rev(uint32_t const x) | |
201 | { | |
202 | return ((0xff & (x >> (0 * 8))) << (3 * 8)) | |
203 | | ((0xff & (x >> (1 * 8))) << (2 * 8)) | |
204 | | ((0xff & (x >> (2 * 8))) << (1 * 8)) | |
205 | | ((0xff & (x >> (3 * 8))) << (0 * 8)); | |
206 | } | |
207 | ||
208 | static uint32_t w2rev(uint16_t const x) | |
209 | { | |
210 | return ((0xff & (x >> (0 * 8))) << (1 * 8)) | |
211 | | ((0xff & (x >> (1 * 8))) << (0 * 8)); | |
212 | } | |
213 | ||
214 | static uint64_t w8nat(uint64_t const x) | |
215 | { | |
216 | return x; | |
217 | } | |
218 | ||
219 | static uint32_t w4nat(uint32_t const x) | |
220 | { | |
221 | return x; | |
222 | } | |
223 | ||
224 | static uint32_t w2nat(uint16_t const x) | |
225 | { | |
226 | return x; | |
227 | } | |
228 | ||
229 | static uint64_t (*w8)(uint64_t); | |
230 | static uint32_t (*w)(uint32_t); | |
231 | static uint32_t (*w2)(uint16_t); | |
232 | ||
233 | /* Names of the sections that could contain calls to mcount. */ | |
234 | static int | |
235 | is_mcounted_section_name(char const *const txtname) | |
236 | { | |
dd5477ff SR |
237 | return strcmp(".text", txtname) == 0 || |
238 | strcmp(".ref.text", txtname) == 0 || | |
239 | strcmp(".sched.text", txtname) == 0 || | |
240 | strcmp(".spinlock.text", txtname) == 0 || | |
241 | strcmp(".irqentry.text", txtname) == 0 || | |
9f087e76 | 242 | strcmp(".kprobes.text", txtname) == 0 || |
dd5477ff | 243 | strcmp(".text.unlikely", txtname) == 0; |
81d3858d JR |
244 | } |
245 | ||
c28d5077 SR |
246 | /* 32 bit and 64 bit are very similar */ |
247 | #include "recordmcount.h" | |
248 | #define RECORD_MCOUNT_64 | |
249 | #include "recordmcount.h" | |
81d3858d | 250 | |
a2d49358 JR |
251 | /* 64-bit EM_MIPS has weird ELF64_Rela.r_info. |
252 | * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf | |
253 | * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] | |
254 | * to imply the order of the members; the spec does not say so. | |
255 | * typedef unsigned char Elf64_Byte; | |
256 | * fails on MIPS64 because their <elf.h> already has it! | |
257 | */ | |
258 | ||
259 | typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ | |
260 | ||
261 | union mips_r_info { | |
262 | Elf64_Xword r_info; | |
263 | struct { | |
264 | Elf64_Word r_sym; /* Symbol index. */ | |
265 | myElf64_Byte r_ssym; /* Special symbol. */ | |
266 | myElf64_Byte r_type3; /* Third relocation. */ | |
267 | myElf64_Byte r_type2; /* Second relocation. */ | |
268 | myElf64_Byte r_type; /* First relocation. */ | |
269 | } r_mips; | |
270 | }; | |
271 | ||
272 | static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) | |
273 | { | |
274 | return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); | |
275 | } | |
276 | ||
277 | static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) | |
278 | { | |
279 | rp->r_info = ((union mips_r_info){ | |
280 | .r_mips = { .r_sym = w(sym), .r_type = type } | |
281 | }).r_info; | |
282 | } | |
283 | ||
81d3858d JR |
284 | static void |
285 | do_file(char const *const fname) | |
286 | { | |
287 | Elf32_Ehdr *const ehdr = mmap_file(fname); | |
288 | unsigned int reltype = 0; | |
289 | ||
290 | ehdr_curr = ehdr; | |
291 | w = w4nat; | |
292 | w2 = w2nat; | |
293 | w8 = w8nat; | |
294 | switch (ehdr->e_ident[EI_DATA]) { | |
295 | static unsigned int const endian = 1; | |
e90b0c8b | 296 | default: |
81d3858d JR |
297 | fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", |
298 | ehdr->e_ident[EI_DATA], fname); | |
299 | fail_file(); | |
e90b0c8b SR |
300 | break; |
301 | case ELFDATA2LSB: | |
dd5477ff | 302 | if (*(unsigned char const *)&endian != 1) { |
81d3858d JR |
303 | /* main() is big endian, file.o is little endian. */ |
304 | w = w4rev; | |
305 | w2 = w2rev; | |
306 | w8 = w8rev; | |
307 | } | |
e90b0c8b SR |
308 | break; |
309 | case ELFDATA2MSB: | |
dd5477ff | 310 | if (*(unsigned char const *)&endian != 0) { |
81d3858d JR |
311 | /* main() is little endian, file.o is big endian. */ |
312 | w = w4rev; | |
313 | w2 = w2rev; | |
314 | w8 = w8rev; | |
315 | } | |
e90b0c8b | 316 | break; |
81d3858d | 317 | } /* end switch */ |
dd5477ff SR |
318 | if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 |
319 | || w2(ehdr->e_type) != ET_REL | |
320 | || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { | |
81d3858d JR |
321 | fprintf(stderr, "unrecognized ET_REL file %s\n", fname); |
322 | fail_file(); | |
323 | } | |
324 | ||
325 | gpfx = 0; | |
326 | switch (w2(ehdr->e_machine)) { | |
e90b0c8b | 327 | default: |
81d3858d JR |
328 | fprintf(stderr, "unrecognized e_machine %d %s\n", |
329 | w2(ehdr->e_machine), fname); | |
330 | fail_file(); | |
e90b0c8b | 331 | break; |
ffd618fa SR |
332 | case EM_386: |
333 | reltype = R_386_32; | |
334 | make_nop = make_nop_x86; | |
335 | ideal_nop = ideal_nop5_x86_32; | |
336 | break; | |
ed60453f RV |
337 | case EM_ARM: reltype = R_ARM_ABS32; |
338 | altmcount = "__gnu_mcount_nc"; | |
339 | break; | |
81d3858d | 340 | case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; |
a2d49358 | 341 | case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; |
81d3858d JR |
342 | case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; |
343 | case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; | |
344 | case EM_S390: /* reltype: e_class */ gpfx = '_'; break; | |
345 | case EM_SH: reltype = R_SH_DIR32; break; | |
346 | case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; | |
ffd618fa SR |
347 | case EM_X86_64: |
348 | make_nop = make_nop_x86; | |
349 | ideal_nop = ideal_nop5_x86_64; | |
350 | reltype = R_X86_64_64; | |
351 | break; | |
81d3858d JR |
352 | } /* end switch */ |
353 | ||
354 | switch (ehdr->e_ident[EI_CLASS]) { | |
e90b0c8b | 355 | default: |
81d3858d JR |
356 | fprintf(stderr, "unrecognized ELF class %d %s\n", |
357 | ehdr->e_ident[EI_CLASS], fname); | |
358 | fail_file(); | |
e90b0c8b SR |
359 | break; |
360 | case ELFCLASS32: | |
dd5477ff SR |
361 | if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) |
362 | || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { | |
81d3858d JR |
363 | fprintf(stderr, |
364 | "unrecognized ET_REL file: %s\n", fname); | |
365 | fail_file(); | |
366 | } | |
dd5477ff | 367 | if (w2(ehdr->e_machine) == EM_S390) |
81d3858d | 368 | reltype = R_390_32; |
dd5477ff | 369 | if (w2(ehdr->e_machine) == EM_MIPS) { |
a2d49358 | 370 | reltype = R_MIPS_32; |
412910cd WZ |
371 | is_fake_mcount32 = MIPS32_is_fake_mcount; |
372 | } | |
81d3858d | 373 | do32(ehdr, fname, reltype); |
e90b0c8b | 374 | break; |
81d3858d JR |
375 | case ELFCLASS64: { |
376 | Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; | |
dd5477ff SR |
377 | if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) |
378 | || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { | |
81d3858d JR |
379 | fprintf(stderr, |
380 | "unrecognized ET_REL file: %s\n", fname); | |
381 | fail_file(); | |
382 | } | |
dd5477ff | 383 | if (w2(ghdr->e_machine) == EM_S390) |
81d3858d | 384 | reltype = R_390_64; |
dd5477ff | 385 | if (w2(ghdr->e_machine) == EM_MIPS) { |
a2d49358 JR |
386 | reltype = R_MIPS_64; |
387 | Elf64_r_sym = MIPS64_r_sym; | |
388 | Elf64_r_info = MIPS64_r_info; | |
412910cd | 389 | is_fake_mcount64 = MIPS64_is_fake_mcount; |
a2d49358 | 390 | } |
81d3858d | 391 | do64(ghdr, fname, reltype); |
e90b0c8b SR |
392 | break; |
393 | } | |
81d3858d JR |
394 | } /* end switch */ |
395 | ||
396 | cleanup(); | |
397 | } | |
398 | ||
399 | int | |
400 | main(int argc, char const *argv[]) | |
401 | { | |
cd3478f2 | 402 | const char ftrace[] = "/ftrace.o"; |
44475863 | 403 | int ftrace_size = sizeof(ftrace) - 1; |
81d3858d | 404 | int n_error = 0; /* gcc-4.3.0 false positive complaint */ |
44475863 SR |
405 | |
406 | if (argc <= 1) { | |
81d3858d | 407 | fprintf(stderr, "usage: recordmcount file.o...\n"); |
44475863 SR |
408 | return 0; |
409 | } | |
410 | ||
411 | /* Process each file in turn, allowing deep failure. */ | |
dd5477ff | 412 | for (--argc, ++argv; argc > 0; --argc, ++argv) { |
81d3858d | 413 | int const sjval = setjmp(jmpenv); |
44475863 SR |
414 | int len; |
415 | ||
416 | /* | |
417 | * The file kernel/trace/ftrace.o references the mcount | |
418 | * function but does not call it. Since ftrace.o should | |
419 | * not be traced anyway, we just skip it. | |
420 | */ | |
421 | len = strlen(argv[0]); | |
422 | if (len >= ftrace_size && | |
423 | strcmp(argv[0] + (len - ftrace_size), ftrace) == 0) | |
424 | continue; | |
425 | ||
81d3858d | 426 | switch (sjval) { |
e90b0c8b | 427 | default: |
81d3858d JR |
428 | fprintf(stderr, "internal error: %s\n", argv[0]); |
429 | exit(1); | |
e90b0c8b SR |
430 | break; |
431 | case SJ_SETJMP: /* normal sequence */ | |
81d3858d JR |
432 | /* Avoid problems if early cleanup() */ |
433 | fd_map = -1; | |
434 | ehdr_curr = NULL; | |
435 | mmap_failed = 1; | |
436 | do_file(argv[0]); | |
e90b0c8b SR |
437 | break; |
438 | case SJ_FAIL: /* error in do_file or below */ | |
81d3858d | 439 | ++n_error; |
e90b0c8b SR |
440 | break; |
441 | case SJ_SUCCEED: /* premature success */ | |
81d3858d | 442 | /* do nothing */ |
e90b0c8b | 443 | break; |
81d3858d JR |
444 | } /* end switch */ |
445 | } | |
446 | return !!n_error; | |
447 | } | |
448 | ||
449 |