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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 */ | |
41 | ||
42 | /* setjmp() return values */ | |
43 | enum { | |
44 | SJ_SETJMP = 0, /* hardwired first return */ | |
45 | SJ_FAIL, | |
46 | SJ_SUCCEED | |
47 | }; | |
48 | ||
49 | /* Per-file resource cleanup when multiple files. */ | |
50 | static void | |
51 | cleanup(void) | |
52 | { | |
53 | if (!mmap_failed) | |
54 | munmap(ehdr_curr, sb.st_size); | |
55 | else | |
56 | free(ehdr_curr); | |
57 | close(fd_map); | |
58 | } | |
59 | ||
60 | static void __attribute__((noreturn)) | |
61 | fail_file(void) | |
62 | { | |
63 | cleanup(); | |
64 | longjmp(jmpenv, SJ_FAIL); | |
65 | } | |
66 | ||
67 | static void __attribute__((noreturn)) | |
68 | succeed_file(void) | |
69 | { | |
70 | cleanup(); | |
71 | longjmp(jmpenv, SJ_SUCCEED); | |
72 | } | |
73 | ||
74 | /* ulseek, uread, ...: Check return value for errors. */ | |
75 | ||
76 | static off_t | |
77 | ulseek(int const fd, off_t const offset, int const whence) | |
78 | { | |
79 | off_t const w = lseek(fd, offset, whence); | |
80 | if ((off_t)-1 == w) { | |
81 | perror("lseek"); | |
82 | fail_file(); | |
83 | } | |
84 | return w; | |
85 | } | |
86 | ||
87 | static size_t | |
88 | uread(int const fd, void *const buf, size_t const count) | |
89 | { | |
90 | size_t const n = read(fd, buf, count); | |
91 | if (n != count) { | |
92 | perror("read"); | |
93 | fail_file(); | |
94 | } | |
95 | return n; | |
96 | } | |
97 | ||
98 | static size_t | |
99 | uwrite(int const fd, void const *const buf, size_t const count) | |
100 | { | |
101 | size_t const n = write(fd, buf, count); | |
102 | if (n != count) { | |
103 | perror("write"); | |
104 | fail_file(); | |
105 | } | |
106 | return n; | |
107 | } | |
108 | ||
109 | static void * | |
110 | umalloc(size_t size) | |
111 | { | |
112 | void *const addr = malloc(size); | |
113 | if (0 == addr) { | |
114 | fprintf(stderr, "malloc failed: %zu bytes\n", size); | |
115 | fail_file(); | |
116 | } | |
117 | return addr; | |
118 | } | |
119 | ||
120 | /* | |
121 | * Get the whole file as a programming convenience in order to avoid | |
122 | * malloc+lseek+read+free of many pieces. If successful, then mmap | |
123 | * avoids copying unused pieces; else just read the whole file. | |
124 | * Open for both read and write; new info will be appended to the file. | |
125 | * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr | |
126 | * do not propagate to the file until an explicit overwrite at the last. | |
127 | * This preserves most aspects of consistency (all except .st_size) | |
128 | * for simultaneous readers of the file while we are appending to it. | |
129 | * However, multiple writers still are bad. We choose not to use | |
130 | * locking because it is expensive and the use case of kernel build | |
131 | * makes multiple writers unlikely. | |
132 | */ | |
133 | static void *mmap_file(char const *fname) | |
134 | { | |
135 | void *addr; | |
136 | ||
137 | fd_map = open(fname, O_RDWR); | |
138 | if (0 > fd_map || 0 > fstat(fd_map, &sb)) { | |
139 | perror(fname); | |
140 | fail_file(); | |
141 | } | |
142 | if (!S_ISREG(sb.st_mode)) { | |
143 | fprintf(stderr, "not a regular file: %s\n", fname); | |
144 | fail_file(); | |
145 | } | |
146 | addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, | |
147 | fd_map, 0); | |
148 | mmap_failed = 0; | |
149 | if (MAP_FAILED == addr) { | |
150 | mmap_failed = 1; | |
151 | addr = umalloc(sb.st_size); | |
152 | uread(fd_map, addr, sb.st_size); | |
153 | } | |
154 | return addr; | |
155 | } | |
156 | ||
157 | /* w8rev, w8nat, ...: Handle endianness. */ | |
158 | ||
159 | static uint64_t w8rev(uint64_t const x) | |
160 | { | |
161 | return ((0xff & (x >> (0 * 8))) << (7 * 8)) | |
162 | | ((0xff & (x >> (1 * 8))) << (6 * 8)) | |
163 | | ((0xff & (x >> (2 * 8))) << (5 * 8)) | |
164 | | ((0xff & (x >> (3 * 8))) << (4 * 8)) | |
165 | | ((0xff & (x >> (4 * 8))) << (3 * 8)) | |
166 | | ((0xff & (x >> (5 * 8))) << (2 * 8)) | |
167 | | ((0xff & (x >> (6 * 8))) << (1 * 8)) | |
168 | | ((0xff & (x >> (7 * 8))) << (0 * 8)); | |
169 | } | |
170 | ||
171 | static uint32_t w4rev(uint32_t const x) | |
172 | { | |
173 | return ((0xff & (x >> (0 * 8))) << (3 * 8)) | |
174 | | ((0xff & (x >> (1 * 8))) << (2 * 8)) | |
175 | | ((0xff & (x >> (2 * 8))) << (1 * 8)) | |
176 | | ((0xff & (x >> (3 * 8))) << (0 * 8)); | |
177 | } | |
178 | ||
179 | static uint32_t w2rev(uint16_t const x) | |
180 | { | |
181 | return ((0xff & (x >> (0 * 8))) << (1 * 8)) | |
182 | | ((0xff & (x >> (1 * 8))) << (0 * 8)); | |
183 | } | |
184 | ||
185 | static uint64_t w8nat(uint64_t const x) | |
186 | { | |
187 | return x; | |
188 | } | |
189 | ||
190 | static uint32_t w4nat(uint32_t const x) | |
191 | { | |
192 | return x; | |
193 | } | |
194 | ||
195 | static uint32_t w2nat(uint16_t const x) | |
196 | { | |
197 | return x; | |
198 | } | |
199 | ||
200 | static uint64_t (*w8)(uint64_t); | |
201 | static uint32_t (*w)(uint32_t); | |
202 | static uint32_t (*w2)(uint16_t); | |
203 | ||
204 | /* Names of the sections that could contain calls to mcount. */ | |
205 | static int | |
206 | is_mcounted_section_name(char const *const txtname) | |
207 | { | |
208 | return 0 == strcmp(".text", txtname) || | |
209 | 0 == strcmp(".sched.text", txtname) || | |
210 | 0 == strcmp(".spinlock.text", txtname) || | |
211 | 0 == strcmp(".irqentry.text", txtname) || | |
212 | 0 == strcmp(".text.unlikely", txtname); | |
213 | } | |
214 | ||
c28d5077 SR |
215 | /* 32 bit and 64 bit are very similar */ |
216 | #include "recordmcount.h" | |
217 | #define RECORD_MCOUNT_64 | |
218 | #include "recordmcount.h" | |
81d3858d JR |
219 | |
220 | static void | |
221 | do_file(char const *const fname) | |
222 | { | |
223 | Elf32_Ehdr *const ehdr = mmap_file(fname); | |
224 | unsigned int reltype = 0; | |
225 | ||
226 | ehdr_curr = ehdr; | |
227 | w = w4nat; | |
228 | w2 = w2nat; | |
229 | w8 = w8nat; | |
230 | switch (ehdr->e_ident[EI_DATA]) { | |
231 | static unsigned int const endian = 1; | |
232 | default: { | |
233 | fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", | |
234 | ehdr->e_ident[EI_DATA], fname); | |
235 | fail_file(); | |
236 | } break; | |
237 | case ELFDATA2LSB: { | |
238 | if (1 != *(unsigned char const *)&endian) { | |
239 | /* main() is big endian, file.o is little endian. */ | |
240 | w = w4rev; | |
241 | w2 = w2rev; | |
242 | w8 = w8rev; | |
243 | } | |
244 | } break; | |
245 | case ELFDATA2MSB: { | |
246 | if (0 != *(unsigned char const *)&endian) { | |
247 | /* main() is little endian, file.o is big endian. */ | |
248 | w = w4rev; | |
249 | w2 = w2rev; | |
250 | w8 = w8rev; | |
251 | } | |
252 | } break; | |
253 | } /* end switch */ | |
254 | if (0 != memcmp(ELFMAG, ehdr->e_ident, SELFMAG) | |
255 | || ET_REL != w2(ehdr->e_type) | |
256 | || EV_CURRENT != ehdr->e_ident[EI_VERSION]) { | |
257 | fprintf(stderr, "unrecognized ET_REL file %s\n", fname); | |
258 | fail_file(); | |
259 | } | |
260 | ||
261 | gpfx = 0; | |
262 | switch (w2(ehdr->e_machine)) { | |
263 | default: { | |
264 | fprintf(stderr, "unrecognized e_machine %d %s\n", | |
265 | w2(ehdr->e_machine), fname); | |
266 | fail_file(); | |
267 | } break; | |
268 | case EM_386: reltype = R_386_32; break; | |
269 | case EM_ARM: reltype = R_ARM_ABS32; break; | |
270 | case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; | |
271 | case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; | |
272 | case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; | |
273 | case EM_S390: /* reltype: e_class */ gpfx = '_'; break; | |
274 | case EM_SH: reltype = R_SH_DIR32; break; | |
275 | case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; | |
276 | case EM_X86_64: reltype = R_X86_64_64; break; | |
277 | } /* end switch */ | |
278 | ||
279 | switch (ehdr->e_ident[EI_CLASS]) { | |
280 | default: { | |
281 | fprintf(stderr, "unrecognized ELF class %d %s\n", | |
282 | ehdr->e_ident[EI_CLASS], fname); | |
283 | fail_file(); | |
284 | } break; | |
285 | case ELFCLASS32: { | |
286 | if (sizeof(Elf32_Ehdr) != w2(ehdr->e_ehsize) | |
287 | || sizeof(Elf32_Shdr) != w2(ehdr->e_shentsize)) { | |
288 | fprintf(stderr, | |
289 | "unrecognized ET_REL file: %s\n", fname); | |
290 | fail_file(); | |
291 | } | |
292 | if (EM_S390 == w2(ehdr->e_machine)) | |
293 | reltype = R_390_32; | |
294 | do32(ehdr, fname, reltype); | |
295 | } break; | |
296 | case ELFCLASS64: { | |
297 | Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; | |
298 | if (sizeof(Elf64_Ehdr) != w2(ghdr->e_ehsize) | |
299 | || sizeof(Elf64_Shdr) != w2(ghdr->e_shentsize)) { | |
300 | fprintf(stderr, | |
301 | "unrecognized ET_REL file: %s\n", fname); | |
302 | fail_file(); | |
303 | } | |
304 | if (EM_S390 == w2(ghdr->e_machine)) | |
305 | reltype = R_390_64; | |
306 | do64(ghdr, fname, reltype); | |
307 | } break; | |
308 | } /* end switch */ | |
309 | ||
310 | cleanup(); | |
311 | } | |
312 | ||
313 | int | |
314 | main(int argc, char const *argv[]) | |
315 | { | |
44475863 SR |
316 | const char ftrace[] = "kernel/trace/ftrace.o"; |
317 | int ftrace_size = sizeof(ftrace) - 1; | |
81d3858d | 318 | int n_error = 0; /* gcc-4.3.0 false positive complaint */ |
44475863 SR |
319 | |
320 | if (argc <= 1) { | |
81d3858d | 321 | fprintf(stderr, "usage: recordmcount file.o...\n"); |
44475863 SR |
322 | return 0; |
323 | } | |
324 | ||
325 | /* Process each file in turn, allowing deep failure. */ | |
81d3858d JR |
326 | for (--argc, ++argv; 0 < argc; --argc, ++argv) { |
327 | int const sjval = setjmp(jmpenv); | |
44475863 SR |
328 | int len; |
329 | ||
330 | /* | |
331 | * The file kernel/trace/ftrace.o references the mcount | |
332 | * function but does not call it. Since ftrace.o should | |
333 | * not be traced anyway, we just skip it. | |
334 | */ | |
335 | len = strlen(argv[0]); | |
336 | if (len >= ftrace_size && | |
337 | strcmp(argv[0] + (len - ftrace_size), ftrace) == 0) | |
338 | continue; | |
339 | ||
81d3858d JR |
340 | switch (sjval) { |
341 | default: { | |
342 | fprintf(stderr, "internal error: %s\n", argv[0]); | |
343 | exit(1); | |
344 | } break; | |
345 | case SJ_SETJMP: { /* normal sequence */ | |
346 | /* Avoid problems if early cleanup() */ | |
347 | fd_map = -1; | |
348 | ehdr_curr = NULL; | |
349 | mmap_failed = 1; | |
350 | do_file(argv[0]); | |
351 | } break; | |
352 | case SJ_FAIL: { /* error in do_file or below */ | |
353 | ++n_error; | |
354 | } break; | |
355 | case SJ_SUCCEED: { /* premature success */ | |
356 | /* do nothing */ | |
357 | } break; | |
358 | } /* end switch */ | |
359 | } | |
360 | return !!n_error; | |
361 | } | |
362 | ||
363 |