blob: 26e1271259ba51d27343d8a946fe47526e9c2e94 [file] [log] [blame]
John Reiser81d38582010-10-13 15:12:54 -04001/*
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
35static int fd_map; /* File descriptor for file being modified. */
36static int mmap_failed; /* Boolean flag. */
37static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
38static char gpfx; /* prefix for global symbol name (sometimes '_') */
39static struct stat sb; /* Remember .st_size, etc. */
40static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
41
42/* setjmp() return values */
43enum {
44 SJ_SETJMP = 0, /* hardwired first return */
45 SJ_FAIL,
46 SJ_SUCCEED
47};
48
49/* Per-file resource cleanup when multiple files. */
50static void
51cleanup(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
60static void __attribute__((noreturn))
61fail_file(void)
62{
63 cleanup();
64 longjmp(jmpenv, SJ_FAIL);
65}
66
67static void __attribute__((noreturn))
68succeed_file(void)
69{
70 cleanup();
71 longjmp(jmpenv, SJ_SUCCEED);
72}
73
74/* ulseek, uread, ...: Check return value for errors. */
75
76static off_t
77ulseek(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
87static size_t
88uread(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
98static size_t
99uwrite(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
109static void *
110umalloc(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 */
133static 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
159static 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
171static 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
179static 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
185static uint64_t w8nat(uint64_t const x)
186{
187 return x;
188}
189
190static uint32_t w4nat(uint32_t const x)
191{
192 return x;
193}
194
195static uint32_t w2nat(uint16_t const x)
196{
197 return x;
198}
199
200static uint64_t (*w8)(uint64_t);
201static uint32_t (*w)(uint32_t);
202static uint32_t (*w2)(uint16_t);
203
204/* Names of the sections that could contain calls to mcount. */
205static int
206is_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
Steven Rostedtc28d5072010-10-13 19:06:14 -0400215/* 32 bit and 64 bit are very similar */
216#include "recordmcount.h"
217#define RECORD_MCOUNT_64
218#include "recordmcount.h"
John Reiser81d38582010-10-13 15:12:54 -0400219
220static void
221do_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
313int
314main(int argc, char const *argv[])
315{
Steven Rostedt44475862010-10-15 11:49:47 -0400316 const char ftrace[] = "kernel/trace/ftrace.o";
317 int ftrace_size = sizeof(ftrace) - 1;
John Reiser81d38582010-10-13 15:12:54 -0400318 int n_error = 0; /* gcc-4.3.0 false positive complaint */
Steven Rostedt44475862010-10-15 11:49:47 -0400319
320 if (argc <= 1) {
John Reiser81d38582010-10-13 15:12:54 -0400321 fprintf(stderr, "usage: recordmcount file.o...\n");
Steven Rostedt44475862010-10-15 11:49:47 -0400322 return 0;
323 }
324
325 /* Process each file in turn, allowing deep failure. */
John Reiser81d38582010-10-13 15:12:54 -0400326 for (--argc, ++argv; 0 < argc; --argc, ++argv) {
327 int const sjval = setjmp(jmpenv);
Steven Rostedt44475862010-10-15 11:49:47 -0400328 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
John Reiser81d38582010-10-13 15:12:54 -0400340 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