blob: 0e18975824f768a4c6d01ba8b1802019035e2e27 [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>
Steven Rostedtdfad3d52011-04-12 18:53:25 -040027#include <getopt.h>
John Reiser81d38582010-10-13 15:12:54 -040028#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
36static int fd_map; /* File descriptor for file being modified. */
37static int mmap_failed; /* Boolean flag. */
38static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
39static char gpfx; /* prefix for global symbol name (sometimes '_') */
40static struct stat sb; /* Remember .st_size, etc. */
41static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
Rabin Vincented604532010-11-30 17:36:48 +010042static const char *altmcount; /* alternate mcount symbol name */
Steven Rostedtdfad3d52011-04-12 18:53:25 -040043static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
John Reiser81d38582010-10-13 15:12:54 -040044
45/* setjmp() return values */
46enum {
47 SJ_SETJMP = 0, /* hardwired first return */
48 SJ_FAIL,
49 SJ_SUCCEED
50};
51
52/* Per-file resource cleanup when multiple files. */
53static void
54cleanup(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
63static void __attribute__((noreturn))
64fail_file(void)
65{
66 cleanup();
67 longjmp(jmpenv, SJ_FAIL);
68}
69
70static void __attribute__((noreturn))
71succeed_file(void)
72{
73 cleanup();
74 longjmp(jmpenv, SJ_SUCCEED);
75}
76
77/* ulseek, uread, ...: Check return value for errors. */
78
79static off_t
80ulseek(int const fd, off_t const offset, int const whence)
81{
82 off_t const w = lseek(fd, offset, whence);
Steven Rostedtdd5477f2011-04-06 13:21:17 -040083 if (w == (off_t)-1) {
John Reiser81d38582010-10-13 15:12:54 -040084 perror("lseek");
85 fail_file();
86 }
87 return w;
88}
89
90static size_t
91uread(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
101static size_t
102uwrite(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
112static void *
113umalloc(size_t size)
114{
115 void *const addr = malloc(size);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400116 if (addr == 0) {
John Reiser81d38582010-10-13 15:12:54 -0400117 fprintf(stderr, "malloc failed: %zu bytes\n", size);
118 fail_file();
119 }
120 return addr;
121}
122
Steven Rostedtffd618f2011-04-08 03:58:48 -0400123static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
124static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
125static unsigned char *ideal_nop;
126
127static char rel_type_nop;
128
129static int (*make_nop)(void *map, size_t const offset);
130
131static 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
John Reiser81d38582010-10-13 15:12:54 -0400151/*
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 */
164static void *mmap_file(char const *fname)
165{
166 void *addr;
167
168 fd_map = open(fname, O_RDWR);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400169 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
John Reiser81d38582010-10-13 15:12:54 -0400170 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;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400180 if (addr == MAP_FAILED) {
John Reiser81d38582010-10-13 15:12:54 -0400181 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
190static 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
202static 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
210static 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
216static uint64_t w8nat(uint64_t const x)
217{
218 return x;
219}
220
221static uint32_t w4nat(uint32_t const x)
222{
223 return x;
224}
225
226static uint32_t w2nat(uint16_t const x)
227{
228 return x;
229}
230
231static uint64_t (*w8)(uint64_t);
232static uint32_t (*w)(uint32_t);
233static uint32_t (*w2)(uint16_t);
234
235/* Names of the sections that could contain calls to mcount. */
236static int
237is_mcounted_section_name(char const *const txtname)
238{
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400239 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 ||
Steven Rostedt9f087e72011-04-06 14:10:22 -0400244 strcmp(".kprobes.text", txtname) == 0 ||
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400245 strcmp(".text.unlikely", txtname) == 0;
John Reiser81d38582010-10-13 15:12:54 -0400246}
247
Steven Rostedtc28d5072010-10-13 19:06:14 -0400248/* 32 bit and 64 bit are very similar */
249#include "recordmcount.h"
250#define RECORD_MCOUNT_64
251#include "recordmcount.h"
John Reiser81d38582010-10-13 15:12:54 -0400252
John Reisera2d493582010-10-27 18:59:07 +0800253/* 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
261typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
262
263union 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
274static 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
279static 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
John Reiser81d38582010-10-13 15:12:54 -0400286static void
287do_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;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400298 default:
John Reiser81d38582010-10-13 15:12:54 -0400299 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
300 ehdr->e_ident[EI_DATA], fname);
301 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400302 break;
303 case ELFDATA2LSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400304 if (*(unsigned char const *)&endian != 1) {
John Reiser81d38582010-10-13 15:12:54 -0400305 /* main() is big endian, file.o is little endian. */
306 w = w4rev;
307 w2 = w2rev;
308 w8 = w8rev;
309 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400310 break;
311 case ELFDATA2MSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400312 if (*(unsigned char const *)&endian != 0) {
John Reiser81d38582010-10-13 15:12:54 -0400313 /* main() is little endian, file.o is big endian. */
314 w = w4rev;
315 w2 = w2rev;
316 w8 = w8rev;
317 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400318 break;
John Reiser81d38582010-10-13 15:12:54 -0400319 } /* end switch */
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400320 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
321 || w2(ehdr->e_type) != ET_REL
322 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
John Reiser81d38582010-10-13 15:12:54 -0400323 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
324 fail_file();
325 }
326
327 gpfx = 0;
328 switch (w2(ehdr->e_machine)) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400329 default:
John Reiser81d38582010-10-13 15:12:54 -0400330 fprintf(stderr, "unrecognized e_machine %d %s\n",
331 w2(ehdr->e_machine), fname);
332 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400333 break;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400334 case EM_386:
335 reltype = R_386_32;
336 make_nop = make_nop_x86;
337 ideal_nop = ideal_nop5_x86_32;
338 break;
Rabin Vincented604532010-11-30 17:36:48 +0100339 case EM_ARM: reltype = R_ARM_ABS32;
340 altmcount = "__gnu_mcount_nc";
341 break;
John Reiser81d38582010-10-13 15:12:54 -0400342 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
John Reisera2d493582010-10-27 18:59:07 +0800343 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
John Reiser81d38582010-10-13 15:12:54 -0400344 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
345 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
346 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
347 case EM_SH: reltype = R_SH_DIR32; break;
348 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400349 case EM_X86_64:
350 make_nop = make_nop_x86;
351 ideal_nop = ideal_nop5_x86_64;
352 reltype = R_X86_64_64;
353 break;
John Reiser81d38582010-10-13 15:12:54 -0400354 } /* end switch */
355
356 switch (ehdr->e_ident[EI_CLASS]) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400357 default:
John Reiser81d38582010-10-13 15:12:54 -0400358 fprintf(stderr, "unrecognized ELF class %d %s\n",
359 ehdr->e_ident[EI_CLASS], fname);
360 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400361 break;
362 case ELFCLASS32:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400363 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
364 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400365 fprintf(stderr,
366 "unrecognized ET_REL file: %s\n", fname);
367 fail_file();
368 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400369 if (w2(ehdr->e_machine) == EM_S390)
John Reiser81d38582010-10-13 15:12:54 -0400370 reltype = R_390_32;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400371 if (w2(ehdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800372 reltype = R_MIPS_32;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800373 is_fake_mcount32 = MIPS32_is_fake_mcount;
374 }
John Reiser81d38582010-10-13 15:12:54 -0400375 do32(ehdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400376 break;
John Reiser81d38582010-10-13 15:12:54 -0400377 case ELFCLASS64: {
378 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400379 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
380 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400381 fprintf(stderr,
382 "unrecognized ET_REL file: %s\n", fname);
383 fail_file();
384 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400385 if (w2(ghdr->e_machine) == EM_S390)
John Reiser81d38582010-10-13 15:12:54 -0400386 reltype = R_390_64;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400387 if (w2(ghdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800388 reltype = R_MIPS_64;
389 Elf64_r_sym = MIPS64_r_sym;
390 Elf64_r_info = MIPS64_r_info;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800391 is_fake_mcount64 = MIPS64_is_fake_mcount;
John Reisera2d493582010-10-27 18:59:07 +0800392 }
John Reiser81d38582010-10-13 15:12:54 -0400393 do64(ghdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400394 break;
395 }
John Reiser81d38582010-10-13 15:12:54 -0400396 } /* end switch */
397
398 cleanup();
399}
400
401int
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400402main(int argc, char *argv[])
John Reiser81d38582010-10-13 15:12:54 -0400403{
Rabin Vincentcd3478f2010-11-30 17:33:53 +0100404 const char ftrace[] = "/ftrace.o";
Steven Rostedt44475862010-10-15 11:49:47 -0400405 int ftrace_size = sizeof(ftrace) - 1;
John Reiser81d38582010-10-13 15:12:54 -0400406 int n_error = 0; /* gcc-4.3.0 false positive complaint */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400407 int c;
408 int i;
Steven Rostedt44475862010-10-15 11:49:47 -0400409
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400410 while ((c = getopt(argc, argv, "w")) >= 0) {
411 switch (c) {
412 case 'w':
413 warn_on_notrace_sect = 1;
414 break;
415 default:
416 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
417 return 0;
418 }
419 }
420
421 if ((argc - optind) < 1) {
422 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
Steven Rostedt44475862010-10-15 11:49:47 -0400423 return 0;
424 }
425
426 /* Process each file in turn, allowing deep failure. */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400427 for (i = optind; i < argc; i++) {
428 char *file = argv[i];
John Reiser81d38582010-10-13 15:12:54 -0400429 int const sjval = setjmp(jmpenv);
Steven Rostedt44475862010-10-15 11:49:47 -0400430 int len;
431
432 /*
433 * The file kernel/trace/ftrace.o references the mcount
434 * function but does not call it. Since ftrace.o should
435 * not be traced anyway, we just skip it.
436 */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400437 len = strlen(file);
Steven Rostedt44475862010-10-15 11:49:47 -0400438 if (len >= ftrace_size &&
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400439 strcmp(file + (len - ftrace_size), ftrace) == 0)
Steven Rostedt44475862010-10-15 11:49:47 -0400440 continue;
441
John Reiser81d38582010-10-13 15:12:54 -0400442 switch (sjval) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400443 default:
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400444 fprintf(stderr, "internal error: %s\n", file);
John Reiser81d38582010-10-13 15:12:54 -0400445 exit(1);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400446 break;
447 case SJ_SETJMP: /* normal sequence */
John Reiser81d38582010-10-13 15:12:54 -0400448 /* Avoid problems if early cleanup() */
449 fd_map = -1;
450 ehdr_curr = NULL;
451 mmap_failed = 1;
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400452 do_file(file);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400453 break;
454 case SJ_FAIL: /* error in do_file or below */
John Reiser81d38582010-10-13 15:12:54 -0400455 ++n_error;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400456 break;
457 case SJ_SUCCEED: /* premature success */
John Reiser81d38582010-10-13 15:12:54 -0400458 /* do nothing */
Steven Rostedte90b0c82011-04-06 13:32:24 -0400459 break;
John Reiser81d38582010-10-13 15:12:54 -0400460 } /* end switch */
461 }
462 return !!n_error;
463}
464
465