blob: 9c22317778eb7e3f995c73845cfcceba15062739 [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
James Hogan00512bd2012-10-05 16:27:31 +010036#ifndef EM_METAG
37/* Remove this when these make it to the standard system elf.h. */
38#define EM_METAG 174
39#define R_METAG_ADDR32 2
40#define R_METAG_NONE 3
41#endif
42
John Reiser81d38582010-10-13 15:12:54 -040043static int fd_map; /* File descriptor for file being modified. */
44static int mmap_failed; /* Boolean flag. */
45static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
46static char gpfx; /* prefix for global symbol name (sometimes '_') */
47static struct stat sb; /* Remember .st_size, etc. */
48static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
Rabin Vincented604532010-11-30 17:36:48 +010049static const char *altmcount; /* alternate mcount symbol name */
Steven Rostedtdfad3d52011-04-12 18:53:25 -040050static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
John Reiser81d38582010-10-13 15:12:54 -040051
52/* setjmp() return values */
53enum {
54 SJ_SETJMP = 0, /* hardwired first return */
55 SJ_FAIL,
56 SJ_SUCCEED
57};
58
59/* Per-file resource cleanup when multiple files. */
60static void
61cleanup(void)
62{
63 if (!mmap_failed)
64 munmap(ehdr_curr, sb.st_size);
65 else
66 free(ehdr_curr);
67 close(fd_map);
68}
69
70static void __attribute__((noreturn))
71fail_file(void)
72{
73 cleanup();
74 longjmp(jmpenv, SJ_FAIL);
75}
76
77static void __attribute__((noreturn))
78succeed_file(void)
79{
80 cleanup();
81 longjmp(jmpenv, SJ_SUCCEED);
82}
83
84/* ulseek, uread, ...: Check return value for errors. */
85
86static off_t
87ulseek(int const fd, off_t const offset, int const whence)
88{
89 off_t const w = lseek(fd, offset, whence);
Steven Rostedtdd5477f2011-04-06 13:21:17 -040090 if (w == (off_t)-1) {
John Reiser81d38582010-10-13 15:12:54 -040091 perror("lseek");
92 fail_file();
93 }
94 return w;
95}
96
97static size_t
98uread(int const fd, void *const buf, size_t const count)
99{
100 size_t const n = read(fd, buf, count);
101 if (n != count) {
102 perror("read");
103 fail_file();
104 }
105 return n;
106}
107
108static size_t
109uwrite(int const fd, void const *const buf, size_t const count)
110{
111 size_t const n = write(fd, buf, count);
112 if (n != count) {
113 perror("write");
114 fail_file();
115 }
116 return n;
117}
118
119static void *
120umalloc(size_t size)
121{
122 void *const addr = malloc(size);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400123 if (addr == 0) {
John Reiser81d38582010-10-13 15:12:54 -0400124 fprintf(stderr, "malloc failed: %zu bytes\n", size);
125 fail_file();
126 }
127 return addr;
128}
129
Steven Rostedtffd618f2011-04-08 03:58:48 -0400130static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
131static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
132static unsigned char *ideal_nop;
133
134static char rel_type_nop;
135
136static int (*make_nop)(void *map, size_t const offset);
137
138static int make_nop_x86(void *map, size_t const offset)
139{
140 uint32_t *ptr;
141 unsigned char *op;
142
143 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
144 ptr = map + offset;
145 if (*ptr != 0)
146 return -1;
147
148 op = map + offset - 1;
149 if (*op != 0xe8)
150 return -1;
151
152 /* convert to nop */
153 ulseek(fd_map, offset - 1, SEEK_SET);
154 uwrite(fd_map, ideal_nop, 5);
155 return 0;
156}
157
John Reiser81d38582010-10-13 15:12:54 -0400158/*
159 * Get the whole file as a programming convenience in order to avoid
160 * malloc+lseek+read+free of many pieces. If successful, then mmap
161 * avoids copying unused pieces; else just read the whole file.
162 * Open for both read and write; new info will be appended to the file.
163 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
164 * do not propagate to the file until an explicit overwrite at the last.
165 * This preserves most aspects of consistency (all except .st_size)
166 * for simultaneous readers of the file while we are appending to it.
167 * However, multiple writers still are bad. We choose not to use
168 * locking because it is expensive and the use case of kernel build
169 * makes multiple writers unlikely.
170 */
171static void *mmap_file(char const *fname)
172{
173 void *addr;
174
175 fd_map = open(fname, O_RDWR);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400176 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
John Reiser81d38582010-10-13 15:12:54 -0400177 perror(fname);
178 fail_file();
179 }
180 if (!S_ISREG(sb.st_mode)) {
181 fprintf(stderr, "not a regular file: %s\n", fname);
182 fail_file();
183 }
184 addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
185 fd_map, 0);
186 mmap_failed = 0;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400187 if (addr == MAP_FAILED) {
John Reiser81d38582010-10-13 15:12:54 -0400188 mmap_failed = 1;
189 addr = umalloc(sb.st_size);
190 uread(fd_map, addr, sb.st_size);
191 }
192 return addr;
193}
194
195/* w8rev, w8nat, ...: Handle endianness. */
196
197static uint64_t w8rev(uint64_t const x)
198{
199 return ((0xff & (x >> (0 * 8))) << (7 * 8))
200 | ((0xff & (x >> (1 * 8))) << (6 * 8))
201 | ((0xff & (x >> (2 * 8))) << (5 * 8))
202 | ((0xff & (x >> (3 * 8))) << (4 * 8))
203 | ((0xff & (x >> (4 * 8))) << (3 * 8))
204 | ((0xff & (x >> (5 * 8))) << (2 * 8))
205 | ((0xff & (x >> (6 * 8))) << (1 * 8))
206 | ((0xff & (x >> (7 * 8))) << (0 * 8));
207}
208
209static uint32_t w4rev(uint32_t const x)
210{
211 return ((0xff & (x >> (0 * 8))) << (3 * 8))
212 | ((0xff & (x >> (1 * 8))) << (2 * 8))
213 | ((0xff & (x >> (2 * 8))) << (1 * 8))
214 | ((0xff & (x >> (3 * 8))) << (0 * 8));
215}
216
217static uint32_t w2rev(uint16_t const x)
218{
219 return ((0xff & (x >> (0 * 8))) << (1 * 8))
220 | ((0xff & (x >> (1 * 8))) << (0 * 8));
221}
222
223static uint64_t w8nat(uint64_t const x)
224{
225 return x;
226}
227
228static uint32_t w4nat(uint32_t const x)
229{
230 return x;
231}
232
233static uint32_t w2nat(uint16_t const x)
234{
235 return x;
236}
237
238static uint64_t (*w8)(uint64_t);
239static uint32_t (*w)(uint32_t);
240static uint32_t (*w2)(uint16_t);
241
242/* Names of the sections that could contain calls to mcount. */
243static int
244is_mcounted_section_name(char const *const txtname)
245{
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400246 return strcmp(".text", txtname) == 0 ||
247 strcmp(".ref.text", txtname) == 0 ||
248 strcmp(".sched.text", txtname) == 0 ||
249 strcmp(".spinlock.text", txtname) == 0 ||
250 strcmp(".irqentry.text", txtname) == 0 ||
Steven Rostedt9f087e72011-04-06 14:10:22 -0400251 strcmp(".kprobes.text", txtname) == 0 ||
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400252 strcmp(".text.unlikely", txtname) == 0;
John Reiser81d38582010-10-13 15:12:54 -0400253}
254
Steven Rostedtc28d5072010-10-13 19:06:14 -0400255/* 32 bit and 64 bit are very similar */
256#include "recordmcount.h"
257#define RECORD_MCOUNT_64
258#include "recordmcount.h"
John Reiser81d38582010-10-13 15:12:54 -0400259
John Reisera2d493582010-10-27 18:59:07 +0800260/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
261 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
262 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
263 * to imply the order of the members; the spec does not say so.
264 * typedef unsigned char Elf64_Byte;
265 * fails on MIPS64 because their <elf.h> already has it!
266 */
267
268typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
269
270union mips_r_info {
271 Elf64_Xword r_info;
272 struct {
273 Elf64_Word r_sym; /* Symbol index. */
274 myElf64_Byte r_ssym; /* Special symbol. */
275 myElf64_Byte r_type3; /* Third relocation. */
276 myElf64_Byte r_type2; /* Second relocation. */
277 myElf64_Byte r_type; /* First relocation. */
278 } r_mips;
279};
280
281static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
282{
283 return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
284}
285
286static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
287{
288 rp->r_info = ((union mips_r_info){
289 .r_mips = { .r_sym = w(sym), .r_type = type }
290 }).r_info;
291}
292
John Reiser81d38582010-10-13 15:12:54 -0400293static void
294do_file(char const *const fname)
295{
296 Elf32_Ehdr *const ehdr = mmap_file(fname);
297 unsigned int reltype = 0;
298
299 ehdr_curr = ehdr;
300 w = w4nat;
301 w2 = w2nat;
302 w8 = w8nat;
303 switch (ehdr->e_ident[EI_DATA]) {
304 static unsigned int const endian = 1;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400305 default:
John Reiser81d38582010-10-13 15:12:54 -0400306 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
307 ehdr->e_ident[EI_DATA], fname);
308 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400309 break;
310 case ELFDATA2LSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400311 if (*(unsigned char const *)&endian != 1) {
John Reiser81d38582010-10-13 15:12:54 -0400312 /* main() is big endian, file.o is little endian. */
313 w = w4rev;
314 w2 = w2rev;
315 w8 = w8rev;
316 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400317 break;
318 case ELFDATA2MSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400319 if (*(unsigned char const *)&endian != 0) {
John Reiser81d38582010-10-13 15:12:54 -0400320 /* main() is little endian, file.o is big endian. */
321 w = w4rev;
322 w2 = w2rev;
323 w8 = w8rev;
324 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400325 break;
John Reiser81d38582010-10-13 15:12:54 -0400326 } /* end switch */
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400327 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
328 || w2(ehdr->e_type) != ET_REL
329 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
John Reiser81d38582010-10-13 15:12:54 -0400330 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
331 fail_file();
332 }
333
334 gpfx = 0;
335 switch (w2(ehdr->e_machine)) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400336 default:
John Reiser81d38582010-10-13 15:12:54 -0400337 fprintf(stderr, "unrecognized e_machine %d %s\n",
338 w2(ehdr->e_machine), fname);
339 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400340 break;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400341 case EM_386:
342 reltype = R_386_32;
343 make_nop = make_nop_x86;
344 ideal_nop = ideal_nop5_x86_32;
Martin Schwidefsky521ccb52011-05-10 10:10:41 +0200345 mcount_adjust_32 = -1;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400346 break;
Rabin Vincented604532010-11-30 17:36:48 +0100347 case EM_ARM: reltype = R_ARM_ABS32;
348 altmcount = "__gnu_mcount_nc";
349 break;
John Reiser81d38582010-10-13 15:12:54 -0400350 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
James Hogan00512bd2012-10-05 16:27:31 +0100351 case EM_METAG: reltype = R_METAG_ADDR32;
352 altmcount = "_mcount_wrapper";
353 rel_type_nop = R_METAG_NONE;
354 /* We happen to have the same requirement as MIPS */
355 is_fake_mcount32 = MIPS32_is_fake_mcount;
356 break;
John Reisera2d493582010-10-27 18:59:07 +0800357 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
John Reiser81d38582010-10-13 15:12:54 -0400358 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
359 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
360 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
361 case EM_SH: reltype = R_SH_DIR32; break;
362 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400363 case EM_X86_64:
364 make_nop = make_nop_x86;
365 ideal_nop = ideal_nop5_x86_64;
366 reltype = R_X86_64_64;
Martin Schwidefsky521ccb52011-05-10 10:10:41 +0200367 mcount_adjust_64 = -1;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400368 break;
John Reiser81d38582010-10-13 15:12:54 -0400369 } /* end switch */
370
371 switch (ehdr->e_ident[EI_CLASS]) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400372 default:
John Reiser81d38582010-10-13 15:12:54 -0400373 fprintf(stderr, "unrecognized ELF class %d %s\n",
374 ehdr->e_ident[EI_CLASS], fname);
375 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400376 break;
377 case ELFCLASS32:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400378 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
379 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400380 fprintf(stderr,
381 "unrecognized ET_REL file: %s\n", fname);
382 fail_file();
383 }
Martin Schwidefskyf2963882011-05-10 10:10:43 +0200384 if (w2(ehdr->e_machine) == EM_S390) {
John Reiser81d38582010-10-13 15:12:54 -0400385 reltype = R_390_32;
Martin Schwidefskyf2963882011-05-10 10:10:43 +0200386 mcount_adjust_32 = -4;
387 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400388 if (w2(ehdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800389 reltype = R_MIPS_32;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800390 is_fake_mcount32 = MIPS32_is_fake_mcount;
391 }
John Reiser81d38582010-10-13 15:12:54 -0400392 do32(ehdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400393 break;
John Reiser81d38582010-10-13 15:12:54 -0400394 case ELFCLASS64: {
395 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400396 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
397 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400398 fprintf(stderr,
399 "unrecognized ET_REL file: %s\n", fname);
400 fail_file();
401 }
Martin Schwidefskyf2963882011-05-10 10:10:43 +0200402 if (w2(ghdr->e_machine) == EM_S390) {
John Reiser81d38582010-10-13 15:12:54 -0400403 reltype = R_390_64;
Martin Schwidefskyf2963882011-05-10 10:10:43 +0200404 mcount_adjust_64 = -8;
405 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400406 if (w2(ghdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800407 reltype = R_MIPS_64;
408 Elf64_r_sym = MIPS64_r_sym;
409 Elf64_r_info = MIPS64_r_info;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800410 is_fake_mcount64 = MIPS64_is_fake_mcount;
John Reisera2d493582010-10-27 18:59:07 +0800411 }
John Reiser81d38582010-10-13 15:12:54 -0400412 do64(ghdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400413 break;
414 }
John Reiser81d38582010-10-13 15:12:54 -0400415 } /* end switch */
416
417 cleanup();
418}
419
420int
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400421main(int argc, char *argv[])
John Reiser81d38582010-10-13 15:12:54 -0400422{
Rabin Vincentcd3478f2010-11-30 17:33:53 +0100423 const char ftrace[] = "/ftrace.o";
Steven Rostedt44475862010-10-15 11:49:47 -0400424 int ftrace_size = sizeof(ftrace) - 1;
John Reiser81d38582010-10-13 15:12:54 -0400425 int n_error = 0; /* gcc-4.3.0 false positive complaint */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400426 int c;
427 int i;
Steven Rostedt44475862010-10-15 11:49:47 -0400428
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400429 while ((c = getopt(argc, argv, "w")) >= 0) {
430 switch (c) {
431 case 'w':
432 warn_on_notrace_sect = 1;
433 break;
434 default:
435 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
436 return 0;
437 }
438 }
439
440 if ((argc - optind) < 1) {
441 fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
Steven Rostedt44475862010-10-15 11:49:47 -0400442 return 0;
443 }
444
445 /* Process each file in turn, allowing deep failure. */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400446 for (i = optind; i < argc; i++) {
447 char *file = argv[i];
John Reiser81d38582010-10-13 15:12:54 -0400448 int const sjval = setjmp(jmpenv);
Steven Rostedt44475862010-10-15 11:49:47 -0400449 int len;
450
451 /*
452 * The file kernel/trace/ftrace.o references the mcount
453 * function but does not call it. Since ftrace.o should
454 * not be traced anyway, we just skip it.
455 */
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400456 len = strlen(file);
Steven Rostedt44475862010-10-15 11:49:47 -0400457 if (len >= ftrace_size &&
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400458 strcmp(file + (len - ftrace_size), ftrace) == 0)
Steven Rostedt44475862010-10-15 11:49:47 -0400459 continue;
460
John Reiser81d38582010-10-13 15:12:54 -0400461 switch (sjval) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400462 default:
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400463 fprintf(stderr, "internal error: %s\n", file);
John Reiser81d38582010-10-13 15:12:54 -0400464 exit(1);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400465 break;
466 case SJ_SETJMP: /* normal sequence */
John Reiser81d38582010-10-13 15:12:54 -0400467 /* Avoid problems if early cleanup() */
468 fd_map = -1;
469 ehdr_curr = NULL;
470 mmap_failed = 1;
Steven Rostedtdfad3d52011-04-12 18:53:25 -0400471 do_file(file);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400472 break;
473 case SJ_FAIL: /* error in do_file or below */
John Reiser81d38582010-10-13 15:12:54 -0400474 ++n_error;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400475 break;
476 case SJ_SUCCEED: /* premature success */
John Reiser81d38582010-10-13 15:12:54 -0400477 /* do nothing */
Steven Rostedte90b0c82011-04-06 13:32:24 -0400478 break;
John Reiser81d38582010-10-13 15:12:54 -0400479 } /* end switch */
480 }
481 return !!n_error;
482}
483
484