blob: 78054a41d134f50e11f9cfe04184a9c284b0916e [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 */
Rabin Vincented604532010-11-30 17:36:48 +010041static const char *altmcount; /* alternate mcount symbol name */
John Reiser81d38582010-10-13 15:12:54 -040042
43/* setjmp() return values */
44enum {
45 SJ_SETJMP = 0, /* hardwired first return */
46 SJ_FAIL,
47 SJ_SUCCEED
48};
49
50/* Per-file resource cleanup when multiple files. */
51static void
52cleanup(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
61static void __attribute__((noreturn))
62fail_file(void)
63{
64 cleanup();
65 longjmp(jmpenv, SJ_FAIL);
66}
67
68static void __attribute__((noreturn))
69succeed_file(void)
70{
71 cleanup();
72 longjmp(jmpenv, SJ_SUCCEED);
73}
74
75/* ulseek, uread, ...: Check return value for errors. */
76
77static off_t
78ulseek(int const fd, off_t const offset, int const whence)
79{
80 off_t const w = lseek(fd, offset, whence);
Steven Rostedtdd5477f2011-04-06 13:21:17 -040081 if (w == (off_t)-1) {
John Reiser81d38582010-10-13 15:12:54 -040082 perror("lseek");
83 fail_file();
84 }
85 return w;
86}
87
88static size_t
89uread(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
99static size_t
100uwrite(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
110static void *
111umalloc(size_t size)
112{
113 void *const addr = malloc(size);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400114 if (addr == 0) {
John Reiser81d38582010-10-13 15:12:54 -0400115 fprintf(stderr, "malloc failed: %zu bytes\n", size);
116 fail_file();
117 }
118 return addr;
119}
120
Steven Rostedtffd618f2011-04-08 03:58:48 -0400121static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
122static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
123static unsigned char *ideal_nop;
124
125static char rel_type_nop;
126
127static int (*make_nop)(void *map, size_t const offset);
128
129static 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
John Reiser81d38582010-10-13 15:12:54 -0400149/*
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 */
162static void *mmap_file(char const *fname)
163{
164 void *addr;
165
166 fd_map = open(fname, O_RDWR);
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400167 if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
John Reiser81d38582010-10-13 15:12:54 -0400168 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;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400178 if (addr == MAP_FAILED) {
John Reiser81d38582010-10-13 15:12:54 -0400179 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
188static 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
200static 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
208static 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
214static uint64_t w8nat(uint64_t const x)
215{
216 return x;
217}
218
219static uint32_t w4nat(uint32_t const x)
220{
221 return x;
222}
223
224static uint32_t w2nat(uint16_t const x)
225{
226 return x;
227}
228
229static uint64_t (*w8)(uint64_t);
230static uint32_t (*w)(uint32_t);
231static uint32_t (*w2)(uint16_t);
232
233/* Names of the sections that could contain calls to mcount. */
234static int
235is_mcounted_section_name(char const *const txtname)
236{
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400237 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 ||
Steven Rostedt9f087e72011-04-06 14:10:22 -0400242 strcmp(".kprobes.text", txtname) == 0 ||
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400243 strcmp(".text.unlikely", txtname) == 0;
John Reiser81d38582010-10-13 15:12:54 -0400244}
245
Steven Rostedtc28d5072010-10-13 19:06:14 -0400246/* 32 bit and 64 bit are very similar */
247#include "recordmcount.h"
248#define RECORD_MCOUNT_64
249#include "recordmcount.h"
John Reiser81d38582010-10-13 15:12:54 -0400250
John Reisera2d493582010-10-27 18:59:07 +0800251/* 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
259typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
260
261union 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
272static 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
277static 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
John Reiser81d38582010-10-13 15:12:54 -0400284static void
285do_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;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400296 default:
John Reiser81d38582010-10-13 15:12:54 -0400297 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
298 ehdr->e_ident[EI_DATA], fname);
299 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400300 break;
301 case ELFDATA2LSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400302 if (*(unsigned char const *)&endian != 1) {
John Reiser81d38582010-10-13 15:12:54 -0400303 /* main() is big endian, file.o is little endian. */
304 w = w4rev;
305 w2 = w2rev;
306 w8 = w8rev;
307 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400308 break;
309 case ELFDATA2MSB:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400310 if (*(unsigned char const *)&endian != 0) {
John Reiser81d38582010-10-13 15:12:54 -0400311 /* main() is little endian, file.o is big endian. */
312 w = w4rev;
313 w2 = w2rev;
314 w8 = w8rev;
315 }
Steven Rostedte90b0c82011-04-06 13:32:24 -0400316 break;
John Reiser81d38582010-10-13 15:12:54 -0400317 } /* end switch */
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400318 if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
319 || w2(ehdr->e_type) != ET_REL
320 || ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
John Reiser81d38582010-10-13 15:12:54 -0400321 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
322 fail_file();
323 }
324
325 gpfx = 0;
326 switch (w2(ehdr->e_machine)) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400327 default:
John Reiser81d38582010-10-13 15:12:54 -0400328 fprintf(stderr, "unrecognized e_machine %d %s\n",
329 w2(ehdr->e_machine), fname);
330 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400331 break;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400332 case EM_386:
333 reltype = R_386_32;
334 make_nop = make_nop_x86;
335 ideal_nop = ideal_nop5_x86_32;
336 break;
Rabin Vincented604532010-11-30 17:36:48 +0100337 case EM_ARM: reltype = R_ARM_ABS32;
338 altmcount = "__gnu_mcount_nc";
339 break;
John Reiser81d38582010-10-13 15:12:54 -0400340 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
John Reisera2d493582010-10-27 18:59:07 +0800341 case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
John Reiser81d38582010-10-13 15:12:54 -0400342 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;
Steven Rostedtffd618f2011-04-08 03:58:48 -0400347 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;
John Reiser81d38582010-10-13 15:12:54 -0400352 } /* end switch */
353
354 switch (ehdr->e_ident[EI_CLASS]) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400355 default:
John Reiser81d38582010-10-13 15:12:54 -0400356 fprintf(stderr, "unrecognized ELF class %d %s\n",
357 ehdr->e_ident[EI_CLASS], fname);
358 fail_file();
Steven Rostedte90b0c82011-04-06 13:32:24 -0400359 break;
360 case ELFCLASS32:
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400361 if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
362 || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400363 fprintf(stderr,
364 "unrecognized ET_REL file: %s\n", fname);
365 fail_file();
366 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400367 if (w2(ehdr->e_machine) == EM_S390)
John Reiser81d38582010-10-13 15:12:54 -0400368 reltype = R_390_32;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400369 if (w2(ehdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800370 reltype = R_MIPS_32;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800371 is_fake_mcount32 = MIPS32_is_fake_mcount;
372 }
John Reiser81d38582010-10-13 15:12:54 -0400373 do32(ehdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400374 break;
John Reiser81d38582010-10-13 15:12:54 -0400375 case ELFCLASS64: {
376 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400377 if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
378 || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
John Reiser81d38582010-10-13 15:12:54 -0400379 fprintf(stderr,
380 "unrecognized ET_REL file: %s\n", fname);
381 fail_file();
382 }
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400383 if (w2(ghdr->e_machine) == EM_S390)
John Reiser81d38582010-10-13 15:12:54 -0400384 reltype = R_390_64;
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400385 if (w2(ghdr->e_machine) == EM_MIPS) {
John Reisera2d493582010-10-27 18:59:07 +0800386 reltype = R_MIPS_64;
387 Elf64_r_sym = MIPS64_r_sym;
388 Elf64_r_info = MIPS64_r_info;
Wu Zhangjin412910c2010-10-27 18:59:08 +0800389 is_fake_mcount64 = MIPS64_is_fake_mcount;
John Reisera2d493582010-10-27 18:59:07 +0800390 }
John Reiser81d38582010-10-13 15:12:54 -0400391 do64(ghdr, fname, reltype);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400392 break;
393 }
John Reiser81d38582010-10-13 15:12:54 -0400394 } /* end switch */
395
396 cleanup();
397}
398
399int
400main(int argc, char const *argv[])
401{
Rabin Vincentcd3478f2010-11-30 17:33:53 +0100402 const char ftrace[] = "/ftrace.o";
Steven Rostedt44475862010-10-15 11:49:47 -0400403 int ftrace_size = sizeof(ftrace) - 1;
John Reiser81d38582010-10-13 15:12:54 -0400404 int n_error = 0; /* gcc-4.3.0 false positive complaint */
Steven Rostedt44475862010-10-15 11:49:47 -0400405
406 if (argc <= 1) {
John Reiser81d38582010-10-13 15:12:54 -0400407 fprintf(stderr, "usage: recordmcount file.o...\n");
Steven Rostedt44475862010-10-15 11:49:47 -0400408 return 0;
409 }
410
411 /* Process each file in turn, allowing deep failure. */
Steven Rostedtdd5477f2011-04-06 13:21:17 -0400412 for (--argc, ++argv; argc > 0; --argc, ++argv) {
John Reiser81d38582010-10-13 15:12:54 -0400413 int const sjval = setjmp(jmpenv);
Steven Rostedt44475862010-10-15 11:49:47 -0400414 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
John Reiser81d38582010-10-13 15:12:54 -0400426 switch (sjval) {
Steven Rostedte90b0c82011-04-06 13:32:24 -0400427 default:
John Reiser81d38582010-10-13 15:12:54 -0400428 fprintf(stderr, "internal error: %s\n", argv[0]);
429 exit(1);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400430 break;
431 case SJ_SETJMP: /* normal sequence */
John Reiser81d38582010-10-13 15:12:54 -0400432 /* Avoid problems if early cleanup() */
433 fd_map = -1;
434 ehdr_curr = NULL;
435 mmap_failed = 1;
436 do_file(argv[0]);
Steven Rostedte90b0c82011-04-06 13:32:24 -0400437 break;
438 case SJ_FAIL: /* error in do_file or below */
John Reiser81d38582010-10-13 15:12:54 -0400439 ++n_error;
Steven Rostedte90b0c82011-04-06 13:32:24 -0400440 break;
441 case SJ_SUCCEED: /* premature success */
John Reiser81d38582010-10-13 15:12:54 -0400442 /* do nothing */
Steven Rostedte90b0c82011-04-06 13:32:24 -0400443 break;
John Reiser81d38582010-10-13 15:12:54 -0400444 } /* end switch */
445 }
446 return !!n_error;
447}
448
449