path: root/scripts/recordmcount.c (plain)
blob: e0c508203c9c9a2a963e457d4b7db01ad22b1b31

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 <getopt.h>
28	#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
36	/*
37	* glibc synced up and added the metag number but didn't add the relocations.
38	* Work around this in a crude manner for now.
39	*/
40	#ifndef EM_METAG
41	#define EM_METAG 174
42	#endif
43	#ifndef R_METAG_ADDR32
44	#define R_METAG_ADDR32 2
45	#endif
46	#ifndef R_METAG_NONE
47	#define R_METAG_NONE 3
48	#endif
49
50	#ifndef EM_AARCH64
51	#define EM_AARCH64 183
52	#define R_AARCH64_NONE 0
53	#define R_AARCH64_ABS64 257
54	#endif
55
56	static int fd_map; /* File descriptor for file being modified. */
57	static int mmap_failed; /* Boolean flag. */
58	static char gpfx; /* prefix for global symbol name (sometimes '_') */
59	static struct stat sb; /* Remember .st_size, etc. */
60	static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
61	static const char *altmcount; /* alternate mcount symbol name */
62	static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
63	static void *file_map; /* pointer of the mapped file */
64	static void *file_end; /* pointer to the end of the mapped file */
65	static int file_updated; /* flag to state file was changed */
66	static void *file_ptr; /* current file pointer location */
67	static void *file_append; /* added to the end of the file */
68	static size_t file_append_size; /* how much is added to end of file */
69
70	/* setjmp() return values */
71	enum {
72	SJ_SETJMP = 0, /* hardwired first return */
73	SJ_FAIL,
74	SJ_SUCCEED
75	};
76
77	/* Per-file resource cleanup when multiple files. */
78	static void
79	cleanup(void)
80	{
81	if (!mmap_failed)
82	munmap(file_map, sb.st_size);
83	else
84	free(file_map);
85	file_map = NULL;
86	free(file_append);
87	file_append = NULL;
88	file_append_size = 0;
89	file_updated = 0;
90	}
91
92	static void __attribute__((noreturn))
93	fail_file(void)
94	{
95	cleanup();
96	longjmp(jmpenv, SJ_FAIL);
97	}
98
99	static void __attribute__((noreturn))
100	succeed_file(void)
101	{
102	cleanup();
103	longjmp(jmpenv, SJ_SUCCEED);
104	}
105
106	/* ulseek, uread, ...: Check return value for errors. */
107
108	static off_t
109	ulseek(int const fd, off_t const offset, int const whence)
110	{
111	switch (whence) {
112	case SEEK_SET:
113	file_ptr = file_map + offset;
114	break;
115	case SEEK_CUR:
116	file_ptr += offset;
117	break;
118	case SEEK_END:
119	file_ptr = file_map + (sb.st_size - offset);
120	break;
121	}
122	if (file_ptr < file_map) {
123	fprintf(stderr, "lseek: seek before file\n");
124	fail_file();
125	}
126	return file_ptr - file_map;
127	}
128
129	static size_t
130	uread(int const fd, void *const buf, size_t const count)
131	{
132	size_t const n = read(fd, buf, count);
133	if (n != count) {
134	perror("read");
135	fail_file();
136	}
137	return n;
138	}
139
140	static size_t
141	uwrite(int const fd, void const *const buf, size_t const count)
142	{
143	size_t cnt = count;
144	off_t idx = 0;
145
146	file_updated = 1;
147
148	if (file_ptr + count >= file_end) {
149	off_t aoffset = (file_ptr + count) - file_end;
150
151	if (aoffset > file_append_size) {
152	file_append = realloc(file_append, aoffset);
153	file_append_size = aoffset;
154	}
155	if (!file_append) {
156	perror("write");
157	fail_file();
158	}
159	if (file_ptr < file_end) {
160	cnt = file_end - file_ptr;
161	} else {
162	cnt = 0;
163	idx = aoffset - count;
164	}
165	}
166
167	if (cnt)
168	memcpy(file_ptr, buf, cnt);
169
170	if (cnt < count)
171	memcpy(file_append + idx, buf + cnt, count - cnt);
172
173	file_ptr += count;
174	return count;
175	}
176
177	static void *
178	umalloc(size_t size)
179	{
180	void *const addr = malloc(size);
181	if (addr == 0) {
182	fprintf(stderr, "malloc failed: %zu bytes\n", size);
183	fail_file();
184	}
185	return addr;
186	}
187
188	static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
189	static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
190	static unsigned char *ideal_nop;
191
192	static char rel_type_nop;
193
194	static int (*make_nop)(void *map, size_t const offset);
195
196	static int make_nop_x86(void *map, size_t const offset)
197	{
198	uint32_t *ptr;
199	unsigned char *op;
200
201	/* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
202	ptr = map + offset;
203	if (*ptr != 0)
204	return -1;
205
206	op = map + offset - 1;
207	if (*op != 0xe8)
208	return -1;
209
210	/* convert to nop */
211	ulseek(fd_map, offset - 1, SEEK_SET);
212	uwrite(fd_map, ideal_nop, 5);
213	return 0;
214	}
215
216	static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
217	static int make_nop_arm64(void *map, size_t const offset)
218	{
219	uint32_t *ptr;
220
221	ptr = map + offset;
222	/* bl <_mcount> is 0x94000000 before relocation */
223	if (*ptr != 0x94000000)
224	return -1;
225
226	/* Convert to nop */
227	ulseek(fd_map, offset, SEEK_SET);
228	uwrite(fd_map, ideal_nop, 4);
229	return 0;
230	}
231
232	/*
233	* Get the whole file as a programming convenience in order to avoid
234	* malloc+lseek+read+free of many pieces. If successful, then mmap
235	* avoids copying unused pieces; else just read the whole file.
236	* Open for both read and write; new info will be appended to the file.
237	* Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
238	* do not propagate to the file until an explicit overwrite at the last.
239	* This preserves most aspects of consistency (all except .st_size)
240	* for simultaneous readers of the file while we are appending to it.
241	* However, multiple writers still are bad. We choose not to use
242	* locking because it is expensive and the use case of kernel build
243	* makes multiple writers unlikely.
244	*/
245	static void *mmap_file(char const *fname)
246	{
247	fd_map = open(fname, O_RDONLY);
248	if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
249	perror(fname);
250	fail_file();
251	}
252	if (!S_ISREG(sb.st_mode)) {
253	fprintf(stderr, "not a regular file: %s\n", fname);
254	fail_file();
255	}
256	file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
257	fd_map, 0);
258	mmap_failed = 0;
259	if (file_map == MAP_FAILED) {
260	mmap_failed = 1;
261	file_map = umalloc(sb.st_size);
262	uread(fd_map, file_map, sb.st_size);
263	}
264	close(fd_map);
265
266	file_end = file_map + sb.st_size;
267
268	return file_map;
269	}
270
271	static void write_file(const char *fname)
272	{
273	char tmp_file[strlen(fname) + 4];
274	size_t n;
275
276	if (!file_updated)
277	return;
278
279	sprintf(tmp_file, "%s.rc", fname);
280
281	/*
282	* After reading the entire file into memory, delete it
283	* and write it back, to prevent weird side effects of modifying
284	* an object file in place.
285	*/
286	fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
287	if (fd_map < 0) {
288	perror(fname);
289	fail_file();
290	}
291	n = write(fd_map, file_map, sb.st_size);
292	if (n != sb.st_size) {
293	perror("write");
294	fail_file();
295	}
296	if (file_append_size) {
297	n = write(fd_map, file_append, file_append_size);
298	if (n != file_append_size) {
299	perror("write");
300	fail_file();
301	}
302	}
303	close(fd_map);
304	if (rename(tmp_file, fname) < 0) {
305	perror(fname);
306	fail_file();
307	}
308	}
309
310	/* w8rev, w8nat, ...: Handle endianness. */
311
312	static uint64_t w8rev(uint64_t const x)
313	{
314	return ((0xff & (x >> (0 * 8))) << (7 * 8))
315	| ((0xff & (x >> (1 * 8))) << (6 * 8))
316	| ((0xff & (x >> (2 * 8))) << (5 * 8))
317	| ((0xff & (x >> (3 * 8))) << (4 * 8))
318	| ((0xff & (x >> (4 * 8))) << (3 * 8))
319	| ((0xff & (x >> (5 * 8))) << (2 * 8))
320	| ((0xff & (x >> (6 * 8))) << (1 * 8))
321	| ((0xff & (x >> (7 * 8))) << (0 * 8));
322	}
323
324	static uint32_t w4rev(uint32_t const x)
325	{
326	return ((0xff & (x >> (0 * 8))) << (3 * 8))
327	| ((0xff & (x >> (1 * 8))) << (2 * 8))
328	| ((0xff & (x >> (2 * 8))) << (1 * 8))
329	| ((0xff & (x >> (3 * 8))) << (0 * 8));
330	}
331
332	static uint32_t w2rev(uint16_t const x)
333	{
334	return ((0xff & (x >> (0 * 8))) << (1 * 8))
335	| ((0xff & (x >> (1 * 8))) << (0 * 8));
336	}
337
338	static uint64_t w8nat(uint64_t const x)
339	{
340	return x;
341	}
342
343	static uint32_t w4nat(uint32_t const x)
344	{
345	return x;
346	}
347
348	static uint32_t w2nat(uint16_t const x)
349	{
350	return x;
351	}
352
353	static uint64_t (*w8)(uint64_t);
354	static uint32_t (*w)(uint32_t);
355	static uint32_t (*w2)(uint16_t);
356
357	/* Names of the sections that could contain calls to mcount. */
358	static int
359	is_mcounted_section_name(char const *const txtname)
360	{
361	return strcmp(".text", txtname) == 0 ||
362	strcmp(".ref.text", txtname) == 0 ||
363	strcmp(".sched.text", txtname) == 0 ||
364	strcmp(".spinlock.text", txtname) == 0 ||
365	strcmp(".irqentry.text", txtname) == 0 ||
366	strcmp(".softirqentry.text", txtname) == 0 ||
367	strcmp(".kprobes.text", txtname) == 0 ||
368	strcmp(".cpuidle.text", txtname) == 0 ||
369	(strncmp(".text.", txtname, 6) == 0 &&
370	strcmp(".text..ftrace", txtname) != 0);
371	}
372
373	/* 32 bit and 64 bit are very similar */
374	#include "recordmcount.h"
375	#define RECORD_MCOUNT_64
376	#include "recordmcount.h"
377
378	/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
379	* http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
380	* We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
381	* to imply the order of the members; the spec does not say so.
382	* typedef unsigned char Elf64_Byte;
383	* fails on MIPS64 because their <elf.h> already has it!
384	*/
385
386	typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
387
388	union mips_r_info {
389	Elf64_Xword r_info;
390	struct {
391	Elf64_Word r_sym; /* Symbol index. */
392	myElf64_Byte r_ssym; /* Special symbol. */
393	myElf64_Byte r_type3; /* Third relocation. */
394	myElf64_Byte r_type2; /* Second relocation. */
395	myElf64_Byte r_type; /* First relocation. */
396	} r_mips;
397	};
398
399	static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
400	{
401	return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
402	}
403
404	static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
405	{
406	rp->r_info = ((union mips_r_info){
407	.r_mips = { .r_sym = w(sym), .r_type = type }
408	}).r_info;
409	}
410
411	static void
412	do_file(char const *const fname)
413	{
414	Elf32_Ehdr *const ehdr = mmap_file(fname);
415	unsigned int reltype = 0;
416
417	w = w4nat;
418	w2 = w2nat;
419	w8 = w8nat;
420	switch (ehdr->e_ident[EI_DATA]) {
421	static unsigned int const endian = 1;
422	default:
423	fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
424	ehdr->e_ident[EI_DATA], fname);
425	fail_file();
426	break;
427	case ELFDATA2LSB:
428	if (*(unsigned char const *)&endian != 1) {
429	/* main() is big endian, file.o is little endian. */
430	w = w4rev;
431	w2 = w2rev;
432	w8 = w8rev;
433	}
434	break;
435	case ELFDATA2MSB:
436	if (*(unsigned char const *)&endian != 0) {
437	/* main() is little endian, file.o is big endian. */
438	w = w4rev;
439	w2 = w2rev;
440	w8 = w8rev;
441	}
442	break;
443	} /* end switch */
444	if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
445	|| w2(ehdr->e_type) != ET_REL
446	|| ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
447	fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
448	fail_file();
449	}
450
451	gpfx = 0;
452	switch (w2(ehdr->e_machine)) {
453	default:
454	fprintf(stderr, "unrecognized e_machine %d %s\n",
455	w2(ehdr->e_machine), fname);
456	fail_file();
457	break;
458	case EM_386:
459	reltype = R_386_32;
460	rel_type_nop = R_386_NONE;
461	make_nop = make_nop_x86;
462	ideal_nop = ideal_nop5_x86_32;
463	mcount_adjust_32 = -1;
464	break;
465	case EM_ARM: reltype = R_ARM_ABS32;
466	altmcount = "__gnu_mcount_nc";
467	break;
468	case EM_AARCH64:
469	reltype = R_AARCH64_ABS64;
470	make_nop = make_nop_arm64;
471	rel_type_nop = R_AARCH64_NONE;
472	ideal_nop = ideal_nop4_arm64;
473	gpfx = '_';
474	break;
475	case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
476	case EM_METAG: reltype = R_METAG_ADDR32;
477	altmcount = "_mcount_wrapper";
478	rel_type_nop = R_METAG_NONE;
479	/* We happen to have the same requirement as MIPS */
480	is_fake_mcount32 = MIPS32_is_fake_mcount;
481	break;
482	case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
483	case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
484	case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
485	case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
486	case EM_SH: reltype = R_SH_DIR32; break;
487	case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
488	case EM_X86_64:
489	make_nop = make_nop_x86;
490	ideal_nop = ideal_nop5_x86_64;
491	reltype = R_X86_64_64;
492	rel_type_nop = R_X86_64_NONE;
493	mcount_adjust_64 = -1;
494	break;
495	} /* end switch */
496
497	switch (ehdr->e_ident[EI_CLASS]) {
498	default:
499	fprintf(stderr, "unrecognized ELF class %d %s\n",
500	ehdr->e_ident[EI_CLASS], fname);
501	fail_file();
502	break;
503	case ELFCLASS32:
504	if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
505	|| w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
506	fprintf(stderr,
507	"unrecognized ET_REL file: %s\n", fname);
508	fail_file();
509	}
510	if (w2(ehdr->e_machine) == EM_MIPS) {
511	reltype = R_MIPS_32;
512	is_fake_mcount32 = MIPS32_is_fake_mcount;
513	}
514	do32(ehdr, fname, reltype);
515	break;
516	case ELFCLASS64: {
517	Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
518	if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
519	|| w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
520	fprintf(stderr,
521	"unrecognized ET_REL file: %s\n", fname);
522	fail_file();
523	}
524	if (w2(ghdr->e_machine) == EM_S390) {
525	reltype = R_390_64;
526	mcount_adjust_64 = -14;
527	}
528	if (w2(ghdr->e_machine) == EM_MIPS) {
529	reltype = R_MIPS_64;
530	Elf64_r_sym = MIPS64_r_sym;
531	Elf64_r_info = MIPS64_r_info;
532	is_fake_mcount64 = MIPS64_is_fake_mcount;
533	}
534	do64(ghdr, fname, reltype);
535	break;
536	}
537	} /* end switch */
538
539	write_file(fname);
540	cleanup();
541	}
542
543	int
544	main(int argc, char *argv[])
545	{
546	const char ftrace[] = "/ftrace.o";
547	int ftrace_size = sizeof(ftrace) - 1;
548	int n_error = 0; /* gcc-4.3.0 false positive complaint */
549	int c;
550	int i;
551
552	while ((c = getopt(argc, argv, "w")) >= 0) {
553	switch (c) {
554	case 'w':
555	warn_on_notrace_sect = 1;
556	break;
557	default:
558	fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
559	return 0;
560	}
561	}
562
563	if ((argc - optind) < 1) {
564	fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
565	return 0;
566	}
567
568	/* Process each file in turn, allowing deep failure. */
569	for (i = optind; i < argc; i++) {
570	char *file = argv[i];
571	int const sjval = setjmp(jmpenv);
572	int len;
573
574	/*
575	* The file kernel/trace/ftrace.o references the mcount
576	* function but does not call it. Since ftrace.o should
577	* not be traced anyway, we just skip it.
578	*/
579	len = strlen(file);
580	if (len >= ftrace_size &&
581	strcmp(file + (len - ftrace_size), ftrace) == 0)
582	continue;
583
584	switch (sjval) {
585	default:
586	fprintf(stderr, "internal error: %s\n", file);
587	exit(1);
588	break;
589	case SJ_SETJMP: /* normal sequence */
590	/* Avoid problems if early cleanup() */
591	fd_map = -1;
592	mmap_failed = 1;
593	file_map = NULL;
594	file_ptr = NULL;
595	file_updated = 0;
596	do_file(file);
597	break;
598	case SJ_FAIL: /* error in do_file or below */
599	fprintf(stderr, "%s: failed\n", file);
600	++n_error;
601	break;
602	case SJ_SUCCEED: /* premature success */
603	/* do nothing */
604	break;
605	} /* end switch */
606	}
607	return !!n_error;
608	}
609