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/scripts/recordmcount.c

http://github.com/mirrors/linux
C | 663 lines | 521 code | 77 blank | 65 comment | 93 complexity | ed7828f81f3391c01e9fc6e48dec8b54 MD5 | raw file
  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * recordmcount.c: construct a table of the locations of calls to 'mcount'
  4 * so that ftrace can find them quickly.
  5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
  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 <stdio.h>
 31#include <stdlib.h>
 32#include <string.h>
 33#include <unistd.h>
 34
 35#ifndef EM_AARCH64
 36#define EM_AARCH64	183
 37#define R_AARCH64_NONE		0
 38#define R_AARCH64_ABS64	257
 39#endif
 40
 41#define R_ARM_PC24		1
 42#define R_ARM_THM_CALL		10
 43#define R_ARM_CALL		28
 44
 45static int fd_map;	/* File descriptor for file being modified. */
 46static int mmap_failed; /* Boolean flag. */
 47static char gpfx;	/* prefix for global symbol name (sometimes '_') */
 48static struct stat sb;	/* Remember .st_size, etc. */
 49static const char *altmcount;	/* alternate mcount symbol name */
 50static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
 51static void *file_map;	/* pointer of the mapped file */
 52static void *file_end;	/* pointer to the end of the mapped file */
 53static int file_updated; /* flag to state file was changed */
 54static void *file_ptr;	/* current file pointer location */
 55
 56static void *file_append; /* added to the end of the file */
 57static size_t file_append_size; /* how much is added to end of file */
 58
 59/* Per-file resource cleanup when multiple files. */
 60static void file_append_cleanup(void)
 61{
 62	free(file_append);
 63	file_append = NULL;
 64	file_append_size = 0;
 65	file_updated = 0;
 66}
 67
 68static void mmap_cleanup(void)
 69{
 70	if (!mmap_failed)
 71		munmap(file_map, sb.st_size);
 72	else
 73		free(file_map);
 74	file_map = NULL;
 75}
 76
 77/* ulseek, uwrite, ...:  Check return value for errors. */
 78
 79static off_t ulseek(off_t const offset, int const whence)
 80{
 81	switch (whence) {
 82	case SEEK_SET:
 83		file_ptr = file_map + offset;
 84		break;
 85	case SEEK_CUR:
 86		file_ptr += offset;
 87		break;
 88	case SEEK_END:
 89		file_ptr = file_map + (sb.st_size - offset);
 90		break;
 91	}
 92	if (file_ptr < file_map) {
 93		fprintf(stderr, "lseek: seek before file\n");
 94		return -1;
 95	}
 96	return file_ptr - file_map;
 97}
 98
 99static ssize_t uwrite(void const *const buf, size_t const count)
100{
101	size_t cnt = count;
102	off_t idx = 0;
103
104	file_updated = 1;
105
106	if (file_ptr + count >= file_end) {
107		off_t aoffset = (file_ptr + count) - file_end;
108
109		if (aoffset > file_append_size) {
110			file_append = realloc(file_append, aoffset);
111			file_append_size = aoffset;
112		}
113		if (!file_append) {
114			perror("write");
115			file_append_cleanup();
116			mmap_cleanup();
117			return -1;
118		}
119		if (file_ptr < file_end) {
120			cnt = file_end - file_ptr;
121		} else {
122			cnt = 0;
123			idx = aoffset - count;
124		}
125	}
126
127	if (cnt)
128		memcpy(file_ptr, buf, cnt);
129
130	if (cnt < count)
131		memcpy(file_append + idx, buf + cnt, count - cnt);
132
133	file_ptr += count;
134	return count;
135}
136
137static void * umalloc(size_t size)
138{
139	void *const addr = malloc(size);
140	if (addr == 0) {
141		fprintf(stderr, "malloc failed: %zu bytes\n", size);
142		file_append_cleanup();
143		mmap_cleanup();
144		return NULL;
145	}
146	return addr;
147}
148
149/*
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	/* Avoid problems if early cleanup() */
165	fd_map = -1;
166	mmap_failed = 1;
167	file_map = NULL;
168	file_ptr = NULL;
169	file_updated = 0;
170	sb.st_size = 0;
171
172	fd_map = open(fname, O_RDONLY);
173	if (fd_map < 0) {
174		perror(fname);
175		return NULL;
176	}
177	if (fstat(fd_map, &sb) < 0) {
178		perror(fname);
179		goto out;
180	}
181	if (!S_ISREG(sb.st_mode)) {
182		fprintf(stderr, "not a regular file: %s\n", fname);
183		goto out;
184	}
185	file_map = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
186			fd_map, 0);
187	if (file_map == MAP_FAILED) {
188		mmap_failed = 1;
189		file_map = umalloc(sb.st_size);
190		if (!file_map) {
191			perror(fname);
192			goto out;
193		}
194		if (read(fd_map, file_map, sb.st_size) != sb.st_size) {
195			perror(fname);
196			free(file_map);
197			file_map = NULL;
198			goto out;
199		}
200	} else
201		mmap_failed = 0;
202out:
203	close(fd_map);
204	fd_map = -1;
205
206	file_end = file_map + sb.st_size;
207
208	return file_map;
209}
210
211
212static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
213static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
214static unsigned char *ideal_nop;
215
216static char rel_type_nop;
217
218static int (*make_nop)(void *map, size_t const offset);
219
220static int make_nop_x86(void *map, size_t const offset)
221{
222	uint32_t *ptr;
223	unsigned char *op;
224
225	/* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
226	ptr = map + offset;
227	if (*ptr != 0)
228		return -1;
229
230	op = map + offset - 1;
231	if (*op != 0xe8)
232		return -1;
233
234	/* convert to nop */
235	if (ulseek(offset - 1, SEEK_SET) < 0)
236		return -1;
237	if (uwrite(ideal_nop, 5) < 0)
238		return -1;
239	return 0;
240}
241
242static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
243static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
244static unsigned char *ideal_nop4_arm;
245
246static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
247static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
248static unsigned char *bl_mcount_arm;
249
250static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
251static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
252static unsigned char *push_arm;
253
254static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
255static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
256static unsigned char *ideal_nop2_thumb;
257
258static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
259static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
260static unsigned char *push_bl_mcount_thumb;
261
262static int make_nop_arm(void *map, size_t const offset)
263{
264	char *ptr;
265	int cnt = 1;
266	int nop_size;
267	size_t off = offset;
268
269	ptr = map + offset;
270	if (memcmp(ptr, bl_mcount_arm, 4) == 0) {
271		if (memcmp(ptr - 4, push_arm, 4) == 0) {
272			off -= 4;
273			cnt = 2;
274		}
275		ideal_nop = ideal_nop4_arm;
276		nop_size = 4;
277	} else if (memcmp(ptr - 2, push_bl_mcount_thumb, 6) == 0) {
278		cnt = 3;
279		nop_size = 2;
280		off -= 2;
281		ideal_nop = ideal_nop2_thumb;
282	} else
283		return -1;
284
285	/* Convert to nop */
286	if (ulseek(off, SEEK_SET) < 0)
287		return -1;
288
289	do {
290		if (uwrite(ideal_nop, nop_size) < 0)
291			return -1;
292	} while (--cnt > 0);
293
294	return 0;
295}
296
297static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
298static int make_nop_arm64(void *map, size_t const offset)
299{
300	uint32_t *ptr;
301
302	ptr = map + offset;
303	/* bl <_mcount> is 0x94000000 before relocation */
304	if (*ptr != 0x94000000)
305		return -1;
306
307	/* Convert to nop */
308	if (ulseek(offset, SEEK_SET) < 0)
309		return -1;
310	if (uwrite(ideal_nop, 4) < 0)
311		return -1;
312	return 0;
313}
314
315static int write_file(const char *fname)
316{
317	char tmp_file[strlen(fname) + 4];
318	size_t n;
319
320	if (!file_updated)
321		return 0;
322
323	sprintf(tmp_file, "%s.rc", fname);
324
325	/*
326	 * After reading the entire file into memory, delete it
327	 * and write it back, to prevent weird side effects of modifying
328	 * an object file in place.
329	 */
330	fd_map = open(tmp_file, O_WRONLY | O_TRUNC | O_CREAT, sb.st_mode);
331	if (fd_map < 0) {
332		perror(fname);
333		return -1;
334	}
335	n = write(fd_map, file_map, sb.st_size);
336	if (n != sb.st_size) {
337		perror("write");
338		close(fd_map);
339		return -1;
340	}
341	if (file_append_size) {
342		n = write(fd_map, file_append, file_append_size);
343		if (n != file_append_size) {
344			perror("write");
345			close(fd_map);
346			return -1;
347		}
348	}
349	close(fd_map);
350	if (rename(tmp_file, fname) < 0) {
351		perror(fname);
352		return -1;
353	}
354	return 0;
355}
356
357/* w8rev, w8nat, ...: Handle endianness. */
358
359static uint64_t w8rev(uint64_t const x)
360{
361	return   ((0xff & (x >> (0 * 8))) << (7 * 8))
362	       | ((0xff & (x >> (1 * 8))) << (6 * 8))
363	       | ((0xff & (x >> (2 * 8))) << (5 * 8))
364	       | ((0xff & (x >> (3 * 8))) << (4 * 8))
365	       | ((0xff & (x >> (4 * 8))) << (3 * 8))
366	       | ((0xff & (x >> (5 * 8))) << (2 * 8))
367	       | ((0xff & (x >> (6 * 8))) << (1 * 8))
368	       | ((0xff & (x >> (7 * 8))) << (0 * 8));
369}
370
371static uint32_t w4rev(uint32_t const x)
372{
373	return   ((0xff & (x >> (0 * 8))) << (3 * 8))
374	       | ((0xff & (x >> (1 * 8))) << (2 * 8))
375	       | ((0xff & (x >> (2 * 8))) << (1 * 8))
376	       | ((0xff & (x >> (3 * 8))) << (0 * 8));
377}
378
379static uint32_t w2rev(uint16_t const x)
380{
381	return   ((0xff & (x >> (0 * 8))) << (1 * 8))
382	       | ((0xff & (x >> (1 * 8))) << (0 * 8));
383}
384
385static uint64_t w8nat(uint64_t const x)
386{
387	return x;
388}
389
390static uint32_t w4nat(uint32_t const x)
391{
392	return x;
393}
394
395static uint32_t w2nat(uint16_t const x)
396{
397	return x;
398}
399
400static uint64_t (*w8)(uint64_t);
401static uint32_t (*w)(uint32_t);
402static uint32_t (*w2)(uint16_t);
403
404/* Names of the sections that could contain calls to mcount. */
405static int is_mcounted_section_name(char const *const txtname)
406{
407	return strncmp(".text",          txtname, 5) == 0 ||
408		strcmp(".init.text",     txtname) == 0 ||
409		strcmp(".ref.text",      txtname) == 0 ||
410		strcmp(".sched.text",    txtname) == 0 ||
411		strcmp(".spinlock.text", txtname) == 0 ||
412		strcmp(".irqentry.text", txtname) == 0 ||
413		strcmp(".softirqentry.text", txtname) == 0 ||
414		strcmp(".kprobes.text", txtname) == 0 ||
415		strcmp(".cpuidle.text", txtname) == 0;
416}
417
418static char const *already_has_rel_mcount = "success"; /* our work here is done! */
419
420/* 32 bit and 64 bit are very similar */
421#include "recordmcount.h"
422#define RECORD_MCOUNT_64
423#include "recordmcount.h"
424
425static int arm_is_fake_mcount(Elf32_Rel const *rp)
426{
427	switch (ELF32_R_TYPE(w(rp->r_info))) {
428	case R_ARM_THM_CALL:
429	case R_ARM_CALL:
430	case R_ARM_PC24:
431		return 0;
432	}
433
434	return 1;
435}
436
437/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
438 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
439 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
440 * to imply the order of the members; the spec does not say so.
441 *	typedef unsigned char Elf64_Byte;
442 * fails on MIPS64 because their <elf.h> already has it!
443 */
444
445typedef uint8_t myElf64_Byte;		/* Type for a 8-bit quantity.  */
446
447union mips_r_info {
448	Elf64_Xword r_info;
449	struct {
450		Elf64_Word r_sym;		/* Symbol index.  */
451		myElf64_Byte r_ssym;		/* Special symbol.  */
452		myElf64_Byte r_type3;		/* Third relocation.  */
453		myElf64_Byte r_type2;		/* Second relocation.  */
454		myElf64_Byte r_type;		/* First relocation.  */
455	} r_mips;
456};
457
458static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
459{
460	return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
461}
462
463static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
464{
465	rp->r_info = ((union mips_r_info){
466		.r_mips = { .r_sym = w(sym), .r_type = type }
467	}).r_info;
468}
469
470static int do_file(char const *const fname)
471{
472	unsigned int reltype = 0;
473	Elf32_Ehdr *ehdr;
474	int rc = -1;
475
476	ehdr = mmap_file(fname);
477	if (!ehdr)
478		goto out;
479
480	w = w4nat;
481	w2 = w2nat;
482	w8 = w8nat;
483	switch (ehdr->e_ident[EI_DATA]) {
484		static unsigned int const endian = 1;
485	default:
486		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
487			ehdr->e_ident[EI_DATA], fname);
488		goto out;
489	case ELFDATA2LSB:
490		if (*(unsigned char const *)&endian != 1) {
491			/* main() is big endian, file.o is little endian. */
492			w = w4rev;
493			w2 = w2rev;
494			w8 = w8rev;
495		}
496		ideal_nop4_arm = ideal_nop4_arm_le;
497		bl_mcount_arm = bl_mcount_arm_le;
498		push_arm = push_arm_le;
499		ideal_nop2_thumb = ideal_nop2_thumb_le;
500		push_bl_mcount_thumb = push_bl_mcount_thumb_le;
501		break;
502	case ELFDATA2MSB:
503		if (*(unsigned char const *)&endian != 0) {
504			/* main() is little endian, file.o is big endian. */
505			w = w4rev;
506			w2 = w2rev;
507			w8 = w8rev;
508		}
509		ideal_nop4_arm = ideal_nop4_arm_be;
510		bl_mcount_arm = bl_mcount_arm_be;
511		push_arm = push_arm_be;
512		ideal_nop2_thumb = ideal_nop2_thumb_be;
513		push_bl_mcount_thumb = push_bl_mcount_thumb_be;
514		break;
515	}  /* end switch */
516	if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 ||
517	    w2(ehdr->e_type) != ET_REL ||
518	    ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
519		fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
520		goto out;
521	}
522
523	gpfx = '_';
524	switch (w2(ehdr->e_machine)) {
525	default:
526		fprintf(stderr, "unrecognized e_machine %u %s\n",
527			w2(ehdr->e_machine), fname);
528		goto out;
529	case EM_386:
530		reltype = R_386_32;
531		rel_type_nop = R_386_NONE;
532		make_nop = make_nop_x86;
533		ideal_nop = ideal_nop5_x86_32;
534		mcount_adjust_32 = -1;
535		gpfx = 0;
536		break;
537	case EM_ARM:
538		reltype = R_ARM_ABS32;
539		altmcount = "__gnu_mcount_nc";
540		make_nop = make_nop_arm;
541		rel_type_nop = R_ARM_NONE;
542		is_fake_mcount32 = arm_is_fake_mcount;
543		gpfx = 0;
544		break;
545	case EM_AARCH64:
546		reltype = R_AARCH64_ABS64;
547		make_nop = make_nop_arm64;
548		rel_type_nop = R_AARCH64_NONE;
549		ideal_nop = ideal_nop4_arm64;
550		break;
551	case EM_IA_64:	reltype = R_IA64_IMM64; break;
552	case EM_MIPS:	/* reltype: e_class    */ break;
553	case EM_PPC:	reltype = R_PPC_ADDR32; break;
554	case EM_PPC64:	reltype = R_PPC64_ADDR64; break;
555	case EM_S390:	/* reltype: e_class    */ break;
556	case EM_SH:	reltype = R_SH_DIR32; gpfx = 0; break;
557	case EM_SPARCV9: reltype = R_SPARC_64; break;
558	case EM_X86_64:
559		make_nop = make_nop_x86;
560		ideal_nop = ideal_nop5_x86_64;
561		reltype = R_X86_64_64;
562		rel_type_nop = R_X86_64_NONE;
563		mcount_adjust_64 = -1;
564		gpfx = 0;
565		break;
566	}  /* end switch */
567
568	switch (ehdr->e_ident[EI_CLASS]) {
569	default:
570		fprintf(stderr, "unrecognized ELF class %d %s\n",
571			ehdr->e_ident[EI_CLASS], fname);
572		goto out;
573	case ELFCLASS32:
574		if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
575		||  w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
576			fprintf(stderr,
577				"unrecognized ET_REL file: %s\n", fname);
578			goto out;
579		}
580		if (w2(ehdr->e_machine) == EM_MIPS) {
581			reltype = R_MIPS_32;
582			is_fake_mcount32 = MIPS32_is_fake_mcount;
583		}
584		if (do32(ehdr, fname, reltype) < 0)
585			goto out;
586		break;
587	case ELFCLASS64: {
588		Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
589		if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
590		||  w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
591			fprintf(stderr,
592				"unrecognized ET_REL file: %s\n", fname);
593			goto out;
594		}
595		if (w2(ghdr->e_machine) == EM_S390) {
596			reltype = R_390_64;
597			mcount_adjust_64 = -14;
598		}
599		if (w2(ghdr->e_machine) == EM_MIPS) {
600			reltype = R_MIPS_64;
601			Elf64_r_sym = MIPS64_r_sym;
602			Elf64_r_info = MIPS64_r_info;
603			is_fake_mcount64 = MIPS64_is_fake_mcount;
604		}
605		if (do64(ghdr, fname, reltype) < 0)
606			goto out;
607		break;
608	}
609	}  /* end switch */
610
611	rc = write_file(fname);
612out:
613	file_append_cleanup();
614	mmap_cleanup();
615	return rc;
616}
617
618int main(int argc, char *argv[])
619{
620	const char ftrace[] = "/ftrace.o";
621	int ftrace_size = sizeof(ftrace) - 1;
622	int n_error = 0;  /* gcc-4.3.0 false positive complaint */
623	int c;
624	int i;
625
626	while ((c = getopt(argc, argv, "w")) >= 0) {
627		switch (c) {
628		case 'w':
629			warn_on_notrace_sect = 1;
630			break;
631		default:
632			fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
633			return 0;
634		}
635	}
636
637	if ((argc - optind) < 1) {
638		fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
639		return 0;
640	}
641
642	/* Process each file in turn, allowing deep failure. */
643	for (i = optind; i < argc; i++) {
644		char *file = argv[i];
645		int len;
646
647		/*
648		 * The file kernel/trace/ftrace.o references the mcount
649		 * function but does not call it. Since ftrace.o should
650		 * not be traced anyway, we just skip it.
651		 */
652		len = strlen(file);
653		if (len >= ftrace_size &&
654		    strcmp(file + (len - ftrace_size), ftrace) == 0)
655			continue;
656
657		if (do_file(file)) {
658			fprintf(stderr, "%s: failed\n", file);
659			++n_error;
660		}
661	}
662	return !!n_error;
663}