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).
7 * Restructured to fit Linux format, as well as other updates:
8 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
12 * Strategy: alter the .o file in-place.
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.]
24 #include <sys/types.h>
37 /* Remove this when these make it to the standard system elf.h. */
39 #define R_METAG_ADDR32 2
40 #define R_METAG_NONE 3
44 #define EM_AARCH64 183
45 #define R_AARCH64_NONE 0
46 #define R_AARCH64_ABS64 257
49 static int fd_map
; /* File descriptor for file being modified. */
50 static int mmap_failed
; /* Boolean flag. */
51 static void *ehdr_curr
; /* current ElfXX_Ehdr * for resource cleanup */
52 static char gpfx
; /* prefix for global symbol name (sometimes '_') */
53 static struct stat sb
; /* Remember .st_size, etc. */
54 static jmp_buf jmpenv
; /* setjmp/longjmp per-file error escape */
55 static const char *altmcount
; /* alternate mcount symbol name */
56 static int warn_on_notrace_sect
; /* warn when section has mcount not being recorded */
58 /* setjmp() return values */
60 SJ_SETJMP
= 0, /* hardwired first return */
65 /* Per-file resource cleanup when multiple files. */
70 munmap(ehdr_curr
, sb
.st_size
);
76 static void __attribute__((noreturn
))
80 longjmp(jmpenv
, SJ_FAIL
);
83 static void __attribute__((noreturn
))
87 longjmp(jmpenv
, SJ_SUCCEED
);
90 /* ulseek, uread, ...: Check return value for errors. */
93 ulseek(int const fd
, off_t
const offset
, int const whence
)
95 off_t
const w
= lseek(fd
, offset
, whence
);
104 uread(int const fd
, void *const buf
, size_t const count
)
106 size_t const n
= read(fd
, buf
, count
);
115 uwrite(int const fd
, void const *const buf
, size_t const count
)
117 size_t const n
= write(fd
, buf
, count
);
128 void *const addr
= malloc(size
);
130 fprintf(stderr
, "malloc failed: %zu bytes\n", size
);
136 static unsigned char ideal_nop5_x86_64
[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
137 static unsigned char ideal_nop5_x86_32
[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
138 static unsigned char *ideal_nop
;
140 static char rel_type_nop
;
142 static int (*make_nop
)(void *map
, size_t const offset
);
144 static int make_nop_x86(void *map
, size_t const offset
)
149 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
154 op
= map
+ offset
- 1;
159 ulseek(fd_map
, offset
- 1, SEEK_SET
);
160 uwrite(fd_map
, ideal_nop
, 5);
164 static unsigned char ideal_nop4_arm64
[4] = {0x1f, 0x20, 0x03, 0xd5};
165 static int make_nop_arm64(void *map
, size_t const offset
)
170 /* bl <_mcount> is 0x94000000 before relocation */
171 if (*ptr
!= 0x94000000)
175 ulseek(fd_map
, offset
, SEEK_SET
);
176 uwrite(fd_map
, ideal_nop
, 4);
181 * Get the whole file as a programming convenience in order to avoid
182 * malloc+lseek+read+free of many pieces. If successful, then mmap
183 * avoids copying unused pieces; else just read the whole file.
184 * Open for both read and write; new info will be appended to the file.
185 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
186 * do not propagate to the file until an explicit overwrite at the last.
187 * This preserves most aspects of consistency (all except .st_size)
188 * for simultaneous readers of the file while we are appending to it.
189 * However, multiple writers still are bad. We choose not to use
190 * locking because it is expensive and the use case of kernel build
191 * makes multiple writers unlikely.
193 static void *mmap_file(char const *fname
)
197 fd_map
= open(fname
, O_RDWR
);
198 if (fd_map
< 0 || fstat(fd_map
, &sb
) < 0) {
202 if (!S_ISREG(sb
.st_mode
)) {
203 fprintf(stderr
, "not a regular file: %s\n", fname
);
206 addr
= mmap(0, sb
.st_size
, PROT_READ
|PROT_WRITE
, MAP_PRIVATE
,
209 if (addr
== MAP_FAILED
) {
211 addr
= umalloc(sb
.st_size
);
212 uread(fd_map
, addr
, sb
.st_size
);
217 /* w8rev, w8nat, ...: Handle endianness. */
219 static uint64_t w8rev(uint64_t const x
)
221 return ((0xff & (x
>> (0 * 8))) << (7 * 8))
222 | ((0xff & (x
>> (1 * 8))) << (6 * 8))
223 | ((0xff & (x
>> (2 * 8))) << (5 * 8))
224 | ((0xff & (x
>> (3 * 8))) << (4 * 8))
225 | ((0xff & (x
>> (4 * 8))) << (3 * 8))
226 | ((0xff & (x
>> (5 * 8))) << (2 * 8))
227 | ((0xff & (x
>> (6 * 8))) << (1 * 8))
228 | ((0xff & (x
>> (7 * 8))) << (0 * 8));
231 static uint32_t w4rev(uint32_t const x
)
233 return ((0xff & (x
>> (0 * 8))) << (3 * 8))
234 | ((0xff & (x
>> (1 * 8))) << (2 * 8))
235 | ((0xff & (x
>> (2 * 8))) << (1 * 8))
236 | ((0xff & (x
>> (3 * 8))) << (0 * 8));
239 static uint32_t w2rev(uint16_t const x
)
241 return ((0xff & (x
>> (0 * 8))) << (1 * 8))
242 | ((0xff & (x
>> (1 * 8))) << (0 * 8));
245 static uint64_t w8nat(uint64_t const x
)
250 static uint32_t w4nat(uint32_t const x
)
255 static uint32_t w2nat(uint16_t const x
)
260 static uint64_t (*w8
)(uint64_t);
261 static uint32_t (*w
)(uint32_t);
262 static uint32_t (*w2
)(uint16_t);
264 /* Names of the sections that could contain calls to mcount. */
266 is_mcounted_section_name(char const *const txtname
)
268 return strcmp(".text", txtname
) == 0 ||
269 strcmp(".ref.text", txtname
) == 0 ||
270 strcmp(".sched.text", txtname
) == 0 ||
271 strcmp(".spinlock.text", txtname
) == 0 ||
272 strcmp(".irqentry.text", txtname
) == 0 ||
273 strcmp(".kprobes.text", txtname
) == 0 ||
274 strcmp(".text.unlikely", txtname
) == 0;
277 /* 32 bit and 64 bit are very similar */
278 #include "recordmcount.h"
279 #define RECORD_MCOUNT_64
280 #include "recordmcount.h"
282 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
283 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
284 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
285 * to imply the order of the members; the spec does not say so.
286 * typedef unsigned char Elf64_Byte;
287 * fails on MIPS64 because their <elf.h> already has it!
290 typedef uint8_t myElf64_Byte
; /* Type for a 8-bit quantity. */
295 Elf64_Word r_sym
; /* Symbol index. */
296 myElf64_Byte r_ssym
; /* Special symbol. */
297 myElf64_Byte r_type3
; /* Third relocation. */
298 myElf64_Byte r_type2
; /* Second relocation. */
299 myElf64_Byte r_type
; /* First relocation. */
303 static uint64_t MIPS64_r_sym(Elf64_Rel
const *rp
)
305 return w(((union mips_r_info
){ .r_info
= rp
->r_info
}).r_mips
.r_sym
);
308 static void MIPS64_r_info(Elf64_Rel
*const rp
, unsigned sym
, unsigned type
)
310 rp
->r_info
= ((union mips_r_info
){
311 .r_mips
= { .r_sym
= w(sym
), .r_type
= type
}
316 do_file(char const *const fname
)
318 Elf32_Ehdr
*const ehdr
= mmap_file(fname
);
319 unsigned int reltype
= 0;
325 switch (ehdr
->e_ident
[EI_DATA
]) {
326 static unsigned int const endian
= 1;
328 fprintf(stderr
, "unrecognized ELF data encoding %d: %s\n",
329 ehdr
->e_ident
[EI_DATA
], fname
);
333 if (*(unsigned char const *)&endian
!= 1) {
334 /* main() is big endian, file.o is little endian. */
341 if (*(unsigned char const *)&endian
!= 0) {
342 /* main() is little endian, file.o is big endian. */
349 if (memcmp(ELFMAG
, ehdr
->e_ident
, SELFMAG
) != 0
350 || w2(ehdr
->e_type
) != ET_REL
351 || ehdr
->e_ident
[EI_VERSION
] != EV_CURRENT
) {
352 fprintf(stderr
, "unrecognized ET_REL file %s\n", fname
);
357 switch (w2(ehdr
->e_machine
)) {
359 fprintf(stderr
, "unrecognized e_machine %d %s\n",
360 w2(ehdr
->e_machine
), fname
);
365 rel_type_nop
= R_386_NONE
;
366 make_nop
= make_nop_x86
;
367 ideal_nop
= ideal_nop5_x86_32
;
368 mcount_adjust_32
= -1;
370 case EM_ARM
: reltype
= R_ARM_ABS32
;
371 altmcount
= "__gnu_mcount_nc";
374 reltype
= R_AARCH64_ABS64
;
375 make_nop
= make_nop_arm64
;
376 rel_type_nop
= R_AARCH64_NONE
;
377 ideal_nop
= ideal_nop4_arm64
;
380 case EM_IA_64
: reltype
= R_IA64_IMM64
; gpfx
= '_'; break;
381 case EM_METAG
: reltype
= R_METAG_ADDR32
;
382 altmcount
= "_mcount_wrapper";
383 rel_type_nop
= R_METAG_NONE
;
384 /* We happen to have the same requirement as MIPS */
385 is_fake_mcount32
= MIPS32_is_fake_mcount
;
387 case EM_MIPS
: /* reltype: e_class */ gpfx
= '_'; break;
388 case EM_PPC
: reltype
= R_PPC_ADDR32
; gpfx
= '_'; break;
389 case EM_PPC64
: reltype
= R_PPC64_ADDR64
; gpfx
= '_'; break;
390 case EM_S390
: /* reltype: e_class */ gpfx
= '_'; break;
391 case EM_SH
: reltype
= R_SH_DIR32
; break;
392 case EM_SPARCV9
: reltype
= R_SPARC_64
; gpfx
= '_'; break;
394 make_nop
= make_nop_x86
;
395 ideal_nop
= ideal_nop5_x86_64
;
396 reltype
= R_X86_64_64
;
397 rel_type_nop
= R_X86_64_NONE
;
398 mcount_adjust_64
= -1;
402 switch (ehdr
->e_ident
[EI_CLASS
]) {
404 fprintf(stderr
, "unrecognized ELF class %d %s\n",
405 ehdr
->e_ident
[EI_CLASS
], fname
);
409 if (w2(ehdr
->e_ehsize
) != sizeof(Elf32_Ehdr
)
410 || w2(ehdr
->e_shentsize
) != sizeof(Elf32_Shdr
)) {
412 "unrecognized ET_REL file: %s\n", fname
);
415 if (w2(ehdr
->e_machine
) == EM_MIPS
) {
417 is_fake_mcount32
= MIPS32_is_fake_mcount
;
419 do32(ehdr
, fname
, reltype
);
422 Elf64_Ehdr
*const ghdr
= (Elf64_Ehdr
*)ehdr
;
423 if (w2(ghdr
->e_ehsize
) != sizeof(Elf64_Ehdr
)
424 || w2(ghdr
->e_shentsize
) != sizeof(Elf64_Shdr
)) {
426 "unrecognized ET_REL file: %s\n", fname
);
429 if (w2(ghdr
->e_machine
) == EM_S390
) {
431 mcount_adjust_64
= -14;
433 if (w2(ghdr
->e_machine
) == EM_MIPS
) {
435 Elf64_r_sym
= MIPS64_r_sym
;
436 Elf64_r_info
= MIPS64_r_info
;
437 is_fake_mcount64
= MIPS64_is_fake_mcount
;
439 do64(ghdr
, fname
, reltype
);
448 main(int argc
, char *argv
[])
450 const char ftrace
[] = "/ftrace.o";
451 int ftrace_size
= sizeof(ftrace
) - 1;
452 int n_error
= 0; /* gcc-4.3.0 false positive complaint */
456 while ((c
= getopt(argc
, argv
, "w")) >= 0) {
459 warn_on_notrace_sect
= 1;
462 fprintf(stderr
, "usage: recordmcount [-w] file.o...\n");
467 if ((argc
- optind
) < 1) {
468 fprintf(stderr
, "usage: recordmcount [-w] file.o...\n");
472 /* Process each file in turn, allowing deep failure. */
473 for (i
= optind
; i
< argc
; i
++) {
474 char *file
= argv
[i
];
475 int const sjval
= setjmp(jmpenv
);
479 * The file kernel/trace/ftrace.o references the mcount
480 * function but does not call it. Since ftrace.o should
481 * not be traced anyway, we just skip it.
484 if (len
>= ftrace_size
&&
485 strcmp(file
+ (len
- ftrace_size
), ftrace
) == 0)
490 fprintf(stderr
, "internal error: %s\n", file
);
493 case SJ_SETJMP
: /* normal sequence */
494 /* Avoid problems if early cleanup() */
500 case SJ_FAIL
: /* error in do_file or below */
503 case SJ_SUCCEED
: /* premature success */
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