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
43 static int fd_map
; /* File descriptor for file being modified. */
44 static int mmap_failed
; /* Boolean flag. */
45 static void *ehdr_curr
; /* current ElfXX_Ehdr * for resource cleanup */
46 static char gpfx
; /* prefix for global symbol name (sometimes '_') */
47 static struct stat sb
; /* Remember .st_size, etc. */
48 static jmp_buf jmpenv
; /* setjmp/longjmp per-file error escape */
49 static const char *altmcount
; /* alternate mcount symbol name */
50 static int warn_on_notrace_sect
; /* warn when section has mcount not being recorded */
52 /* setjmp() return values */
54 SJ_SETJMP
= 0, /* hardwired first return */
59 /* Per-file resource cleanup when multiple files. */
64 munmap(ehdr_curr
, sb
.st_size
);
70 static void __attribute__((noreturn
))
74 longjmp(jmpenv
, SJ_FAIL
);
77 static void __attribute__((noreturn
))
81 longjmp(jmpenv
, SJ_SUCCEED
);
84 /* ulseek, uread, ...: Check return value for errors. */
87 ulseek(int const fd
, off_t
const offset
, int const whence
)
89 off_t
const w
= lseek(fd
, offset
, whence
);
98 uread(int const fd
, void *const buf
, size_t const count
)
100 size_t const n
= read(fd
, buf
, count
);
109 uwrite(int const fd
, void const *const buf
, size_t const count
)
111 size_t const n
= write(fd
, buf
, count
);
122 void *const addr
= malloc(size
);
124 fprintf(stderr
, "malloc failed: %zu bytes\n", size
);
130 static unsigned char ideal_nop5_x86_64
[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
131 static unsigned char ideal_nop5_x86_32
[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
132 static unsigned char *ideal_nop
;
134 static char rel_type_nop
;
136 static int (*make_nop
)(void *map
, size_t const offset
);
138 static int make_nop_x86(void *map
, size_t const offset
)
143 /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
148 op
= map
+ offset
- 1;
153 ulseek(fd_map
, offset
- 1, SEEK_SET
);
154 uwrite(fd_map
, ideal_nop
, 5);
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.
171 static void *mmap_file(char const *fname
)
175 fd_map
= open(fname
, O_RDWR
);
176 if (fd_map
< 0 || fstat(fd_map
, &sb
) < 0) {
180 if (!S_ISREG(sb
.st_mode
)) {
181 fprintf(stderr
, "not a regular file: %s\n", fname
);
184 addr
= mmap(0, sb
.st_size
, PROT_READ
|PROT_WRITE
, MAP_PRIVATE
,
187 if (addr
== MAP_FAILED
) {
189 addr
= umalloc(sb
.st_size
);
190 uread(fd_map
, addr
, sb
.st_size
);
192 if (sb
.st_nlink
!= 1) {
193 /* file is hard-linked, break the hard link */
195 if (unlink(fname
) < 0) {
199 fd_map
= open(fname
, O_RDWR
| O_CREAT
, sb
.st_mode
);
204 uwrite(fd_map
, addr
, sb
.st_size
);
209 /* w8rev, w8nat, ...: Handle endianness. */
211 static uint64_t w8rev(uint64_t const x
)
213 return ((0xff & (x
>> (0 * 8))) << (7 * 8))
214 | ((0xff & (x
>> (1 * 8))) << (6 * 8))
215 | ((0xff & (x
>> (2 * 8))) << (5 * 8))
216 | ((0xff & (x
>> (3 * 8))) << (4 * 8))
217 | ((0xff & (x
>> (4 * 8))) << (3 * 8))
218 | ((0xff & (x
>> (5 * 8))) << (2 * 8))
219 | ((0xff & (x
>> (6 * 8))) << (1 * 8))
220 | ((0xff & (x
>> (7 * 8))) << (0 * 8));
223 static uint32_t w4rev(uint32_t const x
)
225 return ((0xff & (x
>> (0 * 8))) << (3 * 8))
226 | ((0xff & (x
>> (1 * 8))) << (2 * 8))
227 | ((0xff & (x
>> (2 * 8))) << (1 * 8))
228 | ((0xff & (x
>> (3 * 8))) << (0 * 8));
231 static uint32_t w2rev(uint16_t const x
)
233 return ((0xff & (x
>> (0 * 8))) << (1 * 8))
234 | ((0xff & (x
>> (1 * 8))) << (0 * 8));
237 static uint64_t w8nat(uint64_t const x
)
242 static uint32_t w4nat(uint32_t const x
)
247 static uint32_t w2nat(uint16_t const x
)
252 static uint64_t (*w8
)(uint64_t);
253 static uint32_t (*w
)(uint32_t);
254 static uint32_t (*w2
)(uint16_t);
256 /* Names of the sections that could contain calls to mcount. */
258 is_mcounted_section_name(char const *const txtname
)
260 return strcmp(".text", txtname
) == 0 ||
261 strcmp(".ref.text", txtname
) == 0 ||
262 strcmp(".sched.text", txtname
) == 0 ||
263 strcmp(".spinlock.text", txtname
) == 0 ||
264 strcmp(".irqentry.text", txtname
) == 0 ||
265 strcmp(".kprobes.text", txtname
) == 0 ||
266 strcmp(".text.unlikely", txtname
) == 0;
269 /* 32 bit and 64 bit are very similar */
270 #include "recordmcount.h"
271 #define RECORD_MCOUNT_64
272 #include "recordmcount.h"
274 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
275 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
276 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
277 * to imply the order of the members; the spec does not say so.
278 * typedef unsigned char Elf64_Byte;
279 * fails on MIPS64 because their <elf.h> already has it!
282 typedef uint8_t myElf64_Byte
; /* Type for a 8-bit quantity. */
287 Elf64_Word r_sym
; /* Symbol index. */
288 myElf64_Byte r_ssym
; /* Special symbol. */
289 myElf64_Byte r_type3
; /* Third relocation. */
290 myElf64_Byte r_type2
; /* Second relocation. */
291 myElf64_Byte r_type
; /* First relocation. */
295 static uint64_t MIPS64_r_sym(Elf64_Rel
const *rp
)
297 return w(((union mips_r_info
){ .r_info
= rp
->r_info
}).r_mips
.r_sym
);
300 static void MIPS64_r_info(Elf64_Rel
*const rp
, unsigned sym
, unsigned type
)
302 rp
->r_info
= ((union mips_r_info
){
303 .r_mips
= { .r_sym
= w(sym
), .r_type
= type
}
308 do_file(char const *const fname
)
310 Elf32_Ehdr
*const ehdr
= mmap_file(fname
);
311 unsigned int reltype
= 0;
317 switch (ehdr
->e_ident
[EI_DATA
]) {
318 static unsigned int const endian
= 1;
320 fprintf(stderr
, "unrecognized ELF data encoding %d: %s\n",
321 ehdr
->e_ident
[EI_DATA
], fname
);
325 if (*(unsigned char const *)&endian
!= 1) {
326 /* main() is big endian, file.o is little endian. */
333 if (*(unsigned char const *)&endian
!= 0) {
334 /* main() is little endian, file.o is big endian. */
341 if (memcmp(ELFMAG
, ehdr
->e_ident
, SELFMAG
) != 0
342 || w2(ehdr
->e_type
) != ET_REL
343 || ehdr
->e_ident
[EI_VERSION
] != EV_CURRENT
) {
344 fprintf(stderr
, "unrecognized ET_REL file %s\n", fname
);
349 switch (w2(ehdr
->e_machine
)) {
351 fprintf(stderr
, "unrecognized e_machine %d %s\n",
352 w2(ehdr
->e_machine
), fname
);
357 make_nop
= make_nop_x86
;
358 ideal_nop
= ideal_nop5_x86_32
;
359 mcount_adjust_32
= -1;
361 case EM_ARM
: reltype
= R_ARM_ABS32
;
362 altmcount
= "__gnu_mcount_nc";
364 case EM_IA_64
: reltype
= R_IA64_IMM64
; gpfx
= '_'; break;
365 case EM_METAG
: reltype
= R_METAG_ADDR32
;
366 altmcount
= "_mcount_wrapper";
367 rel_type_nop
= R_METAG_NONE
;
368 /* We happen to have the same requirement as MIPS */
369 is_fake_mcount32
= MIPS32_is_fake_mcount
;
371 case EM_MIPS
: /* reltype: e_class */ gpfx
= '_'; break;
372 case EM_PPC
: reltype
= R_PPC_ADDR32
; gpfx
= '_'; break;
373 case EM_PPC64
: reltype
= R_PPC64_ADDR64
; gpfx
= '_'; break;
374 case EM_S390
: /* reltype: e_class */ gpfx
= '_'; break;
375 case EM_SH
: reltype
= R_SH_DIR32
; break;
376 case EM_SPARCV9
: reltype
= R_SPARC_64
; gpfx
= '_'; break;
378 make_nop
= make_nop_x86
;
379 ideal_nop
= ideal_nop5_x86_64
;
380 reltype
= R_X86_64_64
;
381 mcount_adjust_64
= -1;
385 switch (ehdr
->e_ident
[EI_CLASS
]) {
387 fprintf(stderr
, "unrecognized ELF class %d %s\n",
388 ehdr
->e_ident
[EI_CLASS
], fname
);
392 if (w2(ehdr
->e_ehsize
) != sizeof(Elf32_Ehdr
)
393 || w2(ehdr
->e_shentsize
) != sizeof(Elf32_Shdr
)) {
395 "unrecognized ET_REL file: %s\n", fname
);
398 if (w2(ehdr
->e_machine
) == EM_S390
) {
400 mcount_adjust_32
= -4;
402 if (w2(ehdr
->e_machine
) == EM_MIPS
) {
404 is_fake_mcount32
= MIPS32_is_fake_mcount
;
406 do32(ehdr
, fname
, reltype
);
409 Elf64_Ehdr
*const ghdr
= (Elf64_Ehdr
*)ehdr
;
410 if (w2(ghdr
->e_ehsize
) != sizeof(Elf64_Ehdr
)
411 || w2(ghdr
->e_shentsize
) != sizeof(Elf64_Shdr
)) {
413 "unrecognized ET_REL file: %s\n", fname
);
416 if (w2(ghdr
->e_machine
) == EM_S390
) {
418 mcount_adjust_64
= -8;
420 if (w2(ghdr
->e_machine
) == EM_MIPS
) {
422 Elf64_r_sym
= MIPS64_r_sym
;
423 Elf64_r_info
= MIPS64_r_info
;
424 is_fake_mcount64
= MIPS64_is_fake_mcount
;
426 do64(ghdr
, fname
, reltype
);
435 main(int argc
, char *argv
[])
437 const char ftrace
[] = "/ftrace.o";
438 int ftrace_size
= sizeof(ftrace
) - 1;
439 int n_error
= 0; /* gcc-4.3.0 false positive complaint */
443 while ((c
= getopt(argc
, argv
, "w")) >= 0) {
446 warn_on_notrace_sect
= 1;
449 fprintf(stderr
, "usage: recordmcount [-w] file.o...\n");
454 if ((argc
- optind
) < 1) {
455 fprintf(stderr
, "usage: recordmcount [-w] file.o...\n");
459 /* Process each file in turn, allowing deep failure. */
460 for (i
= optind
; i
< argc
; i
++) {
461 char *file
= argv
[i
];
462 int const sjval
= setjmp(jmpenv
);
466 * The file kernel/trace/ftrace.o references the mcount
467 * function but does not call it. Since ftrace.o should
468 * not be traced anyway, we just skip it.
471 if (len
>= ftrace_size
&&
472 strcmp(file
+ (len
- ftrace_size
), ftrace
) == 0)
477 fprintf(stderr
, "internal error: %s\n", file
);
480 case SJ_SETJMP
: /* normal sequence */
481 /* Avoid problems if early cleanup() */
487 case SJ_FAIL
: /* error in do_file or below */
490 case SJ_SUCCEED
: /* premature success */