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>
35 static int fd_map
; /* File descriptor for file being modified. */
36 static int mmap_failed
; /* Boolean flag. */
37 static void *ehdr_curr
; /* current ElfXX_Ehdr * for resource cleanup */
38 static char gpfx
; /* prefix for global symbol name (sometimes '_') */
39 static struct stat sb
; /* Remember .st_size, etc. */
40 static jmp_buf jmpenv
; /* setjmp/longjmp per-file error escape */
41 static const char *altmcount
; /* alternate mcount symbol name */
43 /* setjmp() return values */
45 SJ_SETJMP
= 0, /* hardwired first return */
50 /* Per-file resource cleanup when multiple files. */
55 munmap(ehdr_curr
, sb
.st_size
);
61 static void __attribute__((noreturn
))
65 longjmp(jmpenv
, SJ_FAIL
);
68 static void __attribute__((noreturn
))
72 longjmp(jmpenv
, SJ_SUCCEED
);
75 /* ulseek, uread, ...: Check return value for errors. */
78 ulseek(int const fd
, off_t
const offset
, int const whence
)
80 off_t
const w
= lseek(fd
, offset
, whence
);
89 uread(int const fd
, void *const buf
, size_t const count
)
91 size_t const n
= read(fd
, buf
, count
);
100 uwrite(int const fd
, void const *const buf
, size_t const count
)
102 size_t const n
= write(fd
, buf
, count
);
113 void *const addr
= malloc(size
);
115 fprintf(stderr
, "malloc failed: %zu bytes\n", size
);
122 * Get the whole file as a programming convenience in order to avoid
123 * malloc+lseek+read+free of many pieces. If successful, then mmap
124 * avoids copying unused pieces; else just read the whole file.
125 * Open for both read and write; new info will be appended to the file.
126 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
127 * do not propagate to the file until an explicit overwrite at the last.
128 * This preserves most aspects of consistency (all except .st_size)
129 * for simultaneous readers of the file while we are appending to it.
130 * However, multiple writers still are bad. We choose not to use
131 * locking because it is expensive and the use case of kernel build
132 * makes multiple writers unlikely.
134 static void *mmap_file(char const *fname
)
138 fd_map
= open(fname
, O_RDWR
);
139 if (0 > fd_map
|| 0 > fstat(fd_map
, &sb
)) {
143 if (!S_ISREG(sb
.st_mode
)) {
144 fprintf(stderr
, "not a regular file: %s\n", fname
);
147 addr
= mmap(0, sb
.st_size
, PROT_READ
|PROT_WRITE
, MAP_PRIVATE
,
150 if (MAP_FAILED
== addr
) {
152 addr
= umalloc(sb
.st_size
);
153 uread(fd_map
, addr
, sb
.st_size
);
158 /* w8rev, w8nat, ...: Handle endianness. */
160 static uint64_t w8rev(uint64_t const x
)
162 return ((0xff & (x
>> (0 * 8))) << (7 * 8))
163 | ((0xff & (x
>> (1 * 8))) << (6 * 8))
164 | ((0xff & (x
>> (2 * 8))) << (5 * 8))
165 | ((0xff & (x
>> (3 * 8))) << (4 * 8))
166 | ((0xff & (x
>> (4 * 8))) << (3 * 8))
167 | ((0xff & (x
>> (5 * 8))) << (2 * 8))
168 | ((0xff & (x
>> (6 * 8))) << (1 * 8))
169 | ((0xff & (x
>> (7 * 8))) << (0 * 8));
172 static uint32_t w4rev(uint32_t const x
)
174 return ((0xff & (x
>> (0 * 8))) << (3 * 8))
175 | ((0xff & (x
>> (1 * 8))) << (2 * 8))
176 | ((0xff & (x
>> (2 * 8))) << (1 * 8))
177 | ((0xff & (x
>> (3 * 8))) << (0 * 8));
180 static uint32_t w2rev(uint16_t const x
)
182 return ((0xff & (x
>> (0 * 8))) << (1 * 8))
183 | ((0xff & (x
>> (1 * 8))) << (0 * 8));
186 static uint64_t w8nat(uint64_t const x
)
191 static uint32_t w4nat(uint32_t const x
)
196 static uint32_t w2nat(uint16_t const x
)
201 static uint64_t (*w8
)(uint64_t);
202 static uint32_t (*w
)(uint32_t);
203 static uint32_t (*w2
)(uint16_t);
205 /* Names of the sections that could contain calls to mcount. */
207 is_mcounted_section_name(char const *const txtname
)
209 return 0 == strcmp(".text", txtname
) ||
210 0 == strcmp(".ref.text", txtname
) ||
211 0 == strcmp(".sched.text", txtname
) ||
212 0 == strcmp(".spinlock.text", txtname
) ||
213 0 == strcmp(".irqentry.text", txtname
) ||
214 0 == strcmp(".text.unlikely", txtname
);
217 /* 32 bit and 64 bit are very similar */
218 #include "recordmcount.h"
219 #define RECORD_MCOUNT_64
220 #include "recordmcount.h"
222 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
223 * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
224 * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
225 * to imply the order of the members; the spec does not say so.
226 * typedef unsigned char Elf64_Byte;
227 * fails on MIPS64 because their <elf.h> already has it!
230 typedef uint8_t myElf64_Byte
; /* Type for a 8-bit quantity. */
235 Elf64_Word r_sym
; /* Symbol index. */
236 myElf64_Byte r_ssym
; /* Special symbol. */
237 myElf64_Byte r_type3
; /* Third relocation. */
238 myElf64_Byte r_type2
; /* Second relocation. */
239 myElf64_Byte r_type
; /* First relocation. */
243 static uint64_t MIPS64_r_sym(Elf64_Rel
const *rp
)
245 return w(((union mips_r_info
){ .r_info
= rp
->r_info
}).r_mips
.r_sym
);
248 static void MIPS64_r_info(Elf64_Rel
*const rp
, unsigned sym
, unsigned type
)
250 rp
->r_info
= ((union mips_r_info
){
251 .r_mips
= { .r_sym
= w(sym
), .r_type
= type
}
256 do_file(char const *const fname
)
258 Elf32_Ehdr
*const ehdr
= mmap_file(fname
);
259 unsigned int reltype
= 0;
265 switch (ehdr
->e_ident
[EI_DATA
]) {
266 static unsigned int const endian
= 1;
268 fprintf(stderr
, "unrecognized ELF data encoding %d: %s\n",
269 ehdr
->e_ident
[EI_DATA
], fname
);
273 if (1 != *(unsigned char const *)&endian
) {
274 /* main() is big endian, file.o is little endian. */
281 if (0 != *(unsigned char const *)&endian
) {
282 /* main() is little endian, file.o is big endian. */
289 if (0 != memcmp(ELFMAG
, ehdr
->e_ident
, SELFMAG
)
290 || ET_REL
!= w2(ehdr
->e_type
)
291 || EV_CURRENT
!= ehdr
->e_ident
[EI_VERSION
]) {
292 fprintf(stderr
, "unrecognized ET_REL file %s\n", fname
);
297 switch (w2(ehdr
->e_machine
)) {
299 fprintf(stderr
, "unrecognized e_machine %d %s\n",
300 w2(ehdr
->e_machine
), fname
);
303 case EM_386
: reltype
= R_386_32
; break;
304 case EM_ARM
: reltype
= R_ARM_ABS32
;
305 altmcount
= "__gnu_mcount_nc";
307 case EM_IA_64
: reltype
= R_IA64_IMM64
; gpfx
= '_'; break;
308 case EM_MIPS
: /* reltype: e_class */ gpfx
= '_'; break;
309 case EM_PPC
: reltype
= R_PPC_ADDR32
; gpfx
= '_'; break;
310 case EM_PPC64
: reltype
= R_PPC64_ADDR64
; gpfx
= '_'; break;
311 case EM_S390
: /* reltype: e_class */ gpfx
= '_'; break;
312 case EM_SH
: reltype
= R_SH_DIR32
; break;
313 case EM_SPARCV9
: reltype
= R_SPARC_64
; gpfx
= '_'; break;
314 case EM_X86_64
: reltype
= R_X86_64_64
; break;
317 switch (ehdr
->e_ident
[EI_CLASS
]) {
319 fprintf(stderr
, "unrecognized ELF class %d %s\n",
320 ehdr
->e_ident
[EI_CLASS
], fname
);
324 if (sizeof(Elf32_Ehdr
) != w2(ehdr
->e_ehsize
)
325 || sizeof(Elf32_Shdr
) != w2(ehdr
->e_shentsize
)) {
327 "unrecognized ET_REL file: %s\n", fname
);
330 if (EM_S390
== w2(ehdr
->e_machine
))
332 if (EM_MIPS
== w2(ehdr
->e_machine
)) {
334 is_fake_mcount32
= MIPS32_is_fake_mcount
;
336 do32(ehdr
, fname
, reltype
);
339 Elf64_Ehdr
*const ghdr
= (Elf64_Ehdr
*)ehdr
;
340 if (sizeof(Elf64_Ehdr
) != w2(ghdr
->e_ehsize
)
341 || sizeof(Elf64_Shdr
) != w2(ghdr
->e_shentsize
)) {
343 "unrecognized ET_REL file: %s\n", fname
);
346 if (EM_S390
== w2(ghdr
->e_machine
))
348 if (EM_MIPS
== w2(ghdr
->e_machine
)) {
350 Elf64_r_sym
= MIPS64_r_sym
;
351 Elf64_r_info
= MIPS64_r_info
;
352 is_fake_mcount64
= MIPS64_is_fake_mcount
;
354 do64(ghdr
, fname
, reltype
);
362 main(int argc
, char const *argv
[])
364 const char ftrace
[] = "/ftrace.o";
365 int ftrace_size
= sizeof(ftrace
) - 1;
366 int n_error
= 0; /* gcc-4.3.0 false positive complaint */
369 fprintf(stderr
, "usage: recordmcount file.o...\n");
373 /* Process each file in turn, allowing deep failure. */
374 for (--argc
, ++argv
; 0 < argc
; --argc
, ++argv
) {
375 int const sjval
= setjmp(jmpenv
);
379 * The file kernel/trace/ftrace.o references the mcount
380 * function but does not call it. Since ftrace.o should
381 * not be traced anyway, we just skip it.
383 len
= strlen(argv
[0]);
384 if (len
>= ftrace_size
&&
385 strcmp(argv
[0] + (len
- ftrace_size
), ftrace
) == 0)
390 fprintf(stderr
, "internal error: %s\n", argv
[0]);
393 case SJ_SETJMP
: { /* normal sequence */
394 /* Avoid problems if early cleanup() */
400 case SJ_FAIL
: { /* error in do_file or below */
403 case SJ_SUCCEED
: { /* premature success */
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