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 */
42 /* setjmp() return values */
44 SJ_SETJMP = 0, /* hardwired first return */
49 /* Per-file resource cleanup when multiple files. */
54 munmap(ehdr_curr, sb.st_size);
60 static void __attribute__((noreturn))
64 longjmp(jmpenv, SJ_FAIL);
67 static void __attribute__((noreturn))
71 longjmp(jmpenv, SJ_SUCCEED);
74 /* ulseek, uread, ...: Check return value for errors. */
77 ulseek(int const fd, off_t const offset, int const whence)
79 off_t const w = lseek(fd, offset, whence);
88 uread(int const fd, void *const buf, size_t const count)
90 size_t const n = read(fd, buf, count);
99 uwrite(int const fd, void const *const buf, size_t const count)
101 size_t const n = write(fd, buf, count);
112 void *const addr = malloc(size);
114 fprintf(stderr, "malloc failed: %zu bytes\n", size);
121 * Get the whole file as a programming convenience in order to avoid
122 * malloc+lseek+read+free of many pieces. If successful, then mmap
123 * avoids copying unused pieces; else just read the whole file.
124 * Open for both read and write; new info will be appended to the file.
125 * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
126 * do not propagate to the file until an explicit overwrite at the last.
127 * This preserves most aspects of consistency (all except .st_size)
128 * for simultaneous readers of the file while we are appending to it.
129 * However, multiple writers still are bad. We choose not to use
130 * locking because it is expensive and the use case of kernel build
131 * makes multiple writers unlikely.
133 static void *mmap_file(char const *fname)
137 fd_map = open(fname, O_RDWR);
138 if (0 > fd_map || 0 > fstat(fd_map, &sb)) {
142 if (!S_ISREG(sb.st_mode)) {
143 fprintf(stderr, "not a regular file: %s\n", fname);
146 addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
149 if (MAP_FAILED == addr) {
151 addr = umalloc(sb.st_size);
152 uread(fd_map, addr, sb.st_size);
157 /* w8rev, w8nat, ...: Handle endianness. */
159 static uint64_t w8rev(uint64_t const x)
161 return ((0xff & (x >> (0 * 8))) << (7 * 8))
162 | ((0xff & (x >> (1 * 8))) << (6 * 8))
163 | ((0xff & (x >> (2 * 8))) << (5 * 8))
164 | ((0xff & (x >> (3 * 8))) << (4 * 8))
165 | ((0xff & (x >> (4 * 8))) << (3 * 8))
166 | ((0xff & (x >> (5 * 8))) << (2 * 8))
167 | ((0xff & (x >> (6 * 8))) << (1 * 8))
168 | ((0xff & (x >> (7 * 8))) << (0 * 8));
171 static uint32_t w4rev(uint32_t const x)
173 return ((0xff & (x >> (0 * 8))) << (3 * 8))
174 | ((0xff & (x >> (1 * 8))) << (2 * 8))
175 | ((0xff & (x >> (2 * 8))) << (1 * 8))
176 | ((0xff & (x >> (3 * 8))) << (0 * 8));
179 static uint32_t w2rev(uint16_t const x)
181 return ((0xff & (x >> (0 * 8))) << (1 * 8))
182 | ((0xff & (x >> (1 * 8))) << (0 * 8));
185 static uint64_t w8nat(uint64_t const x)
190 static uint32_t w4nat(uint32_t const x)
195 static uint32_t w2nat(uint16_t const x)
200 static uint64_t (*w8)(uint64_t);
201 static uint32_t (*w)(uint32_t);
202 static uint32_t (*w2)(uint16_t);
204 /* Names of the sections that could contain calls to mcount. */
206 is_mcounted_section_name(char const *const txtname)
208 return 0 == strcmp(".text", txtname) ||
209 0 == strcmp(".sched.text", txtname) ||
210 0 == strcmp(".spinlock.text", txtname) ||
211 0 == strcmp(".irqentry.text", txtname) ||
212 0 == strcmp(".text.unlikely", txtname);
215 /* 32 bit and 64 bit are very similar */
216 #include "recordmcount.h"
217 #define RECORD_MCOUNT_64
218 #include "recordmcount.h"
221 do_file(char const *const fname)
223 Elf32_Ehdr *const ehdr = mmap_file(fname);
224 unsigned int reltype = 0;
230 switch (ehdr->e_ident[EI_DATA]) {
231 static unsigned int const endian = 1;
233 fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
234 ehdr->e_ident[EI_DATA], fname);
238 if (1 != *(unsigned char const *)&endian) {
239 /* main() is big endian, file.o is little endian. */
246 if (0 != *(unsigned char const *)&endian) {
247 /* main() is little endian, file.o is big endian. */
254 if (0 != memcmp(ELFMAG, ehdr->e_ident, SELFMAG)
255 || ET_REL != w2(ehdr->e_type)
256 || EV_CURRENT != ehdr->e_ident[EI_VERSION]) {
257 fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
262 switch (w2(ehdr->e_machine)) {
264 fprintf(stderr, "unrecognized e_machine %d %s\n",
265 w2(ehdr->e_machine), fname);
268 case EM_386: reltype = R_386_32; break;
269 case EM_ARM: reltype = R_ARM_ABS32; break;
270 case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
271 case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
272 case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
273 case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
274 case EM_SH: reltype = R_SH_DIR32; break;
275 case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
276 case EM_X86_64: reltype = R_X86_64_64; break;
279 switch (ehdr->e_ident[EI_CLASS]) {
281 fprintf(stderr, "unrecognized ELF class %d %s\n",
282 ehdr->e_ident[EI_CLASS], fname);
286 if (sizeof(Elf32_Ehdr) != w2(ehdr->e_ehsize)
287 || sizeof(Elf32_Shdr) != w2(ehdr->e_shentsize)) {
289 "unrecognized ET_REL file: %s\n", fname);
292 if (EM_S390 == w2(ehdr->e_machine))
294 do32(ehdr, fname, reltype);
297 Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
298 if (sizeof(Elf64_Ehdr) != w2(ghdr->e_ehsize)
299 || sizeof(Elf64_Shdr) != w2(ghdr->e_shentsize)) {
301 "unrecognized ET_REL file: %s\n", fname);
304 if (EM_S390 == w2(ghdr->e_machine))
306 do64(ghdr, fname, reltype);
314 main(int argc, char const *argv[])
316 const char ftrace[] = "kernel/trace/ftrace.o";
317 int ftrace_size = sizeof(ftrace) - 1;
318 int n_error = 0; /* gcc-4.3.0 false positive complaint */
321 fprintf(stderr, "usage: recordmcount file.o...\n");
325 /* Process each file in turn, allowing deep failure. */
326 for (--argc, ++argv; 0 < argc; --argc, ++argv) {
327 int const sjval = setjmp(jmpenv);
331 * The file kernel/trace/ftrace.o references the mcount
332 * function but does not call it. Since ftrace.o should
333 * not be traced anyway, we just skip it.
335 len = strlen(argv[0]);
336 if (len >= ftrace_size &&
337 strcmp(argv[0] + (len - ftrace_size), ftrace) == 0)
342 fprintf(stderr, "internal error: %s\n", argv[0]);
345 case SJ_SETJMP: { /* normal sequence */
346 /* Avoid problems if early cleanup() */
352 case SJ_FAIL: { /* error in do_file or below */
355 case SJ_SUCCEED: { /* premature success */