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 */