412 lines
11 KiB
C
412 lines
11 KiB
C
/*
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* recordmcount.c: construct a table of the locations of calls to 'mcount'
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* so that ftrace can find them quickly.
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* Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
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* Licensed under the GNU General Public License, version 2 (GPLv2).
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*
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* Restructured to fit Linux format, as well as other updates:
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* Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
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*/
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/*
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* Strategy: alter the .o file in-place.
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*
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* Append a new STRTAB that has the new section names, followed by a new array
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* ElfXX_Shdr[] that has the new section headers, followed by the section
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* contents for __mcount_loc and its relocations. The old shstrtab strings,
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* and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple
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* kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader)
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* will ignore the garbage regions, because they are not designated by the
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* new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage,
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* then use "ld -r" to create a new file that omits the garbage.]
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*/
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <elf.h>
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#include <fcntl.h>
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#include <setjmp.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static int fd_map; /* File descriptor for file being modified. */
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static int mmap_failed; /* Boolean flag. */
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static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
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static char gpfx; /* prefix for global symbol name (sometimes '_') */
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static struct stat sb; /* Remember .st_size, etc. */
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static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
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static const char *altmcount; /* alternate mcount symbol name */
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/* setjmp() return values */
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enum {
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SJ_SETJMP = 0, /* hardwired first return */
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SJ_FAIL,
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SJ_SUCCEED
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};
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/* Per-file resource cleanup when multiple files. */
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static void
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cleanup(void)
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{
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if (!mmap_failed)
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munmap(ehdr_curr, sb.st_size);
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else
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free(ehdr_curr);
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close(fd_map);
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}
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static void __attribute__((noreturn))
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fail_file(void)
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{
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cleanup();
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longjmp(jmpenv, SJ_FAIL);
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}
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static void __attribute__((noreturn))
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succeed_file(void)
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{
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cleanup();
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longjmp(jmpenv, SJ_SUCCEED);
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}
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/* ulseek, uread, ...: Check return value for errors. */
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static off_t
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ulseek(int const fd, off_t const offset, int const whence)
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{
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off_t const w = lseek(fd, offset, whence);
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if ((off_t)-1 == w) {
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perror("lseek");
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fail_file();
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}
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return w;
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}
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static size_t
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uread(int const fd, void *const buf, size_t const count)
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{
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size_t const n = read(fd, buf, count);
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if (n != count) {
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perror("read");
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fail_file();
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}
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return n;
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}
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static size_t
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uwrite(int const fd, void const *const buf, size_t const count)
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{
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size_t const n = write(fd, buf, count);
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if (n != count) {
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perror("write");
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fail_file();
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}
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return n;
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}
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static void *
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umalloc(size_t size)
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{
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void *const addr = malloc(size);
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if (0 == addr) {
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fprintf(stderr, "malloc failed: %zu bytes\n", size);
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fail_file();
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}
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return addr;
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}
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/*
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* Get the whole file as a programming convenience in order to avoid
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* malloc+lseek+read+free of many pieces. If successful, then mmap
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* avoids copying unused pieces; else just read the whole file.
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* Open for both read and write; new info will be appended to the file.
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* Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
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* do not propagate to the file until an explicit overwrite at the last.
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* This preserves most aspects of consistency (all except .st_size)
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* for simultaneous readers of the file while we are appending to it.
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* However, multiple writers still are bad. We choose not to use
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* locking because it is expensive and the use case of kernel build
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* makes multiple writers unlikely.
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*/
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static void *mmap_file(char const *fname)
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{
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void *addr;
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fd_map = open(fname, O_RDWR);
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if (0 > fd_map || 0 > fstat(fd_map, &sb)) {
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perror(fname);
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fail_file();
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}
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if (!S_ISREG(sb.st_mode)) {
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fprintf(stderr, "not a regular file: %s\n", fname);
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fail_file();
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}
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addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
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fd_map, 0);
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mmap_failed = 0;
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if (MAP_FAILED == addr) {
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mmap_failed = 1;
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addr = umalloc(sb.st_size);
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uread(fd_map, addr, sb.st_size);
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}
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return addr;
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}
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/* w8rev, w8nat, ...: Handle endianness. */
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static uint64_t w8rev(uint64_t const x)
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{
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return ((0xff & (x >> (0 * 8))) << (7 * 8))
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| ((0xff & (x >> (1 * 8))) << (6 * 8))
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| ((0xff & (x >> (2 * 8))) << (5 * 8))
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| ((0xff & (x >> (3 * 8))) << (4 * 8))
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| ((0xff & (x >> (4 * 8))) << (3 * 8))
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| ((0xff & (x >> (5 * 8))) << (2 * 8))
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| ((0xff & (x >> (6 * 8))) << (1 * 8))
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| ((0xff & (x >> (7 * 8))) << (0 * 8));
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}
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static uint32_t w4rev(uint32_t const x)
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{
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return ((0xff & (x >> (0 * 8))) << (3 * 8))
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| ((0xff & (x >> (1 * 8))) << (2 * 8))
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| ((0xff & (x >> (2 * 8))) << (1 * 8))
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| ((0xff & (x >> (3 * 8))) << (0 * 8));
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}
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static uint32_t w2rev(uint16_t const x)
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{
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return ((0xff & (x >> (0 * 8))) << (1 * 8))
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| ((0xff & (x >> (1 * 8))) << (0 * 8));
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}
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static uint64_t w8nat(uint64_t const x)
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{
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return x;
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}
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static uint32_t w4nat(uint32_t const x)
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{
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return x;
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}
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static uint32_t w2nat(uint16_t const x)
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{
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return x;
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}
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static uint64_t (*w8)(uint64_t);
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static uint32_t (*w)(uint32_t);
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static uint32_t (*w2)(uint16_t);
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/* Names of the sections that could contain calls to mcount. */
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static int
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is_mcounted_section_name(char const *const txtname)
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{
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return 0 == strcmp(".text", txtname) ||
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0 == strcmp(".ref.text", txtname) ||
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0 == strcmp(".sched.text", txtname) ||
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0 == strcmp(".spinlock.text", txtname) ||
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0 == strcmp(".irqentry.text", txtname) ||
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0 == strcmp(".text.unlikely", txtname);
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}
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/* 32 bit and 64 bit are very similar */
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#include "recordmcount.h"
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#define RECORD_MCOUNT_64
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#include "recordmcount.h"
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/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
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* http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
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* We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
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* to imply the order of the members; the spec does not say so.
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* typedef unsigned char Elf64_Byte;
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* fails on MIPS64 because their <elf.h> already has it!
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*/
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typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
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union mips_r_info {
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Elf64_Xword r_info;
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struct {
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Elf64_Word r_sym; /* Symbol index. */
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myElf64_Byte r_ssym; /* Special symbol. */
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myElf64_Byte r_type3; /* Third relocation. */
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myElf64_Byte r_type2; /* Second relocation. */
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myElf64_Byte r_type; /* First relocation. */
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} r_mips;
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};
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static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
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{
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return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
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}
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static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
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{
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rp->r_info = ((union mips_r_info){
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.r_mips = { .r_sym = w(sym), .r_type = type }
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}).r_info;
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}
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static void
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do_file(char const *const fname)
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{
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Elf32_Ehdr *const ehdr = mmap_file(fname);
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unsigned int reltype = 0;
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ehdr_curr = ehdr;
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w = w4nat;
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w2 = w2nat;
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w8 = w8nat;
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switch (ehdr->e_ident[EI_DATA]) {
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static unsigned int const endian = 1;
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default: {
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fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
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ehdr->e_ident[EI_DATA], fname);
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fail_file();
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} break;
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case ELFDATA2LSB: {
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if (1 != *(unsigned char const *)&endian) {
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/* main() is big endian, file.o is little endian. */
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w = w4rev;
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w2 = w2rev;
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w8 = w8rev;
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}
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} break;
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case ELFDATA2MSB: {
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if (0 != *(unsigned char const *)&endian) {
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/* main() is little endian, file.o is big endian. */
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w = w4rev;
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w2 = w2rev;
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w8 = w8rev;
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}
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} break;
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} /* end switch */
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if (0 != memcmp(ELFMAG, ehdr->e_ident, SELFMAG)
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|| ET_REL != w2(ehdr->e_type)
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|| EV_CURRENT != ehdr->e_ident[EI_VERSION]) {
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fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
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fail_file();
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}
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gpfx = 0;
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switch (w2(ehdr->e_machine)) {
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default: {
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fprintf(stderr, "unrecognized e_machine %d %s\n",
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w2(ehdr->e_machine), fname);
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fail_file();
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} break;
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case EM_386: reltype = R_386_32; break;
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case EM_ARM: reltype = R_ARM_ABS32;
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altmcount = "__gnu_mcount_nc";
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break;
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case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
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case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
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case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
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case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
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case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
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case EM_SH: reltype = R_SH_DIR32; break;
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case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
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case EM_X86_64: reltype = R_X86_64_64; break;
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} /* end switch */
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switch (ehdr->e_ident[EI_CLASS]) {
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default: {
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fprintf(stderr, "unrecognized ELF class %d %s\n",
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ehdr->e_ident[EI_CLASS], fname);
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fail_file();
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} break;
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case ELFCLASS32: {
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if (sizeof(Elf32_Ehdr) != w2(ehdr->e_ehsize)
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|| sizeof(Elf32_Shdr) != w2(ehdr->e_shentsize)) {
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fprintf(stderr,
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"unrecognized ET_REL file: %s\n", fname);
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fail_file();
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}
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if (EM_S390 == w2(ehdr->e_machine))
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reltype = R_390_32;
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if (EM_MIPS == w2(ehdr->e_machine)) {
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reltype = R_MIPS_32;
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is_fake_mcount32 = MIPS32_is_fake_mcount;
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}
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do32(ehdr, fname, reltype);
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} break;
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case ELFCLASS64: {
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Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
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if (sizeof(Elf64_Ehdr) != w2(ghdr->e_ehsize)
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|| sizeof(Elf64_Shdr) != w2(ghdr->e_shentsize)) {
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fprintf(stderr,
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"unrecognized ET_REL file: %s\n", fname);
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fail_file();
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}
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if (EM_S390 == w2(ghdr->e_machine))
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reltype = R_390_64;
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if (EM_MIPS == w2(ghdr->e_machine)) {
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reltype = R_MIPS_64;
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Elf64_r_sym = MIPS64_r_sym;
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Elf64_r_info = MIPS64_r_info;
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is_fake_mcount64 = MIPS64_is_fake_mcount;
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}
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do64(ghdr, fname, reltype);
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} break;
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} /* end switch */
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cleanup();
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}
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int
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main(int argc, char const *argv[])
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{
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const char ftrace[] = "/ftrace.o";
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int ftrace_size = sizeof(ftrace) - 1;
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int n_error = 0; /* gcc-4.3.0 false positive complaint */
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if (argc <= 1) {
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fprintf(stderr, "usage: recordmcount file.o...\n");
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return 0;
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}
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/* Process each file in turn, allowing deep failure. */
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for (--argc, ++argv; 0 < argc; --argc, ++argv) {
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int const sjval = setjmp(jmpenv);
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int len;
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/*
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* The file kernel/trace/ftrace.o references the mcount
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* function but does not call it. Since ftrace.o should
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* not be traced anyway, we just skip it.
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*/
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len = strlen(argv[0]);
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if (len >= ftrace_size &&
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strcmp(argv[0] + (len - ftrace_size), ftrace) == 0)
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continue;
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switch (sjval) {
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default: {
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fprintf(stderr, "internal error: %s\n", argv[0]);
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exit(1);
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} break;
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case SJ_SETJMP: { /* normal sequence */
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/* Avoid problems if early cleanup() */
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fd_map = -1;
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ehdr_curr = NULL;
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mmap_failed = 1;
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do_file(argv[0]);
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} break;
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case SJ_FAIL: { /* error in do_file or below */
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++n_error;
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} break;
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case SJ_SUCCEED: { /* premature success */
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/* do nothing */
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} break;
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} /* end switch */
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}
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return !!n_error;
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}
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