diff options
Diffstat (limited to 'scripts/recordmcount.c')
-rw-r--r-- | scripts/recordmcount.c | 471 |
1 files changed, 471 insertions, 0 deletions
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c new file mode 100644 index 00000000..ee52cb8e --- /dev/null +++ b/scripts/recordmcount.c @@ -0,0 +1,471 @@ +/* + * recordmcount.c: construct a table of the locations of calls to 'mcount' + * so that ftrace can find them quickly. + * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. + * Licensed under the GNU General Public License, version 2 (GPLv2). + * + * Restructured to fit Linux format, as well as other updates: + * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. + */ + +/* + * Strategy: alter the .o file in-place. + * + * Append a new STRTAB that has the new section names, followed by a new array + * ElfXX_Shdr[] that has the new section headers, followed by the section + * contents for __mcount_loc and its relocations. The old shstrtab strings, + * and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple + * kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader) + * will ignore the garbage regions, because they are not designated by the + * new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage, + * then use "ld -r" to create a new file that omits the garbage.] + */ + +#include <sys/types.h> +#include <sys/mman.h> +#include <sys/stat.h> +#include <getopt.h> +#include <elf.h> +#include <fcntl.h> +#include <setjmp.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +static int fd_map; /* File descriptor for file being modified. */ +static int mmap_failed; /* Boolean flag. */ +static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */ +static char gpfx; /* prefix for global symbol name (sometimes '_') */ +static struct stat sb; /* Remember .st_size, etc. */ +static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */ +static const char *altmcount; /* alternate mcount symbol name */ +static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */ + +/* setjmp() return values */ +enum { + SJ_SETJMP = 0, /* hardwired first return */ + SJ_FAIL, + SJ_SUCCEED +}; + +/* Per-file resource cleanup when multiple files. */ +static void +cleanup(void) +{ + if (!mmap_failed) + munmap(ehdr_curr, sb.st_size); + else + free(ehdr_curr); + close(fd_map); +} + +static void __attribute__((noreturn)) +fail_file(void) +{ + cleanup(); + longjmp(jmpenv, SJ_FAIL); +} + +static void __attribute__((noreturn)) +succeed_file(void) +{ + cleanup(); + longjmp(jmpenv, SJ_SUCCEED); +} + +/* ulseek, uread, ...: Check return value for errors. */ + +static off_t +ulseek(int const fd, off_t const offset, int const whence) +{ + off_t const w = lseek(fd, offset, whence); + if (w == (off_t)-1) { + perror("lseek"); + fail_file(); + } + return w; +} + +static size_t +uread(int const fd, void *const buf, size_t const count) +{ + size_t const n = read(fd, buf, count); + if (n != count) { + perror("read"); + fail_file(); + } + return n; +} + +static size_t +uwrite(int const fd, void const *const buf, size_t const count) +{ + size_t const n = write(fd, buf, count); + if (n != count) { + perror("write"); + fail_file(); + } + return n; +} + +static void * +umalloc(size_t size) +{ + void *const addr = malloc(size); + if (addr == 0) { + fprintf(stderr, "malloc failed: %zu bytes\n", size); + fail_file(); + } + return addr; +} + +static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; +static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; +static unsigned char *ideal_nop; + +static char rel_type_nop; + +static int (*make_nop)(void *map, size_t const offset); + +static int make_nop_x86(void *map, size_t const offset) +{ + uint32_t *ptr; + unsigned char *op; + + /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ + ptr = map + offset; + if (*ptr != 0) + return -1; + + op = map + offset - 1; + if (*op != 0xe8) + return -1; + + /* convert to nop */ + ulseek(fd_map, offset - 1, SEEK_SET); + uwrite(fd_map, ideal_nop, 5); + return 0; +} + +/* + * Get the whole file as a programming convenience in order to avoid + * malloc+lseek+read+free of many pieces. If successful, then mmap + * avoids copying unused pieces; else just read the whole file. + * Open for both read and write; new info will be appended to the file. + * Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr + * do not propagate to the file until an explicit overwrite at the last. + * This preserves most aspects of consistency (all except .st_size) + * for simultaneous readers of the file while we are appending to it. + * However, multiple writers still are bad. We choose not to use + * locking because it is expensive and the use case of kernel build + * makes multiple writers unlikely. + */ +static void *mmap_file(char const *fname) +{ + void *addr; + + fd_map = open(fname, O_RDWR); + if (fd_map < 0 || fstat(fd_map, &sb) < 0) { + perror(fname); + fail_file(); + } + if (!S_ISREG(sb.st_mode)) { + fprintf(stderr, "not a regular file: %s\n", fname); + fail_file(); + } + addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, + fd_map, 0); + mmap_failed = 0; + if (addr == MAP_FAILED) { + mmap_failed = 1; + addr = umalloc(sb.st_size); + uread(fd_map, addr, sb.st_size); + } + return addr; +} + +/* w8rev, w8nat, ...: Handle endianness. */ + +static uint64_t w8rev(uint64_t const x) +{ + return ((0xff & (x >> (0 * 8))) << (7 * 8)) + | ((0xff & (x >> (1 * 8))) << (6 * 8)) + | ((0xff & (x >> (2 * 8))) << (5 * 8)) + | ((0xff & (x >> (3 * 8))) << (4 * 8)) + | ((0xff & (x >> (4 * 8))) << (3 * 8)) + | ((0xff & (x >> (5 * 8))) << (2 * 8)) + | ((0xff & (x >> (6 * 8))) << (1 * 8)) + | ((0xff & (x >> (7 * 8))) << (0 * 8)); +} + +static uint32_t w4rev(uint32_t const x) +{ + return ((0xff & (x >> (0 * 8))) << (3 * 8)) + | ((0xff & (x >> (1 * 8))) << (2 * 8)) + | ((0xff & (x >> (2 * 8))) << (1 * 8)) + | ((0xff & (x >> (3 * 8))) << (0 * 8)); +} + +static uint32_t w2rev(uint16_t const x) +{ + return ((0xff & (x >> (0 * 8))) << (1 * 8)) + | ((0xff & (x >> (1 * 8))) << (0 * 8)); +} + +static uint64_t w8nat(uint64_t const x) +{ + return x; +} + +static uint32_t w4nat(uint32_t const x) +{ + return x; +} + +static uint32_t w2nat(uint16_t const x) +{ + return x; +} + +static uint64_t (*w8)(uint64_t); +static uint32_t (*w)(uint32_t); +static uint32_t (*w2)(uint16_t); + +/* Names of the sections that could contain calls to mcount. */ +static int +is_mcounted_section_name(char const *const txtname) +{ + return strcmp(".text", txtname) == 0 || + strcmp(".ref.text", txtname) == 0 || + strcmp(".sched.text", txtname) == 0 || + strcmp(".spinlock.text", txtname) == 0 || + strcmp(".irqentry.text", txtname) == 0 || + strcmp(".kprobes.text", txtname) == 0 || + strcmp(".text.unlikely", txtname) == 0; +} + +/* 32 bit and 64 bit are very similar */ +#include "recordmcount.h" +#define RECORD_MCOUNT_64 +#include "recordmcount.h" + +/* 64-bit EM_MIPS has weird ELF64_Rela.r_info. + * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf + * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40] + * to imply the order of the members; the spec does not say so. + * typedef unsigned char Elf64_Byte; + * fails on MIPS64 because their <elf.h> already has it! + */ + +typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */ + +union mips_r_info { + Elf64_Xword r_info; + struct { + Elf64_Word r_sym; /* Symbol index. */ + myElf64_Byte r_ssym; /* Special symbol. */ + myElf64_Byte r_type3; /* Third relocation. */ + myElf64_Byte r_type2; /* Second relocation. */ + myElf64_Byte r_type; /* First relocation. */ + } r_mips; +}; + +static uint64_t MIPS64_r_sym(Elf64_Rel const *rp) +{ + return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym); +} + +static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) +{ + rp->r_info = ((union mips_r_info){ + .r_mips = { .r_sym = w(sym), .r_type = type } + }).r_info; +} + +static void +do_file(char const *const fname) +{ + Elf32_Ehdr *const ehdr = mmap_file(fname); + unsigned int reltype = 0; + + ehdr_curr = ehdr; + w = w4nat; + w2 = w2nat; + w8 = w8nat; + switch (ehdr->e_ident[EI_DATA]) { + static unsigned int const endian = 1; + default: + fprintf(stderr, "unrecognized ELF data encoding %d: %s\n", + ehdr->e_ident[EI_DATA], fname); + fail_file(); + break; + case ELFDATA2LSB: + if (*(unsigned char const *)&endian != 1) { + /* main() is big endian, file.o is little endian. */ + w = w4rev; + w2 = w2rev; + w8 = w8rev; + } + break; + case ELFDATA2MSB: + if (*(unsigned char const *)&endian != 0) { + /* main() is little endian, file.o is big endian. */ + w = w4rev; + w2 = w2rev; + w8 = w8rev; + } + break; + } /* end switch */ + if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0 + || w2(ehdr->e_type) != ET_REL + || ehdr->e_ident[EI_VERSION] != EV_CURRENT) { + fprintf(stderr, "unrecognized ET_REL file %s\n", fname); + fail_file(); + } + + gpfx = 0; + switch (w2(ehdr->e_machine)) { + default: + fprintf(stderr, "unrecognized e_machine %d %s\n", + w2(ehdr->e_machine), fname); + fail_file(); + break; + case EM_386: + reltype = R_386_32; + make_nop = make_nop_x86; + ideal_nop = ideal_nop5_x86_32; + mcount_adjust_32 = -1; + break; + case EM_ARM: reltype = R_ARM_ABS32; + altmcount = "__gnu_mcount_nc"; + break; + case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break; + case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break; + case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break; + case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break; + case EM_S390: /* reltype: e_class */ gpfx = '_'; break; + case EM_SH: reltype = R_SH_DIR32; break; + case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break; + case EM_X86_64: + make_nop = make_nop_x86; + ideal_nop = ideal_nop5_x86_64; + reltype = R_X86_64_64; + mcount_adjust_64 = -1; + break; + } /* end switch */ + + switch (ehdr->e_ident[EI_CLASS]) { + default: + fprintf(stderr, "unrecognized ELF class %d %s\n", + ehdr->e_ident[EI_CLASS], fname); + fail_file(); + break; + case ELFCLASS32: + if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr) + || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) { + fprintf(stderr, + "unrecognized ET_REL file: %s\n", fname); + fail_file(); + } + if (w2(ehdr->e_machine) == EM_S390) { + reltype = R_390_32; + mcount_adjust_32 = -4; + } + if (w2(ehdr->e_machine) == EM_MIPS) { + reltype = R_MIPS_32; + is_fake_mcount32 = MIPS32_is_fake_mcount; + } + do32(ehdr, fname, reltype); + break; + case ELFCLASS64: { + Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr; + if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr) + || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) { + fprintf(stderr, + "unrecognized ET_REL file: %s\n", fname); + fail_file(); + } + if (w2(ghdr->e_machine) == EM_S390) { + reltype = R_390_64; + mcount_adjust_64 = -8; + } + if (w2(ghdr->e_machine) == EM_MIPS) { + reltype = R_MIPS_64; + Elf64_r_sym = MIPS64_r_sym; + Elf64_r_info = MIPS64_r_info; + is_fake_mcount64 = MIPS64_is_fake_mcount; + } + do64(ghdr, fname, reltype); + break; + } + } /* end switch */ + + cleanup(); +} + +int +main(int argc, char *argv[]) +{ + const char ftrace[] = "/ftrace.o"; + int ftrace_size = sizeof(ftrace) - 1; + int n_error = 0; /* gcc-4.3.0 false positive complaint */ + int c; + int i; + + while ((c = getopt(argc, argv, "w")) >= 0) { + switch (c) { + case 'w': + warn_on_notrace_sect = 1; + break; + default: + fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); + return 0; + } + } + + if ((argc - optind) < 1) { + fprintf(stderr, "usage: recordmcount [-w] file.o...\n"); + return 0; + } + + /* Process each file in turn, allowing deep failure. */ + for (i = optind; i < argc; i++) { + char *file = argv[i]; + int const sjval = setjmp(jmpenv); + int len; + + /* + * The file kernel/trace/ftrace.o references the mcount + * function but does not call it. Since ftrace.o should + * not be traced anyway, we just skip it. + */ + len = strlen(file); + if (len >= ftrace_size && + strcmp(file + (len - ftrace_size), ftrace) == 0) + continue; + + switch (sjval) { + default: + fprintf(stderr, "internal error: %s\n", file); + exit(1); + break; + case SJ_SETJMP: /* normal sequence */ + /* Avoid problems if early cleanup() */ + fd_map = -1; + ehdr_curr = NULL; + mmap_failed = 1; + do_file(file); + break; + case SJ_FAIL: /* error in do_file or below */ + ++n_error; + break; + case SJ_SUCCEED: /* premature success */ + /* do nothing */ + break; + } /* end switch */ + } + return !!n_error; +} + + |