linux/scripts/recordmcount.c at master · microinfo/linux · GitHub

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* recordmcount.c: construct a table of the locations of calls to 'mcount'

* so that ftrace can find them quickly.

* Licensed under the GNU General Public License, version 2 (GPLv2).

* Restructured to fit Linux format, as well as other updates:

* 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;

}

linux/scripts/recordmcount.c at master · microinfo/linux · GitHub

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