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// SPDX-License-Identifier: GPL-2.0-only
/*
* 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.
*
* 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifndef EM_AARCH64
#define EM_AARCH64 183
#define R_AARCH64_NONE 0
#define R_AARCH64_ABS64 257
#endif
static int fd_map; /* File descriptor for file being modified. */
static int mmap_failed; /* Boolean flag. */
static char gpfx; /* prefix for global symbol name (sometimes '_') */
static struct stat sb; /* Remember .st_size, etc. */
static const char *altmcount; /* alternate mcount symbol name */
static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
static void *file_map; /* pointer of the mapped file */
static void *file_end; /* pointer to the end of the mapped file */
static int file_updated; /* flag to state file was changed */
static void *file_ptr; /* current file pointer location */
static void *file_append; /* added to the end of the file */
static size_t file_append_size; /* how much is added to end of file */
/* Per-file resource cleanup when multiple files. */
static void cleanup(void)
{
if (!mmap_failed)
munmap(file_map, sb.st_size);
else
free(file_map);
file_map = NULL;
free(file_append);
file_append = NULL;
file_append_size = 0;
file_updated = 0;
}
/* ulseek, uwrite, ...: Check return value for errors. */
static off_t ulseek(off_t const offset, int const whence)
{
switch (whence) {
case SEEK_SET:
file_ptr = file_map + offset;
break;
case SEEK_CUR:
file_ptr += offset;
break;
case SEEK_END:
file_ptr = file_map + (sb.st_size - offset);
break;
}
if (file_ptr < file_map) {
fprintf(stderr, "lseek: seek before file\n");
return -1;
}
return file_ptr - file_map;
}
static ssize_t uwrite(void const *const buf, size_t const count)
{
size_t cnt = count;
off_t idx = 0;
file_updated = 1;
if (file_ptr + count >= file_end) {
off_t aoffset = (file_ptr + count) - file_end;
if (aoffset > file_append_size) {
file_append = realloc(file_append, aoffset);
file_append_size = aoffset;
}
if (!file_append) {
perror("write");
cleanup();
return -1;
}
if (file_ptr < file_end) {
cnt = file_end - file_ptr;
} else {
cnt = 0;
idx = aoffset - count;
}
}
if (cnt)
memcpy(file_ptr, buf, cnt);
if (cnt < count)
memcpy(file_append + idx, buf + cnt, count - cnt);
file_ptr += count;
return count;
}
static void * umalloc(size_t size)
{
void *const addr = malloc(size);
if (addr == 0) {
fprintf(stderr, "malloc failed: %zu bytes\n", size);
cleanup();
return NULL;
}
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 */
if (ulseek(offset - 1, SEEK_SET) < 0)
return -1;
if (uwrite(ideal_nop, 5) < 0)
return -1;
return 0;
}
static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */
static unsigned char *ideal_nop4_arm;
static unsigned char bl_mcount_arm_le[4] = { 0xfe, 0xff, 0xff, 0xeb }; /* bl */
static unsigned char bl_mcount_arm_be[4] = { 0xeb, 0xff, 0xff, 0xfe }; /* bl */
static unsigned char *bl_mcount_arm;
static unsigned char push_arm_le[4] = { 0x04, 0xe0, 0x2d, 0xe5 }; /* push {lr} */
static unsigned char push_arm_be[4] = { 0xe5, 0x2d, 0xe0, 0x04 }; /* push {lr} */
static unsigned char *push_arm;
static unsigned char ideal_nop2_thumb_le[2] = { 0x00, 0xbf }; /* nop */
static unsigned char ideal_nop2_thumb_be[2] = { 0xbf, 0x00 }; /* nop */
static unsigned char *ideal_nop2_thumb;
static unsigned char push_bl_mcount_thumb_le[6] = { 0x00, 0xb5, 0xff, 0xf7, 0xfe, 0xff }; /* push {lr}, bl */
static unsigned char push_bl_mcount_thumb_be[6] = { 0xb5, 0x00, 0xf7, 0xff, 0xff, 0xfe }; /* push {lr}, bl */
static unsigned char *push_bl_mcount_thumb;
static int make_nop_arm(void *map, size_t const
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