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@emonti emonti/dyldcache.c
Created Mar 8, 2012

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dyldcache.c dyld_shared_cache dumper
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
struct dyld_cache_header
char magic[16]; // e.g. "dyld_v0 ppc"
uint32_t mappingOffset; // file offset to first shared_file_mapping
uint32_t mappingCount; // number of shared_file_mapping entries
uint32_t imagesOffset; // file offset to first dyld_cache_image_info
uint32_t imagesCount; // number of dyld_cache_image_info entries
uint64_t dyldBaseAddress; // base address of dyld when cache was built
uint64_t codeSignOffset; // speculation?
struct shared_file_mapping {
uint64_t address;
uint64_t size;
uint64_t file_offset;
uint32_t max_prot;
uint32_t init_prot;
struct dyld_cache_image_info
uint64_t address;
uint64_t modTime;
uint64_t inode;
uint32_t pathFileOffset;
uint32_t pad;
void dump_dyld_shared_cache(void *data, size_t fsize) {
struct dyld_cache_header *header = data;
size_t i;
printf(" magic = %s\n", header->magic);
printf(" mappingOffset = 0x%08lx\n", header->mappingOffset);
printf(" mappingCount = %lu\n", header->mappingCount);
printf(" imagesOffset = 0x%08lx\n", header->imagesOffset);
printf(" imagesCount = %lu\n", header->imagesCount);
printf(" dyldBaseAddress = 0x%08llx\n", header->dyldBaseAddress);
printf(" codesignOffset = 0x%08llx\n\n", header->codeSignOffset);
struct shared_file_mapping *sfm = data + header->mappingOffset;
for (i=0; i < header->mappingCount; i++) {
printf("shared_file_mapping[%i]:\n", i);
printf(" address = 0x%08llx\n", sfm->address);
printf(" size = 0x%08llx\n", sfm->size);
printf(" file_offset = 0x%08llx\n", sfm->file_offset);
printf(" max_prot = 0x%08lx\n", sfm->max_prot);
printf(" init_prot = 0x%08lx\n\n", sfm->init_prot);
sfm ++;
struct dyld_cache_image_info *dcimg = data + header->imagesOffset;
for (i=0; i < header->imagesCount; i++) {
printf("dyld_cache_image_info[%i]:\n", i);
printf(" pathFileOff = 0x%08lx\n", dcimg->pathFileOffset);
printf(" pathFile = %s\n", (char *)data+dcimg->pathFileOffset);
printf(" address = 0x%08lx\n", dcimg->address);
printf(" modTime = 0x%08lx\n", dcimg->modTime);
printf(" inode = 0x%08lx\n", dcimg->inode);
void dump_dyld_shared_cache_file(char *fname) {
void *cachedata;
struct stat st;
int fd;
if ((fd = open(fname, O_RDONLY)) >=0 ) {
if (fstat(fd, &st) >= 0) {
cachedata = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (cachedata) {
dump_dyld_shared_cache(cachedata, st.st_size);
munmap(cachedata, st.st_size);
perror("Cannot mmap()");
} else {
perror("Cannot fstat() file-descriptor");
} else {
perror("Cannot open file");
int main(int argc, char **argv) {
int i;
for (i=1; i < argc; i++)
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