71 lines
2.0 KiB
C
71 lines
2.0 KiB
C
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/* how trivial...
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extract the symbols into a new mach-o
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that contains just the symbols */
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#include <data/mach-o/binary.h>
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#include <mach-o/loader.h>
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#include <mach-o/nlist.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <assert.h>
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struct header {
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struct mach_header mh;
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struct segment_command segment;
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struct symtab_command symtab;
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struct nlist nl[0];
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} __attribute__((packed));
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int main(int argc, char **argv) {
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assert(argc == 3);
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struct binary binary;
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b_init(&binary);
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b_load_macho(&binary, argv[1]);
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int out = open(argv[2], O_WRONLY | O_TRUNC | O_CREAT, 0755);
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assert(out != -1);
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int size = sizeof(struct header) + binary.mach->ext_nsyms * sizeof(struct nlist);
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struct header *hdr = calloc(1, size);
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lseek(out, size + 1, SEEK_SET);
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int off = 1;
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for(uint32_t i = 0; i < binary.mach->ext_nsyms; i++) {
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hdr->nl[i] = binary.mach->ext_symtab[i];
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const char *name = binary.mach->strtab + hdr->nl[i].n_un.n_strx;
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int diff = strlen(name) + 1;
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hdr->nl[i].n_un.n_strx = off;
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assert(write(out, name, diff) == diff);
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off += diff;
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}
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size_t end = lseek(out, 0, SEEK_CUR);
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memcpy(&hdr->mh, binary.mach->hdr, sizeof(hdr->mh));
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hdr->mh.ncmds = 2;
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hdr->mh.sizeofcmds = sizeof(*hdr) - sizeof(hdr->mh);
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hdr->segment.cmd = LC_SEGMENT;
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hdr->segment.cmdsize = sizeof(hdr->segment);
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strcpy(hdr->segment.segname, "__LINKEDIT");
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hdr->segment.vmaddr = 0;
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hdr->segment.vmsize = (end + 0xfff) & ~0xfff;
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hdr->segment.fileoff = 0;
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hdr->segment.filesize = end;
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hdr->segment.maxprot = PROT_READ | PROT_EXEC;
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hdr->segment.initprot = PROT_READ | PROT_EXEC;
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hdr->segment.nsects = 0;
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hdr->segment.flags = 0;
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hdr->symtab.cmd = LC_SYMTAB;
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hdr->symtab.cmdsize = sizeof(hdr->symtab);
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hdr->symtab.symoff = sizeof(*hdr);
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hdr->symtab.nsyms = binary.mach->ext_nsyms;
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hdr->symtab.stroff = size;
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hdr->symtab.strsize = end - size;
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assert(pwrite(out, hdr, size, 0) == size);
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}
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