90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
#include "twn_elf.h"
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#include "twn_game_object_c.h"
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/auxv.h>
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#include <elf.h>
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#include <linux/limits.h>
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#define __USE_GNU
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#include <dlfcn.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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bool infer_elf_section_bounds(const char *const restrict name,
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const char **restrict vm_start,
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const char **restrict vm_end)
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{
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bool result = false;
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char buf[PATH_MAX];
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bool from_shared_object;
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Dl_info info;
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if (!dladdr(game_object_get_game_tick_address(), &info)) {
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/* statically linked */
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from_shared_object = false;
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ssize_t l = readlink("/proc/self/exe", buf, PATH_MAX);
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if (l == -1)
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goto ERR_CANT_READLINK;
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buf[l] = 0; /* readlink() doesn't write a terminator */
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} else {
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/* dynamically linked */
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from_shared_object = true;
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memcpy(buf, "libgame.so", sizeof "libgame.so");
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}
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int elf = open(buf, O_RDONLY);
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if (elf == -1)
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goto ERR_CANT_OPEN_SELF;
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/* elf header */
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Elf64_Ehdr ehdr;
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read(elf, &ehdr, sizeof ehdr);
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if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
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ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
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ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
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ehdr.e_ident[EI_MAG3] != ELFMAG3)
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goto ERR_NOT_ELF;
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/* section header string table */
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Elf64_Shdr shstrdr;
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lseek(elf, ehdr.e_shoff + ehdr.e_shstrndx * sizeof (Elf64_Shdr), SEEK_SET);
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read(elf, &shstrdr, sizeof shstrdr);
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char *sh = malloc(shstrdr.sh_size);
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lseek(elf, shstrdr.sh_offset, SEEK_SET);
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read(elf, sh, shstrdr.sh_size);
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/* walk sections searching for needed name */
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lseek(elf, ehdr.e_shoff, SEEK_SET);
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for (size_t s = 0; s < ehdr.e_shnum; ++s) {
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Elf64_Shdr shdr;
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read(elf, &shdr, sizeof shdr);
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if (strcmp(&sh[shdr.sh_name], name) == 0) {
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result = true;
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if (!from_shared_object) {
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*vm_start = getauxval(AT_ENTRY) - ehdr.e_entry + (char *)shdr.sh_addr;
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*vm_end = getauxval(AT_ENTRY) - ehdr.e_entry + (char *)shdr.sh_addr + shdr.sh_size;
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} else {
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*vm_start = (uintptr_t)info.dli_fbase + (char *)shdr.sh_addr;
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*vm_end = (uintptr_t)info.dli_fbase + (char *)shdr.sh_addr + shdr.sh_size;
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}
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break;
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}
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}
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free(sh);
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ERR_NOT_ELF:
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close(elf);
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ERR_CANT_OPEN_SELF:
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ERR_CANT_READLINK:
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return result;
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}
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