forked from mirrors/gecko-dev
95 lines
2.7 KiB
C
95 lines
2.7 KiB
C
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include <stdint.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include <elf.h>
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/* The Android NDK headers define those */
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#undef Elf_Ehdr
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#undef Elf_Addr
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#if defined(__LP64__)
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#define Elf_Ehdr Elf64_Ehdr
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#define Elf_Addr Elf64_Addr
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#else
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#define Elf_Ehdr Elf32_Ehdr
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#define Elf_Addr Elf32_Addr
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#endif
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extern __attribute__((visibility("hidden"))) void original_init(int argc, char **argv, char **env);
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extern __attribute__((visibility("hidden"))) Elf32_Rel relhack[];
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extern __attribute__((visibility("hidden"))) Elf_Ehdr elf_header;
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extern __attribute__((visibility("hidden"))) int (*mprotect_cb)(void *addr, size_t len, int prot);
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extern __attribute__((visibility("hidden"))) char relro_start[];
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extern __attribute__((visibility("hidden"))) char relro_end[];
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static inline __attribute__((always_inline))
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void do_relocations(void)
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{
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Elf32_Rel *rel;
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Elf_Addr *ptr, *start;
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for (rel = relhack; rel->r_offset; rel++) {
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start = (Elf_Addr *)((intptr_t)&elf_header + rel->r_offset);
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for (ptr = start; ptr < &start[rel->r_info]; ptr++)
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*ptr += (intptr_t)&elf_header;
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}
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}
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__attribute__((section(".text._init_noinit")))
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int init_noinit(int argc, char **argv, char **env)
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{
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do_relocations();
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return 0;
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}
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__attribute__((section(".text._init")))
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int init(int argc, char **argv, char **env)
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{
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do_relocations();
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original_init(argc, argv, env);
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// Ensure there is no tail-call optimization, avoiding the use of the
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// B.W instruction in Thumb for the call above.
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return 0;
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}
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static inline __attribute__((always_inline))
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void relro_pre()
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{
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// By the time the injected code runs, the relro segment is read-only. But
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// we want to apply relocations in it, so we set it r/w first. We'll restore
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// it to read-only in relro_post.
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mprotect_cb(relro_start, relro_end - relro_start, PROT_READ | PROT_WRITE);
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}
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static inline __attribute__((always_inline))
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void relro_post()
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{
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mprotect_cb(relro_start, relro_end - relro_start, PROT_READ);
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// mprotect_cb is a pointer allocated in .bss, so we need to restore it to
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// a NULL value.
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mprotect_cb = NULL;
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}
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__attribute__((section(".text._init_noinit_relro")))
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int init_noinit_relro(int argc, char **argv, char **env)
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{
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relro_pre();
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do_relocations();
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relro_post();
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return 0;
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}
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__attribute__((section(".text._init_relro")))
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int init_relro(int argc, char **argv, char **env)
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{
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relro_pre();
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do_relocations();
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relro_post();
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original_init(argc, argv, env);
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return 0;
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}
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