void copy_and_fixup_insn(struct insn *src_insn, void *dest, const struct kernsym *func) { u32 *to_fixup; unsigned long addr; BUG_ON(src_insn->length == 0); memcpy((void *)dest, (const void *)src_insn->kaddr, src_insn->length); if(src_insn->opcode.bytes[0] == OP_CALL_REL32 || src_insn->opcode.bytes[0] == OP_JMP_REL32) { addr = (unsigned long)CODE_ADDR_FROM_OFFSET( src_insn->kaddr, src_insn->length, src_insn->immediate.value); if(addr >= (unsigned long)func->addr && addr < (unsigned long)func->addr + func->size) return; to_fixup = (u32 *)((unsigned long)dest + insn_offset_immediate(src_insn)); *to_fixup = CODE_OFFSET_FROM_ADDR(dest, src_insn->length, (void *)addr); return; } #ifdef CONFIG_X86_64 if(!tpe_insn_rip_relative(src_insn)) return; addr = (unsigned long)CODE_ADDR_FROM_OFFSET( src_insn->kaddr, src_insn->length, src_insn->displacement.value); if(addr >= (unsigned long)func->addr && addr < (unsigned long)func->addr + func->size) return; to_fixup = (u32 *)((unsigned long)dest + insn_offset_displacement(src_insn)); *to_fixup = CODE_OFFSET_FROM_ADDR(dest, src_insn->length, (void *)addr); #endif return; }
int symbol_hijack(struct kernsym *sym, const char *symbol_name, unsigned long *code) { int ret; unsigned long orig_addr; unsigned long dest_addr; unsigned long end_addr; u32 *poffset; struct insn insn; bool pte_ro; ret = find_symbol_address(sym, symbol_name); if (IN_ERR(ret)) return ret; if (*(u8 *)sym->addr == OP_JMP_REL32) { printk(PKPRE "error: %s already appears to be hijacked\n", symbol_name); return -EFAULT; } sym->new_addr = malloc(sym->size); if (sym->new_addr == NULL) { printk(PKPRE "Failed to allocate buffer of size %lu for %s\n", sym->size, sym->name); return -ENOMEM; } memset(sym->new_addr, 0, (size_t)sym->size); if (sym->size < OP_JMP_SIZE) { ret = -EFAULT; goto out_error; } orig_addr = (unsigned long)sym->addr; dest_addr = (unsigned long)sym->new_addr; end_addr = orig_addr + sym->size; while (end_addr > orig_addr && *(u8 *)(end_addr - 1) == '\0') --end_addr; if (orig_addr == end_addr) { printk(PKPRE "A spurious symbol \"%s\" (address: %p) seems to contain only zeros\n", sym->name, sym->addr); ret = -EILSEQ; goto out_error; } while (orig_addr < end_addr) { tpe_insn_init(&insn, (void *)orig_addr); tpe_insn_get_length(&insn); if (insn.length == 0) { printk(PKPRE "Failed to decode instruction at %p (%s+0x%lx)\n", (const void *)orig_addr, sym->name, orig_addr - (unsigned long)sym->addr); ret = -EILSEQ; goto out_error; } copy_and_fixup_insn(&insn, (void *)dest_addr, sym); orig_addr += insn.length; dest_addr += insn.length; } sym->new_size = dest_addr - (unsigned long)sym->new_addr; sym->run = sym->new_addr; set_addr_rw((unsigned long) sym->addr, &pte_ro); memcpy(&sym->orig_start_bytes[0], sym->addr, OP_JMP_SIZE); *(u8 *)sym->addr = OP_JMP_REL32; poffset = (u32 *)((unsigned long)sym->addr + 1); *poffset = CODE_OFFSET_FROM_ADDR((unsigned long)sym->addr, OP_JMP_SIZE, (unsigned long)code); set_addr_ro((unsigned long) sym->addr, pte_ro); sym->hijacked = true; return 0; out_error: malloc_free(sym->new_addr); return ret; }