/*
* Copyright 2016, The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdint.h>
#include <stdio.h>
#include "apf.h"
// If "c" is of an unsigned type, generate a compile warning that gets promoted to an error.
// This makes bounds checking simpler because ">= 0" can be avoided. Otherwise adding
// superfluous ">= 0" with unsigned expressions generates compile warnings.
#define ENFORCE_UNSIGNED(c) ((c)==(uint32_t)(c))
static void print_opcode(const char* opcode) {
printf("%-6s", opcode);
}
// Mapping from opcode number to opcode name.
static const char* opcode_names [] = {
[LDB_OPCODE] = "ldb",
[LDH_OPCODE] = "ldh",
[LDW_OPCODE] = "ldw",
[LDBX_OPCODE] = "ldb",
[LDHX_OPCODE] = "ldh",
[LDWX_OPCODE] = "ldw",
[ADD_OPCODE] = "add",
[MUL_OPCODE] = "mul",
[DIV_OPCODE] = "div",
[AND_OPCODE] = "and",
[OR_OPCODE] = "or",
[SH_OPCODE] = "sh",
[LI_OPCODE] = "li",
[JMP_OPCODE] = "jmp",
[JEQ_OPCODE] = "jeq",
[JNE_OPCODE] = "jne",
[JGT_OPCODE] = "jgt",
[JLT_OPCODE] = "jlt",
[JSET_OPCODE] = "jset",
[JNEBS_OPCODE] = "jnebs",
};
static void print_jump_target(uint32_t target, uint32_t program_len) {
if (target == program_len) {
printf("pass");
} else if (target == program_len + 1) {
printf("drop");
} else {
printf("%u", target);
}
}
// Disassembles an APF program. A hex dump of the program is supplied on stdin.
//
// NOTE: This is a simple debugging tool not meant for shipping or production use. It is by no
// means hardened against malicious input and contains known vulnerabilities.
//
// Example usage:
// adb shell dumpsys wifi ipmanager | sed '/Last program:/,+1!d;/Last program:/d;s/[ ]*//' | out/host/linux-x86/bin/apf_disassembler
int main(void) {
uint32_t program_len = 0;
uint8_t program[10000];
// Read in hex program bytes
int byte;
while (scanf("%2x", &byte) == 1 && program_len < sizeof(program)) {
program[program_len++] = byte;
}
for (uint32_t pc = 0; pc < program_len;) {
printf("%8u: ", pc);
const uint8_t bytecode = program[pc++];
const uint32_t opcode = EXTRACT_OPCODE(bytecode);
#define PRINT_OPCODE() print_opcode(opcode_names[opcode])
const uint32_t reg_num = EXTRACT_REGISTER(bytecode);
// All instructions have immediate fields, so load them now.
const uint32_t len_field = EXTRACT_IMM_LENGTH(bytecode);
uint32_t imm = 0;
int32_t signed_imm = 0;
if (len_field != 0) {
const uint32_t imm_len = 1 << (len_field - 1);
uint32_t i;
for (i = 0; i < imm_len; i++)
imm = (imm << 8) | program[pc++];
// Sign extend imm into signed_imm.
signed_imm = imm << ((4 - imm_len) * 8);
signed_imm >>= (4 - imm_len) * 8;
}
switch (opcode) {
case LDB_OPCODE:
case LDH_OPCODE:
case LDW_OPCODE:
PRINT_OPCODE();
printf("r%d, [%u]", reg_num, imm);
break;
case LDBX_OPCODE:
case LDHX_OPCODE:
case LDWX_OPCODE:
PRINT_OPCODE();
printf("r%d, [%u+r1]", reg_num, imm);
break;
case JMP_OPCODE:
PRINT_OPCODE();
print_jump_target(pc + imm, program_len);
break;
case JEQ_OPCODE:
case JNE_OPCODE:
case JGT_OPCODE:
case JLT_OPCODE:
case JSET_OPCODE:
case JNEBS_OPCODE: {
PRINT_OPCODE();
printf("r0, ");
// Load second immediate field.
uint32_t cmp_imm = 0;
if (reg_num == 1) {
printf("r1, ");
} else if (len_field == 0) {
printf("0, ");
} else {
uint32_t cmp_imm_len = 1 << (len_field - 1);
uint32_t i;
for (i = 0; i < cmp_imm_len; i++)
cmp_imm = (cmp_imm << 8) | program[pc++];
printf("0x%x, ", cmp_imm);
}
if (opcode == JNEBS_OPCODE) {
print_jump_target(pc + imm + cmp_imm, program_len);
printf(", ");
while (cmp_imm--)
printf("%02x", program[pc++]);
} else {
print_jump_target(pc + imm, program_len);
}
break;
}
case ADD_OPCODE:
case SH_OPCODE:
PRINT_OPCODE();
if (reg_num) {
printf("r0, r1");
} else {
printf("r0, %d", signed_imm);
}
break;
case MUL_OPCODE:
case DIV_OPCODE:
case AND_OPCODE:
case OR_OPCODE:
PRINT_OPCODE();
if (reg_num) {
printf("r0, r1");
} else {
printf("r0, %u", imm);
}
break;
case LI_OPCODE:
PRINT_OPCODE();
printf("r%d, %d", reg_num, signed_imm);
break;
case EXT_OPCODE:
if (
// If LDM_EXT_OPCODE is 0 and imm is compared with it, a compiler error will result,
// instead just enforce that imm is unsigned (so it's always greater or equal to 0).
#if LDM_EXT_OPCODE == 0
ENFORCE_UNSIGNED(imm) &&
#else
imm >= LDM_EXT_OPCODE &&
#endif
imm < (LDM_EXT_OPCODE + MEMORY_ITEMS)) {
print_opcode("ldm");
printf("r%d, m[%u]", reg_num, imm - LDM_EXT_OPCODE);
} else if (imm >= STM_EXT_OPCODE && imm < (STM_EXT_OPCODE + MEMORY_ITEMS)) {
print_opcode("stm");
printf("r%d, m[%u]", reg_num, imm - STM_EXT_OPCODE);
} else switch (imm) {
case NOT_EXT_OPCODE:
print_opcode("not");
printf("r%d", reg_num);
break;
case NEG_EXT_OPCODE:
print_opcode("neg");
printf("r%d", reg_num);
break;
case SWAP_EXT_OPCODE:
print_opcode("swap");
break;
case MOV_EXT_OPCODE:
print_opcode("mov");
printf("r%d, r%d", reg_num, reg_num ^ 1);
break;
default:
printf("unknown_ext %u", imm);
break;
}
break;
// Unknown opcode
default:
printf("unknown %u", opcode);
break;
}
printf("\n");
}
return 0;
}