Assembly Idiom Parser Generator

Write human readable assembly idioms and generate fast PowerPC parsers

• The idiom grammar is human-readable and PowerPC assembly-like, see GRAMMAR.md
• The generated parser is (afaik) nearly optimal, only checking whatever is needed and at the binary level, so no disassembly is performed.
• After parsing, if some code matches, a Context struct is returned that can be used to retrieve the values of captured variables and the offset of each instruction that matched.

Example

The idiom

lis      $GPR9,$IMM1
...
addi     $GPR8,$GPR9,$IMM2
...
mulhw    $GPR3,$GPR8,$GPR1
...
srawi    $GPR4,$GPR2,$IMM3

generates a parser that matches unsigned integer division.

You can invoke aipg to create a C++ parser for it

./aipg Udiv.idiom

which will generate Udiv.hpp for you. You can now include that file and use it to parse your binary, for example:

#include <iostream>
#include "opcode/ppc.h"
#include "aipg/aipg.hpp"
#include "Udiv.hpp"

int main(int argc, char** argv) {
/*
original ASM:
lis     r3, 0x8889
lwz     r8, 0x14(r28)
addi    r0, r3, -0x7777
li      r3, 0
mulhw   r0, r0, r7
li      r3, 1
add     r0, r0, r7
srawi   r0, r0, 5
srwi    r5, r0, 0x1f
add     r6, r0, r5
*/
  uint32_t ins[] = {0x3c608889, 0x811c0014, 0x38038889, 0x38800000, 0x7c003896, 0x38600001, 0x7c003a14, 0x7c002e70, 0x54050ffe, 0x7cc02a14};
  aipg::Context parseCtx;
  bool match = aipg::matchUdiv(std::begin(ins), std::end(ins), PPC_OPCODE_PPC, parseCtx);
  std::cout << (match ? "Found match" : "No match found") << std::endl;
  for (uint32_t idx : parseCtx.matchInsIdxs)
    std::cout << "Matcing ins idx: " << idx << std::endl;
  for (auto& it : parseCtx.gprs) {
    std::cout << "GPR var " << it.first << " value is r" << it.second << std::endl;
  }
  for (auto& it : parseCtx.imms) {
    std::cout << "Immediate var " << it.first << " value is " << it.second << std::endl;
  }
}

which produces the following output:

Found match
Matcing ins idx: 0
Matcing ins idx: 2
Matcing ins idx: 4
Matcing ins idx: 7
GPR var 2 value is r0
GPR var 4 value is r0
GPR var 1 value is r7
GPR var 3 value is r0
GPR var 8 value is r0
GPR var 9 value is r3
Immediate var 3 value is 5
Immediate var 2 value is -30583
Immediate var 1 value is -30583

Dependencies

Both the generator and the runtime parser depend on ppcdisasm-cpp. The generator requires a compiler with c++17 support and the runtime parser c++20 support

Building

• mkdir build && cd build
• cmake ..
• make

Usage

Command line

./aipg aipg [--out output_parser_location file1.idiom file2.idiom ..

In build system

When using this project's parsers in your own project, usually you will want to perform the parser generation at build time, before your targets that use them are built. You can find an example of doing this with CMake in this project's CMakeLists.txt

Limitations

• Currently, rotate-shift instruction idioms can only use the 4 argument forms.
• No SPR operands in idioms. You can get around this using extended mnemonics.