marfrit
00d655187a
Three small functions extracted from the v1.19 conservative blob with
ground-truth C and per-tool (Ghidra / retdec / decomp.me) docs:
01_memset — byte memset, 28 B
02_memcpy32 — word-aligned memcpy, 36 B
03_magic_memset — magic check + tail-call to memset, 40 B
04_train_phy_block — first real poll-site function (104 B, 26 insts),
contains poll sites 12-15
Results in RESULTS.md:
- Ghidra: A on all four. Auto-decompile is close to final.
- retdec: A on #3, F on #1 and #2 (no register-arg inference on raw),
C on #4 (mistakes & 0xF0000000 for < 0x10000000).
GRIND_LOG.md (in 04_train_phy_block/) records the matching-decomp
iteration: 116-byte candidate.c at -Os vs vendor 104 bytes = 89.7%
size match on first real iteration. Remaining gap is GCC's choice of
`cmp w, w_const; b.ls` over vendor's `tst w, #imm; b.eq` for the
mask tests.
gdb_debug/ holds a native-aarch64 GDB single-stepper for the three
benchmark functions — boltzmann smoke test passed (memset:
buf[10] 0x00→0xab).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
1.4 KiB
1.4 KiB
retdec recipe — 01_memset
retdec runs fully automated — hand it the binary, ask for C.
Invocation (on the decompme container at pve4, or wherever retdec lives)
retdec --mode raw --arch arm --endian little --bit-size 64 \
--raw-entry-point 0x0aac \
--raw-section-vma 0x0aac \
func.bin -o retdec.c
The flags:
--mode raw— input is a flat binary, no PE/ELF headers.--arch arm --endian little --bit-size 64— AArch64 LE.--raw-entry-point 0x0aac— tell retdec where execution starts.--raw-section-vma 0x0aac— load the binary at address 0x0aac so branch targets resolve correctly.
Output goes to retdec.c. retdec emits a .ll (LLVM IR) and a .dsm
(disasm) alongside — all useful for comparison.
What to expect
retdec is the least "smart" of the three tools. For a raw 28-byte blob with no headers, it will:
- Detect the function at 0x0aac.
- Produce a C function named
function_aacor similar. - Often inserts pseudo-intrinsics like
__asm_mov(x3, 0)for instructions it doesn't fold into C. For this tiny loop it usually manages clean C.
Benchmark notes
- Strength: zero-touch, scriptable, good for bulk processing.
- Weakness: no interactive refinement — you get what you get. Type
inference is conservative (
int32_t *instead ofvoid */uint8_t *). - Often emits control flow as
gotorather than structured loops.