From 2c2124aff2f4ed6df23512603b6e1ecdcd4b699b Mon Sep 17 00:00:00 2001 From: blasty Date: Sun, 26 Jul 2026 15:04:51 +0200 Subject: arm: offer 32-bit ARM at load, and fix `p` on carved code MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Reported as "after c a few times and p at the entry point, Tab just flashes and nothing decompiles". Three separate things, found by following it down: **1. `p` failed on hand-carved code.** ida_funcs.add_func(ea) asks IDA to find the function's end and on carved code it often can't — a run ending in a tail call, or whose last instruction isn't recognised as a return, fails with no reason given. add_func(ea, end) with an explicit end succeeds. define_func_run tries IDA's way first, then falls back to the end of the contiguous instruction run, and says which it used. **2. The database was 64-bit, so Hex-Rays refused it regardless.** Bare `-parm` gives an AArch64 database. Ask Hex-Rays for the failure object rather than reading None as "dunno" and it says exactly what's wrong: "only 64-bit functions can be decompiled in the current database". So the disassembly looked right and F5 could never work. That is decided at LOAD and cannot be corrected — inf_set_app_bitness(32) afterwards makes the decompiler INTERR 50735. The fix is at the load dialog: arm:ARMv7-A (most firmware), arm:ARMv7-M / arm:ARMv6-M (Cortex-M, Thumb only) and arm:ARMv5TE now sit alongside 64-bit `arm`, labelled with their bitness. With arm:ARMv7-A, experiments/fibonacci.bin decompiles: void __fastcall __noreturn sub_0(int a1) { int v2; v2 = sub_E3C(a1, 0); ... } — and IDA's own auto-analysis finds 54 Thumb functions on load, versus none as plain `arm`. **3. `t` was silently building an undecompilable state.** It forced the SEGMENT to 32-bit in a 64-bit database, which produces correct-looking disassembly that F5 will never touch. It now says so and names the fix (Ctrl+L, arm:ARMv7-A) rather than leaving you to discover it. tools/verify_procs.py now reports each processor's resulting bitness, since that is the reason the variants exist — and it compares against the base module name, because a variant reports "ARM". tests: test_thumb_ui.py +5 (13 total) — a 64-bit database warns and names the fix, a 32-bit one finds functions by itself, Tab decompiles a Thumb function and the result reads like C. test_formats.py +2 (34) pinning that a 32-bit variant is offered and the ARM labels state their bitness. 209/0 scenarios, 26/0 blob, 30/0 project UI. --- idatui/app.py | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'idatui/app.py') diff --git a/idatui/app.py b/idatui/app.py index ff67eef..ec55911 100644 --- a/idatui/app.py +++ b/idatui/app.py @@ -5191,13 +5191,22 @@ class IdaTui(App): verb = f"{mode} @ {ea:#x}" if r.get("forced_32bit"): verb += " (segment set to 32-bit; Thumb needs ARM32)" + if r.get("db_64bit"): + # Disassembly will look right and F5 will never work. + verb += (" \u26a0 this database is 64-bit, so Hex-Rays " + "won't decompile it \u2014 Ctrl+L and pick " + "arm:ARMv7-A") verb += (f" \u2014 {n} instruction{'s' if n != 1 else ''}" if n else " \u2014 still doesn't decode") # falls through to the shared reload: same cache bump, same # anchor restore, same flash. That is the whole point of having # one path. elif kind == "func": - self.program.define_func(ea) + r = self.program.define_func(ea) + if r.get("start") and r.get("end"): + verb = (f"created function {r['start']}\u2013{r['end']}" + + (" (end worked out from the code)" + if r.get("how") == "explicit-end" else "")) elif kind == "string": s = self.program.make_string(ea) verb = f"made string ({s[:24]!r})" if s else verb -- cgit v1.3.1-sl0p