Re: [RFC PATCH v1 08/16] unwind_user: Enable archs that save RA/FP in other registers

On Thu, Jul 17, 2025 at 02:07:05PM +0200, Jens Remus wrote:

On 17.07.2025 04:50, Josh Poimboeuf wrote:

quoted

So the following is wrong:

	case UNWIND_USER_LOC_STACK:
		if (!frame->fp.frame_off)
			goto done;
		if (unwind_get_user_long(fp, cfa + frame->fp.frame_off, state))
			goto done;
		break;

Instead of having !fp.frame_off stopping the unwind, it should just
break out of the switch statement and keep going.

If frame->fp.loc is UNWIND_USER_LOC_STACK then frame->fp.frame_off must
have a value != 0.  At least if we keep the original semantic.

We can omit this check, if we assume all producers of frame behave
correctly.  For instance user unwind sframe would not produce that
(see below).  Could it somehow be made a debug-config-only check?

Ah... the !frame->fp.frame_off check for the UNWIND_USER_LOC_STACK case
completely threw me for a loop.  I was confusing that with
UNWIND_USER_LOC_NONE.  So never mind.

And yes, I think that check has no use and can be removed.

-- 
Josh