Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers
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- Subject: Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers
- From: David Laight <david.laight.linux@xxxxxxxxx>
- Date: Sat, 8 Mar 2025 08:15:30 +0000
- Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, tip-bot2 for Josh Poimboeuf <tip-bot2@xxxxxxxxxxxxx>, linux-tip-commits@xxxxxxxxxxxxxxx, "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, x86@xxxxxxxxxx
- In-reply-to: <20250308013814.sa745d25m3ddlu2b@jpoimboe>
- References: <174108458405.14745.4864877018394987266.tip-bot2@tip-bot2> <90B1074B-E7D4-4CE0-8A82-ADEB7BAED7AD@zytor.com> <Z8t7ubUE5P7woAr5@gmail.com> <20250307232157.comm4lycebr7zmre@jpoimboe> <A669251B-7414-4EE7-B0AD-735E845C0B5B@zytor.com> <20250308013814.sa745d25m3ddlu2b@jpoimboe>
On Fri, 7 Mar 2025 17:38:14 -0800
Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
...
> We hopefully won't need those hacks much longer anyway, as I'll have
> another series to propose removing frame pointers for x86-64.
>
> x86-32 can keep frame pointers, but doesn't need the constraints. It's
> not supported for livepatch so it doesn't need to be 100% reliable.
> Worst case, an unwind skips a frame, but the call address still shows up
> on stack trace dumps prepended with '?'.
Doesn't 'user copy hardening' also do stack following?
That needs to find all the stack frames (that have locals) and I think
is is more reliable with frame pointers.
David
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