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Message-ID: <20250222010608.GK1827@brightrain.aerifal.cx>
Date: Fri, 21 Feb 2025 20:06:08 -0500
From: Rich Felker <dalias@...c.org>
To: Alex Rønne Petersen <alex@...xrp.com>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH v2] clone: clear the frame pointer in the child
process on relevant ports
On Thu, Dec 12, 2024 at 05:56:04PM +0100, Alex Rønne Petersen wrote:
> This just mirrors what is done in the start code for the affected ports, as well
> as what is already done for the three x86 ports.
>
> Clearing the frame pointer helps protect FP-based unwinders which have no way of
> knowing that the FP register should be considered undefined in the child process
> portion of clone(). In practice, we found this change to be necessary when
> running the Zig standard library tests under qemu-aarch64_be with musl linked.
>
> This version of the patch omits the branch inversion on x86 and powerpc from the
> previous version, per the discussion there.
Trying to apply this, but...
> diff --git a/src/thread/m68k/clone.s b/src/thread/m68k/clone.s
> index f6dfa06f..42ec19f7 100644
> --- a/src/thread/m68k/clone.s
> +++ b/src/thread/m68k/clone.s
> @@ -18,7 +18,8 @@ __clone:
> beq 1f
> movem.l (%sp)+,%d2-%d5
> rts
> -1: move.l %a1,-(%sp)
> +1: suba.l %%fp,%%fp
> + move.l %a1,-(%sp)
> jsr (%a0)
> move.l #1,%d0
> trap #0
This does not assemble and is most likely not valid. I get:
src/thread/m68k/clone.s:21: Error: operands mismatch -- statement `suba.l %%fp,%%fp' ignored
Do you know what the right instruction to use here is for m68k? And,
have you tested that the rest of the affected archs build?
Rich
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