Re: [PATCH 2/2] microblaze: reserve the ABI argument-home area in the signal frame

[Michal Simek]

On 6/4/26 17:37, Ramin Moussavi wrote:
> The MicroBlaze procedure call standard lets a callee store its incoming
> register arguments r5..r10 into the caller-provided home slots at
> [r1+4]..[r1+28].  When the kernel enters a signal handler it sets r1 to
> point at struct rt_sigframe, whose leading members are the siginfo and
> ucontext prepared for the handler.  A handler that homes its arguments -
> which an unoptimised (-O0) build always does - therefore overwrites the
> start of siginfo/ucontext, corrupting the signal state that the handler
> and sys_rt_sigreturn() depend on.
>
> Reserve the home area by making an eight-word gap the first member of
> struct rt_sigframe, so the handler's argument stores land in scratch space
> instead of clobbering siginfo.
>
> Tested on qemu-system-microblazeel (petalogix-s3adsp1800) with the
> uClibc-ng NPTL test suite: tst-timer4, tst-timer5, tst-mqueue5 and
> tst-signal6 pass; before this change they failed because the handler
> clobbered the signal frame.
>
> Signed-off-by: Ramin Moussavi <ramin.moussavi@xxxxxxxxx>
> ---
>   arch/microblaze/kernel/signal.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/arch/microblaze/kernel/signal.c b/arch/microblaze/kernel/signal.c
> index c78a0ff48..df9c07d77 100644
> --- a/arch/microblaze/kernel/signal.c
> +++ b/arch/microblaze/kernel/signal.c
> @@ -49,6 +49,13 @@ struct sigframe {
>   };
>   
>   struct rt_sigframe {
> +	/*
> +	 * Home area for the handler's register arguments: the MicroBlaze
> +	 * ABI lets the callee store r5..r10 at [r1+4]..[r1+28], and r1


Actually I have created similar patch a month ago but I have only 7 spaces here.

r15 - r1 + 0
r5 - r1+4
r6 - r1+8
r7 - r1+12
r8 - r1+16
r9 - r1+20
r10 - r1+24

It means 7 should be enough. Can you please retest it?

Thanks,
Michal


--
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
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