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Message-ID: <20261104131501.GL20479@brightrain.aerifal.cx>
Date: Wed, 4 Nov 2026 08:15:01 -0500
From: Rich Felker <dalias@...c.org>
To: Imre Kaloz <kaloz@...nel.org>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH 04/10] add SYSCALL_RT_SIGACTION_RESTORER hook for
sparc
On Wed, Nov 04, 2026 at 10:12:03AM +0100, Imre Kaloz wrote:
> Hi Rich,
>
> On Wed, Nov 4, 2026, at 04:44, Rich Felker wrote:
>
> > I think this patch misses other places SYS_rt_sigaction is used, and
> > puts arch-specific ifdefs we shouldn't be doing inline each place the
> > syscall is used.
>
> Right, abort() still makes the generic call, which on sparc passes
> _NSIG/8 as the restorer and no valid sigsetsize, so resetting SIGABRT
> to SIG_DFL fails.
>
> > Probably we should either (or both) replace direct use of the syscall
> > with a __sys_sigaction (like __sys_open, etc.) defined in
> > src/internal/syscall.h if the arch doesn't first define it, or #undef
> > SYS_rt_sigaction on sparc and have a case for where that's not
> > defined, to be safe against missing instances of its use or adding new
> > ones with silent breakage.
>
> I'd do both. The generic part is below as an RFC; with it, sparc64
> would define
>
> #define __sys_sigaction(sig,sa,old) \
> __syscall(__NR_rt_sigaction,sig,sa,old,__restore,_NSIG/8)
> #undef SYS_rt_sigaction
I'm pretty sure this breaks expansion of __sys_sigaction.
> > Note that since __restore and __restore_rt are the same,
> > __sys_sigaction does not need a conditional on flags. It can just
> > always pass __restore in the extra slot.
>
> They are on sparc64. 32-bit sparc builds a different frame for
> handlers without SA_SIGINFO and returns from it with sigreturn rather
> than rt_sigreturn, so there the restorer has to follow SA_SIGINFO:
>
> #define __sys_sigaction(sig,sa,old) \
> __syscall(__NR_rt_sigaction,sig,sa,old, \
> (long)(sa) && ((sa)->flags & SA_SIGINFO) ? __restore_rt : __restore, \
> _NSIG/8)
> #undef SYS_rt_sigaction
>
> (sa is tested as an integer because gcc warns on the address of
> abort's compound literal.) Does this look right before I fold it
> into v2?
Which warning is this? I don't like casts to avoid warnings.
It might be better to write an inline function by the same name and
just define the macro to itself. That gets rid of the multi-line
macros too.
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