From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Tue, 20 Mar 2018 17:02:26 +0000
> While looking through the syscall wrappers there:
> sys_sigreturn:
> call do_sigreturn
> add %sp, STACKFRAME_SZ, %o0
>
> ld [%curptr + TI_FLAGS], %l5
> andcc %l5, _TIF_SYSCALL_TRACE, %g0
> be 1f
> nop
>
> call syscall_trace
> mov 1, %o1
> which seems to rely upon do_sigreturn() leaving its %i0 alone, while
> sys_rt_sigreturn:
> call do_rt_sigreturn
> add %sp, STACKFRAME_SZ, %o0
>
> ld [%curptr + TI_FLAGS], %l5
> andcc %l5, _TIF_SYSCALL_TRACE, %g0
> be 1f
> nop
>
> add %sp, STACKFRAME_SZ, %o0
> call syscall_trace
> mov 1, %o1
> doesn't count upon the same for do_rt_sigreturn(). I'm not saying that
> any of that is in any way critical (sparc32 kernel, for fsck sake...),
> just curious about the difference here. IIRC, there's nothing to
> prevent void foo(void *p) stomping on its %i0; it's unlikely to happen
> in either case, but why the difference in callers?
Good catch, I think %o0 has to be reloaded in the do_sigreturn case.
> Anyway, I've put together some cleanups ({COMPAT_,}SYSCALL_DEFINE
> conversions, getting rid of SIGN... wrappers) in
> git.kernel.org:/pub/scm/linux/kernel/git/viro/vfs.git misc.sparc
> Do you see any obviour problems with the stuff in there? It's not
> urgent - the real fun with compat wrappers will be on mips and s390,
> anyway; sparc is fairly benign in that respect...
Nothing in there seems objectionable to me.
Thanks Al!
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