From: Mike Frysinger <vap...@gentoo.org>
Date: Mon, 18 Jan 2016 06:32:30 -0500
> looks like the bug is in arch/sparc/kernel/syscalls.S:linux_syscall_trace32
> (and linux_syscall_trace). they don't reload the args from the pt_regs
> struct after calling syscall_trace_enter. i put in a small hack:
> linux_syscall_trace32:
> call syscall_trace_enter
> add %sp, PTREGS_OFF, %o0
> brnz,pn %o0, 3f
> mov -ENOSYS, %o0
> +
> + ldx [%sp + PTREGS_OFF + PT_V9_G1], %g1
> + cmp %g1, NR_syscalls
> = bgeu,pn %xcc, 3f
> + mov -ENOSYS, %o0
> +
> srl %i0, 0, %o0
> srl %i4, 0, %o4
> ...
>
> it's enough for my use case (cancel the call), but it's not entirely correct.
> i think it needs to re-initialize %l7 with the final syscall pointer via the
> syscall table, and it needs to reload PT_V9_I{0..5}. i have no idea which
> regs need stuffing though, especially in light of the %l7 optimization. and
> i'm not familiar at all with the apparent parallelism via IEU0/IEU1 groups.
> so i won't bother with trying to write a full patch. hopefully sparc guys
> will notice & post a fix ;).
Thanks Mike, indeed this code is problematic.
We definitely need to reload all of the syscall registers (%o0-%o5,
%g1), revalidate the range of the syscall number in %g1, and if that
passes recompute the syscall table entry.
I'll work on a complete fix, thanks a lot for reporting this!
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