[SPARC64]: Fix ptrace/strace

Don't clobber register %l0 while checking TI_SYS_NOERROR value in
syscall return path.  This bug was introduced by:

db7d9a4eb700be766cc9f29241483dbb1e748832

Problem narrowed down by Luis F. Ortiz and Richard Mortimer.

I tried using %l2 as suggested by Luis and that works for me.

Looking at the code I wonder if it makes sense to simplify the code
a little bit. The following works for me but I'm not sure how to
exercise the "NOERROR" codepath.

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc64/kernel/entry.S b/arch/sparc64/kernel/entry.S
index 11a8484..7100029 100644 (file)
--- a/arch/sparc64/kernel/entry.S
+++ b/arch/sparc64/kernel/entry.S
@@ -1657,13 +1657,10 @@ ret_sys_call:
        /* Check if force_successful_syscall_return()
         * was invoked.
         */
-       ldub            [%curptr + TI_SYS_NOERROR], %l0
-       brz,pt          %l0, 1f
-        nop
-       ba,pt           %xcc, 80f
+       ldub            [%curptr + TI_SYS_NOERROR], %l2
+       brnz,a,pn       %l2, 80f
         stb            %g0, [%curptr + TI_SYS_NOERROR]
 
-1:
        cmp             %o0, -ERESTART_RESTARTBLOCK
        bgeu,pn         %xcc, 1f
         andcc          %l0, (_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT), %l6