powerpc: Fix system calls on Cell entered with XER.SO=1

[linux-2.6-omap-h63xx.git] / arch / powerpc / kernel / entry_64.S

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index e6d52845854f8e1ea67d60f48332ff8206c9fa7e..e0bcf93542867d79e20c1d5951397813535545a2 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -57,12 +57,18 @@ system_call_common:
        beq-    1f
        ld      r1,PACAKSAVE(r13)
 1:     std     r10,0(r1)
-       crclr   so
        std     r11,_NIP(r1)
        std     r12,_MSR(r1)
        std     r0,GPR0(r1)
        std     r10,GPR1(r1)
        ACCOUNT_CPU_USER_ENTRY(r10, r11)
+       /*
+        * This "crclr so" clears CR0.SO, which is the error indication on
+        * return from this system call.  There must be no cmp instruction
+        * between it and the "mfcr r9" below, otherwise if XER.SO is set,
+        * CR0.SO will get set, causing all system calls to appear to fail.
+        */
+       crclr   so
        std     r2,GPR2(r1)
        std     r3,GPR3(r1)
        std     r4,GPR4(r1)