powerpc: Fix error path in kernel_thread function

The powerpc 32-bit and 64-bit kernel_thread functions don't properly
propagate errors being returned by the clone syscall.  (In the case of
error, the syscall exit code returns a positive errno in r3 and sets
the CR0[SO] bit.)

This patch fixes that by negating r3 if CR0[SO] is set after the syscall.

Signed-off-by: Josh Poimboeuf <jpoimboe@us.ibm.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 10 insertions, 6 deletions

diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index e9c8ab6eabfe..6a9b4bf0d173 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -900,8 +900,10 @@ _GLOBAL(kernel_thread)
         li      r4,0            /* new sp (unused) */
         li      r0,__NR_clone
         sc
-        cmpwi   0,r3,0          /* parent or child? */
-        bne     1f              /* return if parent */
+        bns+    1f              /* did system call indicate error? */
+        neg     r3,r3           /* if so, make return code negative */
+1:      cmpwi   0,r3,0          /* parent or child? */
+        bne     2f              /* return if parent */
         li      r0,0            /* make top-level stack frame */
         stwu    r0,-16(r1)
         mtlr    r30             /* fn addr in lr */
@@ -911,7 +913,7 @@ _GLOBAL(kernel_thread)
         li      r0,__NR_exit    /* exit if function returns */
         li      r3,0
         sc
-1:      lwz     r30,8(r1)
+2:      lwz     r30,8(r1)
         lwz     r31,12(r1)
         addi    r1,r1,16
         blr
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 4dd70cf7bb4e..3053fe5c62f2 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -426,8 +426,10 @@ _GLOBAL(kernel_thread)
         li      r4,0            /* new sp (unused) */
         li      r0,__NR_clone
         sc
-        cmpdi   0,r3,0          /* parent or child? */
-        bne     1f              /* return if parent */
+        bns+    1f              /* did system call indicate error? */
+        neg     r3,r3           /* if so, make return code negative */
+1:      cmpdi   0,r3,0          /* parent or child? */
+        bne     2f              /* return if parent */
         li      r0,0
         stdu    r0,-STACK_FRAME_OVERHEAD(r1)
         ld      r2,8(r29)
@@ -438,7 +440,7 @@ _GLOBAL(kernel_thread)
         li      r0,__NR_exit    /* exit after child exits */
         li      r3,0
         sc
-1:      addi    r1,r1,STACK_FRAME_OVERHEAD      
+2:      addi    r1,r1,STACK_FRAME_OVERHEAD
         ld      r29,-24(r1)
         ld      r30,-16(r1)
         blr