powerpc/32: Don't add dummy frames when calling trace_hardirqs_on/off

No need to add dummy frames when calling trace_hardirqs_on or
trace_hardirqs_off. GCC properly handles empty stacks.

In addition, powerpc doesn't set CONFIG_FRAME_POINTER, therefore
__builtin_return_address(1..) returns NULL at all time. So the
dummy frames are definitely unneeded here.

In the meantime, avoid reading memory for loading r1 with a value
we already know.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index e65c3e70c64891d42c3db710702b15d572b1967c..235a01d34b6d0b9e2df9a9e1ee2a4654f5acc211 100644 (file)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -243,12 +243,7 @@ transfer_to_handler_cont:
 
 reenable_mmu:
        /*
-        * The trace_hardirqs_off will use CALLER_ADDR0 and CALLER_ADDR1.
-        * If from user mode there is only one stack frame on the stack, and
-        * accessing CALLER_ADDR1 will cause oops. So we need create a dummy
-        * stack frame to make trace_hardirqs_off happy.
-        *
-        * This is handy because we also need to save a bunch of GPRs,
+        * We save a bunch of GPRs,
         * r3 can be different from GPR3(r1) at this point, r9 and r11
         * contains the old MSR and handler address respectively,
         * r4 & r5 can contain page fault arguments that need to be passed
@@ -950,18 +945,11 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_47x)
         */
        andi.   r10,r9,MSR_EE
        beq     1f
-       /*
-        * Since the ftrace irqsoff latency trace checks CALLER_ADDR1,
-        * which is the stack frame here, we need to force a stack frame
-        * in case we came from user space.
-        */
        stwu    r1,-32(r1)
        mflr    r0
        stw     r0,4(r1)
-       stwu    r1,-32(r1)
        bl      trace_hardirqs_on
-       lwz     r1,0(r1)
-       lwz     r1,0(r1)
+       addi    r1, r1, 32
        lwz     r9,_MSR(r1)
 1:
 #endif /* CONFIG_TRACE_IRQFLAGS */