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

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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>
This commit is contained in:
Christophe Leroy 2019-04-30 12:39:05 +00:00 committed by Michael Ellerman
parent 38b4564cf0
commit d1865e71cd
1 changed files with 2 additions and 14 deletions
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16
arch/powerpc/kernel/entry_32.S
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@ -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 */