powerpc/32: Don't add dummy frames when calling trace_hardirqs_on/off (d1865e71) · Commits · 戴 / test

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>

arch/powerpc/kernel/entry_32.S

+2 −14

Original line number	Diff line number	Diff line
		@@ -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 */

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