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Commit 7100e870 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
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powerpc/64s/radix: Fix radix segment exception handling 



Commit 48e7b769 ("powerpc/64s/hash: Convert SLB miss handlers to C")
broke the radix-mode segment exception handler. In radix mode, this is
exception is not an SLB miss, rather it signals that the EA is outside
the range translated by any page table.

The commit lost the radix feature alternate code patch, which can
cause faults to some EAs to kernel BUG at arch/powerpc/mm/slb.c:639!

The original radix code would send faults to slb_miss_large_addr,
which would end up faulting due to slb_addr_limit being 0. This patch
sends radix directly to do_bad_slb_fault, which is a bit clearer.

Fixes: 48e7b769 ("powerpc/64s/hash: Convert SLB miss handlers to C")
Cc: stable@vger.kernel.org # v4.20+
Reported-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent dd9a994f

arch/powerpc/kernel/exceptions-64s.S

+12 −0
Original line number Diff line number Diff line
@@ -656,11 +656,17 @@ EXC_COMMON_BEGIN(data_access_slb_common) 
	ld	r4,PACA_EXSLB+EX_DAR(r13)

	std	r4,_DAR(r1)

	addi	r3,r1,STACK_FRAME_OVERHEAD

BEGIN_MMU_FTR_SECTION

	/* HPT case, do SLB fault */

	bl	do_slb_fault

	cmpdi	r3,0

	bne-	1f

	b	fast_exception_return

1:	/* Error case */

MMU_FTR_SECTION_ELSE

	/* Radix case, access is outside page table range */

	li	r3,-EFAULT

ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)

	std	r3,RESULT(r1)

	bl	save_nvgprs

	RECONCILE_IRQ_STATE(r10, r11)
@@ -705,11 +711,17 @@ EXC_COMMON_BEGIN(instruction_access_slb_common) 
	EXCEPTION_PROLOG_COMMON(0x480, PACA_EXSLB)

	ld	r4,_NIP(r1)

	addi	r3,r1,STACK_FRAME_OVERHEAD

BEGIN_MMU_FTR_SECTION

	/* HPT case, do SLB fault */

	bl	do_slb_fault

	cmpdi	r3,0

	bne-	1f

	b	fast_exception_return

1:	/* Error case */

MMU_FTR_SECTION_ELSE

	/* Radix case, access is outside page table range */

	li	r3,-EFAULT

ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)

	std	r3,RESULT(r1)

	bl	save_nvgprs

	RECONCILE_IRQ_STATE(r10, r11)