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authorPaul Mackerras <paulus@ozlabs.org>2016-09-02 21:49:21 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2016-09-13 17:37:03 +1000
commitf0f558b131db0e793fd90aac5d93f694362973d2 (patch)
tree63835fc7bcd3283ff5a81a4930c5dd6fdcb02b7a /arch/powerpc/mm
parentb42d9023a31e384504f5b53fc9a437d5536a3f63 (diff)
downloadblackbird-op-linux-f0f558b131db0e793fd90aac5d93f694362973d2.tar.gz
blackbird-op-linux-f0f558b131db0e793fd90aac5d93f694362973d2.zip
powerpc/mm: Preserve CFAR value on SLB miss caused by access to bogus address
Currently, if userspace or the kernel accesses a completely bogus address, for example with any of bits 46-59 set, we first take an SLB miss interrupt, install a corresponding SLB entry with VSID 0, retry the instruction, then take a DSI/ISI interrupt because there is no HPT entry mapping the address. However, by the time of the second interrupt, the Come-From Address Register (CFAR) has been overwritten by the rfid instruction at the end of the SLB miss interrupt handler. Since bogus accesses can often be caused by a function return after the stack has been overwritten, the CFAR value would be very useful as it could indicate which function it was whose return had led to the bogus address. This patch adds code to create a full exception frame in the SLB miss handler in the case of a bogus address, rather than inserting an SLB entry with a zero VSID field. Then we call a new slb_miss_bad_addr() function in C code, which delivers a signal for a user access or creates an oops for a kernel access. In the latter case the oops message will show the CFAR value at the time of the access. In the case of the radix MMU, a segment miss interrupt indicates an access outside the ranges mapped by the page tables. Previously this was handled by the code for an unrecoverable SLB miss (one with MSR[RI] = 0), which is not really correct. With this patch, we now handle these interrupts with slb_miss_bad_addr(), which is much more consistent. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/slb_low.S8
1 files changed, 3 insertions, 5 deletions
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index dfdb90cb4403..eda1c7a2416a 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -173,11 +173,9 @@ BEGIN_FTR_SECTION
END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
b slb_finish_load
-8: /* invalid EA */
- li r10,0 /* BAD_VSID */
- li r9,0 /* BAD_VSID */
- li r11,SLB_VSID_USER /* flags don't much matter */
- b slb_finish_load
+8: /* invalid EA - return an error indication */
+ crset 4*cr0+eq /* indicate failure */
+ blr
/*
* Finish loading of an SLB entry and return
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