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Subject[PATCH] powerpc/603: fix handling of the DIRTY flag
Date
If a page is already mapped RW without the DIRTY flag, the DIRTY
flag is never set and a TLB store miss exception is taken forever.

This is easily reproduced with the following app:

void main(void)
{
volatile char *ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);

*ptr = *ptr;
}

When DIRTY flag is not set, bail out of TLB miss handler and take
a minor page fault which will set the DIRTY flag.

Fixes: f8b58c64eaef ("powerpc/603: let's handle PAGE_DIRTY directly")
Cc: stable@vger.kernel.org
Reported-by: Doug Crawford <doug.crawford@intelight-its.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/kernel/head_32.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index f255e22184b4..534dd2718795 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -557,9 +557,9 @@ DataStoreTLBMiss:
cmplw 0,r1,r3
mfspr r2, SPRN_SPRG_PGDIR
#ifdef CONFIG_SWAP
- li r1, _PAGE_RW | _PAGE_PRESENT | _PAGE_ACCESSED
+ li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED
#else
- li r1, _PAGE_RW | _PAGE_PRESENT
+ li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT
#endif
bge- 112f
lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */
--
2.13.3
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