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powerpc/8xx: fix handling of early NULL pointer dereference 

NULL pointers are pointers to user memory space. So user pagetable
has to be set in order to avoid random behaviour in case of NULL
pointer dereference, otherwise we may encounter random memory
access hence Machine Check Exception from TLB Miss handlers.

Set user pagetable as early as possible in order to properly
catch early kernel NULL pointer dereference.

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 2018-07-13 13:10:47 +00:00 committed by Michael Ellerman
parent ce57c6610c
commit 8c8c10b90d
1 changed files with 4 additions and 3 deletions
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7
arch/powerpc/kernel/head_8xx.S
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@ -873,6 +873,10 @@ start_here:
li r0,0
stwu r0,THREAD_SIZE-STACK_FRAME_OVERHEAD(r1)
lis r6, swapper_pg_dir@ha
tophys(r6,r6)
mtspr SPRN_M_TW, r6
bl early_init /* We have to do this with MMU on */
/*
@ -893,9 +897,6 @@ start_here:
* init's THREAD like the context switch code does, but this is
* easier......until someone changes init's static structures.
*/
lis r6, swapper_pg_dir@ha
tophys(r6,r6)
mtspr SPRN_M_TW, r6
lis r4,2f@h
ori r4,r4,2f@l
tophys(r4,r4)