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powerpc/32: Fix vmap stack - Properly set r1 before activating MMU on syscall too 

We need r1 to be properly set before activating MMU, otherwise any new
exception taken while saving registers into the stack in syscall
prologs will use the user stack, which is wrong and will even lockup
or crash when KUAP is selected.

Do that by switching the meaning of r11 and r1 until we have saved r1
to the stack: copy r1 into r11 and setup the new stack pointer in r1.
To avoid complicating and impacting all generic and specific prolog
code (and more), copy back r1 into r11 once r11 is save onto
the stack.

We could get rid of copying r1 back and forth at the cost of rewriting
everything to use r1 instead of r11 all the way when CONFIG_VMAP_STACK
is set, but the effort is probably not worth it for now.

Fixes: da7bb43ab9 ("powerpc/32: Fix vmap stack - Properly set r1 before activating MMU")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a3d819d5c348cee9783a311d5d3f3ba9b48fd219.1608531452.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2020-12-21 06:18:03 +00:00 committed by Michael Ellerman
parent 2eda7f1100
commit d5c243989f
1 changed files with 17 additions and 10 deletions
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27
arch/powerpc/kernel/head_32.h
View File

@ -121,18 +121,28 @@
#ifdef CONFIG_VMAP_STACK
mfspr r11, SPRN_SRR0
mtctr r11
#endif
andi. r11, r9, MSR_PR
mr r11, r1
lwz r1,TASK_STACK-THREAD(r12)
beq- 99f
addi r1, r1, THREAD_SIZE - INT_FRAME_SIZE
li r10, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
mtmsr r10
isync
tovirt(r12, r12)
stw r11,GPR1(r1)
stw r11,0(r1)
mr r11, r1
#else
andi. r11, r9, MSR_PR
lwz r11,TASK_STACK-THREAD(r12)
beq- 99f
addi r11, r11, THREAD_SIZE - INT_FRAME_SIZE
#ifdef CONFIG_VMAP_STACK
li r10, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */
mtmsr r10
isync
tophys(r11, r11)
stw r1,GPR1(r11)
stw r1,0(r11)
tovirt(r1, r11) /* set new kernel sp */
#endif
tovirt_vmstack r12, r12
tophys_novmstack r11, r11
mflr r10
stw r10, _LINK(r11)
#ifdef CONFIG_VMAP_STACK
@ -140,9 +150,6 @@
#else
mfspr r10,SPRN_SRR0
#endif
stw r1,GPR1(r11)
stw r1,0(r11)
tovirt_novmstack r1, r11 /* set new kernel sp */
stw r10,_NIP(r11)
mfcr r10
rlwinm r10,r10,0,4,2 /* Clear SO bit in CR */