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powerpc/32s: Implement Kernel Userspace Execution Prevention.

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To implement Kernel Userspace Execution Prevention, this patch
sets NX bit on all user segments on kernel entry and clears NX bit
on all user segments on kernel exit.

Note that powerpc 601 doesn't have the NX bit, so KUEP will not
work on it. A warning is displayed at startup.

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
2019-03-11 08:30:35 +00:00
committed by Michael Ellerman
parent 2679f9bd0a
commit 31ed2b13c4
7 changed files with 85 additions and 1 deletions
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9
arch/powerpc/kernel/entry_32.S
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@@ -162,6 +162,9 @@ transfer_to_handler:
andis. r12,r12,DBCR0_IDM@h
#endif
ACCOUNT_CPU_USER_ENTRY(r2, r11, r12)
#ifdef CONFIG_PPC_BOOK3S_32
kuep_lock r11, r12
#endif
#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
beq+ 3f
/* From user and task is ptraced - load up global dbcr0 */
@@ -427,6 +430,9 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
stwcx. r0,0,r1 /* to clear the reservation */
ACCOUNT_CPU_USER_EXIT(r2, r5, r7)
#ifdef CONFIG_PPC_BOOK3S_32
kuep_unlock r5, r7
#endif
kuap_check r2, r4
lwz r4,_LINK(r1)
lwz r5,_CCR(r1)
@@ -821,6 +827,9 @@ restore_user:
bnel- load_dbcr0
#endif
ACCOUNT_CPU_USER_EXIT(r2, r10, r11)
#ifdef CONFIG_PPC_BOOK3S_32
kuep_unlock r10, r11
#endif
b restore