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powerpc/8xx: Activate KUEP at all time

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On the 8xx, there is absolutely no runtime impact with KUEP. Protection
against execution of user code in kernel mode is set up at boot time
by configuring the groups with contain all user pages as having swapped
protection rights, in extenso EX for user and NA for supervisor.

Configure KUEP at startup and force selection of CONFIG_PPC_KUEP.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2129e86944323ffe9ed07fffbeafdfd2e363690a.1634627931.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-10-19 09:29:13 +02:00 committed by Michael Ellerman
parent 6c1fa60d36
commit 13dac4e31e
3 changed files with 3 additions and 9 deletions
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6
arch/powerpc/include/asm/nohash/32/mmu-8xx.h
View file

@ -39,12 +39,10 @@
* 0 => Kernel => 11 (all accesses performed according as user iaw page definition)
* 1 => Kernel+Accessed => 01 (all accesses performed according to page definition)
* 2 => User => 11 (all accesses performed according as user iaw page definition)
* 3 => User+Accessed => 00 (all accesses performed as supervisor iaw page definition) for INIT
* => 10 (all accesses performed according to swaped page definition) for KUEP
* 3 => User+Accessed => 10 (all accesses performed according to swaped page definition) for KUEP
* 4-15 => Not Used
*/
#define MI_APG_INIT 0xdc000000
#define MI_APG_KUEP 0xde000000
#define MI_APG_INIT 0xde000000
/* The effective page number register. When read, contains the information
* about the last instruction TLB miss. When MI_RPN is written, bits in

5
arch/powerpc/mm/nohash/8xx.c
View file

@ -215,12 +215,7 @@ void __init setup_initial_memory_limit(phys_addr_t first_memblock_base,
#ifdef CONFIG_PPC_KUEP
void setup_kuep(bool disabled)
{
if (disabled)
return;
pr_info("Activating Kernel Userspace Execution Prevention\n");
mtspr(SPRN_MI_AP, MI_APG_KUEP);
}
#endif

1
arch/powerpc/platforms/Kconfig.cputype
View file

@ -43,6 +43,7 @@ config PPC_8xx
select ARCH_SUPPORTS_HUGETLBFS
select FSL_SOC
select PPC_HAVE_KUEP
select PPC_KUEP
select PPC_HAVE_KUAP
select HAVE_ARCH_VMAP_STACK
select HUGETLBFS