Re: [PATCH v6 04/22] powerpc/book3s64/kuap/kuep: Move uamor setup to pkey init
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-11-26 03:29:46
"Aneesh Kumar K.V" [off-list ref] writes:
quoted hunk ↗ jump to hunk
This patch consolidates UAMOR update across pkey, kuap and kuep features. The boot cpu initialize UAMOR via pkey init and both radix/hash do the secondary cpu UAMOR init in early_init_mmu_secondary. We don't check for mmu_feature in radix secondary init because UAMOR is a supported SPRN with all CPUs supporting radix translation. The old code was not updating UAMOR if we had smap disabled and smep enabled. This change handles that case. Signed-off-by: Aneesh Kumar K.V <redacted> --- arch/powerpc/mm/book3s64/radix_pgtable.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 3adcf730f478..bfe441af916a 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c@@ -620,9 +620,6 @@ void setup_kuap(bool disabled) cur_cpu_spec->mmu_features |= MMU_FTR_RADIX_KUAP; } - /* Make sure userspace can't change the AMR */ - mtspr(SPRN_UAMOR, 0); - /* * Set the default kernel AMR values on all cpus. */@@ -721,6 +718,11 @@ void radix__early_init_mmu_secondary(void) radix__switch_mmu_context(NULL, &init_mm); tlbiel_all(); + +#ifdef CONFIG_PPC_PKEY + /* Make sure userspace can't change the AMR */ + mtspr(SPRN_UAMOR, 0); +#endif
If PPC_PKEY is disabled I think this leaves UAMOR unset, which means it could potentially allow AMR to be used as a covert channel between processes. cheers