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| author | Christophe Leroy <christophe.leroy@c-s.fr> | 2019-03-11 11:30:38 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2019-04-21 16:11:47 +0300 |
| commit | a68c31fc01ef7863acc0fc74694bf279456a58c4 (patch) | |
| tree | dca29a37f12c08381742abc20dc7364aec9fab67 /arch/powerpc/kernel | |
| parent | f342adca3afc84c4ef648352440ed6331518d72d (diff) | |
| download | linux-a68c31fc01ef7863acc0fc74694bf279456a58c4.tar.xz | |
powerpc/32s: Implement Kernel Userspace Access Protection
This patch implements Kernel Userspace Access Protection for
book3s/32.
Due to limitations of the processor page protection capabilities,
the protection is only against writing. read protection cannot be
achieved using page protection.
The previous patch modifies the page protection so that RW user
pages are RW for Key 0 and RO for Key 1, and it sets Key 0 for
both user and kernel.
This patch changes userspace segment registers are set to Ku 0
and Ks 1. When kernel needs to write to RW pages, the associated
segment register is then changed to Ks 0 in order to allow write
access to the kernel.
In order to avoid having the read all segment registers when
locking/unlocking the access, some data is kept in the thread_struct
and saved on stack on exceptions. The field identifies both the
first unlocked segment and the first segment following the last
unlocked one. When no segment is unlocked, it contains value 0.
As the hash_page() function is not able to easily determine if a
protfault is due to a bad kernel access to userspace, protfaults
need to be handled by handle_page_fault when KUAP is set.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Drop allow_read/write_to/from_user() as they're now in kup.h,
and adapt allow_user_access() to do nothing when to == NULL]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
| -rw-r--r-- | arch/powerpc/kernel/asm-offsets.c | 3 | ||||
| -rw-r--r-- | arch/powerpc/kernel/head_32.S | 11 |
2 files changed, 14 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 66202e02fee2..60b82198de7c 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -147,6 +147,9 @@ int main(void) #if defined(CONFIG_KVM) && defined(CONFIG_BOOKE) OFFSET(THREAD_KVM_VCPU, thread_struct, kvm_vcpu); #endif +#if defined(CONFIG_PPC_BOOK3S_32) && defined(CONFIG_PPC_KUAP) + OFFSET(KUAP, thread_struct, kuap); +#endif #ifdef CONFIG_PPC_TRANSACTIONAL_MEM OFFSET(PACATMSCRATCH, paca_struct, tm_scratch); diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S index 69b97cc7079f..40aec3f00a05 100644 --- a/arch/powerpc/kernel/head_32.S +++ b/arch/powerpc/kernel/head_32.S @@ -387,7 +387,11 @@ DataAccess: EXCEPTION_PROLOG mfspr r10,SPRN_DSISR stw r10,_DSISR(r11) +#ifdef CONFIG_PPC_KUAP + andis. r0,r10,(DSISR_BAD_FAULT_32S | DSISR_DABRMATCH | DSISR_PROTFAULT)@h +#else andis. r0,r10,(DSISR_BAD_FAULT_32S|DSISR_DABRMATCH)@h +#endif bne 1f /* if not, try to put a PTE */ mfspr r4,SPRN_DAR /* into the hash table */ rlwinm r3,r10,32-15,21,21 /* DSISR_STORE -> _PAGE_RW */ @@ -902,6 +906,9 @@ load_up_mmu: #ifdef CONFIG_PPC_KUEP oris r3, r3, SR_NX@h /* Set Nx */ #endif +#ifdef CONFIG_PPC_KUAP + oris r3, r3, SR_KS@h /* Set Ks */ +#endif li r4,0 3: mtsrin r3,r4 addi r3,r3,0x111 /* increment VSID */ @@ -910,6 +917,7 @@ load_up_mmu: li r0, 16 - NUM_USER_SEGMENTS /* load up kernel segment registers */ mtctr r0 /* for context 0 */ rlwinm r3, r3, 0, ~SR_NX /* Nx = 0 */ + rlwinm r3, r3, 0, ~SR_KS /* Ks = 0 */ oris r3, r3, SR_KP@h /* Kp = 1 */ 3: mtsrin r3, r4 addi r3, r3, 0x111 /* increment VSID */ @@ -1020,6 +1028,9 @@ _ENTRY(switch_mmu_context) #ifdef CONFIG_PPC_KUEP oris r3, r3, SR_NX@h /* Set Nx */ #endif +#ifdef CONFIG_PPC_KUAP + oris r3, r3, SR_KS@h /* Set Ks */ +#endif li r0,NUM_USER_SEGMENTS mtctr r0 |