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| author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2020-11-16 19:09:31 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-12-09 08:59:46 +0300 |
| commit | 1b03e71ff6f2bd10b45a0128ce76e0e42014a44c (patch) | |
| tree | ad45d97aa550f4d3afe6011bdee1cef1d1aee41d /arch/powerpc/mm/book3s32 | |
| parent | 44e9754d63c7b419874e4c18c0b5e7a770e058c6 (diff) | |
| download | linux-1b03e71ff6f2bd10b45a0128ce76e0e42014a44c.tar.xz | |
powerpc/32s: Handle PROTFAULT in hash_page() also for CONFIG_PPC_KUAP
On hash 32 bits, handling minor protection faults like unsetting
dirty flag is heavy if done from the normal page_fault processing,
because it implies hash table software lookup for flushing the entry
and then a DSI is taken anyway to add the entry back.
When KUAP was implemented, as explained in commit a68c31fc01ef
("powerpc/32s: Implement Kernel Userspace Access Protection"),
protection faults has been diverted from hash_page() because
hash_page() was not able to identify a KUAP fault.
Implement KUAP verification in hash_page(), by clearing write
permission when the access is a kernel access and Ks is 1.
This works regardless of the address because kernel segments always
have Ks set to 0 while user segments have Ks set to 0 only
when kernel write to userspace is granted.
Then protection faults can be handled by hash_page() even for KUAP.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8a4ffe4798e9ea32aaaccdf85e411bb1beed3500.1605542955.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch/powerpc/mm/book3s32')
| -rw-r--r-- | arch/powerpc/mm/book3s32/hash_low.S | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/arch/powerpc/mm/book3s32/hash_low.S b/arch/powerpc/mm/book3s32/hash_low.S index ceb90a6e3256..98b8d8a5ad64 100644 --- a/arch/powerpc/mm/book3s32/hash_low.S +++ b/arch/powerpc/mm/book3s32/hash_low.S @@ -89,8 +89,6 @@ _GLOBAL(hash_page) #else rlwimi r8,r4,23,20,28 /* compute pte address */ #endif - rlwinm r0,r3,32-3,24,24 /* _PAGE_RW access -> _PAGE_DIRTY */ - ori r0,r0,_PAGE_ACCESSED|_PAGE_HASHPTE /* * Update the linux PTE atomically. We do the lwarx up-front @@ -106,7 +104,18 @@ _GLOBAL(hash_page) #endif .Lretry: lwarx r6,0,r8 /* get linux-style pte, flag word */ +#ifdef CONFIG_PPC_KUAP + mfsrin r5,r4 + rlwinm r0,r9,28,_PAGE_RW /* MSR[PR] => _PAGE_RW */ + rlwinm r5,r5,12,_PAGE_RW /* Ks => _PAGE_RW */ + andc r5,r5,r0 /* Ks & ~MSR[PR] */ + andc r5,r6,r5 /* Clear _PAGE_RW when Ks = 1 && MSR[PR] = 0 */ + andc. r5,r3,r5 /* check access & ~permission */ +#else andc. r5,r3,r6 /* check access & ~permission */ +#endif + rlwinm r0,r3,32-3,24,24 /* _PAGE_RW access -> _PAGE_DIRTY */ + ori r0,r0,_PAGE_ACCESSED|_PAGE_HASHPTE #ifdef CONFIG_SMP bne- .Lhash_page_out /* return if access not permitted */ #else |