From 2865d08dd9ea876524652f3900b4b3b9c8b22e77 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Wed, 19 Jul 2017 14:49:39 +1000 Subject: [PATCH] powerpc/mm: Move the DSISR_PROTFAULT sanity check This has a page of comment explaining what's going on right in the middle of do_page_fault() which makes things a bit hard to follow. Move it to a helper instead. Also do the test earlier as there's no point waiting until after we found the VMA. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Michael Ellerman --- arch/powerpc/mm/fault.c | 75 +++++++++++++++++++++++++++---------------------- 1 file changed, 42 insertions(+), 33 deletions(-) diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index bd5d668b47ff..6f3a2437008a 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -239,6 +239,45 @@ static inline void cmo_account_page_fault(void) static inline void cmo_account_page_fault(void) { } #endif /* CONFIG_PPC_SMLPAR */ +#ifdef CONFIG_PPC_STD_MMU +static void sanity_check_fault(bool is_write, unsigned long error_code) +{ + /* + * For hash translation mode, we should never get a + * PROTFAULT. Any update to pte to reduce access will result in us + * removing the hash page table entry, thus resulting in a DSISR_NOHPTE + * fault instead of DSISR_PROTFAULT. + * + * A pte update to relax the access will not result in a hash page table + * entry invalidate and hence can result in DSISR_PROTFAULT. + * ptep_set_access_flags() doesn't do a hpte flush. This is why we have + * the special !is_write in the below conditional. + * + * For platforms that doesn't supports coherent icache and do support + * per page noexec bit, we do setup things such that we do the + * sync between D/I cache via fault. But that is handled via low level + * hash fault code (hash_page_do_lazy_icache()) and we should not reach + * here in such case. + * + * For wrong access that can result in PROTFAULT, the above vma->vm_flags + * check should handle those and hence we should fall to the bad_area + * handling correctly. + * + * For embedded with per page exec support that doesn't support coherent + * icache we do get PROTFAULT and we handle that D/I cache sync in + * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON + * is conditional for server MMU. + * + * For radix, we can get prot fault for autonuma case, because radix + * page table will have them marked noaccess for user. + */ + if (!radix_enabled() && !is_write) + WARN_ON_ONCE(error_code & DSISR_PROTFAULT); +} +#else +static void sanity_check_fault(bool is_write, unsigned long error_code) { } +#endif /* CONFIG_PPC_STD_MMU */ + /* * Define the correct "is_write" bit in error_code based * on the processor family @@ -306,6 +345,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, return SIGBUS; } + /* Additional sanity check(s) */ + sanity_check_fault(is_write, error_code); + /* * The kernel should never take an execute fault nor should it * take a page fault to a kernel address. @@ -441,39 +483,6 @@ good_area: if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) return bad_area(regs, address); } -#ifdef CONFIG_PPC_STD_MMU - /* - * For hash translation mode, we should never get a - * PROTFAULT. Any update to pte to reduce access will result in us - * removing the hash page table entry, thus resulting in a DSISR_NOHPTE - * fault instead of DSISR_PROTFAULT. - * - * A pte update to relax the access will not result in a hash page table - * entry invalidate and hence can result in DSISR_PROTFAULT. - * ptep_set_access_flags() doesn't do a hpte flush. This is why we have - * the special !is_write in the below conditional. - * - * For platforms that doesn't supports coherent icache and do support - * per page noexec bit, we do setup things such that we do the - * sync between D/I cache via fault. But that is handled via low level - * hash fault code (hash_page_do_lazy_icache()) and we should not reach - * here in such case. - * - * For wrong access that can result in PROTFAULT, the above vma->vm_flags - * check should handle those and hence we should fall to the bad_area - * handling correctly. - * - * For embedded with per page exec support that doesn't support coherent - * icache we do get PROTFAULT and we handle that D/I cache sync in - * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON - * is conditional for server MMU. - * - * For radix, we can get prot fault for autonuma case, because radix - * page table will have them marked noaccess for user. - */ - if (!radix_enabled() && !is_write) - WARN_ON_ONCE(error_code & DSISR_PROTFAULT); -#endif /* CONFIG_PPC_STD_MMU */ /* * If for any reason at all we couldn't handle the fault, -- 2.11.0