| Message ID | 1403612604-2645-3-git-send-email-steve.capper@linaro.org |
|---|---|
| State | New |
| Headers | show |
Hey Steve, On Tue, Jun 24, 2014 at 01:23:24PM +0100, Steve Capper wrote: > For LPAE, we have the following means for encoding writable or dirty > ptes: > L_PTE_DIRTY L_PTE_RDONLY > !pte_dirty && !pte_write 0 1 > !pte_dirty && pte_write 0 1 > pte_dirty && !pte_write 1 1 > pte_dirty && pte_write 1 0 > > So we can't distinguish between writeable clean ptes and read only > ptes. This can cause problems with ptes being incorrectly flagged as > read only when they are writeable but not dirty. > > This patch renumbers L_PTE_RDONLY from AP[2] to a software bit #58, > and adds additional logic to set AP[2] whenever the pte is read only > or not dirty. That way we can distinguish between clean writeable ptes > and read only ptes. > > HugeTLB pages will use this new logic automatically. > > We need to add some logic to Transparent HugePages to ensure that they > correctly interpret the revised pgprot permissions (L_PTE_RDONLY has > moved and no longer matches PMD_SECT_RDONLY). In the process of > revising THP, the names of the PMD software bits have been prefixed > with L_ to make them easier to distinguish from their hardware bit > counterparts. > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > --- > Changed in V5 -> rather than re-introduce L_PTE_WRITE we change > L_PTE_RDONLY to be a software bit #58. This allows us to leave the > two level code alone. Damnit, you owe me a beer every time I have to review this patch ;) At least proc-macros.S is unscathed this time around! > --- > arch/arm/include/asm/pgtable-3level-hwdef.h | 1 + > arch/arm/include/asm/pgtable-3level.h | 37 +++++++++++++++++------------ > arch/arm/mm/proc-v7-3level.S | 9 +++++-- > 3 files changed, 30 insertions(+), 17 deletions(-) > > diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h > index 626989f..552a5f7 100644 > --- a/arch/arm/include/asm/pgtable-3level-hwdef.h > +++ b/arch/arm/include/asm/pgtable-3level-hwdef.h > @@ -72,6 +72,7 @@ > #define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1) > #define PTE_BUFFERABLE (_AT(pteval_t, 1) << 2) /* AttrIndx[0] */ > #define PTE_CACHEABLE (_AT(pteval_t, 1) << 3) /* AttrIndx[1] */ > +#define PTE_AP2 (_AT(pteval_t, 1) << 7) /* AP[2] */ PTE_RDONLY? AP2 is pretty cryptic. > #define PTE_EXT_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ > #define PTE_EXT_AF (_AT(pteval_t, 1) << 10) /* Access Flag */ > #define PTE_EXT_NG (_AT(pteval_t, 1) << 11) /* nG */ > diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h > index 3b10ec6..24ba2d7 100644 > --- a/arch/arm/include/asm/pgtable-3level.h > +++ b/arch/arm/include/asm/pgtable-3level.h > @@ -79,18 +79,19 @@ > #define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Present */ > #define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */ > #define L_PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */ > -#define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */ > #define L_PTE_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ > #define L_PTE_YOUNG (_AT(pteval_t, 1) << 10) /* AF */ > #define L_PTE_XN (_AT(pteval_t, 1) << 54) /* XN */ > #define L_PTE_DIRTY (_AT(pteval_t, 1) << 55) /* unused */ > #define L_PTE_SPECIAL (_AT(pteval_t, 1) << 56) /* unused */ > #define L_PTE_NONE (_AT(pteval_t, 1) << 57) /* PROT_NONE */ > +#define L_PTE_RDONLY (_AT(pteval_t, 1) << 58) /* READ ONLY */ Can you fix those `unused' comments above while you're here, please? Whilst they are unused by the hardware, they're very much used by Linux. Well, SPECIAL isn't yet, but it could be... > -#define PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) > -#define PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) > -#define PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) > -#define PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) > +#define L_PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) > +#define L_PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) > +#define L_PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) > +#define L_PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) > +#define L_PMD_SECT_RDONLY (_AT(pteval_t, 1) << 58) Boo-hoo, that's our last remaining software bit for LPAE. It's a sad day. > /* > * To be used in assembly code with the upper page attributes. > @@ -214,24 +215,25 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) > #define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF)) > > #define __HAVE_ARCH_PMD_WRITE > -#define pmd_write(pmd) (pmd_isclear((pmd), PMD_SECT_RDONLY)) > +#define pmd_write(pmd) (pmd_isclear((pmd), L_PMD_SECT_RDONLY)) > +#define pmd_dirty(pmd) (pmd_isset((pmd), L_PMD_SECT_DIRTY)) > > #define pmd_hugewillfault(pmd) (!pmd_young(pmd) || !pmd_write(pmd)) > #define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd)) > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > #define pmd_trans_huge(pmd) (pmd_val(pmd) && pmd_isclear((pmd), PMD_TABLE_BIT)) > -#define pmd_trans_splitting(pmd) (pmd_isset((pmd), PMD_SECT_SPLITTING)) > +#define pmd_trans_splitting(pmd) (pmd_isset((pmd), L_PMD_SECT_SPLITTING)) I take it we only call this on something we've decided is huge already (as opposed to, e.g. a swap entry)? > #endif > > #define PMD_BIT_FUNC(fn,op) \ > static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; } > > -PMD_BIT_FUNC(wrprotect, |= PMD_SECT_RDONLY); > +PMD_BIT_FUNC(wrprotect, |= L_PMD_SECT_RDONLY); > PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF); > -PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING); > -PMD_BIT_FUNC(mkwrite, &= ~PMD_SECT_RDONLY); > -PMD_BIT_FUNC(mkdirty, |= PMD_SECT_DIRTY); > +PMD_BIT_FUNC(mksplitting, |= L_PMD_SECT_SPLITTING); > +PMD_BIT_FUNC(mkwrite, &= ~L_PMD_SECT_RDONLY); > +PMD_BIT_FUNC(mkdirty, |= L_PMD_SECT_DIRTY); > PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); > > #define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT)) > @@ -245,8 +247,8 @@ PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); > > static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) > { > - const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | PMD_SECT_RDONLY | > - PMD_SECT_VALID | PMD_SECT_NONE; > + const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | L_PMD_SECT_RDONLY | > + L_PMD_SECT_VALID | L_PMD_SECT_NONE; > pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask); > return pmd; > } > @@ -257,8 +259,13 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr, > BUG_ON(addr >= TASK_SIZE); > > /* create a faulting entry if PROT_NONE protected */ > - if (pmd_val(pmd) & PMD_SECT_NONE) > - pmd_val(pmd) &= ~PMD_SECT_VALID; > + if (pmd_val(pmd) & L_PMD_SECT_NONE) > + pmd_val(pmd) &= ~L_PMD_SECT_VALID; > + > + if (pmd_write(pmd) && pmd_dirty(pmd)) > + pmd_val(pmd) &= ~PMD_SECT_RDONLY; pmd_mkwrite? > + else > + pmd_val(pmd) |= PMD_SECT_RDONLY; pmd_wrprotect? > > *pmdp = __pmd(pmd_val(pmd) | PMD_SECT_nG); > flush_pmd_entry(pmdp); > diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S > index 22e3ad6..eb81123 100644 > --- a/arch/arm/mm/proc-v7-3level.S > +++ b/arch/arm/mm/proc-v7-3level.S > @@ -86,8 +86,13 @@ ENTRY(cpu_v7_set_pte_ext) > tst rh, #1 << (57 - 32) @ L_PTE_NONE > bicne rl, #L_PTE_VALID > bne 1f > - tst rh, #1 << (55 - 32) @ L_PTE_DIRTY > - orreq rl, #L_PTE_RDONLY > + > + eor ip, rh, #1 << (55 - 32) @ toggle L_PTE_DIRTY in temp reg to > + @ test for !L_PTE_DIRTY || L_PTE_RDONLY Since you already set RDONLY for pmds based on dirty, can we do the same for ptes and avoid this check here...? > + tst ip, #1 << (55 - 32) | 1 << (58 - 32) > + orrne rl, #PTE_AP2 > + biceq rl, #PTE_AP2 ... Then use Russell's ubfx trick to copy L_PTE_RDONLY into PTE_RDONLY? Will
On Fri, Jun 27, 2014 at 12:39:34PM +0100, Will Deacon wrote: > Hey Steve, > > On Tue, Jun 24, 2014 at 01:23:24PM +0100, Steve Capper wrote: > > For LPAE, we have the following means for encoding writable or dirty > > ptes: > > L_PTE_DIRTY L_PTE_RDONLY > > !pte_dirty && !pte_write 0 1 > > !pte_dirty && pte_write 0 1 > > pte_dirty && !pte_write 1 1 > > pte_dirty && pte_write 1 0 > > > > So we can't distinguish between writeable clean ptes and read only > > ptes. This can cause problems with ptes being incorrectly flagged as > > read only when they are writeable but not dirty. > > > > This patch renumbers L_PTE_RDONLY from AP[2] to a software bit #58, > > and adds additional logic to set AP[2] whenever the pte is read only > > or not dirty. That way we can distinguish between clean writeable ptes > > and read only ptes. > > > > HugeTLB pages will use this new logic automatically. > > > > We need to add some logic to Transparent HugePages to ensure that they > > correctly interpret the revised pgprot permissions (L_PTE_RDONLY has > > moved and no longer matches PMD_SECT_RDONLY). In the process of > > revising THP, the names of the PMD software bits have been prefixed > > with L_ to make them easier to distinguish from their hardware bit > > counterparts. > > > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > > --- > > Changed in V5 -> rather than re-introduce L_PTE_WRITE we change > > L_PTE_RDONLY to be a software bit #58. This allows us to leave the > > two level code alone. > > Damnit, you owe me a beer every time I have to review this patch ;) > At least proc-macros.S is unscathed this time around! It's thirsty work writing and testing it too, I have a cunning plan that can fix both our problems.... :-) > > > --- > > arch/arm/include/asm/pgtable-3level-hwdef.h | 1 + > > arch/arm/include/asm/pgtable-3level.h | 37 +++++++++++++++++------------ > > arch/arm/mm/proc-v7-3level.S | 9 +++++-- > > 3 files changed, 30 insertions(+), 17 deletions(-) > > > > diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h > > index 626989f..552a5f7 100644 > > --- a/arch/arm/include/asm/pgtable-3level-hwdef.h > > +++ b/arch/arm/include/asm/pgtable-3level-hwdef.h > > @@ -72,6 +72,7 @@ > > #define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1) > > #define PTE_BUFFERABLE (_AT(pteval_t, 1) << 2) /* AttrIndx[0] */ > > #define PTE_CACHEABLE (_AT(pteval_t, 1) << 3) /* AttrIndx[1] */ > > +#define PTE_AP2 (_AT(pteval_t, 1) << 7) /* AP[2] */ > > PTE_RDONLY? AP2 is pretty cryptic. That is probably better, but could it be confused with L_PRE_RDONLY? (Please see below for the pmd analogue). > > > #define PTE_EXT_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ > > #define PTE_EXT_AF (_AT(pteval_t, 1) << 10) /* Access Flag */ > > #define PTE_EXT_NG (_AT(pteval_t, 1) << 11) /* nG */ > > diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h > > index 3b10ec6..24ba2d7 100644 > > --- a/arch/arm/include/asm/pgtable-3level.h > > +++ b/arch/arm/include/asm/pgtable-3level.h > > @@ -79,18 +79,19 @@ > > #define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Present */ > > #define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */ > > #define L_PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */ > > -#define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */ > > #define L_PTE_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ > > #define L_PTE_YOUNG (_AT(pteval_t, 1) << 10) /* AF */ > > #define L_PTE_XN (_AT(pteval_t, 1) << 54) /* XN */ > > #define L_PTE_DIRTY (_AT(pteval_t, 1) << 55) /* unused */ > > #define L_PTE_SPECIAL (_AT(pteval_t, 1) << 56) /* unused */ > > #define L_PTE_NONE (_AT(pteval_t, 1) << 57) /* PROT_NONE */ > > +#define L_PTE_RDONLY (_AT(pteval_t, 1) << 58) /* READ ONLY */ > > Can you fix those `unused' comments above while you're here, please? Whilst > they are unused by the hardware, they're very much used by Linux. Well, > SPECIAL isn't yet, but it could be... Sure. > > > -#define PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) > > -#define PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) > > -#define PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) > > -#define PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) > > +#define L_PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) > > +#define L_PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) > > +#define L_PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) > > +#define L_PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) > > +#define L_PMD_SECT_RDONLY (_AT(pteval_t, 1) << 58) > > Boo-hoo, that's our last remaining software bit for LPAE. It's a sad day. > > > /* > > * To be used in assembly code with the upper page attributes. > > @@ -214,24 +215,25 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) > > #define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF)) > > > > #define __HAVE_ARCH_PMD_WRITE > > -#define pmd_write(pmd) (pmd_isclear((pmd), PMD_SECT_RDONLY)) > > +#define pmd_write(pmd) (pmd_isclear((pmd), L_PMD_SECT_RDONLY)) > > +#define pmd_dirty(pmd) (pmd_isset((pmd), L_PMD_SECT_DIRTY)) > > > > #define pmd_hugewillfault(pmd) (!pmd_young(pmd) || !pmd_write(pmd)) > > #define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd)) > > > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > > #define pmd_trans_huge(pmd) (pmd_val(pmd) && pmd_isclear((pmd), PMD_TABLE_BIT)) > > -#define pmd_trans_splitting(pmd) (pmd_isset((pmd), PMD_SECT_SPLITTING)) > > +#define pmd_trans_splitting(pmd) (pmd_isset((pmd), L_PMD_SECT_SPLITTING)) > > I take it we only call this on something we've decided is huge already (as > opposed to, e.g. a swap entry)? Yes that's correct, the sequence is pmd_trans_huge(blah), then later on pmd_trans_splitting(blah). > > > #endif > > > > #define PMD_BIT_FUNC(fn,op) \ > > static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; } > > > > -PMD_BIT_FUNC(wrprotect, |= PMD_SECT_RDONLY); > > +PMD_BIT_FUNC(wrprotect, |= L_PMD_SECT_RDONLY); > > PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF); > > -PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING); > > -PMD_BIT_FUNC(mkwrite, &= ~PMD_SECT_RDONLY); > > -PMD_BIT_FUNC(mkdirty, |= PMD_SECT_DIRTY); > > +PMD_BIT_FUNC(mksplitting, |= L_PMD_SECT_SPLITTING); > > +PMD_BIT_FUNC(mkwrite, &= ~L_PMD_SECT_RDONLY); > > +PMD_BIT_FUNC(mkdirty, |= L_PMD_SECT_DIRTY); > > PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); > > > > #define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT)) > > @@ -245,8 +247,8 @@ PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); > > > > static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) > > { > > - const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | PMD_SECT_RDONLY | > > - PMD_SECT_VALID | PMD_SECT_NONE; > > + const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | L_PMD_SECT_RDONLY | > > + L_PMD_SECT_VALID | L_PMD_SECT_NONE; > > pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask); > > return pmd; > > } > > @@ -257,8 +259,13 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr, > > BUG_ON(addr >= TASK_SIZE); > > > > /* create a faulting entry if PROT_NONE protected */ > > - if (pmd_val(pmd) & PMD_SECT_NONE) > > - pmd_val(pmd) &= ~PMD_SECT_VALID; > > + if (pmd_val(pmd) & L_PMD_SECT_NONE) > > + pmd_val(pmd) &= ~L_PMD_SECT_VALID; > > + > > + if (pmd_write(pmd) && pmd_dirty(pmd)) > > + pmd_val(pmd) &= ~PMD_SECT_RDONLY; > > pmd_mkwrite? > > > + else > > + pmd_val(pmd) |= PMD_SECT_RDONLY; > > pmd_wrprotect? I'm setting the hardware bits here. I tried to distinguish: PMD_SECT_RDONLY and L_PMD_SECT_RDONLY. I think I should probably rename PMD_SECT_RDONLY to something else? > > > > > *pmdp = __pmd(pmd_val(pmd) | PMD_SECT_nG); > > flush_pmd_entry(pmdp); > > diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S > > index 22e3ad6..eb81123 100644 > > --- a/arch/arm/mm/proc-v7-3level.S > > +++ b/arch/arm/mm/proc-v7-3level.S > > @@ -86,8 +86,13 @@ ENTRY(cpu_v7_set_pte_ext) > > tst rh, #1 << (57 - 32) @ L_PTE_NONE > > bicne rl, #L_PTE_VALID > > bne 1f > > - tst rh, #1 << (55 - 32) @ L_PTE_DIRTY > > - orreq rl, #L_PTE_RDONLY > > + > > + eor ip, rh, #1 << (55 - 32) @ toggle L_PTE_DIRTY in temp reg to > > + @ test for !L_PTE_DIRTY || L_PTE_RDONLY > > Since you already set RDONLY for pmds based on dirty, can we do the same for > ptes and avoid this check here...? Isn't the pte check logically equivalent to the pmd case? if (pmd_write(pmd) && pmd_dirty(pmd)) > > > + tst ip, #1 << (55 - 32) | 1 << (58 - 32) > > + orrne rl, #PTE_AP2 > > + biceq rl, #PTE_AP2 > > ... Then use Russell's ubfx trick to copy L_PTE_RDONLY into PTE_RDONLY? > I will have another think about this. Cheers,
On Fri, Jun 27, 2014 at 01:42:00PM +0100, Steve Capper wrote: > On Fri, Jun 27, 2014 at 12:39:34PM +0100, Will Deacon wrote: > > On Tue, Jun 24, 2014 at 01:23:24PM +0100, Steve Capper wrote: > > > diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h > > > index 626989f..552a5f7 100644 > > > --- a/arch/arm/include/asm/pgtable-3level-hwdef.h > > > +++ b/arch/arm/include/asm/pgtable-3level-hwdef.h > > > @@ -72,6 +72,7 @@ > > > #define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1) > > > #define PTE_BUFFERABLE (_AT(pteval_t, 1) << 2) /* AttrIndx[0] */ > > > #define PTE_CACHEABLE (_AT(pteval_t, 1) << 3) /* AttrIndx[1] */ > > > +#define PTE_AP2 (_AT(pteval_t, 1) << 7) /* AP[2] */ > > > > PTE_RDONLY? AP2 is pretty cryptic. > > That is probably better, but could it be confused with L_PRE_RDONLY? > (Please see below for the pmd analogue). Comments below, I seem to have fallen into my own trap. > > > @@ -257,8 +259,13 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr, > > > BUG_ON(addr >= TASK_SIZE); > > > > > > /* create a faulting entry if PROT_NONE protected */ > > > - if (pmd_val(pmd) & PMD_SECT_NONE) > > > - pmd_val(pmd) &= ~PMD_SECT_VALID; > > > + if (pmd_val(pmd) & L_PMD_SECT_NONE) > > > + pmd_val(pmd) &= ~L_PMD_SECT_VALID; > > > + > > > + if (pmd_write(pmd) && pmd_dirty(pmd)) > > > + pmd_val(pmd) &= ~PMD_SECT_RDONLY; > > > > pmd_mkwrite? > > > > > + else > > > + pmd_val(pmd) |= PMD_SECT_RDONLY; > > > > pmd_wrprotect? > > I'm setting the hardware bits here. I tried to distinguish: > PMD_SECT_RDONLY and L_PMD_SECT_RDONLY. I think I should probably rename > PMD_SECT_RDONLY to something else? Ok, so that's actually a really good argument to keep AP2 as the name for both ptes and pmds. In that case, the comment we have " /* AP[2] */ is useless and should say "RDONLY". Then we have non-ambiguous symbol names alongside descriptive comments -- not something I'm used to in the kernel sources! Will
diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h index 626989f..552a5f7 100644 --- a/arch/arm/include/asm/pgtable-3level-hwdef.h +++ b/arch/arm/include/asm/pgtable-3level-hwdef.h @@ -72,6 +72,7 @@ #define PTE_TABLE_BIT (_AT(pteval_t, 1) << 1) #define PTE_BUFFERABLE (_AT(pteval_t, 1) << 2) /* AttrIndx[0] */ #define PTE_CACHEABLE (_AT(pteval_t, 1) << 3) /* AttrIndx[1] */ +#define PTE_AP2 (_AT(pteval_t, 1) << 7) /* AP[2] */ #define PTE_EXT_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ #define PTE_EXT_AF (_AT(pteval_t, 1) << 10) /* Access Flag */ #define PTE_EXT_NG (_AT(pteval_t, 1) << 11) /* nG */ diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h index 3b10ec6..24ba2d7 100644 --- a/arch/arm/include/asm/pgtable-3level.h +++ b/arch/arm/include/asm/pgtable-3level.h @@ -79,18 +79,19 @@ #define L_PTE_PRESENT (_AT(pteval_t, 3) << 0) /* Present */ #define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */ #define L_PTE_USER (_AT(pteval_t, 1) << 6) /* AP[1] */ -#define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) /* AP[2] */ #define L_PTE_SHARED (_AT(pteval_t, 3) << 8) /* SH[1:0], inner shareable */ #define L_PTE_YOUNG (_AT(pteval_t, 1) << 10) /* AF */ #define L_PTE_XN (_AT(pteval_t, 1) << 54) /* XN */ #define L_PTE_DIRTY (_AT(pteval_t, 1) << 55) /* unused */ #define L_PTE_SPECIAL (_AT(pteval_t, 1) << 56) /* unused */ #define L_PTE_NONE (_AT(pteval_t, 1) << 57) /* PROT_NONE */ +#define L_PTE_RDONLY (_AT(pteval_t, 1) << 58) /* READ ONLY */ -#define PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) -#define PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) -#define PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) -#define PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) +#define L_PMD_SECT_VALID (_AT(pmdval_t, 1) << 0) +#define L_PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55) +#define L_PMD_SECT_SPLITTING (_AT(pmdval_t, 1) << 56) +#define L_PMD_SECT_NONE (_AT(pmdval_t, 1) << 57) +#define L_PMD_SECT_RDONLY (_AT(pteval_t, 1) << 58) /* * To be used in assembly code with the upper page attributes. @@ -214,24 +215,25 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) #define pmd_young(pmd) (pmd_isset((pmd), PMD_SECT_AF)) #define __HAVE_ARCH_PMD_WRITE -#define pmd_write(pmd) (pmd_isclear((pmd), PMD_SECT_RDONLY)) +#define pmd_write(pmd) (pmd_isclear((pmd), L_PMD_SECT_RDONLY)) +#define pmd_dirty(pmd) (pmd_isset((pmd), L_PMD_SECT_DIRTY)) #define pmd_hugewillfault(pmd) (!pmd_young(pmd) || !pmd_write(pmd)) #define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd)) #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define pmd_trans_huge(pmd) (pmd_val(pmd) && pmd_isclear((pmd), PMD_TABLE_BIT)) -#define pmd_trans_splitting(pmd) (pmd_isset((pmd), PMD_SECT_SPLITTING)) +#define pmd_trans_splitting(pmd) (pmd_isset((pmd), L_PMD_SECT_SPLITTING)) #endif #define PMD_BIT_FUNC(fn,op) \ static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; } -PMD_BIT_FUNC(wrprotect, |= PMD_SECT_RDONLY); +PMD_BIT_FUNC(wrprotect, |= L_PMD_SECT_RDONLY); PMD_BIT_FUNC(mkold, &= ~PMD_SECT_AF); -PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING); -PMD_BIT_FUNC(mkwrite, &= ~PMD_SECT_RDONLY); -PMD_BIT_FUNC(mkdirty, |= PMD_SECT_DIRTY); +PMD_BIT_FUNC(mksplitting, |= L_PMD_SECT_SPLITTING); +PMD_BIT_FUNC(mkwrite, &= ~L_PMD_SECT_RDONLY); +PMD_BIT_FUNC(mkdirty, |= L_PMD_SECT_DIRTY); PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); #define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT)) @@ -245,8 +247,8 @@ PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) { - const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | PMD_SECT_RDONLY | - PMD_SECT_VALID | PMD_SECT_NONE; + const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | L_PMD_SECT_RDONLY | + L_PMD_SECT_VALID | L_PMD_SECT_NONE; pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask); return pmd; } @@ -257,8 +259,13 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr, BUG_ON(addr >= TASK_SIZE); /* create a faulting entry if PROT_NONE protected */ - if (pmd_val(pmd) & PMD_SECT_NONE) - pmd_val(pmd) &= ~PMD_SECT_VALID; + if (pmd_val(pmd) & L_PMD_SECT_NONE) + pmd_val(pmd) &= ~L_PMD_SECT_VALID; + + if (pmd_write(pmd) && pmd_dirty(pmd)) + pmd_val(pmd) &= ~PMD_SECT_RDONLY; + else + pmd_val(pmd) |= PMD_SECT_RDONLY; *pmdp = __pmd(pmd_val(pmd) | PMD_SECT_nG); flush_pmd_entry(pmdp); diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S index 22e3ad6..eb81123 100644 --- a/arch/arm/mm/proc-v7-3level.S +++ b/arch/arm/mm/proc-v7-3level.S @@ -86,8 +86,13 @@ ENTRY(cpu_v7_set_pte_ext) tst rh, #1 << (57 - 32) @ L_PTE_NONE bicne rl, #L_PTE_VALID bne 1f - tst rh, #1 << (55 - 32) @ L_PTE_DIRTY - orreq rl, #L_PTE_RDONLY + + eor ip, rh, #1 << (55 - 32) @ toggle L_PTE_DIRTY in temp reg to + @ test for !L_PTE_DIRTY || L_PTE_RDONLY + tst ip, #1 << (55 - 32) | 1 << (58 - 32) + orrne rl, #PTE_AP2 + biceq rl, #PTE_AP2 + 1: strd r2, r3, [r0] ALT_SMP(W(nop)) ALT_UP (mcr p15, 0, r0, c7, c10, 1) @ flush_pte
For LPAE, we have the following means for encoding writable or dirty ptes: L_PTE_DIRTY L_PTE_RDONLY !pte_dirty && !pte_write 0 1 !pte_dirty && pte_write 0 1 pte_dirty && !pte_write 1 1 pte_dirty && pte_write 1 0 So we can't distinguish between writeable clean ptes and read only ptes. This can cause problems with ptes being incorrectly flagged as read only when they are writeable but not dirty. This patch renumbers L_PTE_RDONLY from AP[2] to a software bit #58, and adds additional logic to set AP[2] whenever the pte is read only or not dirty. That way we can distinguish between clean writeable ptes and read only ptes. HugeTLB pages will use this new logic automatically. We need to add some logic to Transparent HugePages to ensure that they correctly interpret the revised pgprot permissions (L_PTE_RDONLY has moved and no longer matches PMD_SECT_RDONLY). In the process of revising THP, the names of the PMD software bits have been prefixed with L_ to make them easier to distinguish from their hardware bit counterparts. Signed-off-by: Steve Capper <steve.capper@linaro.org> --- Changed in V5 -> rather than re-introduce L_PTE_WRITE we change L_PTE_RDONLY to be a software bit #58. This allows us to leave the two level code alone. --- arch/arm/include/asm/pgtable-3level-hwdef.h | 1 + arch/arm/include/asm/pgtable-3level.h | 37 +++++++++++++++++------------ arch/arm/mm/proc-v7-3level.S | 9 +++++-- 3 files changed, 30 insertions(+), 17 deletions(-)