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stevecapperarmctmarinas
stevecapperarm
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arm64: mm: Introduce PTE_WRITE
We have the following means for encoding writable or dirty ptes: PTE_DIRTY 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 writable clean ptes and read only ptes. This can cause problems with ptes being incorrectly flagged as read only when they are writable but not dirty. This patch introduces a new software bit PTE_WRITE which allows us to correctly identify writable ptes. PTE_RDONLY is now only clear for valid ptes where a page is both writable and dirty. Signed-off-by: Steve Capper <steve.capper@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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‎arch/arm64/include/asm/pgtable.h

Lines changed: 25 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,7 @@
2828
#define PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !pte_present() */
2929
#define PTE_DIRTY (_AT(pteval_t, 1) << 55)
3030
#define PTE_SPECIAL (_AT(pteval_t, 1) << 56)
31-
/* bit 57 for PMD_SECT_SPLITTING */
31+
#define PTE_WRITE (_AT(pteval_t, 1) << 57)
3232
#define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */
3333

3434
/*
@@ -67,29 +67,29 @@ extern pgprot_t pgprot_default;
6767

6868
#define _MOD_PROT(p, b) __pgprot_modify(p, 0, b)
6969

70-
#define PAGE_NONE __pgprot_modify(pgprot_default, PTE_TYPE_MASK, PTE_PROT_NONE | PTE_RDONLY | PTE_PXN | PTE_UXN)
71-
#define PAGE_SHARED _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
72-
#define PAGE_SHARED_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN)
73-
#define PAGE_COPY _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
74-
#define PAGE_COPY_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
75-
#define PAGE_READONLY _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
76-
#define PAGE_READONLY_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
77-
#define PAGE_KERNEL _MOD_PROT(pgprot_default, PTE_PXN | PTE_UXN | PTE_DIRTY)
78-
#define PAGE_KERNEL_EXEC _MOD_PROT(pgprot_default, PTE_UXN | PTE_DIRTY)
70+
#define PAGE_NONE __pgprot_modify(pgprot_default, PTE_TYPE_MASK, PTE_PROT_NONE | PTE_PXN | PTE_UXN)
71+
#define PAGE_SHARED _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
72+
#define PAGE_SHARED_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_WRITE)
73+
#define PAGE_COPY _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
74+
#define PAGE_COPY_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN)
75+
#define PAGE_READONLY _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
76+
#define PAGE_READONLY_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN)
77+
#define PAGE_KERNEL _MOD_PROT(pgprot_default, PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE)
78+
#define PAGE_KERNEL_EXEC _MOD_PROT(pgprot_default, PTE_UXN | PTE_DIRTY | PTE_WRITE)
7979

8080
#define PAGE_HYP _MOD_PROT(pgprot_default, PTE_HYP)
8181
#define PAGE_HYP_DEVICE __pgprot(PROT_DEVICE_nGnRE | PTE_HYP)
8282

8383
#define PAGE_S2 __pgprot_modify(pgprot_default, PTE_S2_MEMATTR_MASK, PTE_S2_MEMATTR(MT_S2_NORMAL) | PTE_S2_RDONLY)
8484
#define PAGE_S2_DEVICE __pgprot(PROT_DEFAULT | PTE_S2_MEMATTR(MT_S2_DEVICE_nGnRE) | PTE_S2_RDWR | PTE_UXN)
8585

86-
#define __PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE | PTE_RDONLY | PTE_PXN | PTE_UXN)
87-
#define __PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
88-
#define __PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
89-
#define __PAGE_COPY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
90-
#define __PAGE_COPY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
91-
#define __PAGE_READONLY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY)
92-
#define __PAGE_READONLY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_RDONLY)
86+
#define __PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE | PTE_PXN | PTE_UXN)
87+
#define __PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
88+
#define __PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_WRITE)
89+
#define __PAGE_COPY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
90+
#define __PAGE_COPY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
91+
#define __PAGE_READONLY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
92+
#define __PAGE_READONLY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
9393

9494
#endif /* __ASSEMBLY__ */
9595

@@ -140,21 +140,21 @@ extern struct page *empty_zero_page;
140140
#define pte_dirty(pte) (pte_val(pte) & PTE_DIRTY)
141141
#define pte_young(pte) (pte_val(pte) & PTE_AF)
142142
#define pte_special(pte) (pte_val(pte) & PTE_SPECIAL)
143-
#define pte_write(pte) (!(pte_val(pte) & PTE_RDONLY))
143+
#define pte_write(pte) (pte_val(pte) & PTE_WRITE)
144144
#define pte_exec(pte) (!(pte_val(pte) & PTE_UXN))
145145

146146
#define pte_valid_user(pte) \
147147
((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER))
148148

149149
static inline pte_t pte_wrprotect(pte_t pte)
150150
{
151-
pte_val(pte) |= PTE_RDONLY;
151+
pte_val(pte) &= ~PTE_WRITE;
152152
return pte;
153153
}
154154

155155
static inline pte_t pte_mkwrite(pte_t pte)
156156
{
157-
pte_val(pte) &= ~PTE_RDONLY;
157+
pte_val(pte) |= PTE_WRITE;
158158
return pte;
159159
}
160160

@@ -201,8 +201,10 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
201201
if (pte_valid_user(pte)) {
202202
if (pte_exec(pte))
203203
__sync_icache_dcache(pte, addr);
204-
if (!pte_dirty(pte))
205-
pte = pte_wrprotect(pte);
204+
if (pte_dirty(pte) && pte_write(pte))
205+
pte_val(pte) &= ~PTE_RDONLY;
206+
else
207+
pte_val(pte) |= PTE_RDONLY;
206208
}
207209

208210
set_pte(ptep, pte);
@@ -376,7 +378,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
376378
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
377379
{
378380
const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY |
379-
PTE_PROT_NONE | PTE_VALID;
381+
PTE_PROT_NONE | PTE_VALID | PTE_WRITE;
380382
pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask);
381383
return pte;
382384
}

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