ARM: 8109/1: mm: Modify pte_write and pmd_write logic for LPAE

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_AP2). 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>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/pgtable-3level-hwdef.h b/arch/arm/include/asm/pgtable-3level-hwdef.h
index 626989fec4d334ef8c01f707f87de6a25c1d8a8e..9fd61c72a33a1417704881274239e2fd29053cce 100644 (file)
--- a/arch/arm/include/asm/pgtable-3level-hwdef.h
+++ b/arch/arm/include/asm/pgtable-3level-hwdef.h
@@ -43,7 +43,7 @@
 #define PMD_SECT_BUFFERABLE    (_AT(pmdval_t, 1) << 2)
 #define PMD_SECT_CACHEABLE     (_AT(pmdval_t, 1) << 3)
 #define PMD_SECT_USER          (_AT(pmdval_t, 1) << 6)         /* AP[1] */
-#define PMD_SECT_RDONLY                (_AT(pmdval_t, 1) << 7)         /* AP[2] */
+#define PMD_SECT_AP2           (_AT(pmdval_t, 1) << 7)         /* read only */
 #define PMD_SECT_S             (_AT(pmdval_t, 3) << 8)
 #define PMD_SECT_AF            (_AT(pmdval_t, 1) << 10)
 #define PMD_SECT_nG            (_AT(pmdval_t, 1) << 11)
@@ -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 34f371c4bbb224d40ae1dfa4ac0937609b524353..06e0bc0f8b00b2c7f9fe9f6dac97c81b00b803bb 100644 (file)
--- 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_DIRTY            (_AT(pteval_t, 1) << 55)
+#define L_PTE_SPECIAL          (_AT(pteval_t, 1) << 56)
 #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_table(pmd))
-#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_AP2;
+       else
+               pmd_val(pmd) |= PMD_SECT_AP2;
 
        *pmdp = __pmd(pmd_val(pmd) | PMD_SECT_nG);
        flush_pmd_entry(pmdp);

diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
index c508f41a43bcb9f2f97c9d4afaf131ef77b4dc44..59424937e52b8839c4fb4504aedbc93584b4304e 100644 (file)
--- a/arch/arm/mm/dump.c
+++ b/arch/arm/mm/dump.c
@@ -126,8 +126,8 @@ static const struct prot_bits section_bits[] = {
                .val    = PMD_SECT_USER,
                .set    = "USR",
        }, {
-               .mask   = PMD_SECT_RDONLY,
-               .val    = PMD_SECT_RDONLY,
+               .mask   = L_PMD_SECT_RDONLY,
+               .val    = L_PMD_SECT_RDONLY,
                .set    = "ro",
                .clear  = "RW",
 #elif __LINUX_ARM_ARCH__ >= 6

diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index 564f4b934ceb96fac160b36305fc8e501fd0a71d..e4c8acfc13236549146a98ba14de0576fcc00818 100644 (file)
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -87,8 +87,13 @@ 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