Page table check performs extra verifications at the time when new
pages become accessible from the userspace by getting their page
table entries (PTEs PMDs etc.) added into the table. It is supported
on X86[1].
This patchset made some simple changes and make it easier to support
new architecture, then we support this feature on ARM64 and RISCV.
[1]https://lore.kernel.org/lkml/[email protected]/
v5 -> v6:
According to Anshuman's suggestion, optimized partial implementation and
commit message:
1. Remove redundant IS_ENABLED() in ptep_clear().
2. Remove redundant __HAVE_ARCH_PTEP_CLEAR usage in pgtable.h.
3. Remove redundant __ptep_get_and_clear() on arm64 and riscv.
v4 -> v5:
According to Anshuman's suggestion, using PxD_SIZE instead of
PxD_PAGE_SIZE in mm/page_table_check.c and it is checked by Pasha.
v3 -> v4:
Adapt to next-20220414
v2 -> v3:
Modify ptep_clear() in include/linux/pgtable.h, using IS_ENABLED according
to the suggestions of Pasha.
v1 -> v2:
1. Fix arm64's pte/pmd/pud_user_accessible_page() according to the
suggestions of Catalin.
2. Also fix riscv's pte_pmd_pud_user_accessible_page().
Kefeng Wang (2):
mm: page_table_check: move pxx_user_accessible_page into x86
arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK
Tong Tiangen (4):
mm: page_table_check: using PxD_SIZE instead of PxD_PAGE_SIZE
mm: page_table_check: add hooks to public helpers
mm: remove __HAVE_ARCH_PTEP_CLEAR in pgtable.h
riscv/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/pgtable.h | 59 +++++++++++++++++++++++---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/pgtable.h | 71 +++++++++++++++++++++++++++++---
arch/x86/include/asm/pgtable.h | 27 +++++++-----
include/linux/pgtable.h | 21 ++++++----
mm/page_table_check.c | 25 ++---------
7 files changed, 155 insertions(+), 50 deletions(-)
--
2.25.1
From: Kefeng Wang <[email protected]>
The pxx_user_accessible_page() checks the PTE bit, it's
architecture-specific code, move them into x86's pgtable.h.
These helpers are being moved out to make the page table check framework
platform independent.
Signed-off-by: Kefeng Wang <[email protected]>
Signed-off-by: Tong Tiangen <[email protected]>
Acked-by: Pasha Tatashin <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
---
arch/x86/include/asm/pgtable.h | 17 +++++++++++++++++
mm/page_table_check.c | 17 -----------------
2 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 0821f87d495f..46fa65d818bd 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1447,6 +1447,23 @@ static inline bool arch_faults_on_old_pte(void)
return false;
}
+#ifdef CONFIG_PAGE_TABLE_CHECK
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return (pte_val(pte) & _PAGE_PRESENT) && (pte_val(pte) & _PAGE_USER);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_leaf(pmd) && (pmd_val(pmd) & _PAGE_PRESENT) && (pmd_val(pmd) & _PAGE_USER);
+}
+
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+ return pud_leaf(pud) && (pud_val(pud) & _PAGE_PRESENT) && (pud_val(pud) & _PAGE_USER);
+}
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_PGTABLE_H */
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index eb0d0b71cdf6..3692bea2ea2c 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -52,23 +52,6 @@ static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
return (void *)(page_ext) + page_table_check_ops.offset;
}
-static inline bool pte_user_accessible_page(pte_t pte)
-{
- return (pte_val(pte) & _PAGE_PRESENT) && (pte_val(pte) & _PAGE_USER);
-}
-
-static inline bool pmd_user_accessible_page(pmd_t pmd)
-{
- return pmd_leaf(pmd) && (pmd_val(pmd) & _PAGE_PRESENT) &&
- (pmd_val(pmd) & _PAGE_USER);
-}
-
-static inline bool pud_user_accessible_page(pud_t pud)
-{
- return pud_leaf(pud) && (pud_val(pud) & _PAGE_PRESENT) &&
- (pud_val(pud) & _PAGE_USER);
-}
-
/*
* An enty is removed from the page table, decrement the counters for that page
* verify that it is of correct type and counters do not become negative.
--
2.25.1
Currently, there is no architecture definition __HAVE_ARCH_PTEP_CLEAR,
Generic ptep_clear() is the only definition for all architecture, So
drop the "#ifndef __HAVE_ARCH_PTEP_CLEAR".
Suggested-by: Anshuman Khandual <[email protected]>
Signed-off-by: Tong Tiangen <[email protected]>
---
include/linux/pgtable.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 3c825162c8da..b7a785e787b5 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -272,13 +272,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
}
#endif
-#ifndef __HAVE_ARCH_PTEP_CLEAR
static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
ptep_get_and_clear(mm, addr, ptep);
}
-#endif
#ifndef __HAVE_ARCH_PTEP_GET
static inline pte_t ptep_get(pte_t *ptep)
--
2.25.1
Move ptep_clear() to the include/linux/pgtable.h and add page table check
relate hooks to some helpers, it's prepare for support page table check
feature on new architecture.
Optimize the implementation of ptep_clear(), page table hooks added page
table check stubs, the interface control should be at stubs, there is no
rationale for doing a IS_ENABLED() check here.
For architectures that do not enable CONFIG_PAGE_TABLE_CHECK, they will
call a fallback page table check stubs[1] when getting their page table
helpers[2] in include/linux/pgtable.h.
[1] page table check stubs defined in include/linux/page_table_check.h
[2] ptep_clear() ptep_get_and_clear() pmdp_huge_get_and_clear()
pudp_huge_get_and_clear()
Signed-off-by: Tong Tiangen <[email protected]>
Acked-by: Pasha Tatashin <[email protected]>
---
arch/x86/include/asm/pgtable.h | 10 ----------
include/linux/pgtable.h | 23 +++++++++++++++--------
2 files changed, 15 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 46fa65d818bd..44e2d6f1dbaa 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1072,16 +1072,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
return pte;
}
-#define __HAVE_ARCH_PTEP_CLEAR
-static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
- pte_t *ptep)
-{
- if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK))
- ptep_get_and_clear(mm, addr, ptep);
- else
- pte_clear(mm, addr, ptep);
-}
-
#define __HAVE_ARCH_PTEP_SET_WRPROTECT
static inline void ptep_set_wrprotect(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 530b1817b58c..3c825162c8da 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -12,6 +12,7 @@
#include <linux/bug.h>
#include <linux/errno.h>
#include <asm-generic/pgtable_uffd.h>
+#include <linux/page_table_check.h>
#if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
@@ -259,14 +260,6 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif
-#ifndef __HAVE_ARCH_PTEP_CLEAR
-static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
- pte_t *ptep)
-{
- pte_clear(mm, addr, ptep);
-}
-#endif
-
#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address,
@@ -274,10 +267,19 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
{
pte_t pte = *ptep;
pte_clear(mm, address, ptep);
+ page_table_check_pte_clear(mm, address, pte);
return pte;
}
#endif
+#ifndef __HAVE_ARCH_PTEP_CLEAR
+static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep)
+{
+ ptep_get_and_clear(mm, addr, ptep);
+}
+#endif
+
#ifndef __HAVE_ARCH_PTEP_GET
static inline pte_t ptep_get(pte_t *ptep)
{
@@ -347,7 +349,10 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
pmd_t *pmdp)
{
pmd_t pmd = *pmdp;
+
pmd_clear(pmdp);
+ page_table_check_pmd_clear(mm, address, pmd);
+
return pmd;
}
#endif /* __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR */
@@ -359,6 +364,8 @@ static inline pud_t pudp_huge_get_and_clear(struct mm_struct *mm,
pud_t pud = *pudp;
pud_clear(pudp);
+ page_table_check_pud_clear(mm, address, pud);
+
return pud;
}
#endif /* __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR */
--
2.25.1
As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
, enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on riscv.
Add additional page table check stubs for page table helpers, these stubs
can be used to check the existing page table entries.
Signed-off-by: Tong Tiangen <[email protected]>
Reviewed-by: Pasha Tatashin <[email protected]>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/pgtable.h | 71 +++++++++++++++++++++++++++++---
2 files changed, 66 insertions(+), 6 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 63f7258984f3..66d241cee52c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -38,6 +38,7 @@ config RISCV
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
select ARCH_SUPPORTS_HUGETLBFS if MMU
+ select ARCH_SUPPORTS_PAGE_TABLE_CHECK
select ARCH_USE_MEMTEST
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 046b44225623..5af8aebbdd92 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -114,6 +114,8 @@
#include <asm/pgtable-32.h>
#endif /* CONFIG_64BIT */
+#include <linux/page_table_check.h>
+
#ifdef CONFIG_XIP_KERNEL
#define XIP_FIXUP(addr) ({ \
uintptr_t __a = (uintptr_t)(addr); \
@@ -315,6 +317,11 @@ static inline int pte_exec(pte_t pte)
return pte_val(pte) & _PAGE_EXEC;
}
+static inline int pte_user(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_USER;
+}
+
static inline int pte_huge(pte_t pte)
{
return pte_present(pte) && (pte_val(pte) & _PAGE_LEAF);
@@ -446,7 +453,7 @@ static inline void set_pte(pte_t *ptep, pte_t pteval)
void flush_icache_pte(pte_t pte);
-static inline void set_pte_at(struct mm_struct *mm,
+static inline void __set_pte_at(struct mm_struct *mm,
unsigned long addr, pte_t *ptep, pte_t pteval)
{
if (pte_present(pteval) && pte_exec(pteval))
@@ -455,10 +462,17 @@ static inline void set_pte_at(struct mm_struct *mm,
set_pte(ptep, pteval);
}
+static inline void set_pte_at(struct mm_struct *mm,
+ unsigned long addr, pte_t *ptep, pte_t pteval)
+{
+ page_table_check_pte_set(mm, addr, ptep, pteval);
+ __set_pte_at(mm, addr, ptep, pteval);
+}
+
static inline void pte_clear(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
- set_pte_at(mm, addr, ptep, __pte(0));
+ __set_pte_at(mm, addr, ptep, __pte(0));
}
#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
@@ -479,7 +493,11 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma,
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address, pte_t *ptep)
{
- return __pte(atomic_long_xchg((atomic_long_t *)ptep, 0));
+ pte_t pte = __pte(atomic_long_xchg((atomic_long_t *)ptep, 0));
+
+ page_table_check_pte_clear(mm, address, pte);
+
+ return pte;
}
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
@@ -546,6 +564,13 @@ static inline unsigned long pmd_pfn(pmd_t pmd)
return ((__pmd_to_phys(pmd) & PMD_MASK) >> PAGE_SHIFT);
}
+#define __pud_to_phys(pud) (pud_val(pud) >> _PAGE_PFN_SHIFT << PAGE_SHIFT)
+
+static inline unsigned long pud_pfn(pud_t pud)
+{
+ return ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT);
+}
+
static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
{
return pte_pmd(pte_modify(pmd_pte(pmd), newprot));
@@ -567,6 +592,11 @@ static inline int pmd_young(pmd_t pmd)
return pte_young(pmd_pte(pmd));
}
+static inline int pmd_user(pmd_t pmd)
+{
+ return pte_user(pmd_pte(pmd));
+}
+
static inline pmd_t pmd_mkold(pmd_t pmd)
{
return pte_pmd(pte_mkold(pmd_pte(pmd)));
@@ -600,15 +630,39 @@ static inline pmd_t pmd_mkdirty(pmd_t pmd)
static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, pmd_t pmd)
{
- return set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
+ page_table_check_pmd_set(mm, addr, pmdp, pmd);
+ return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
+}
+
+static inline int pud_user(pud_t pud)
+{
+ return pte_user(pud_pte(pud));
}
static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
pud_t *pudp, pud_t pud)
{
- return set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
+ page_table_check_pud_set(mm, addr, pudp, pud);
+ return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
+}
+
+#ifdef CONFIG_PAGE_TABLE_CHECK
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return pte_present(pte) && pte_user(pte);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_leaf(pmd) && pmd_user(pmd);
}
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+ return pud_leaf(pud) && pud_user(pud);
+}
+#endif
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline int pmd_trans_huge(pmd_t pmd)
{
@@ -634,7 +688,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
unsigned long address, pmd_t *pmdp)
{
- return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
+ pmd_t pmd = pte_pmd(__pte(atomic_long_xchg((atomic_long_t *)(pte_t *)pmdp, 0)));
+
+ page_table_check_pmd_clear(mm, address, pmd);
+
+ return pmd;
}
#define __HAVE_ARCH_PMDP_SET_WRPROTECT
@@ -648,6 +706,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp, pmd_t pmd)
{
+ page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
return __pmd(atomic_long_xchg((atomic_long_t *)pmdp, pmd_val(pmd)));
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
--
2.25.1
Compared with PxD_PAGE_SIZE, which is defined and used only on X86,
PxD_SIZE is more common in each architecture. Therefore, it is more
reasonable to use PxD_SIZE instead of PxD_PAGE_SIZE in page_table_check.c.
At the same time, it is easier to support page table check in other
architectures. The substitution has no functional impact on the x86.
Suggested-by: Anshuman Khandual <[email protected]>
Signed-off-by: Tong Tiangen <[email protected]>
Acked-by: Pasha Tatashin <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
---
mm/page_table_check.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 2458281bff89..eb0d0b71cdf6 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -177,7 +177,7 @@ void __page_table_check_pmd_clear(struct mm_struct *mm, unsigned long addr,
if (pmd_user_accessible_page(pmd)) {
page_table_check_clear(mm, addr, pmd_pfn(pmd),
- PMD_PAGE_SIZE >> PAGE_SHIFT);
+ PMD_SIZE >> PAGE_SHIFT);
}
}
EXPORT_SYMBOL(__page_table_check_pmd_clear);
@@ -190,7 +190,7 @@ void __page_table_check_pud_clear(struct mm_struct *mm, unsigned long addr,
if (pud_user_accessible_page(pud)) {
page_table_check_clear(mm, addr, pud_pfn(pud),
- PUD_PAGE_SIZE >> PAGE_SHIFT);
+ PUD_SIZE >> PAGE_SHIFT);
}
}
EXPORT_SYMBOL(__page_table_check_pud_clear);
@@ -219,7 +219,7 @@ void __page_table_check_pmd_set(struct mm_struct *mm, unsigned long addr,
__page_table_check_pmd_clear(mm, addr, *pmdp);
if (pmd_user_accessible_page(pmd)) {
page_table_check_set(mm, addr, pmd_pfn(pmd),
- PMD_PAGE_SIZE >> PAGE_SHIFT,
+ PMD_SIZE >> PAGE_SHIFT,
pmd_write(pmd));
}
}
@@ -234,7 +234,7 @@ void __page_table_check_pud_set(struct mm_struct *mm, unsigned long addr,
__page_table_check_pud_clear(mm, addr, *pudp);
if (pud_user_accessible_page(pud)) {
page_table_check_set(mm, addr, pud_pfn(pud),
- PUD_PAGE_SIZE >> PAGE_SHIFT,
+ PUD_SIZE >> PAGE_SHIFT,
pud_write(pud));
}
}
--
2.25.1
From: Kefeng Wang <[email protected]>
As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
, enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on arm64.
Add additional page table check stubs for page table helpers, these stubs
can be used to check the existing page table entries.
Signed-off-by: Kefeng Wang <[email protected]>
Signed-off-by: Tong Tiangen <[email protected]>
Reviewed-by: Pasha Tatashin <[email protected]>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/pgtable.h | 59 +++++++++++++++++++++++++++++---
2 files changed, 55 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 18a18a0e855d..c1509525ab8e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -92,6 +92,7 @@ config ARM64
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
select ARCH_SUPPORTS_NUMA_BALANCING
+ select ARCH_SUPPORTS_PAGE_TABLE_CHECK
select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
select ARCH_WANT_DEFAULT_BPF_JIT
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index ad9b221963d4..fe17788a6885 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -33,6 +33,7 @@
#include <linux/mmdebug.h>
#include <linux/mm_types.h>
#include <linux/sched.h>
+#include <linux/page_table_check.h>
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
@@ -96,6 +97,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
#define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
#define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL))
#define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
+#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
#define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN))
#define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
#define pte_devmap(pte) (!!(pte_val(pte) & PTE_DEVMAP))
@@ -312,7 +314,7 @@ static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *ptep,
__func__, pte_val(old_pte), pte_val(pte));
}
-static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
+static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
@@ -343,6 +345,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
set_pte(ptep, pte);
}
+static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+ page_table_check_pte_set(mm, addr, ptep, pte);
+ return __set_pte_at(mm, addr, ptep, pte);
+}
+
/*
* Huge pte definitions.
*/
@@ -454,6 +463,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
#define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd))
#define pmd_young(pmd) pte_young(pmd_pte(pmd))
#define pmd_valid(pmd) pte_valid(pmd_pte(pmd))
+#define pmd_user(pmd) pte_user(pmd_pte(pmd))
+#define pmd_user_exec(pmd) pte_user_exec(pmd_pte(pmd))
#define pmd_cont(pmd) pte_cont(pmd_pte(pmd))
#define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd)))
#define pmd_mkold(pmd) pte_pmd(pte_mkold(pmd_pte(pmd)))
@@ -501,8 +512,19 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
#define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
#define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
-#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
-#define set_pud_at(mm, addr, pudp, pud) set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
+static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
+ pmd_t *pmdp, pmd_t pmd)
+{
+ page_table_check_pmd_set(mm, addr, pmdp, pmd);
+ return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
+}
+
+static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
+ pud_t *pudp, pud_t pud)
+{
+ page_table_check_pud_set(mm, addr, pudp, pud);
+ return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
+}
#define __p4d_to_phys(p4d) __pte_to_phys(p4d_pte(p4d))
#define __phys_to_p4d_val(phys) __phys_to_pte_val(phys)
@@ -643,6 +665,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
#define pud_present(pud) pte_present(pud_pte(pud))
#define pud_leaf(pud) pud_sect(pud)
#define pud_valid(pud) pte_valid(pud_pte(pud))
+#define pud_user(pud) pte_user(pud_pte(pud))
+
+#ifdef CONFIG_PAGE_TABLE_CHECK
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte));
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
+}
+
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+ return pud_present(pud) && pud_user(pud);
+}
+#endif
static inline void set_pud(pud_t *pudp, pud_t pud)
{
@@ -876,7 +916,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address, pte_t *ptep)
{
- return __pte(xchg_relaxed(&pte_val(*ptep), 0));
+ pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
+
+ page_table_check_pte_clear(mm, address, pte);
+
+ return pte;
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
unsigned long address, pmd_t *pmdp)
{
- return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
+ pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));
+
+ page_table_check_pmd_clear(mm, address, pmd);
+
+ return pmd;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -918,6 +966,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp, pmd_t pmd)
{
+ page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
}
#endif
--
2.25.1
On 4/26/22 13:40, Tong Tiangen wrote:
> From: Kefeng Wang <[email protected]>
>
> As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
> , enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on arm64.
>
> Add additional page table check stubs for page table helpers, these stubs
> can be used to check the existing page table entries.
>
> Signed-off-by: Kefeng Wang <[email protected]>
> Signed-off-by: Tong Tiangen <[email protected]>
> Reviewed-by: Pasha Tatashin <[email protected]>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/pgtable.h | 59 +++++++++++++++++++++++++++++---
> 2 files changed, 55 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 18a18a0e855d..c1509525ab8e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -92,6 +92,7 @@ config ARM64
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> select ARCH_SUPPORTS_NUMA_BALANCING
> + select ARCH_SUPPORTS_PAGE_TABLE_CHECK
> select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
> select ARCH_WANT_DEFAULT_BPF_JIT
> select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index ad9b221963d4..fe17788a6885 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -33,6 +33,7 @@
> #include <linux/mmdebug.h>
> #include <linux/mm_types.h>
> #include <linux/sched.h>
> +#include <linux/page_table_check.h>
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
> @@ -96,6 +97,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
> #define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
> #define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL))
> #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
> +#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
> #define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN))
> #define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
> #define pte_devmap(pte) (!!(pte_val(pte) & PTE_DEVMAP))
> @@ -312,7 +314,7 @@ static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *ptep,
> __func__, pte_val(old_pte), pte_val(pte));
> }
>
> -static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> +static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, pte_t pte)
A small nit. Subsequent line containing the arguments "pte_t *ptep ..."
needs to be aligned properly, after '__' got added into set_pte_at().
> {
> if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
> @@ -343,6 +345,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> set_pte(ptep, pte);
> }
>
> +static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> + pte_t *ptep, pte_t pte)
> +{
> + page_table_check_pte_set(mm, addr, ptep, pte);
> + return __set_pte_at(mm, addr, ptep, pte);
> +}
> +
> /*
> * Huge pte definitions.
> */
> @@ -454,6 +463,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
> #define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd))
> #define pmd_young(pmd) pte_young(pmd_pte(pmd))
> #define pmd_valid(pmd) pte_valid(pmd_pte(pmd))
> +#define pmd_user(pmd) pte_user(pmd_pte(pmd))
> +#define pmd_user_exec(pmd) pte_user_exec(pmd_pte(pmd))
> #define pmd_cont(pmd) pte_cont(pmd_pte(pmd))
> #define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd)))
> #define pmd_mkold(pmd) pte_pmd(pte_mkold(pmd_pte(pmd)))
> @@ -501,8 +512,19 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
> #define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
> #define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>
> -#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
> -#define set_pud_at(mm, addr, pudp, pud) set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
> +static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
> + pmd_t *pmdp, pmd_t pmd)
> +{
> + page_table_check_pmd_set(mm, addr, pmdp, pmd);
> + return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
> +}
> +
> +static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
> + pud_t *pudp, pud_t pud)
> +{
> + page_table_check_pud_set(mm, addr, pudp, pud);
> + return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
> +}
>
> #define __p4d_to_phys(p4d) __pte_to_phys(p4d_pte(p4d))
> #define __phys_to_p4d_val(phys) __phys_to_pte_val(phys)
> @@ -643,6 +665,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
> #define pud_present(pud) pte_present(pud_pte(pud))
> #define pud_leaf(pud) pud_sect(pud)
> #define pud_valid(pud) pte_valid(pud_pte(pud))
> +#define pud_user(pud) pte_user(pud_pte(pud))
> +
> +#ifdef CONFIG_PAGE_TABLE_CHECK
> +static inline bool pte_user_accessible_page(pte_t pte)
> +{
> + return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte));
> +}
> +
> +static inline bool pmd_user_accessible_page(pmd_t pmd)
> +{
> + return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +}
> +
> +static inline bool pud_user_accessible_page(pud_t pud)
> +{
> + return pud_present(pud) && pud_user(pud);
> +}
> +#endif
>
> static inline void set_pud(pud_t *pudp, pud_t pud)
> {
> @@ -876,7 +916,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
> static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> unsigned long address, pte_t *ptep)
> {
> - return __pte(xchg_relaxed(&pte_val(*ptep), 0));
> + pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +
> + page_table_check_pte_clear(mm, address, pte);
> +
> + return pte;
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
> unsigned long address, pmd_t *pmdp)
> {
> - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> + pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));
Why there is any change here ? Why not just the following instead, like what you did
in ptep_get_and_clear() above. The page table entry return value here just needs to
be preserved for subsequent page table check helpers.
pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> +
> + page_table_check_pmd_clear(mm, address, pmd);
> +
> + return pmd;
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> @@ -918,6 +966,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
> static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> unsigned long address, pmd_t *pmdp, pmd_t pmd)
> {
> + page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
> return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
> }
> #endif
在 2022/4/29 14:18, Anshuman Khandual 写道:
>
>
> On 4/26/22 13:40, Tong Tiangen wrote:
>> From: Kefeng Wang <[email protected]>
>>
>> As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
>> , enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on arm64.
>>
>> Add additional page table check stubs for page table helpers, these stubs
>> can be used to check the existing page table entries.
>>
>> Signed-off-by: Kefeng Wang <[email protected]>
>> Signed-off-by: Tong Tiangen <[email protected]>
>> Reviewed-by: Pasha Tatashin <[email protected]>
>> ---
>> arch/arm64/Kconfig | 1 +
>> arch/arm64/include/asm/pgtable.h | 59 +++++++++++++++++++++++++++++---
>> 2 files changed, 55 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 18a18a0e855d..c1509525ab8e 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -92,6 +92,7 @@ config ARM64
>> select ARCH_SUPPORTS_ATOMIC_RMW
>> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>> select ARCH_SUPPORTS_NUMA_BALANCING
>> + select ARCH_SUPPORTS_PAGE_TABLE_CHECK
>> select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
>> select ARCH_WANT_DEFAULT_BPF_JIT
>> select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index ad9b221963d4..fe17788a6885 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -33,6 +33,7 @@
>> #include <linux/mmdebug.h>
>> #include <linux/mm_types.h>
>> #include <linux/sched.h>
>> +#include <linux/page_table_check.h>
>>
>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>> @@ -96,6 +97,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
>> #define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
>> #define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL))
>> #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
>> +#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
>> #define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN))
>> #define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
>> #define pte_devmap(pte) (!!(pte_val(pte) & PTE_DEVMAP))
>> @@ -312,7 +314,7 @@ static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *ptep,
>> __func__, pte_val(old_pte), pte_val(pte));
>> }
>>
>> -static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
>> +static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
>> pte_t *ptep, pte_t pte)
>
> A small nit. Subsequent line containing the arguments "pte_t *ptep ..."
> needs to be aligned properly, after '__' got added into set_pte_at().
OK, missing that, .will fix it next version.
>
>> {
>> if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
>> @@ -343,6 +345,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
>> set_pte(ptep, pte);
>> }
>>
>> +static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
>> + pte_t *ptep, pte_t pte)
>> +{
>> + page_table_check_pte_set(mm, addr, ptep, pte);
>> + return __set_pte_at(mm, addr, ptep, pte);
>> +}
>> +
>> /*
>> * Huge pte definitions.
>> */
>> @@ -454,6 +463,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
>> #define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd))
>> #define pmd_young(pmd) pte_young(pmd_pte(pmd))
>> #define pmd_valid(pmd) pte_valid(pmd_pte(pmd))
>> +#define pmd_user(pmd) pte_user(pmd_pte(pmd))
>> +#define pmd_user_exec(pmd) pte_user_exec(pmd_pte(pmd))
>> #define pmd_cont(pmd) pte_cont(pmd_pte(pmd))
>> #define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd)))
>> #define pmd_mkold(pmd) pte_pmd(pte_mkold(pmd_pte(pmd)))
>> @@ -501,8 +512,19 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>> #define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
>> #define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>>
>> -#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
>> -#define set_pud_at(mm, addr, pudp, pud) set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
>> +static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
>> + pmd_t *pmdp, pmd_t pmd)
>> +{
>> + page_table_check_pmd_set(mm, addr, pmdp, pmd);
>> + return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
>> +}
>> +
>> +static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
>> + pud_t *pudp, pud_t pud)
>> +{
>> + page_table_check_pud_set(mm, addr, pudp, pud);
>> + return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
>> +}
>>
>> #define __p4d_to_phys(p4d) __pte_to_phys(p4d_pte(p4d))
>> #define __phys_to_p4d_val(phys) __phys_to_pte_val(phys)
>> @@ -643,6 +665,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
>> #define pud_present(pud) pte_present(pud_pte(pud))
>> #define pud_leaf(pud) pud_sect(pud)
>> #define pud_valid(pud) pte_valid(pud_pte(pud))
>> +#define pud_user(pud) pte_user(pud_pte(pud))
>> +
>> +#ifdef CONFIG_PAGE_TABLE_CHECK
>> +static inline bool pte_user_accessible_page(pte_t pte)
>> +{
>> + return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte));
>> +}
>> +
>> +static inline bool pmd_user_accessible_page(pmd_t pmd)
>> +{
>> + return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
>> +}
>> +
>> +static inline bool pud_user_accessible_page(pud_t pud)
>> +{
>> + return pud_present(pud) && pud_user(pud);
>> +}
>> +#endif
>>
>> static inline void set_pud(pud_t *pudp, pud_t pud)
>> {
>> @@ -876,7 +916,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
>> static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>> unsigned long address, pte_t *ptep)
>> {
>> - return __pte(xchg_relaxed(&pte_val(*ptep), 0));
>> + pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
>> +
>> + page_table_check_pte_clear(mm, address, pte);
>> +
>> + return pte;
>> }
>>
>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
>> unsigned long address, pmd_t *pmdp)
>> {
>> - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
>> + pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));
>
> Why there is any change here ? Why not just the following instead, like what you did
> in ptep_get_and_clear() above. The page table entry return value here just needs to
> be preserved for subsequent page table check helpers.
>
> pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
>
Hi Anshuman:
The purpose of what I do here is to avoid doing
page_table_check_pte_clear() in ptep_get_and_clear(). there is no
functional change here.
Thanks,
Tong.
>> +
>> + page_table_check_pmd_clear(mm, address, pmd);
>> +
>> + return pmd;
>> }
>> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>>
>> @@ -918,6 +966,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
>> static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
>> unsigned long address, pmd_t *pmdp, pmd_t pmd)
>> {
>> + page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
>> return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
>> }
>> #endif
> .
On Tue, May 03, 2022 at 09:13:20AM +0800, Tong Tiangen wrote:
> 在 2022/4/29 14:18, Anshuman Khandual 写道:
> > On 4/26/22 13:40, Tong Tiangen wrote:
> > > @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
> > > static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
> > > unsigned long address, pmd_t *pmdp)
> > > {
> > > - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> > > + pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));
> >
> > Why there is any change here ? Why not just the following instead, like what you did
> > in ptep_get_and_clear() above. The page table entry return value here just needs to
> > be preserved for subsequent page table check helpers.
> >
> > pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
>
> The purpose of what I do here is to avoid doing page_table_check_pte_clear()
> in ptep_get_and_clear(). there is no functional change here.
I'm fine with using xchg here but I'd go for pmd_val directly, no need
for conversion to pte_t:
pmd_t pmd = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0));
--
Catalin
在 2022/5/5 1:26, Catalin Marinas 写道:
> On Tue, May 03, 2022 at 09:13:20AM +0800, Tong Tiangen wrote:
>> 在 2022/4/29 14:18, Anshuman Khandual 写道:
>>> On 4/26/22 13:40, Tong Tiangen wrote:
>>>> @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>>>> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
>>>> unsigned long address, pmd_t *pmdp)
>>>> {
>>>> - return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
>>>> + pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));
>>>
>>> Why there is any change here ? Why not just the following instead, like what you did
>>> in ptep_get_and_clear() above. The page table entry return value here just needs to
>>> be preserved for subsequent page table check helpers.
>>>
>>> pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
>>
>> The purpose of what I do here is to avoid doing page_table_check_pte_clear()
>> in ptep_get_and_clear(). there is no functional change here.
>
> I'm fine with using xchg here but I'd go for pmd_val directly, no need
> for conversion to pte_t:
>
> pmd_t pmd = __pmd(xchg_relaxed(&pmd_val(*pmdp), 0));
>
OK, This implementation is good and avoids redundant conversion, will
fix it next version.
Thanks,
Tong.