| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20230704133633.1918147-1-npache@redhat.com>
Date: Tue, 4 Jul 2023 09:36:33 -0400
From: Nico Pache <npache@...hat.com>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: aquini@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
Anshuman Khandual <anshuman.khandual@....com>,
Catalin Marinas <catalin.marinas@....com>,
David Hildenbrand <david@...hat.com>,
Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
Liu Shixin <liushixin2@...wei.com>,
Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH V2] arm64: properly define SOFT_DIRTY functionality
ARM64 has a soft-dirty bit (software dirty) but never properly defines
CONFIG_ARCH_HAS_SOFT_DIRTY or its necessary functions. This patch
introduces the ability to set/clear the soft dirty bit in a similar
manner as the other arches that utilize it.
However, we must be careful... there are cases where the DBM bit is not
available and the software dirty bit plays a essential role in determining
whether or not a page is dirty. In these cases we must not allow the
user to clear the software dirty bit. We can check for these cases by
utilizing the arch_has_hw_pte_young() function which tests the availability
of DBM.
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
Cc: Liu Shixin <liushixin2@...wei.com>
Cc: Will Deacon <will@...nel.org>
Cc: Yu Zhao <yuzhao@...gle.com>
Signed-off-by: Nico Pache <npache@...hat.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/pgtable.h | 104 ++++++++++++++++++++++++++-----
2 files changed, 90 insertions(+), 15 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7856c3a3e35a..6ea73b8148c5 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -173,6 +173,7 @@ config ARM64
select HAVE_ARCH_PREL32_RELOCATIONS
select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
select HAVE_ARCH_SECCOMP_FILTER
+ select HAVE_ARCH_SOFT_DIRTY
select HAVE_ARCH_STACKLEAK
select HAVE_ARCH_THREAD_STRUCT_WHITELIST
select HAVE_ARCH_TRACEHOOK
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 0bd18de9fd97..c4970c9ed114 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -51,6 +51,20 @@ static inline bool arch_thp_swp_supported(void)
}
#define arch_thp_swp_supported arch_thp_swp_supported
+/*
+ * On arm64 without hardware Access Flag, copying from user will fail because
+ * the pte is old and cannot be marked young. So we always end up with zeroed
+ * page after fork() + CoW for pfn mappings. We don't always have a
+ * hardware-managed access flag on arm64.
+ */
+#define arch_has_hw_pte_young cpu_has_hw_af
+
+/*
+ * Experimentally, it's cheap to set the access flag in hardware and we
+ * benefit from prefaulting mappings as 'old' to start with.
+ */
+#define arch_wants_old_prefaulted_pte cpu_has_hw_af
+
/*
* Outside of a few very special situations (e.g. hibernation), we always
* use broadcast TLB invalidation instructions, therefore a spurious page
@@ -121,8 +135,9 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
})
#define pte_hw_dirty(pte) (pte_write(pte) && !(pte_val(pte) & PTE_RDONLY))
-#define pte_sw_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY))
-#define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte))
+#define pte_soft_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY))
+#define pte_dirty(pte) (pte_soft_dirty(pte) || pte_hw_dirty(pte))
+#define pte_swp_soft_dirty(pte) pte_soft_dirty(pte)
#define pte_valid(pte) (!!(pte_val(pte) & PTE_VALID))
/*
@@ -189,7 +204,8 @@ static inline pte_t pte_mkwrite(pte_t pte)
static inline pte_t pte_mkclean(pte_t pte)
{
- pte = clear_pte_bit(pte, __pgprot(PTE_DIRTY));
+ if (!arch_has_hw_pte_young())
+ pte = clear_pte_bit(pte, __pgprot(PTE_DIRTY));
pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
return pte;
@@ -1077,25 +1093,83 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
#define phys_to_ttbr(addr) (addr)
#endif
-/*
- * On arm64 without hardware Access Flag, copying from user will fail because
- * the pte is old and cannot be marked young. So we always end up with zeroed
- * page after fork() + CoW for pfn mappings. We don't always have a
- * hardware-managed access flag on arm64.
- */
-#define arch_has_hw_pte_young cpu_has_hw_af
+static inline bool pud_sect_supported(void)
+{
+ return PAGE_SIZE == SZ_4K;
+}
+#ifdef CONFIG_ARM64_HW_AFDBM
/*
- * Experimentally, it's cheap to set the access flag in hardware and we
- * benefit from prefaulting mappings as 'old' to start with.
+ * if we have the DBM bit we can utilize the software dirty bit as
+ * a mechanism to introduce the soft_dirty functionality; however, without
+ * it this bit is crucial to determining if a entry is dirty and we cannot
+ * clear it via software. DBM can also be disabled or broken on some early
+ * armv8 devices, so check its availability before modifying it.
*/
-#define arch_wants_old_prefaulted_pte cpu_has_hw_af
+static inline pte_t pte_clear_soft_dirty(pte_t pte)
+{
+ if (!arch_has_hw_pte_young())
+ return pte;
-static inline bool pud_sect_supported(void)
+ return clear_pte_bit(pte, __pgprot(PTE_DIRTY));
+}
+
+static inline pte_t pte_mksoft_dirty(pte_t pte)
{
- return PAGE_SIZE == SZ_4K;
+ if (!arch_has_hw_pte_young())
+ return pte;
+
+ return set_pte_bit(pte, __pgprot(PTE_DIRTY));
+}
+
+static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
+{
+ if (!arch_has_hw_pte_young())
+ return pte;
+
+ return clear_pte_bit(pte, __pgprot(PTE_DIRTY));
+}
+
+static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
+{
+ if (!arch_has_hw_pte_young())
+ return pte;
+
+ return set_pte_bit(pte, __pgprot(PTE_DIRTY));
+}
+
+static inline int pmd_soft_dirty(pmd_t pmd)
+{
+ return pte_soft_dirty(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_clear_soft_dirty(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_mksoft_dirty(pmd_pte(pmd)));
}
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline int pmd_swp_soft_dirty(pmd_t pmd)
+{
+ return pmd_soft_dirty(pmd);
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+ return pmd_clear_soft_dirty(pmd);
+}
+
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+ return pmd_mksoft_dirty(pmd);
+}
+#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
+#endif /* CONFIG_ARM64_HW_AFDBM */
#define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
#define ptep_modify_prot_start ptep_modify_prot_start
--
2.41.0
Powered by blists - more mailing lists