The patch titled
Subject: arm64: add support for sub-page faults user probing
has been added to the -mm tree. Its filename is
arm64-add-support-for-sub-page-faults-user-probing.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/arm64-add-support-for-sub-page-faults-user-probing.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/arm64-add-support-for-sub-page-faults-user-probing.patch
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------------------------------------------------------
From: Catalin Marinas <catalin.marinas@xxxxxxx>
Subject: arm64: add support for sub-page faults user probing
With MTE, even if the pte allows an access, a mismatched tag somewhere
within a page can still cause a fault. Select ARCH_HAS_SUBPAGE_FAULTS if
MTE is enabled and implement probe_user_writeable().
Link: https://lkml.kernel.org/r/20211124192024.2408218-3-catalin.marinas@xxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/Kconfig | 1
arch/arm64/include/asm/uaccess.h | 33 +++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
--- a/arch/arm64/include/asm/uaccess.h~arm64-add-support-for-sub-page-faults-user-probing
+++ a/arch/arm64/include/asm/uaccess.h
@@ -445,4 +445,37 @@ static inline int __copy_from_user_flush
}
#endif
+#ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
+static inline size_t __mte_probe_user_range(const char __user *uaddr,
+ size_t size)
+{
+ const char __user *end = uaddr + size;
+ int err = 0;
+ char val;
+
+ uaddr = PTR_ALIGN_DOWN(uaddr, MTE_GRANULE_SIZE);
+ while (uaddr < end) {
+ /*
+ * A read is sufficient for MTE, the caller should have probed
+ * for the pte write permission.
+ */
+ __raw_get_user(val, uaddr, err);
+ if (err)
+ return end - uaddr;
+ uaddr += MTE_GRANULE_SIZE;
+ }
+ (void)val;
+
+ return 0;
+}
+
+static inline size_t probe_user_writable(const void __user *uaddr,
+ size_t size)
+{
+ if (!system_supports_mte())
+ return 0;
+ return __mte_probe_user_range(uaddr, size);
+}
+#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
+
#endif /* __ASM_UACCESS_H */
--- a/arch/arm64/Kconfig~arm64-add-support-for-sub-page-faults-user-probing
+++ a/arch/arm64/Kconfig
@@ -1777,6 +1777,7 @@ config ARM64_MTE
depends on AS_HAS_LSE_ATOMICS
# Required for tag checking in the uaccess routines
depends on ARM64_PAN
+ select ARCH_HAS_SUBPAGE_FAULTS
select ARCH_USES_HIGH_VMA_FLAGS
help
Memory Tagging (part of the ARMv8.5 Extensions) provides
_
Patches currently in -mm which might be from catalin.marinas@xxxxxxx are
mm-introduce-fault_in_exact_writeable-to-probe-for-sub-page-faults.patch
arm64-add-support-for-sub-page-faults-user-probing.patch
btrfs-avoid-live-lock-in-search_ioctl-on-hardware-with-sub-page-faults.patch
