Thread (139 messages) 139 messages, 12 authors, 2024-08-20

Re: [PATCH v4 13/29] arm64: convert protection key into vm_flags and pgprot values

From: Dave Martin <Dave.Martin@arm.com>
Date: 2024-07-25 15:49:57
Also in: kvmarm, linux-arm-kernel, linux-fsdevel, linux-mm

On Fri, May 03, 2024 at 02:01:31PM +0100, Joey Gouly wrote:
quoted hunk ↗ jump to hunk
Modify arch_calc_vm_prot_bits() and vm_get_page_prot() such that the pkey
value is set in the vm_flags and then into the pgprot value.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/mman.h | 8 +++++++-
 arch/arm64/mm/mmap.c          | 9 +++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 5966ee4a6154..ecb2d18dc4d7 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -7,7 +7,7 @@
 #include <uapi/asm/mman.h>
 
 static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
-	unsigned long pkey __always_unused)
+	unsigned long pkey)
 {
 	unsigned long ret = 0;
 
@@ -17,6 +17,12 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
 	if (system_supports_mte() && (prot & PROT_MTE))
 		ret |= VM_MTE;
 
+#if defined(CONFIG_ARCH_HAS_PKEYS)
+	ret |= pkey & 0x1 ? VM_PKEY_BIT0 : 0;
+	ret |= pkey & 0x2 ? VM_PKEY_BIT1 : 0;
+	ret |= pkey & 0x4 ? VM_PKEY_BIT2 : 0;
Out of interest, is this as bad as it looks or does the compiler turn
it into a shift and mask?

quoted hunk ↗ jump to hunk
+#endif
+
 	return ret;
 }
 #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 642bdf908b22..86eda6bc7893 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -102,6 +102,15 @@ pgprot_t vm_get_page_prot(unsigned long vm_flags)
 	if (vm_flags & VM_MTE)
 		prot |= PTE_ATTRINDX(MT_NORMAL_TAGGED);
 
+#ifdef CONFIG_ARCH_HAS_PKEYS
+	if (vm_flags & VM_PKEY_BIT0)
+		prot |= PTE_PO_IDX_0;
+	if (vm_flags & VM_PKEY_BIT1)
+		prot |= PTE_PO_IDX_1;
+	if (vm_flags & VM_PKEY_BIT2)
+		prot |= PTE_PO_IDX_2;
+#endif
+
Ditto.  At least we only have three bits to cope with either way.

I'm guessing that these functions are not super-hot path.

[...]

Cheers
---Dave
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