diff mbox series

[v1,13/18] arm64: add PTE_WRITE to PROT_SECT_NORMAL

Message ID 20230309145246.22787-14-joey.gouly@arm.com (mailing list archive)
State New, archived
Headers show
Series Permission Indirection Extension | expand

Commit Message

Joey Gouly March 9, 2023, 2:52 p.m. UTC 
With PIE enabled, PROT_SECT_NORMAL would map onto PAGE_KERNEL_RO.
Add PTE_WRITE so that this maps onto PAGE_KERNEL, so that it is writable.

Without PIE, this should enable DBM for PROT_SECT_NORMAL, which should be
functionally equivalent.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
---
 arch/arm64/include/asm/pgtable-prot.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Catalin Marinas March 27, 2023, 4:47 p.m. UTC | #1 
On Thu, Mar 09, 2023 at 02:52:41PM +0000, Joey Gouly wrote:
> With PIE enabled, PROT_SECT_NORMAL would map onto PAGE_KERNEL_RO.
> Add PTE_WRITE so that this maps onto PAGE_KERNEL, so that it is writable.
> 
> Without PIE, this should enable DBM for PROT_SECT_NORMAL, which should be
> functionally equivalent.

It's worth mentioning that since PTE_RDONLY (a.k.a. PTE_NDIRTY with PIE)
is already cleared, we don't even rely on the DBM mechanism to make it
writable.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 9b165117a454..d26d0b427c0a 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -60,7 +60,7 @@  extern bool arm64_use_ng_mappings;
 #define PROT_NORMAL_TAGGED	(PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_TAGGED))
 
 #define PROT_SECT_DEVICE_nGnRE	(PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
-#define PROT_SECT_NORMAL	(PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
+#define PROT_SECT_NORMAL	(PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PTE_WRITE | PMD_ATTRINDX(MT_NORMAL))
 #define PROT_SECT_NORMAL_EXEC	(PROT_SECT_DEFAULT | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
 
 #define _PAGE_DEFAULT		(_PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))