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Commit fb226c3d authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
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arm64: fix R/O permissions of FDT mapping 



The mapping permissions of the FDT are set to 'PAGE_KERNEL | PTE_RDONLY'
in an attempt to map the FDT as read-only. However, not only does this
break at build time under STRICT_MM_TYPECHECKS (since the two terms are
of different types in that case), it also results in both the PTE_WRITE
and PTE_RDONLY attributes to be set, which means the region is still
writable under ARMv8.1 DBM (and an attempted write will simply clear the
PT_RDONLY bit).

So instead, define PAGE_KERNEL_RO (which already has an established
meaning across architectures) and use that instead.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent b219545e

arch/arm64/include/asm/pgtable.h

+1 −0
Original line number Diff line number Diff line
@@ -78,6 +78,7 @@ extern void __pgd_error(const char *file, int line, unsigned long val); 
#define _PAGE_DEFAULT		(PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))



#define PAGE_KERNEL		__pgprot(_PAGE_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE)

#define PAGE_KERNEL_RO		__pgprot(_PAGE_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_RDONLY)

#define PAGE_KERNEL_EXEC	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)

#define PAGE_KERNEL_EXEC_CONT	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)

arch/arm64/mm/mmu.c

+1 −1
Original line number Diff line number Diff line
@@ -691,7 +691,7 @@ void __set_fixmap(enum fixed_addresses idx, 
void *__init fixmap_remap_fdt(phys_addr_t dt_phys)

{

	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);

	pgprot_t prot = PAGE_KERNEL | PTE_RDONLY;

	pgprot_t prot = PAGE_KERNEL_RO;

	int size, offset;

	void *dt_virt;