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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: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2015-11-09 09:55:46 +01:00 committed by Catalin Marinas
parent b219545e96
commit fb226c3d7c
2 changed files with 2 additions and 1 deletions
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1
arch/arm64/include/asm/pgtable.h
View File

@ -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)

2
arch/arm64/mm/mmu.c
View File

@ -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;