Commit d907387c authored by Catalin Marinas's avatar Catalin Marinas Committed by Russell King
Browse files

ARM: 6383/1: Implement phys_mem_access_prot() to avoid attributes aliasing 



ARMv7 onwards requires that there are no aliases to the same physical
location using different memory types (i.e. Normal vs Strongly Ordered).
Access to SO mappings when the unaligned accesses are handled in
hardware is also Unpredictable (pgprot_noncached() mappings in user
space).

The /dev/mem driver requires uncached mappings with O_SYNC. The patch
implements the phys_mem_access_prot() function which generates Strongly
Ordered memory attributes if !pfn_valid() (independent of O_SYNC) and
Normal Noncacheable (writecombine) if O_SYNC.

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 79e27dc0

arch/arm/include/asm/pgtable.h

+4 −0
Original line number Diff line number Diff line
@@ -317,6 +317,10 @@ static inline pte_t pte_mkspecial(pte_t pte) { return pte; } 
#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE

#define pgprot_dmacoherent(prot) \

	__pgprot_modify(prot, L_PTE_MT_MASK|L_PTE_EXEC, L_PTE_MT_BUFFERABLE)

#define __HAVE_PHYS_MEM_ACCESS_PROT

struct file;

extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

				     unsigned long size, pgprot_t vma_prot);

#else

#define pgprot_dmacoherent(prot) \

	__pgprot_modify(prot, L_PTE_MT_MASK|L_PTE_EXEC, L_PTE_MT_UNCACHED)

arch/arm/mm/mmu.c

+14 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/nodemask.h>

#include <linux/memblock.h>

#include <linux/sort.h>

#include <linux/fs.h>



#include <asm/cputype.h>

#include <asm/sections.h>
@@ -498,6 +499,19 @@ static void __init build_mem_type_table(void) 
	}

}



#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE

pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

			      unsigned long size, pgprot_t vma_prot)

{

	if (!pfn_valid(pfn))

		return pgprot_noncached(vma_prot);

	else if (file->f_flags & O_SYNC)

		return pgprot_writecombine(vma_prot);

	return vma_prot;

}

EXPORT_SYMBOL(phys_mem_access_prot);

#endif



#define vectors_base()	(vectors_high() ? 0xffff0000 : 0)



static void __init *early_alloc(unsigned long sz)

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