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ARM: 6913/1: sparsemem: allow pfn_valid to be overridden when using SPARSEMEM

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In commit eb33575c ("[ARM] Double check memmap is actually valid with a
memmap has unexpected holes V2"), a new function, memmap_valid_within,
was introduced to mmzone.h so that holes in the memmap which pass
pfn_valid in SPARSEMEM configurations can be detected and avoided.

The fix to this problem checks that the pfn <-> page linkages are
correct by calculating the page for the pfn and then checking that
page_to_pfn on that page returns the original pfn. Unfortunately, in
SPARSEMEM configurations, this results in reading from the page flags to
determine the correct section. Since the memmap here has been freed,
junk is read from memory and the check is no longer robust.

In the best case, reading from /proc/pagetypeinfo will give you the
wrong answer. In the worst case, you get SEGVs, Kernel OOPses and hung
CPUs. Furthermore, ioremap implementations that use pfn_valid to
disallow the remapping of normal memory will break.

This patch allows architectures to provide their own pfn_valid function
instead of using the default implementation used by sparsemem. The
architecture-specific version is aware of the memmap state and will
return false when passed a pfn for a freed page within a valid section.

Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2011-05-19 13:21:14 +01:00 committed by Russell King
parent 4db70f73e5
commit 7b7bf499f7
4 changed files with 9 additions and 2 deletions
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3
arch/arm/Kconfig
View File

@ -1516,6 +1516,9 @@ config ARCH_SPARSEMEM_DEFAULT
config ARCH_SELECT_MEMORY_MODEL
def_bool ARCH_SPARSEMEM_ENABLE
config HAVE_ARCH_PFN_VALID
def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
config HIGHMEM
bool "High Memory Support"
depends on MMU

2
arch/arm/include/asm/page.h
View File

@ -197,7 +197,7 @@ typedef unsigned long pgprot_t;
typedef struct page *pgtable_t;
#ifndef CONFIG_SPARSEMEM
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
extern int pfn_valid(unsigned long);
#endif

4
arch/arm/mm/init.c
View File

@ -273,13 +273,15 @@ static void __init arm_bootmem_free(unsigned long min, unsigned long max_low,
free_area_init_node(0, zone_size, min, zhole_size);
}
#ifndef CONFIG_SPARSEMEM
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{
return memblock_is_memory(pfn << PAGE_SHIFT);
}
EXPORT_SYMBOL(pfn_valid);
#endif
#ifndef CONFIG_SPARSEMEM
static void arm_memory_present(void)
{
}

2
include/linux/mmzone.h
View File

@ -1056,12 +1056,14 @@ static inline struct mem_section *__pfn_to_section(unsigned long pfn)
return __nr_to_section(pfn_to_section_nr(pfn));
}
#ifndef CONFIG_HAVE_ARCH_PFN_VALID
static inline int pfn_valid(unsigned long pfn)
{
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;
return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
}
#endif
static inline int pfn_present(unsigned long pfn)
{