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

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>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7275009686e64a9336ff6fb902d57c6363f1d4fd..5be55d950ab5428586b14608bce5dc379ef30560 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -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

diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index f51a69595f6ed53bc2d46d07a146f8b08ac6b83d..ac75d08488892f22dace530691de9a001d884f48 100644 (file)
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -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
 

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 3f17ea146f0ee5950259e1558da64bfdb64e556d..bbc3346e8bcdf978a60678a65fc9a1b342d2db0c 100644 (file)
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -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)
 {
 }

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 217bcf6bca775315e2ccce93dcb7ff6678a877a8..261f299c94412be90e5b24e6b2406bc9815ee608 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -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)
 {