[PATCH] [RESEND] arm: limit memblock base address for early_pte_alloc

Minchan Kim
2012-06-05T07:11:56Z

If we do arm_memblock_steal with a page which is not aligned with section size,
panic can happen during boot by page fault in map_lowmem.

Detail:

1) mdesc->reserve can steal a page which is allocated at 0x1ffff000 by memblock
which prefers tail pages of regions.
2) map_lowmem maps 0x00000000 - 0x1fe00000
3) map_lowmem try to map 0x1fe00000 but it's not aligned by section due to 1.
4) calling alloc_init_pte allocates a new page for new pte by memblock_alloc
5) allocated memory for pte is 0x1fffe000 -> it's not mapped yet.
6) memset(ptr, 0, sz) in early_alloc_aligned got PANICed!

This patch fix it by limiting memblock to mapped memory range.

Reported-by: Jongsung Kim <neidhard.kim@lge.com>
Suggested-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
arch/arm/mm/mmu.c | 37 ++++++++++++++++++++++---------------
1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index e5dad60..a15aafe 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -594,7 +594,7 @@ static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,

static void __init alloc_init_section(pud_t *pud, unsigned long addr,
unsigned long end, phys_addr_t phys,
- const struct mem_type *type)
+ const struct mem_type *type, bool lowmem)
{
pmd_t *pmd = pmd_offset(pud, addr);

@@ -619,6 +619,8 @@ static void __init alloc_init_section(pud_t *pud, unsigned long addr,

flush_pmd_entry(p);
} else {
+ if (lowmem)
+ memblock_set_current_limit(__pa(addr));
/*
* No need to loop; pte's aren't interested in the
* individual L1 entries.
@@ -628,14 +630,15 @@ static void __init alloc_init_section(pud_t *pud, unsigned long addr,
}

static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
- unsigned long end, unsigned long phys, const struct mem_type *type)
+ unsigned long end, unsigned long phys,
+ const struct mem_type *type, bool lowmem)
{
pud_t *pud = pud_offset(pgd, addr);
unsigned long next;

do {
next = pud_addr_end(addr, end);
- alloc_init_section(pud, addr, next, phys, type);
+ alloc_init_section(pud, addr, next, phys, type, lowmem);
phys += next - addr;
} while (pud++, addr = next, addr != end);
}
@@ -702,14 +705,7 @@ static void __init create_36bit_mapping(struct map_desc *md,
}
#endif /* !CONFIG_ARM_LPAE */

-/*
- * Create the page directory entries and any necessary
- * page tables for the mapping specified by `md'. We
- * are able to cope here with varying sizes and address
- * offsets, and we take full advantage of sections and
- * supersections.
- */
-static void __init create_mapping(struct map_desc *md)
+static inline void __create_mapping(struct map_desc *md, bool lowmem)
{
unsigned long addr, length, end;
phys_addr_t phys;
@@ -759,7 +755,7 @@ static void __init create_mapping(struct map_desc *md)
do {
unsigned long next = pgd_addr_end(addr, end);

- alloc_init_pud(pgd, addr, next, phys, type);
+ alloc_init_pud(pgd, addr, next, phys, type, lowmem);

phys += next - addr;
addr = next;
@@ -767,6 +763,18 @@ static void __init create_mapping(struct map_desc *md)
}

/*
+ * Create the page directory entries and any necessary
+ * page tables for the mapping specified by `md'. We
+ * are able to cope here with varying sizes and address
+ * offsets, and we take full advantage of sections and
+ * supersections.
+ */
+static void __init create_mapping(struct map_desc *md)
+{
+ __create_mapping(md, false);
+}
+
+/*
* Create the architecture specific mappings
*/
void __init iotable_init(struct map_desc *io_desc, int nr)
@@ -1111,7 +1119,7 @@ static void __init map_lowmem(void)
map.length = end - start;
map.type = MT_MEMORY;

- create_mapping(&map);
+ __create_mapping(&map, true);
}
}

@@ -1123,11 +1131,10 @@ void __init paging_init(struct machine_desc *mdesc)
{
void *zero_page;

- memblock_set_current_limit(arm_lowmem_limit);
-
build_mem_type_table();
prepare_page_table();
map_lowmem();
+ memblock_set_current_limit(arm_lowmem_limit);
dma_contiguous_remap();
devicemaps_init(mdesc);
kmap_init();
--
1.7.9.5