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


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