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

Minchan Kim
2012-06-19T08:38:14Z

Resend.

Could you please see this problem?

Thanks.

On Tue, Jun 5, 2012 at 4:11 PM, Minchan Kim <minchan@kernel.org> wrote:
> 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
>

--
Kind regards,
Minchan Kim