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    Subject[PATCH 3/3] Limit E820 map when a user-defined memory map is specified
    Date
    This patch brings back limiting of the E820 map when a user-defined
    E820 map is specified. While the behaviour of i386 (32 bit) was to limit
    the E820 map (and /proc/iomem), the behaviour of x86-64 (64 bit) was not to
    limit.

    That patch limits the E820 map again for both x86 architectures.

    Code was tested for compilation and booting on a 32 bit and 64 bit system.


    Signed-off-by: Bernhard Walle <bwalle@suse.de>
    ---
    arch/x86/kernel/e820.c | 30 ++++++++++++++++++++++++++++++
    1 files changed, 30 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
    index f5b1736..2e7d385 100644
    --- a/arch/x86/kernel/e820.c
    +++ b/arch/x86/kernel/e820.c
    @@ -934,6 +934,33 @@ static void early_panic(char *msg)
    panic(msg);
    }

    +void __init e820_limit_regions(unsigned long long size)
    +{
    + unsigned long long current_addr;
    + int i;
    +
    + for (i = 0; i < e820.nr_map; i++) {
    + current_addr = e820.map[i].addr + e820.map[i].size;
    + if (current_addr < size)
    + continue;
    +
    + if (e820.map[i].type != E820_RAM)
    + continue;
    +
    + if (e820.map[i].addr >= size) {
    + /*
    + * This region starts past the end of the
    + * requested size, skip it completely.
    + */
    + e820.nr_map = i;
    + } else {
    + e820.nr_map = i + 1;
    + e820.map[i].size -= current_addr - size;
    + }
    + return;
    + }
    +}
    +
    /* "mem=nopentium" disables the 4MB page tables. */
    static int __init parse_memopt(char *p)
    {
    @@ -951,6 +978,8 @@ static int __init parse_memopt(char *p)

    mem_size = memparse(p, &p);
    end_user_pfn = mem_size>>PAGE_SHIFT;
    + e820_limit_regions(mem_size);
    +
    return 0;
    }
    early_param("mem", parse_memopt);
    @@ -995,6 +1024,7 @@ static int __init parse_memmap_opt(char *p)
    e820_add_region(start_at, mem_size, E820_RESERVED);
    } else {
    end_user_pfn = (mem_size >> PAGE_SHIFT);
    + e820_limit_regions(mem_size);
    }
    return *p == '\0' ? 0 : -EINVAL;
    }
    --
    1.5.4.5


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