lkml.org 
[lkml]   [2012]   [Feb]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] x86, efi: Fix unaligned access and endian issues
    Date
    From: Matt Fleming <matt.fleming@intel.com>

    We need to read from and write to 'buf' a byte at a time otherwise
    it's possible we'll perform an unaligned access, which can lead to a
    segfault when cross-building an x86 kernel on risc architectures.

    Also, we may need to convert the endianness of the data we read
    from/write to buf, so let's add some helper functions to do that.

    Stephen Rothwell noticed this bug when he hit a segfault while
    cross-building an x86_64 allmodconfig kernel on PowerPC.

    Cc: H. Peter Anvin <hpa@zytor.com>
    Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
    Signed-off-by: Matt Fleming <matt.fleming@intel.com>
    ---
    arch/x86/boot/tools/build.c | 44 ++++++++++++++++++++++++++++++------------
    1 files changed, 31 insertions(+), 13 deletions(-)

    diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
    index 4e9bd6b..4030cb7 100644
    --- a/arch/x86/boot/tools/build.c
    +++ b/arch/x86/boot/tools/build.c
    @@ -133,6 +133,26 @@ static void usage(void)
    die("Usage: build setup system [> image]");
    }

    +static inline u32 read32_le(u8 *src)
    +{
    + u32 data;
    +
    + data = *src++;
    + data |= *src++ << 8;
    + data |= *src++ << 16;
    + data |= *src++ << 24;
    +
    + return data;
    +}
    +
    +static inline void write32_le(u8 *dst, u32 data)
    +{
    + *dst++ = data;
    + *dst++ = data >> 8;
    + *dst++ = data >> 16;
    + *dst++ = data >> 24;
    +}
    +
    int main(int argc, char ** argv)
    {
    #ifdef CONFIG_EFI_STUB
    @@ -192,44 +212,42 @@ int main(int argc, char ** argv)

    /* Patch the setup code with the appropriate size parameters */
    buf[0x1f1] = setup_sectors-1;
    - buf[0x1f4] = sys_size;
    - buf[0x1f5] = sys_size >> 8;
    - buf[0x1f6] = sys_size >> 16;
    - buf[0x1f7] = sys_size >> 24;
    + write32_le(&buf[0x1f4], sys_size);

    #ifdef CONFIG_EFI_STUB
    file_sz = sz + i + ((sys_size * 16) - sz);

    - pe_header = *(unsigned int *)&buf[0x3c];
    + pe_header = read32_le(&buf[0x3c]);

    /* Size of code */
    - *(unsigned int *)&buf[pe_header + 0x1c] = file_sz;
    + write32_le(&buf[pe_header + 0x1c], file_sz);

    /* Size of image */
    - *(unsigned int *)&buf[pe_header + 0x50] = file_sz;
    + write32_le(&buf[pe_header + 0x50], file_sz);

    #ifdef CONFIG_X86_32
    /* Address of entry point */
    - *(unsigned int *)&buf[pe_header + 0x28] = i;
    + write32_le(&buf[pe_header + 0x28], i);

    /* .text size */
    - *(unsigned int *)&buf[pe_header + 0xb0] = file_sz;
    + write32_le(&buf[pe_header + 0xb0], file_sz);

    /* .text size of initialised data */
    - *(unsigned int *)&buf[pe_header + 0xb8] = file_sz;
    + write32_le(&buf[pe_header + 0xb8], file_sz);
    #else
    /*
    * Address of entry point. startup_32 is at the beginning and
    * the 64-bit entry point (startup_64) is always 512 bytes
    * after.
    */
    - *(unsigned int *)&buf[pe_header + 0x28] = i + 512;
    + write32_le(&buf[pe_header + 0x28], i + 512);

    /* .text size */
    - *(unsigned int *)&buf[pe_header + 0xc0] = file_sz;
    + write32_le(&buf[pe_header + 0xc0], file_sz);

    /* .text size of initialised data */
    - *(unsigned int *)&buf[pe_header + 0xc8] = file_sz;
    + write32_le(&buf[pe_header + 0xc8], file_sz);
    +
    #endif /* CONFIG_X86_32 */
    #endif /* CONFIG_EFI_STUB */

    --
    1.7.4.4


    \
     
     \ /
      Last update: 2012-02-22 15:03    [W:0.024 / U:29.988 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site