[coreboot-gerrit] Patch merged into coreboot/master: 24fc08b AMD IMC AGESA: Access the data in stack by correct length

gerrit at coreboot.org gerrit at coreboot.org
Thu Dec 5 03:52:26 CET 2013


the following patch was just integrated into master:
commit 24fc08b10ef1ae1d94372486c6be9668e255ffca
Author: Zheng Bao <fishbaozi at gmail.com>
Date:   Wed Dec 4 10:22:25 2013 +0800

    AMD IMC AGESA: Access the data in stack by correct length
    
    The bug is hard to find. We were adding the feature of fan control. We
    met some strange things which could not be explained. Like, sometimes
    adding printk let the error disappear. Then we traced the code by hardware
    debug tool (HDT). It turned out the data in stack was overwritten.
    
    The values of AccessWidthxx are
    { AccessWidth8 = 1,
      AccessWidth16,
      AccessWidth32,}
    For the case of AccessWidth8, we only need to access the index/data
    once. But ReadECmsg and WriteECmsg did the loop twice, 1 more time
    than they are supposed to do. The data in stack next to "Value" would
    be overwritten.
    
    For all the cases, the code should be
     OpFlag = OpFlag & 0x7f;
     switch (OpFlag) {
        case 1:              /* AccessWidth8 */
             OpFlag = 0;break;
        case 2:              /* AccessWidth16 */
             OpFlag = 1;break;
        case 3:              /* AccessWidth32 */
             OpFlag = 3;break;
        case 4:              /* AccessWidth64 */
             OpFlag = 7;break;
        default:
             error;
     }
    
    Actually, the caller only takes AccessWidth8 as the parameter. We can ignore other
    cases for now.
    
    That is an AGESA bug. AMD's AGESA team own this code. They have given the
    response that they are going to update this in next release. I presume let them
    decide the proper way to fix that. Before that, I change the code as little
    as possible to make it run without crash.
    
    Change-Id: I566f74c242ce93f4569eedf69ca07d2fb7fb368d
    Signed-off-by: Zheng Bao <zheng.bao at amd.com>
    Signed-off-by: Zheng Bao <fishbaozi at gmail.com>


See http://review.coreboot.org/4297 for details.

-gerrit



More information about the coreboot-gerrit mailing list