• Namhyung Kim's avatar
    x86, dumpstack: Correct stack dump info when frame pointer is available · e8e999cf
    Namhyung Kim authored
    Current stack dump code scans entire stack and check each entry
    contains a pointer to kernel code. If CONFIG_FRAME_POINTER=y it
    could mark whether the pointer is valid or not based on value of
    the frame pointer. Invalid entries could be preceded by '?' sign.
    
    However this was not going to happen because scan start point
    was always higher than the frame pointer so that they could not
    meet.
    
    Commit 9c0729dc ("x86: Eliminate bp argument from the stack
    tracing routines") delayed bp acquisition point, so the bp was
    read in lower frame, thus all of the entries were marked
    invalid.
    
    This patch fixes this by reverting above commit while retaining
    stack_frame() helper as suggested by Frederic Weisbecker.
    
    End result looks like below:
    
    before:
    
     [    3.508329] Call Trace:
     [    3.508551]  [<ffffffff814f35c9>] ? panic+0x91/0x199
     [    3.508662]  [<ffffffff814f3739>] ? printk+0x68/0x6a
     [    3.508770]  [<ffffffff81a981b2>] ? mount_block_root+0x257/0x26e
     [    3.508876]  [<ffffffff81a9821f>] ? mount_root+0x56/0x5a
     [    3.508975]  [<ffffffff81a98393>] ? prepare_namespace+0x170/0x1a9
     [    3.509216]  [<ffffffff81a9772b>] ? kernel_init+0x1d2/0x1e2
     [    3.509335]  [<ffffffff81003894>] ? kernel_thread_helper+0x4/0x10
     [    3.509442]  [<ffffffff814f6880>] ? restore_args+0x0/0x30
     [    3.509542]  [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
     [    3.509641]  [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10
    
    after:
    
     [    3.522991] Call Trace:
     [    3.523351]  [<ffffffff814f35b9>] panic+0x91/0x199
     [    3.523468]  [<ffffffff814f3729>] ? printk+0x68/0x6a
     [    3.523576]  [<ffffffff81a981b2>] mount_block_root+0x257/0x26e
     [    3.523681]  [<ffffffff81a9821f>] mount_root+0x56/0x5a
     [    3.523780]  [<ffffffff81a98393>] prepare_namespace+0x170/0x1a9
     [    3.523885]  [<ffffffff81a9772b>] kernel_init+0x1d2/0x1e2
     [    3.523987]  [<ffffffff81003894>] kernel_thread_helper+0x4/0x10
     [    3.524228]  [<ffffffff814f6880>] ? restore_args+0x0/0x30
     [    3.524345]  [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
     [    3.524445]  [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10
    
     -v5:
       * fix build breakage with oprofile
    
     -v4:
       * use 0 instead of regs->bp
       * separate out printk changes
    
     -v3:
       * apply comment from Frederic
       * add a couple of printk fixes
    Signed-off-by: default avatarNamhyung Kim <namhyung@gmail.com>
    Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Soren Sandmann <ssp@redhat.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Robert Richter <robert.richter@amd.com>
    LKML-Reference: <1300416006-3163-1-git-send-email-namhyung@gmail.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    e8e999cf
dumpstack_32.c 3.02 KB