• Stafford Horne's avatar
    openrisc: Fix oops caused when dumping stack · 57b8e277
    Stafford Horne authored
    When dumping a stack with 'cat /proc/#/stack' the kernel would oops.
    For example:
    
        # cat /proc/690/stack
        Unable to handle kernel access
         at virtual address 0x7fc60f58
    
        Oops#: 0000
        CPU #: 0
           PC: c00097fc    SR: 0000807f    SP: d6f09b9c
        GPR00: 00000000 GPR01: d6f09b9c GPR02: d6f09bb8 GPR03: d6f09bc4
        GPR04: 7fc60f5c GPR05: c00099b4 GPR06: 00000000 GPR07: d6f09ba3
        GPR08: ffffff00 GPR09: c0009804 GPR10: d6f08000 GPR11: 00000000
        GPR12: ffffe000 GPR13: dbb86000 GPR14: 00000001 GPR15: dbb86250
        GPR16: 7fc60f63 GPR17: 00000f5c GPR18: d6f09bc4 GPR19: 00000000
        GPR20: c00099b4 GPR21: ffffffc0 GPR22: 00000000 GPR23: 00000000
        GPR24: 00000001 GPR25: 000002c6 GPR26: d78b6850 GPR27: 00000001
        GPR28: 00000000 GPR29: dbb86000 GPR30: ffffffff GPR31: dbb862fc
          RES: 00000000 oGPR11: ffffffff
        Process cat (pid: 702, stackpage=d79d6000)
    
        Stack:
        Call trace:
        [<598977f2>] save_stack_trace_tsk+0x40/0x74
        [<95063f0e>] stack_trace_save_tsk+0x44/0x58
        [<b557bfdd>] proc_pid_stack+0xd0/0x13c
        [<a2df8eda>] proc_single_show+0x6c/0xf0
        [<e5a737b7>] seq_read+0x1b4/0x688
        [<2d6c7480>] do_iter_read+0x208/0x248
        [<2182a2fb>] vfs_readv+0x64/0x90
    
    This was caused by the stack trace code in save_stack_trace_tsk using
    the wrong stack pointer.  It was using the user stack pointer instead of
    the kernel stack pointer.  Fix this by using the right stack.
    
    Also for good measure we add try_get_task_stack/put_task_stack to ensure
    the task is not lost while we are walking it's stack.
    
    Fixes: eecac38b ("openrisc: support framepointers and STACKTRACE_SUPPORT")
    Signed-off-by: default avatarStafford Horne <shorne@gmail.com>
    57b8e277
stacktrace.c 2.12 KB