• Jiri Slaby's avatar
    x86/dumpstack: Fix printk_address for direct addresses · 5f01c988
    Jiri Slaby authored
    Consider a kernel crash in a module, simulated the following way:
    
     static int my_init(void)
     {
             char *map = (void *)0x5;
             *map = 3;
             return 0;
     }
     module_init(my_init);
    
    When we turn off FRAME_POINTERs, the very first instruction in
    that function causes a BUG. The problem is that we print IP in
    the BUG report using %pB (from printk_address). And %pB
    decrements the pointer by one to fix printing addresses of
    functions with tail calls.
    
    This was added in commit 71f9e598
    
     ("x86, dumpstack: Use
    %pB format specifier for stack trace") to fix the call stack
    printouts.
    
    So instead of correct output:
    
      BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
      IP: [<ffffffffa01ac000>] my_init+0x0/0x10 [pb173]
    
    We get:
    
      BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
      IP: [<ffffffffa0152000>] 0xffffffffa0151fff
    
    To fix that, we use %pS only for stack addresses printouts (via
    newly added printk_stack_address) and %pB for regs->ip (via
    printk_address). I.e. we revert to the old behaviour for all
    except call stacks. And since from all those reliable is 1, we
    remove that parameter from printk_address.
    Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
    Cc: Namhyung Kim <namhyung@gmail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: joe@perches.com
    Cc: jirislaby@gmail.com
    Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@suse.cz
    
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    5f01c988
fault.c 29.2 KB