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5f01c98859
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 71f9e59800 ("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: Jiri 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: Ingo Molnar <mingo@kernel.org>
40 lines
937 B
C
40 lines
937 B
C
#ifndef _ASM_X86_KDEBUG_H
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#define _ASM_X86_KDEBUG_H
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#include <linux/notifier.h>
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struct pt_regs;
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/* Grossly misnamed. */
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enum die_val {
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DIE_OOPS = 1,
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DIE_INT3,
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DIE_DEBUG,
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DIE_PANIC,
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DIE_NMI,
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DIE_DIE,
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DIE_KERNELDEBUG,
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DIE_TRAP,
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DIE_GPF,
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DIE_CALL,
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DIE_PAGE_FAULT,
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DIE_NMIUNKNOWN,
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};
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extern void printk_address(unsigned long address);
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extern void die(const char *, struct pt_regs *,long);
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extern int __must_check __die(const char *, struct pt_regs *, long);
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extern void show_trace(struct task_struct *t, struct pt_regs *regs,
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unsigned long *sp, unsigned long bp);
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extern void __show_regs(struct pt_regs *regs, int all);
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extern unsigned long oops_begin(void);
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extern void oops_end(unsigned long, struct pt_regs *, int signr);
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#ifdef CONFIG_KEXEC
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extern int in_crash_kexec;
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#else
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/* no crash dump is ever in progress if no crash kernel can be kexec'd */
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#define in_crash_kexec 0
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#endif
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#endif /* _ASM_X86_KDEBUG_H */
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