7ee991fbc6
Impact: better dumpstack output
I noticed in my crash dumps and even in the stack tracer that a
lot of functions listed in the stack trace are simply
return_to_handler which is ftrace graphs way to insert its own
call into the return of a function.
But we lose out where the actually function was called from.
This patch adds in hooks to the dumpstack mechanism that detects
this and finds the real function to print. Both are printed to
let the user know that a hook is still in place.
This does give a funny side effect in the stack tracer output:
Depth Size Location (80 entries)
----- ---- --------
0) 4144 48 save_stack_trace+0x2f/0x4d
1) 4096 128 ftrace_call+0x5/0x2b
2) 3968 16 mempool_alloc_slab+0x16/0x18
3) 3952 384 return_to_handler+0x0/0x73
4) 3568 -240 stack_trace_call+0x11d/0x209
5) 3808 144 return_to_handler+0x0/0x73
6) 3664 -128 mempool_alloc+0x4d/0xfe
7) 3792 128 return_to_handler+0x0/0x73
8) 3664 -32 scsi_sg_alloc+0x48/0x4a [scsi_mod]
As you can see, the real functions are now negative. This is due
to them not being found inside the stack.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
40 lines
1 KiB
C
40 lines
1 KiB
C
/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
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*/
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#ifndef DUMPSTACK_H
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#define DUMPSTACK_H
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#ifdef CONFIG_X86_32
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#define STACKSLOTS_PER_LINE 8
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#define get_bp(bp) asm("movl %%ebp, %0" : "=r" (bp) :)
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#else
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#define STACKSLOTS_PER_LINE 4
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#define get_bp(bp) asm("movq %%rbp, %0" : "=r" (bp) :)
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#endif
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extern unsigned long
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print_context_stack(struct thread_info *tinfo,
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unsigned long *stack, unsigned long bp,
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const struct stacktrace_ops *ops, void *data,
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unsigned long *end, int *graph);
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extern void
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show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
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unsigned long *stack, unsigned long bp, char *log_lvl);
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extern void
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show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
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unsigned long *sp, unsigned long bp, char *log_lvl);
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extern unsigned int code_bytes;
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extern int kstack_depth_to_print;
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/* The form of the top of the frame on the stack */
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struct stack_frame {
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struct stack_frame *next_frame;
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unsigned long return_address;
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};
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#endif
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