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20380bb390
Function graph tracer modifies a return address (LR) in a stack frame
to hook a function return. This will result in many useless entries
(return_to_handler) showing up in
a) a stack tracer's output
b) perf call graph (with perf record -g)
c) dump_backtrace (at panic et al.)
For example, in case of a),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ echo 1 > /proc/sys/kernel/stack_trace_enabled
$ cat /sys/kernel/debug/tracing/stack_trace
Depth Size Location (54 entries)
----- ---- --------
0) 4504 16 gic_raise_softirq+0x28/0x150
1) 4488 80 smp_cross_call+0x38/0xb8
2) 4408 48 return_to_handler+0x0/0x40
3) 4360 32 return_to_handler+0x0/0x40
...
In case of b),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ perf record -e mem:XXX:x -ag -- sleep 10
$ perf report
...
| | |--0.22%-- 0x550f8
| | | 0x10888
| | | el0_svc_naked
| | | sys_openat
| | | return_to_handler
| | | return_to_handler
...
In case of c),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ echo c > /proc/sysrq-trigger
...
Call trace:
[<ffffffc00044d3ac>] sysrq_handle_crash+0x24/0x30
[<ffffffc000092250>] return_to_handler+0x0/0x40
[<ffffffc000092250>] return_to_handler+0x0/0x40
...
This patch replaces such entries with real addresses preserved in
current->ret_stack[] at unwind_frame(). This way, we can cover all
the cases.
Reviewed-by: Jungseok Lee <jungseoklee85@gmail.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[will: fixed minor context changes conflicting with irq stack bits]
Signed-off-by: Will Deacon <will.deacon@arm.com>
62 lines
1.5 KiB
C
62 lines
1.5 KiB
C
/*
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* arch/arm64/include/asm/ftrace.h
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*
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* Copyright (C) 2013 Linaro Limited
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* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef __ASM_FTRACE_H
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#define __ASM_FTRACE_H
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#include <asm/insn.h>
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#define MCOUNT_ADDR ((unsigned long)_mcount)
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#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
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#ifndef __ASSEMBLY__
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#include <linux/compat.h>
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extern void _mcount(unsigned long);
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extern void *return_address(unsigned int);
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struct dyn_arch_ftrace {
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/* No extra data needed for arm64 */
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};
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extern unsigned long ftrace_graph_call;
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extern void return_to_handler(void);
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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/*
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* addr is the address of the mcount call instruction.
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* recordmcount does the necessary offset calculation.
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*/
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return addr;
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}
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#define ftrace_return_address(n) return_address(n)
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/*
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* Because AArch32 mode does not share the same syscall table with AArch64,
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* tracing compat syscalls may result in reporting bogus syscalls or even
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* hang-up, so just do not trace them.
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* See kernel/trace/trace_syscalls.c
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*
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* x86 code says:
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* If the user realy wants these, then they should use the
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* raw syscall tracepoints with filtering.
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*/
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#define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
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static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
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{
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return is_compat_task();
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}
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#endif /* ifndef __ASSEMBLY__ */
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#endif /* __ASM_FTRACE_H */
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