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>
61 lines
1.5 KiB
C
61 lines
1.5 KiB
C
/*
|
|
* arch/arm64/include/asm/ftrace.h
|
|
*
|
|
* Copyright (C) 2013 Linaro Limited
|
|
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
#ifndef __ASM_FTRACE_H
|
|
#define __ASM_FTRACE_H
|
|
|
|
#include <asm/insn.h>
|
|
|
|
#define MCOUNT_ADDR ((unsigned long)_mcount)
|
|
#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
|
|
|
|
#ifndef __ASSEMBLY__
|
|
#include <linux/compat.h>
|
|
|
|
extern void _mcount(unsigned long);
|
|
extern void *return_address(unsigned int);
|
|
|
|
struct dyn_arch_ftrace {
|
|
/* No extra data needed for arm64 */
|
|
};
|
|
|
|
extern unsigned long ftrace_graph_call;
|
|
|
|
extern void return_to_handler(void);
|
|
|
|
static inline unsigned long ftrace_call_adjust(unsigned long addr)
|
|
{
|
|
/*
|
|
* addr is the address of the mcount call instruction.
|
|
* recordmcount does the necessary offset calculation.
|
|
*/
|
|
return addr;
|
|
}
|
|
|
|
#define ftrace_return_address(n) return_address(n)
|
|
|
|
/*
|
|
* Because AArch32 mode does not share the same syscall table with AArch64,
|
|
* tracing compat syscalls may result in reporting bogus syscalls or even
|
|
* hang-up, so just do not trace them.
|
|
* See kernel/trace/trace_syscalls.c
|
|
*
|
|
* x86 code says:
|
|
* If the user realy wants these, then they should use the
|
|
* raw syscall tracepoints with filtering.
|
|
*/
|
|
#define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
|
|
static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
|
|
{
|
|
return is_compat_task();
|
|
}
|
|
#endif /* ifndef __ASSEMBLY__ */
|
|
|
|
#endif /* __ASM_FTRACE_H */
|