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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>
84 lines
2.1 KiB
C
84 lines
2.1 KiB
C
/*
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* Based on arch/arm/kernel/time.c
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*
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* Copyright (C) 1991, 1992, 1995 Linus Torvalds
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* Modifications for ARM (C) 1994-2001 Russell King
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* Copyright (C) 2012 ARM Ltd.
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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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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/clockchips.h>
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#include <linux/export.h>
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/smp.h>
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#include <linux/timex.h>
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#include <linux/errno.h>
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#include <linux/profile.h>
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#include <linux/syscore_ops.h>
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#include <linux/timer.h>
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#include <linux/irq.h>
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#include <linux/delay.h>
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#include <linux/clocksource.h>
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#include <linux/clk-provider.h>
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#include <linux/acpi.h>
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#include <clocksource/arm_arch_timer.h>
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#include <asm/thread_info.h>
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#include <asm/stacktrace.h>
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unsigned long profile_pc(struct pt_regs *regs)
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{
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struct stackframe frame;
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if (!in_lock_functions(regs->pc))
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return regs->pc;
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frame.fp = regs->regs[29];
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frame.sp = regs->sp;
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frame.pc = regs->pc;
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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frame.graph = -1; /* no task info */
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#endif
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do {
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int ret = unwind_frame(NULL, &frame);
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if (ret < 0)
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return 0;
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} while (in_lock_functions(frame.pc));
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return frame.pc;
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}
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EXPORT_SYMBOL(profile_pc);
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void __init time_init(void)
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{
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u32 arch_timer_rate;
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of_clk_init(NULL);
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clocksource_probe();
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tick_setup_hrtimer_broadcast();
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arch_timer_rate = arch_timer_get_rate();
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if (!arch_timer_rate)
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panic("Unable to initialise architected timer.\n");
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/* Calibrate the delay loop directly */
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lpj_fine = arch_timer_rate / HZ;
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}
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