2
0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-24 21:24:00 +08:00
linux-next/arch/arm64/kernel/time.c
AKASHI Takahiro 20380bb390 arm64: ftrace: fix a stack tracer's output under function graph tracer
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>
2015-12-21 17:26:02 +00:00

84 lines
2.1 KiB
C

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