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ARM: 9234/1: stacktrace: Avoid duplicate saving of exception PC value

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Because an exception stack frame is not created in the exception entry,
save_trace() does special handling for the exception PC, but this is
only needed when CONFIG_FRAME_POINTER_UNWIND=y. When
CONFIG_ARM_UNWIND=y, unwind annotations have been added to the exception
entry and save_trace() will repeatedly save the exception PC:

    [0x7f000090] hrtimer_hander+0x8/0x10 [hrtimer]
    [0x8019ec50] __hrtimer_run_queues+0x18c/0x394
    [0x8019f760] hrtimer_run_queues+0xbc/0xd0
    [0x8019def0] update_process_times+0x34/0x80
    [0x801ad2a4] tick_periodic+0x48/0xd0
    [0x801ad3dc] tick_handle_periodic+0x1c/0x7c
    [0x8010f2e0] twd_handler+0x30/0x40
    [0x80177620] handle_percpu_devid_irq+0xa0/0x23c
    [0x801718d0] generic_handle_domain_irq+0x24/0x34
    [0x80502d28] gic_handle_irq+0x74/0x88
    [0x8085817c] generic_handle_arch_irq+0x58/0x78
    [0x80100ba8] __irq_svc+0x88/0xc8
    [0x80108114] arch_cpu_idle+0x38/0x3c
    [0x80108114] arch_cpu_idle+0x38/0x3c    <==== duplicate saved exception PC
    [0x80861bf8] default_idle_call+0x38/0x130
    [0x8015d5cc] do_idle+0x150/0x214
    [0x8015d978] cpu_startup_entry+0x18/0x1c
    [0x808589c0] rest_init+0xd8/0xdc
    [0x80c00a44] arch_post_acpi_subsys_init+0x0/0x8

We can move the special handling of the exception PC in save_trace() to
the unwind_frame() of the frame pointer unwinder.

Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: Linus Waleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Li Huafei 2022-08-26 09:08:46 +01:00 committed by Russell King (Oracle)
parent 5854e4d853
commit 752ec621ef
3 changed files with 37 additions and 14 deletions
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6
arch/arm/include/asm/stacktrace.h
View File

@ -21,6 +21,9 @@ struct stackframe {
struct llist_node *kr_cur;
struct task_struct *tsk;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
bool ex_frame;
#endif
};
static __always_inline
@ -34,6 +37,9 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
frame->kr_cur = NULL;
frame->tsk = current;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame->ex_frame = in_entry_text(frame->pc);
#endif
}
extern int unwind_frame(struct stackframe *frame);

1
arch/arm/kernel/return_address.c
View File

@ -47,6 +47,7 @@ here:
frame.kr_cur = NULL;
frame.tsk = current;
#endif
frame.ex_frame = false;
walk_stackframe(&frame, save_return_addr, &data);

44
arch/arm/kernel/stacktrace.c
View File

@ -82,6 +82,27 @@ int notrace unwind_frame(struct stackframe *frame)
if (frame_pointer_check(frame))
return -EINVAL;
/*
* When we unwind through an exception stack, include the saved PC
* value into the stack trace.
*/
if (frame->ex_frame) {
struct pt_regs *regs = (struct pt_regs *)frame->sp;
/*
* We check that 'regs + sizeof(struct pt_regs)' (that is,
* &regs[1]) does not exceed the bottom of the stack to avoid
* accessing data outside the task's stack. This may happen
* when frame->ex_frame is a false positive.
*/
if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
return -EINVAL;
frame->pc = regs->ARM_pc;
frame->ex_frame = false;
return 0;
}
/* restore the registers from the stack frame */
#ifdef CONFIG_CC_IS_CLANG
frame->sp = frame->fp;
@ -98,6 +119,9 @@ int notrace unwind_frame(struct stackframe *frame)
(void *)frame->fp, &frame->kr_cur);
#endif
if (in_entry_text(frame->pc))
frame->ex_frame = true;
return 0;
}
#endif
@ -128,7 +152,6 @@ static int save_trace(struct stackframe *frame, void *d)
{
struct stack_trace_data *data = d;
struct stack_trace *trace = data->trace;
struct pt_regs *regs;
unsigned long addr = frame->pc;
if (data->no_sched_functions && in_sched_functions(addr))
@ -139,19 +162,6 @@ static int save_trace(struct stackframe *frame, void *d)
}
trace->entries[trace->nr_entries++] = addr;
if (trace->nr_entries >= trace->max_entries)
return 1;
if (!in_entry_text(frame->pc))
return 0;
regs = (struct pt_regs *)frame->sp;
if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
return 0;
trace->entries[trace->nr_entries++] = regs->ARM_pc;
return trace->nr_entries >= trace->max_entries;
}
@ -193,6 +203,9 @@ here:
frame.kr_cur = NULL;
frame.tsk = tsk;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame.ex_frame = false;
#endif
walk_stackframe(&frame, save_trace, &data);
}
@ -214,6 +227,9 @@ void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
frame.kr_cur = NULL;
frame.tsk = current;
#endif
#ifdef CONFIG_UNWINDER_FRAME_POINTER
frame.ex_frame = in_entry_text(frame.pc);
#endif
walk_stackframe(&frame, save_trace, &data);
}