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    Subject[PATCH 6.0 790/862] ARM: 9234/1: stacktrace: Avoid duplicate saving of exception PC value
    Date
    From: Li Huafei <lihuafei1@huawei.com>

    [ Upstream commit 752ec621ef5c30777958cc5eb5f1cf394f7733f4 ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm/include/asm/stacktrace.h | 6 +++++
    arch/arm/kernel/return_address.c | 1 +
    arch/arm/kernel/stacktrace.c | 44 +++++++++++++++++++++----------
    3 files changed, 37 insertions(+), 14 deletions(-)

    diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
    index 3e78f921b8b2..39be2d1aa27b 100644
    --- a/arch/arm/include/asm/stacktrace.h
    +++ b/arch/arm/include/asm/stacktrace.h
    @@ -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);
    diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
    index 8aac1e10b117..38f1ea9c724d 100644
    --- a/arch/arm/kernel/return_address.c
    +++ b/arch/arm/kernel/return_address.c
    @@ -47,6 +47,7 @@ void *return_address(unsigned int level)
    frame.kr_cur = NULL;
    frame.tsk = current;
    #endif
    + frame.ex_frame = false;

    walk_stackframe(&frame, save_return_addr, &data);

    diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
    index af87040b0353..85443b5d1922 100644
    --- a/arch/arm/kernel/stacktrace.c
    +++ b/arch/arm/kernel/stacktrace.c
    @@ -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 @@ static noinline void __save_stack_trace(struct task_struct *tsk,
    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);
    }
    --
    2.35.1


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