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Subject: Re: [PATCH v3] tracing: Function stack size and its name mismatch in
 arm64
To:     Steven Rostedt <rostedt@goodmis.org>
CC:     <catalin.marinas@arm.com>, <will.deacon@arm.com>,
        <linux-kernel@vger.kernel.org>, <mingo@redhat.com>,
        <joel@joelfernandes.org>, <linux-arm-kernel@lists.infradead.org>
References: <20190802094103.163576-1-jiping.ma2@windriver.com>
 <20190802112259.0530a648@gandalf.local.home>
 <20190802120920.3b1f4351@gandalf.local.home>
From:   Jiping Ma <Jiping.Ma2@windriver.com>
Message-ID: <50eb7362-1f61-71a2-0a89-5d3bf054716e@windriver.com>
Date:   Tue, 6 Aug 2019 14:01:37 +0800
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On 2019年08月03日 00:09, Steven Rostedt wrote:
> On Fri, 2 Aug 2019 11:22:59 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> I think you are not explaining the issue correctly. From looking at the
>> document, I think what you want to say is that the LR is saved *after*
>> the data for the function. Is that correct? If so, then yes, it would
>> cause the stack tracing algorithm to be incorrect.
>>
> [..]
>
>> Can someone confirm that this is the real issue?
> Does this patch fix your issue?
Yes, it does.

-- Jiping
>
> -- Steve
>
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index 5ab5200b2bdc..13a4832cfb00 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -13,6 +13,7 @@
>   #define HAVE_FUNCTION_GRAPH_FP_TEST
>   #define MCOUNT_ADDR		((unsigned long)_mcount)
>   #define MCOUNT_INSN_SIZE	AARCH64_INSN_SIZE
> +#define ARCH_RET_ADDR_AFTER_LOCAL_VARS 1
>   
>   #ifndef __ASSEMBLY__
>   #include <linux/compat.h>
> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> index 5d16f73898db..050c6bd9beac 100644
> --- a/kernel/trace/trace_stack.c
> +++ b/kernel/trace/trace_stack.c
> @@ -158,6 +158,18 @@ static void check_stack(unsigned long ip, unsigned long *stack)
>   			i++;
>   	}
>   
> +#ifdef ARCH_RET_ADDR_AFTER_LOCAL_VARS
> +	/*
> +	 * Most archs store the return address before storing the
> +	 * function's local variables. But some archs do this backwards.
> +	 */
> +	if (x > 1) {
> +		memmove(&stack_trace_index[0], &stack_trace_index[1],
> +			sizeof(stack_trace_index[0]) * (x - 1));
> +		x--;
> +	}
> +#endif
> +
>   	stack_trace_nr_entries = x;
>   
>   	if (task_stack_end_corrupted(current)) {
>
>
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