From: Mark Rutland <mark.rutland@arm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
Joel Fernandes <joel@joelfernandes.org>,
Jiping Ma <jiping.ma2@windriver.com>,
mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2 v2] tracing/arm64: Have max stack tracer handle the case of return address after data
Date: Fri, 9 Aug 2019 09:55:21 +0100 [thread overview]
Message-ID: <20190809085520.GC48423@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20190807172907.155165959@goodmis.org>
On Wed, Aug 07, 2019 at 01:28:27PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> Most archs (well at least x86) store the function call return address on the
> stack before storing the local variables for the function. The max stack
> tracer depends on this in its algorithm to display the stack size of each
> function it finds in the back trace.
>
> Some archs (arm64), may store the return address (from its link register)
> just before calling a nested function. There's no reason to save the link
> register on leaf functions, as it wont be updated. This breaks the algorithm
> of the max stack tracer.
>
> Add a new define ARCH_RET_ADDR_AFTER_LOCAL_VARS that an architecture may set
> if it stores the return address (link register) after it stores the
> function's local variables, and have the stack trace shift the values of the
> mapped stack size to the appropriate functions.
>
> Link: 20190802094103.163576-1-jiping.ma2@windriver.com
>
> Reported-by: Jiping Ma <jiping.ma2@windriver.com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> arch/arm64/include/asm/ftrace.h | 13 +++++++++++++
> kernel/trace/trace_stack.c | 14 ++++++++++++++
> 2 files changed, 27 insertions(+)
>
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index 5ab5200b2bdc..961e98618db4 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -14,6 +14,19 @@
> #define MCOUNT_ADDR ((unsigned long)_mcount)
> #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE
>
> +/*
> + * Currently, gcc tends to save the link register after the local variables
> + * on the stack. This causes the max stack tracer to report the function
> + * frame sizes for the wrong functions. By defining
> + * ARCH_RET_ADDR_AFTER_LOCAL_VARS, it will tell the stack tracer to expect
> + * to find the return address on the stack after the local variables have
> + * been set up.
> + *
> + * Note, this may change in the future, and we will need to deal with that
> + * if it were to happen.
> + */
> +#define ARCH_RET_ADDR_AFTER_LOCAL_VARS 1
FWIW (with whatever this got renamed to):
Acked-by: Mark Rutland <mark.rutland@arm.com>
Thanks,
Mark.
next prev parent reply other threads:[~2019-08-09 8:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 17:28 [PATCH 0/2 v2] tracing/arm: Fix the stack tracer when LR is saved after local storage Steven Rostedt
2019-08-07 17:28 ` [PATCH 1/2 v2] tracing/arm64: Have max stack tracer handle the case of return address after data Steven Rostedt
2019-08-07 19:29 ` Steven Rostedt
2019-08-08 16:28 ` Will Deacon
2019-08-08 16:36 ` Steven Rostedt
2019-08-08 17:11 ` Will Deacon
2019-08-08 17:24 ` Steven Rostedt
2019-08-09 2:17 ` Jiping Ma
2019-08-09 2:24 ` Steven Rostedt
2019-08-13 17:31 ` Will Deacon
2019-08-13 17:47 ` Steven Rostedt
2019-08-09 8:55 ` Mark Rutland [this message]
2019-08-07 17:28 ` [PATCH 2/2 v2] tracing: Document the stack trace algorithm in the comments Steven Rostedt
2019-08-08 20:17 ` Joel Fernandes
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