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Date:   Fri, 30 Nov 2018 10:21:02 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Anders Roxell <anders.roxell@linaro.org>
Cc:     keescook@chromium.org, mingo@redhat.com, catalin.marinas@arm.com,
        will.deacon@arm.com, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH 1/3] stackleak: mark stackleak_track_stack() as notrace
Message-ID: <20181130102102.041b8291@gandalf.local.home>
In-Reply-To: <20181130150859.27366-1-anders.roxell@linaro.org>
References: <20181130150859.27366-1-anders.roxell@linaro.org>
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On Fri, 30 Nov 2018 16:08:59 +0100
Anders Roxell <anders.roxell@linaro.org> wrote:

> Function graph tracing recurses into itself when stackleak is enabled,
> causing the ftrace graph selftest to run for up to 90 seconds and
> trigger the softlockup watchdog.
> 
> Breakpoint 2, ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:200
> 200             mcount_get_lr_addr        x0    //     pointer to function's saved lr
> (gdb) bt
> \#0  ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:200
> \#1  0xffffff80081d5280 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:153
> \#2  0xffffff8008555484 in stackleak_track_stack () at ../kernel/stackleak.c:106
> \#3  0xffffff8008421ff8 in ftrace_ops_test (ops=0xffffff8009eaa840 <graph_ops>, ip=18446743524091297036, regs=<optimized out>) at ../kernel/trace/ftrace.c:1507
> \#4  0xffffff8008428770 in __ftrace_ops_list_func (regs=<optimized out>, ignored=<optimized out>, parent_ip=<optimized out>, ip=<optimized out>) at ../kernel/trace/ftrace.c:6286
> \#5  ftrace_ops_no_ops (ip=18446743524091297036, parent_ip=18446743524091242824) at ../kernel/trace/ftrace.c:6321
> \#6  0xffffff80081d5280 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:153
> \#7  0xffffff800832fd10 in irq_find_mapping (domain=0xffffffc03fc4bc80, hwirq=27) at ../kernel/irq/irqdomain.c:876
> \#8  0xffffff800832294c in __handle_domain_irq (domain=0xffffffc03fc4bc80, hwirq=27, lookup=true, regs=0xffffff800814b840) at ../kernel/irq/irqdesc.c:650
> \#9  0xffffff80081d52b4 in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:205
> 
> Rework so we mark stackleak_track_stack as notrace
> 
> Co-developed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

> ---
>  kernel/stackleak.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
> index e42892926244..5de3bf596dd7 100644
> --- a/kernel/stackleak.c
> +++ b/kernel/stackleak.c
> @@ -102,7 +102,7 @@ asmlinkage void stackleak_erase(void)
>  	current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64;
>  }
>  
> -void __used stackleak_track_stack(void)
> +void __used notrace stackleak_track_stack(void)
>  {
>  	/*
>  	 * N.B. stackleak_erase() fills the kernel stack with the poison value,