linux-kernel - [PATCH 1/3] stackleak: mark stackleak_track

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Date:   Fri, 30 Nov 2018 16:08:59 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     keescook@...omium.org
Cc:     rostedt@...dmis.org, mingo@...hat.com, catalin.marinas@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Anders Roxell <anders.roxell@...aro.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 1/3] stackleak: mark stackleak_track_stack() as notrace

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@...db.de>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
---
 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,
-- 
2.19.2