This is a note to let you know that I've just added the patch titled
ARM: 9066/1: ftrace: pause/unpause function graph tracer in cpu_suspend()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-9066-1-ftrace-pause-unpause-function-graph-trace.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bf3f6994f42f577960dadb224aed17f9ecefd316
Author: louis.wang <liang26812@xxxxxxxxx>
Date: Wed Feb 24 13:25:53 2021 +0100
ARM: 9066/1: ftrace: pause/unpause function graph tracer in cpu_suspend()
[ Upstream commit 8252ca87c7a2111502ee13994956f8c309faad7f ]
Enabling function_graph tracer on ARM causes kernel panic, because the
function graph tracer updates the "return address" of a function in order
to insert a trace callback on function exit, it saves the function's
original return address in a return trace stack, but cpu_suspend() may not
return through the normal return path.
cpu_suspend() will resume directly via the cpu_resume path, but the return
trace stack has been set-up by the subfunctions of cpu_suspend(), which
makes the "return address" inconsistent with cpu_suspend().
This patch refers to Commit de818bd4522c40ea02a81b387d2fa86f989c9623
("arm64: kernel: pause/unpause function graph tracer in cpu_suspend()"),
fixes the issue by pausing/resuming the function graph tracer on the thread
executing cpu_suspend(), so that the function graph tracer state is kept
consistent across functions that enter power down states and never return
by effectively disabling graph tracer while they are executing.
Signed-off-by: louis.wang <liang26812@xxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm/kernel/suspend.c b/arch/arm/kernel/suspend.c
index d08099269e35..e126386fb78a 100644
--- a/arch/arm/kernel/suspend.c
+++ b/arch/arm/kernel/suspend.c
@@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
+#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/mm_types.h>
@@ -26,6 +27,13 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
if (!idmap_pgd)
return -EINVAL;
+ /*
+ * Function graph tracer state gets incosistent when the kernel
+ * calls functions that never return (aka suspend finishers) hence
+ * disable graph tracing during their execution.
+ */
+ pause_graph_tracing();
+
/*
* Provide a temporary page table with an identity mapping for
* the MMU-enable code, required for resuming. On successful
@@ -33,6 +41,9 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
* back to the correct page tables.
*/
ret = __cpu_suspend(arg, fn, __mpidr);
+
+ unpause_graph_tracing();
+
if (ret == 0) {
cpu_switch_mm(mm->pgd, mm);
local_flush_bp_all();
@@ -46,7 +57,13 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
{
u32 __mpidr = cpu_logical_map(smp_processor_id());
- return __cpu_suspend(arg, fn, __mpidr);
+ int ret;
+
+ pause_graph_tracing();
+ ret = __cpu_suspend(arg, fn, __mpidr);
+ unpause_graph_tracing();
+
+ return ret;
}
#define idmap_pgd NULL
#endif
