[PATCH v3 2/7] optee: Refuse to load the driver under the kdump kernel

Tyler Hicks
2021-06-09T00:25:49Z

Fix a hung task issue, seen when booting the kdump kernel, that is
caused by all of the secure world threads being in a permanent suspended
state:

INFO: task swapper/0:1 blocked for more than 120 seconds.
Not tainted 5.4.83 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
swapper/0 D 0 1 0 0x00000028
Call trace:
__switch_to+0xc8/0x118
__schedule+0x2e0/0x700
schedule+0x38/0xb8
schedule_timeout+0x258/0x388
wait_for_completion+0x16c/0x4b8
optee_cq_wait_for_completion+0x28/0xa8
optee_disable_shm_cache+0xb8/0xf8
optee_probe+0x560/0x61c
platform_drv_probe+0x58/0xa8
really_probe+0xe0/0x338
driver_probe_device+0x5c/0xf0
device_driver_attach+0x74/0x80
__driver_attach+0x64/0xe0
bus_for_each_dev+0x84/0xd8
driver_attach+0x30/0x40
bus_add_driver+0x188/0x1e8
driver_register+0x64/0x110
__platform_driver_register+0x54/0x60
optee_driver_init+0x20/0x28
do_one_initcall+0x54/0x24c
kernel_init_freeable+0x1e8/0x2c0
kernel_init+0x18/0x118
ret_from_fork+0x10/0x18

The invoke_fn hook returned OPTEE_SMC_RETURN_ETHREAD_LIMIT, indicating
that the secure world threads were all in a suspended state at the time
of the kernel crash. This intermittently prevented the kdump kernel from
booting, resulting in a failure to collect the kernel dump.

Make kernel dump collection more reliable on systems utilizing OP-TEE by
refusing to load the driver under the kdump kernel.

Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
---
drivers/tee/optee/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
index ddb8f9ecf307..5288cd767d82 100644
--- a/drivers/tee/optee/core.c
+++ b/drivers/tee/optee/core.c
@@ -6,6 +6,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/arm-smccc.h>
+#include <linux/crash_dump.h>
#include <linux/errno.h>
#include <linux/io.h>
#include <linux/module.h>
@@ -612,6 +613,16 @@ static int optee_probe(struct platform_device *pdev)
u32 sec_caps;
int rc;

+ /*
+ * The kernel may have crashed at the same time that all available
+ * secure world threads were suspended and we cannot reschedule the
+ * suspended threads without access to the crashed kernel's wait_queue.
+ * Therefore, we cannot reliably initialize the OP-TEE driver in the
+ * kdump kernel.
+ */
+ if (is_kdump_kernel())
+ return -ENODEV;
+
invoke_fn = get_invoke_func(&pdev->dev);
if (IS_ERR(invoke_fn))
return PTR_ERR(invoke_fn);
--
2.25.1