This is a note to let you know that I've just added the patch titled
coresight: Fix crash when Perf and sysfs modes are used concurrently
to the 6.6-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:
coresight-fix-crash-when-perf-and-sysfs-modes-are-us.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2555bfdf5322a0ce6bbe9073eccdfbd1c33c35fd
Author: James Clark <james.clark@xxxxxxx>
Date: Fri Oct 6 14:14:52 2023 +0100
coresight: Fix crash when Perf and sysfs modes are used concurrently
[ Upstream commit 287e82cf69aa264a52bc37591bd0eb407e20f85c ]
Partially revert the change in commit 6148652807ba ("coresight: Enable
and disable helper devices adjacent to the path") which changed the bare
call from source_ops(csdev)->enable() to coresight_enable_source() for
Perf sessions. It was missed that coresight_enable_source() is
specifically for the sysfs interface, rather than being a generic call.
This interferes with the sysfs reference counting to cause the following
crash:
$ perf record -e cs_etm/@tmc_etr0/ -C 0 &
$ echo 1 > /sys/bus/coresight/devices/tmc_etr0/enable_sink
$ echo 1 > /sys/bus/coresight/devices/etm0/enable_source
$ echo 0 > /sys/bus/coresight/devices/etm0/enable_source
Unable to handle kernel NULL pointer dereference at virtual
address 00000000000001d0
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
...
Call trace:
etm4_disable+0x54/0x150 [coresight_etm4x]
coresight_disable_source+0x6c/0x98 [coresight]
coresight_disable+0x74/0x1c0 [coresight]
enable_source_store+0x88/0xa0 [coresight]
dev_attr_store+0x20/0x40
sysfs_kf_write+0x4c/0x68
kernfs_fop_write_iter+0x120/0x1b8
vfs_write+0x2dc/0x3b0
ksys_write+0x70/0x108
__arm64_sys_write+0x24/0x38
invoke_syscall+0x50/0x128
el0_svc_common.constprop.0+0x104/0x130
do_el0_svc+0x40/0xb8
el0_svc+0x2c/0xb8
el0t_64_sync_handler+0xc0/0xc8
el0t_64_sync+0x1a4/0x1a8
Code: d53cd042 91002000 b9402a81 b8626800 (f940ead5)
---[ end trace 0000000000000000 ]---
This commit linked below also fixes the issue, but has unlocked updates
to the mode which could potentially race. So until we come up with a
more complete solution that takes all locking and interaction between
both modes into account, just revert back to the old behavior for Perf.
Reported-by: Junhao He <hejunhao3@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-arm-kernel/20230921132904.60996-1-hejunhao3@xxxxxxxxxx/
Fixes: 6148652807ba ("coresight: Enable and disable helper devices adjacent to the path")
Tested-by: Junhao He <hejunhao3@xxxxxxxxxx>
Signed-off-by: James Clark <james.clark@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Link: https://lore.kernel.org/r/20231006131452.646721-1-james.clark@xxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 5ca6278baff4f..89e8ed214ea49 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -493,7 +493,7 @@ static void etm_event_start(struct perf_event *event, int flags)
goto fail_end_stop;
/* Finally enable the tracer */
- if (coresight_enable_source(csdev, CS_MODE_PERF, event))
+ if (source_ops(csdev)->enable(csdev, event, CS_MODE_PERF))
goto fail_disable_path;
/*
@@ -587,7 +587,7 @@ static void etm_event_stop(struct perf_event *event, int mode)
return;
/* stop tracer */
- coresight_disable_source(csdev, event);
+ source_ops(csdev)->disable(csdev, event);
/* tell the core */
event->hw.state = PERF_HES_STOPPED;
