[PATCH v2 0/4] Fixed some issues and cleanup of ultrasoc-smb

[PATCH v2 0/4] Fixed some issues and cleanup of ultrasoc-smb

[Junhao He]

Fix the Three issues listed below and use guards to cleanup
a) Fixed the BUG of atomic-sleep
b) Fixed uninitialized before use buf_hw_base
c) Fixed use unreset SMB buffer

Changes since V1:
 * Add comment for remove lock from smb_read()
 * Move reset buffer to before register sink
 * Remove patch "simplify the code for check to_copy valid"
 * Add two new patches

Link to V1: https://lore.kernel.org/lkml/20231012094706.21565-1-hejunhao3@huawei.com/

Junhao He (4):
  coresight: ultrasoc-smb: Fix sleep while close preempt in enable_smb
  coresight: ultrasoc-smb: Config SMB buffer before register sink
  coresight: ultrasoc-smb: Fix uninitialized before use buf_hw_base
  coresight: ultrasoc-smb: Use guards to cleanup

 drivers/hwtracing/coresight/ultrasoc-smb.c | 108 +++++++--------------
 drivers/hwtracing/coresight/ultrasoc-smb.h |   6 +-
 2 files changed, 37 insertions(+), 77 deletions(-)

-- 
2.33.0

[PATCH v2 1/4] coresight: ultrasoc-smb: Fix sleep while close preempt in enable_smb

[Junhao He]

When we to enable the SMB by perf, the perf sched will call perf_ctx_lock()
to close system preempt in event_function_call(). But SMB::enable_smb() use
mutex to lock the critical section, which may sleep.

 BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf
 preempt_count: 2, expected: 0
 RCU nest depth: 0, expected: 0
 INFO: lockdep is turned off.
 irq event stamp: 0
 hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 hardirqs last disabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
 softirqs last  enabled at (0): [<ffffa2983f5c5f40>] copy_process+0xae8/0x2b48
 softirqs last disabled at (0): [<0000000000000000>] 0x0
 CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G   W  O   6.5.0-rc4+ #1

 Call trace:
 ...
  __mutex_lock+0xbc/0xa70
  mutex_lock_nested+0x34/0x48
  smb_update_buffer+0x58/0x360 [ultrasoc_smb]
  etm_event_stop+0x204/0x2d8 [coresight]
  etm_event_del+0x1c/0x30 [coresight]
  event_sched_out+0x17c/0x3b8
  group_sched_out.part.0+0x5c/0x208
  __perf_event_disable+0x15c/0x210
  event_function+0xe0/0x230
  remote_function+0xb4/0xe8
  generic_exec_single+0x160/0x268
  smp_call_function_single+0x20c/0x2a0
  event_function_call+0x20c/0x220
  _perf_event_disable+0x5c/0x90
  perf_event_for_each_child+0x58/0xc0
  _perf_ioctl+0x34c/0x1250
  perf_ioctl+0x64/0x98
 ...

Use spinlock to replace mutex to control driver data access to one at a
time. The function copy_to_user() may sleep, it cannot be in a spinlock
context, so we can't simply replace it in smb_read(). But we can ensure
that only one user gets the SMB device fd by smb_open(), so remove the
locks from smb_read() and buffer synchronization is guaranteed by the user.

Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 35 +++++++++-------------
 drivers/hwtracing/coresight/ultrasoc-smb.h |  6 ++--
 2 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index e9a32a97fbee..0a0fe9fcc57f 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -99,7 +99,7 @@ static int smb_open(struct inode *inode, struct file *file)
 					struct smb_drv_data, miscdev);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	if (drvdata->reading) {
 		ret = -EBUSY;
@@ -115,7 +115,7 @@ static int smb_open(struct inode *inode, struct file *file)
 
 	drvdata->reading = true;
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
 	if (!len)
 		return 0;
 
-	mutex_lock(&drvdata->mutex);
-
 	if (!sdb->data_size)
-		goto out;
+		return 0;
 
 	to_copy = min(sdb->data_size, len);
 
@@ -145,20 +143,15 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len,
 
 	if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) {
 		dev_dbg(dev, "Failed to copy data to user\n");
-		to_copy = -EFAULT;
-		goto out;
+		return -EFAULT;
 	}
 
 	*ppos += to_copy;
-
 	smb_update_read_ptr(drvdata, to_copy);
-
-	dev_dbg(dev, "%zu bytes copied\n", to_copy);
-out:
 	if (!sdb->data_size)
 		smb_reset_buffer(drvdata);
-	mutex_unlock(&drvdata->mutex);
 
+	dev_dbg(dev, "%zu bytes copied\n", to_copy);
 	return to_copy;
 }
 
@@ -167,9 +160,9 @@ static int smb_release(struct inode *inode, struct file *file)
 	struct smb_drv_data *drvdata = container_of(file->private_data,
 					struct smb_drv_data, miscdev);
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 	drvdata->reading = false;
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return 0;
 }
@@ -262,7 +255,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	/* Do nothing, the trace data is reading by other interface now */
 	if (drvdata->reading) {
@@ -294,7 +287,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 
 	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled\n");
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -304,7 +297,7 @@ static int smb_disable(struct coresight_device *csdev)
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int ret = 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	if (drvdata->reading) {
 		ret = -EBUSY;
@@ -327,7 +320,7 @@ static int smb_disable(struct coresight_device *csdev)
 
 	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -408,7 +401,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	if (!buf)
 		return 0;
 
-	mutex_lock(&drvdata->mutex);
+	spin_lock(&drvdata->spinlock);
 
 	/* Don't do anything if another tracer is using this sink. */
 	if (atomic_read(&csdev->refcnt) != 1)
@@ -432,7 +425,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	if (!buf->snapshot && lost)
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
 out:
-	mutex_unlock(&drvdata->mutex);
+	spin_unlock(&drvdata->spinlock);
 
 	return data_size;
 }
@@ -590,7 +583,7 @@ static int smb_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	mutex_init(&drvdata->mutex);
+	spin_lock_init(&drvdata->spinlock);
 	drvdata->pid = -1;
 
 	ret = smb_register_sink(pdev, drvdata);
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
index d2e14e8d2c8a..82a44c14a882 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.h
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
@@ -8,7 +8,7 @@
 #define _ULTRASOC_SMB_H
 
 #include <linux/miscdevice.h>
-#include <linux/mutex.h>
+#include <linux/spinlock.h>
 
 /* Offset of SMB global registers */
 #define SMB_GLB_CFG_REG		0x00
@@ -105,7 +105,7 @@ struct smb_data_buffer {
  * @csdev:	Component vitals needed by the framework.
  * @sdb:	Data buffer for SMB.
  * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
- * @mutex:	Control data access to one at a time.
+ * @spinlock:	Control data access to one at a time.
  * @reading:	Synchronise user space access to SMB buffer.
  * @pid:	Process ID of the process being monitored by the
  *		session that is using this component.
@@ -116,7 +116,7 @@ struct smb_drv_data {
 	struct coresight_device	*csdev;
 	struct smb_data_buffer sdb;
 	struct miscdevice miscdev;
-	struct mutex mutex;
+	spinlock_t spinlock;
 	bool reading;
 	pid_t pid;
 	enum cs_mode mode;
-- 
2.33.0

[PATCH v2 2/4] coresight: ultrasoc-smb: Config SMB buffer before register sink

[Junhao He]

The SMB dirver register the enable/disable sysfs interface in function
smb_register_sink(), however the buffer depends on the following
configuration to work well. So it'll be possible for user to access an
unreset one.

Move the config buffer operation to before register_sink().

Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index 0a0fe9fcc57f..c61450f74cb1 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -583,38 +583,31 @@ static int smb_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = smb_config_inport(dev, true);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, drvdata);
 	spin_lock_init(&drvdata->spinlock);
 	drvdata->pid = -1;
 
 	ret = smb_register_sink(pdev, drvdata);
 	if (ret) {
+		smb_config_inport(&pdev->dev, false);
 		dev_err(dev, "Failed to register SMB sink\n");
 		return ret;
 	}
 
-	ret = smb_config_inport(dev, true);
-	if (ret) {
-		smb_unregister_sink(drvdata);
-		return ret;
-	}
-
-	platform_set_drvdata(pdev, drvdata);
-
 	return 0;
 }
 
 static int smb_remove(struct platform_device *pdev)
 {
 	struct smb_drv_data *drvdata = platform_get_drvdata(pdev);
-	int ret;
-
-	ret = smb_config_inport(&pdev->dev, false);
-	if (ret)
-		return ret;
 
 	smb_unregister_sink(drvdata);
 
-	return 0;
+	return smb_config_inport(&pdev->dev, false);
 }
 
 #ifdef CONFIG_ACPI
-- 
2.33.0

[PATCH v2 3/4] coresight: ultrasoc-smb: Fix uninitialized before use buf_hw_base

[Junhao He]

In smb_reset_buffer, the sdb->buf_hw_base variable is uninitialized
before use, which initializes it in smb_init_data_buffer. And the SMB
regiester are set in smb_config_inport.
So move the call after smb_config_inport.

Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index c61450f74cb1..2ee6bf5b725e 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -477,7 +477,6 @@ static int smb_init_data_buffer(struct platform_device *pdev,
 static void smb_init_hw(struct smb_drv_data *drvdata)
 {
 	smb_disable_hw(drvdata);
-	smb_reset_buffer(drvdata);
 
 	writel(SMB_LB_CFG_LO_DEFAULT, drvdata->base + SMB_LB_CFG_LO_REG);
 	writel(SMB_LB_CFG_HI_DEFAULT, drvdata->base + SMB_LB_CFG_HI_REG);
@@ -587,6 +586,7 @@ static int smb_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	smb_reset_buffer(drvdata);
 	platform_set_drvdata(pdev, drvdata);
 	spin_lock_init(&drvdata->spinlock);
 	drvdata->pid = -1;
-- 
2.33.0

[PATCH v2 4/4] coresight: ultrasoc-smb: Use guards to cleanup

[Junhao He]

Use guards to reduce gotos and simplify control flow.

Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 70 +++++++---------------
 1 file changed, 22 insertions(+), 48 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index 2ee6bf5b725e..5140782b1b5d 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -97,27 +97,19 @@ static int smb_open(struct inode *inode, struct file *file)
 {
 	struct smb_drv_data *drvdata = container_of(file->private_data,
 					struct smb_drv_data, miscdev);
-	int ret = 0;
 
-	spin_lock(&drvdata->spinlock);
+	guard(spinlock)(&drvdata->spinlock);
 
-	if (drvdata->reading) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (drvdata->reading)
+		return -EBUSY;
 
-	if (atomic_read(&drvdata->csdev->refcnt)) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (atomic_read(&drvdata->csdev->refcnt))
+		return -EBUSY;
 
 	smb_update_data_size(drvdata);
-
 	drvdata->reading = true;
-out:
-	spin_unlock(&drvdata->spinlock);
 
-	return ret;
+	return 0;
 }
 
 static ssize_t smb_read(struct file *file, char __user *data, size_t len,
@@ -160,9 +152,8 @@ static int smb_release(struct inode *inode, struct file *file)
 	struct smb_drv_data *drvdata = container_of(file->private_data,
 					struct smb_drv_data, miscdev);
 
-	spin_lock(&drvdata->spinlock);
+	guard(spinlock)(&drvdata->spinlock);
 	drvdata->reading = false;
-	spin_unlock(&drvdata->spinlock);
 
 	return 0;
 }
@@ -255,19 +246,15 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	int ret = 0;
 
-	spin_lock(&drvdata->spinlock);
+	guard(spinlock)(&drvdata->spinlock);
 
 	/* Do nothing, the trace data is reading by other interface now */
-	if (drvdata->reading) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (drvdata->reading)
+		return -EBUSY;
 
 	/* Do nothing, the SMB is already enabled as other mode */
-	if (drvdata->mode != CS_MODE_DISABLED && drvdata->mode != mode) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (drvdata->mode != CS_MODE_DISABLED && drvdata->mode != mode)
+		return -EBUSY;
 
 	switch (mode) {
 	case CS_MODE_SYSFS:
@@ -281,13 +268,10 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 	}
 
 	if (ret)
-		goto out;
+		return ret;
 
 	atomic_inc(&csdev->refcnt);
-
 	dev_dbg(&csdev->dev, "Ultrasoc SMB enabled\n");
-out:
-	spin_unlock(&drvdata->spinlock);
 
 	return ret;
 }
@@ -295,19 +279,14 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
 static int smb_disable(struct coresight_device *csdev)
 {
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
-	int ret = 0;
 
-	spin_lock(&drvdata->spinlock);
+	guard(spinlock)(&drvdata->spinlock);
 
-	if (drvdata->reading) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (drvdata->reading)
+		return -EBUSY;
 
-	if (atomic_dec_return(&csdev->refcnt)) {
-		ret = -EBUSY;
-		goto out;
-	}
+	if (atomic_dec_return(&csdev->refcnt))
+		return -EBUSY;
 
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
@@ -317,12 +296,9 @@ static int smb_disable(struct coresight_device *csdev)
 	/* Dissociate from the target process. */
 	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
-
 	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");
-out:
-	spin_unlock(&drvdata->spinlock);
 
-	return ret;
+	return 0;
 }
 
 static void *smb_alloc_buffer(struct coresight_device *csdev,
@@ -395,17 +371,17 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct smb_data_buffer *sdb = &drvdata->sdb;
 	struct cs_buffers *buf = sink_config;
-	unsigned long data_size = 0;
+	unsigned long data_size;
 	bool lost = false;
 
 	if (!buf)
 		return 0;
 
-	spin_lock(&drvdata->spinlock);
+	guard(spinlock)(&drvdata->spinlock);
 
 	/* Don't do anything if another tracer is using this sink. */
 	if (atomic_read(&csdev->refcnt) != 1)
-		goto out;
+		return 0;
 
 	smb_disable_hw(drvdata);
 	smb_update_data_size(drvdata);
@@ -424,8 +400,6 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
 	smb_sync_perf_buffer(drvdata, buf, handle->head);
 	if (!buf->snapshot && lost)
 		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
-out:
-	spin_unlock(&drvdata->spinlock);
 
 	return data_size;
 }
-- 
2.33.0