binder: Add binder_proc logging to binderfs

Currently /sys/kernel/debug/binder/proc contains
the debug data for every binder_proc instance.
This patch makes this information also available
in a binderfs instance mounted with a mount option
"stats=global" in addition to debugfs. The patch does
not affect the presence of the file in debugfs.

If a binderfs instance is mounted at path /dev/binderfs,
this file would be present at /dev/binderfs/binder_logs/proc.
This change provides an alternate way to access this file when debugfs
is not mounted.

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Link: https://lore.kernel.org/r/20190903161655.107408-5-hridya@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -458,6 +458,7 @@ enum binder_deferred_state {
  * @inner_lock:           can nest under outer_lock and/or node lock
  * @outer_lock:           no nesting under innor or node lock
  *                        Lock order: 1) outer, 2) node, 3) inner
+ * @binderfs_entry:       process-specific binderfs log file
  *
  * Bookkeeping structure for binder processes
  */
@@ -487,6 +488,7 @@ struct binder_proc {
 	struct binder_context *context;
 	spinlock_t inner_lock;
 	spinlock_t outer_lock;
+	struct dentry *binderfs_entry;
 };
 
 enum {
@@ -5208,6 +5210,8 @@ static int binder_open(struct inode *nodp, struct file *filp)
 {
 	struct binder_proc *proc;
 	struct binder_device *binder_dev;
+	struct binderfs_info *info;
+	struct dentry *binder_binderfs_dir_entry_proc = NULL;
 
 	binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d:%d\n", __func__,
 		     current->group_leader->pid, current->pid);
@@ -5222,11 +5226,14 @@ static int binder_open(struct inode *nodp, struct file *filp)
 	INIT_LIST_HEAD(&proc->todo);
 	proc->default_priority = task_nice(current);
 	/* binderfs stashes devices in i_private */
-	if (is_binderfs_device(nodp))
+	if (is_binderfs_device(nodp)) {
 		binder_dev = nodp->i_private;
-	else
+		info = nodp->i_sb->s_fs_info;
+		binder_binderfs_dir_entry_proc = info->proc_log_dir;
+	} else {
 		binder_dev = container_of(filp->private_data,
 					  struct binder_device, miscdev);
+	}
 	proc->context = &binder_dev->context;
 	binder_alloc_init(&proc->alloc);
 
@@ -5257,6 +5264,35 @@ static int binder_open(struct inode *nodp, struct file *filp)
 			&proc_fops);
 	}
 
+	if (binder_binderfs_dir_entry_proc) {
+		char strbuf[11];
+		struct dentry *binderfs_entry;
+
+		snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);
+		/*
+		 * Similar to debugfs, the process specific log file is shared
+		 * between contexts. If the file has already been created for a
+		 * process, the following binderfs_create_file() call will
+		 * fail with error code EEXIST if another context of the same
+		 * process invoked binder_open(). This is ok since same as
+		 * debugfs, the log file will contain information on all
+		 * contexts of a given PID.
+		 */
+		binderfs_entry = binderfs_create_file(binder_binderfs_dir_entry_proc,
+			strbuf, &proc_fops, (void *)(unsigned long)proc->pid);
+		if (!IS_ERR(binderfs_entry)) {
+			proc->binderfs_entry = binderfs_entry;
+		} else {
+			int error;
+
+			error = PTR_ERR(binderfs_entry);
+			if (error != -EEXIST) {
+				pr_warn("Unable to create file %s in binderfs (error %d)\n",
+					strbuf, error);
+			}
+		}
+	}
+
 	return 0;
 }
 
@@ -5296,6 +5332,12 @@ static int binder_release(struct inode *nodp, struct file *filp)
 	struct binder_proc *proc = filp->private_data;
 
 	debugfs_remove(proc->debugfs_entry);
+
+	if (proc->binderfs_entry) {
+		binderfs_remove_file(proc->binderfs_entry);
+		proc->binderfs_entry = NULL;
+	}
+
 	binder_defer_work(proc, BINDER_DEFERRED_RELEASE);
 
 	return 0;

drivers/android/binder_internal.h

@@ -35,17 +35,63 @@ struct binder_device {
 	struct inode *binderfs_inode;
 };
 
+/**
+ * binderfs_mount_opts - mount options for binderfs
+ * @max: maximum number of allocatable binderfs binder devices
+ * @stats_mode: enable binder stats in binderfs.
+ */
+struct binderfs_mount_opts {
+	int max;
+	int stats_mode;
+};
+
+/**
+ * binderfs_info - information about a binderfs mount
+ * @ipc_ns:         The ipc namespace the binderfs mount belongs to.
+ * @control_dentry: This records the dentry of this binderfs mount
+ *                  binder-control device.
+ * @root_uid:       uid that needs to be used when a new binder device is
+ *                  created.
+ * @root_gid:       gid that needs to be used when a new binder device is
+ *                  created.
+ * @mount_opts:     The mount options in use.
+ * @device_count:   The current number of allocated binder devices.
+ * @proc_log_dir:   Pointer to the directory dentry containing process-specific
+ *                  logs.
+ */
+struct binderfs_info {
+	struct ipc_namespace *ipc_ns;
+	struct dentry *control_dentry;
+	kuid_t root_uid;
+	kgid_t root_gid;
+	struct binderfs_mount_opts mount_opts;
+	int device_count;
+	struct dentry *proc_log_dir;
+};
+
 extern const struct file_operations binder_fops;
 
 extern char *binder_devices_param;
 
 #ifdef CONFIG_ANDROID_BINDERFS
 extern bool is_binderfs_device(const struct inode *inode);
+extern struct dentry *binderfs_create_file(struct dentry *dir, const char *name,
+					   const struct file_operations *fops,
+					   void *data);
+extern void binderfs_remove_file(struct dentry *dentry);
 #else
 static inline bool is_binderfs_device(const struct inode *inode)
 {
 	return false;
 }
+static inline struct dentry *binderfs_create_file(struct dentry *dir,
+					   const char *name,
+					   const struct file_operations *fops,
+					   void *data)
+{
+	return NULL;
+}
+static inline void binderfs_remove_file(struct dentry *dentry) {}
 #endif
 
 #ifdef CONFIG_ANDROID_BINDERFS

drivers/android/binderfs.c

@@ -48,16 +48,6 @@ static dev_t binderfs_dev;
 static DEFINE_MUTEX(binderfs_minors_mutex);
 static DEFINE_IDA(binderfs_minors);
 
-/**
- * binderfs_mount_opts - mount options for binderfs
- * @max: maximum number of allocatable binderfs binder devices
- * @stats_mode: enable binder stats in binderfs.
- */
-struct binderfs_mount_opts {
-	int max;
-	int stats_mode;
-};
-
 enum {
 	Opt_max,
 	Opt_stats_mode,
@@ -75,27 +65,6 @@ static const match_table_t tokens = {
 	{ Opt_err, NULL     }
 };
 
-/**
- * binderfs_info - information about a binderfs mount
- * @ipc_ns:         The ipc namespace the binderfs mount belongs to.
- * @control_dentry: This records the dentry of this binderfs mount
- *                  binder-control device.
- * @root_uid:       uid that needs to be used when a new binder device is
- *                  created.
- * @root_gid:       gid that needs to be used when a new binder device is
- *                  created.
- * @mount_opts:     The mount options in use.
- * @device_count:   The current number of allocated binder devices.
- */
-struct binderfs_info {
-	struct ipc_namespace *ipc_ns;
-	struct dentry *control_dentry;
-	kuid_t root_uid;
-	kgid_t root_gid;
-	struct binderfs_mount_opts mount_opts;
-	int device_count;
-};
-
 static inline struct binderfs_info *BINDERFS_I(const struct inode *inode)
 {
 	return inode->i_sb->s_fs_info;
@@ -533,8 +502,22 @@ static struct dentry *binderfs_create_dentry(struct dentry *parent,
 	return dentry;
 }
 
-static struct dentry *binderfs_create_file(struct dentry *parent,
+void binderfs_remove_file(struct dentry *dentry)
-					   const char *name,
+{
+	struct inode *parent_inode;
+
+	parent_inode = d_inode(dentry->d_parent);
+	inode_lock(parent_inode);
+	if (simple_positive(dentry)) {
+		dget(dentry);
+		simple_unlink(parent_inode, dentry);
+		d_delete(dentry);
+		dput(dentry);
+	}
+	inode_unlock(parent_inode);
+}
+
+struct dentry *binderfs_create_file(struct dentry *parent, const char *name,
 				    const struct file_operations *fops,
 				    void *data)
 {
@@ -604,7 +587,8 @@ out:
 
 static int init_binder_logs(struct super_block *sb)
 {
-	struct dentry *binder_logs_root_dir, *dentry;
+	struct dentry *binder_logs_root_dir, *dentry, *proc_log_dir;
+	struct binderfs_info *info;
 	int ret = 0;
 
 	binder_logs_root_dir = binderfs_create_dir(sb->s_root,
@@ -648,8 +632,18 @@ static int init_binder_logs(struct super_block *sb)
 				      "failed_transaction_log",
 				      &binder_transaction_log_fops,
 				      &binder_transaction_log_failed);
-	if (IS_ERR(dentry))
+	if (IS_ERR(dentry)) {
 		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	proc_log_dir = binderfs_create_dir(binder_logs_root_dir, "proc");
+	if (IS_ERR(proc_log_dir)) {
+		ret = PTR_ERR(proc_log_dir);
+		goto out;
+	}
+	info = sb->s_fs_info;
+	info->proc_log_dir = proc_log_dir;
 
 out:
 	return ret;