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>

1 files changed, 44 insertions, 2 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index fe44236de2bd..c0a491277aca 100644
--- a/drivers/android/binder.c
+++ b/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;