Re: [PATCH 4/4] binder: Add binder_proc logging to binderfs

[Hridya Valsaraju]

On Wed, Aug 28, 2019 at 9:21 AM Todd Kjos <tkjos@xxxxxxxxxx> wrote:
>
> On Wed, Aug 28, 2019 at 6:08 AM Christian Brauner
> <christian.brauner@xxxxxxxxxx> wrote:
> >
> > On Tue, Aug 27, 2019 at 01:41:52PM -0700, Hridya Valsaraju wrote:
> > > 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.
> > >
> > > Signed-off-by: Hridya Valsaraju <hridya@xxxxxxxxxx>
> >
> > I'm still wondering whether there's a nicer way to create those debuf
> > files per-process without doing it in binder_open() but it has worked
> > fine for a long time with debugfs.
> >
> > Also, one minor question below. Otherwise
> >
> > Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
>
> Acked-by: Todd Kjos <tkjos@xxxxxxxxxx>
>
> >
> > > ---
> > >  drivers/android/binder.c          | 38 ++++++++++++++++++-
> > >  drivers/android/binder_internal.h | 46 ++++++++++++++++++++++
> > >  drivers/android/binderfs.c        | 63 ++++++++++++++-----------------
> > >  3 files changed, 111 insertions(+), 36 deletions(-)
> > >
> > > diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> > > index bed217310197..37189838f32a 100644
> > > --- a/drivers/android/binder.c
> > > +++ b/drivers/android/binder.c
> > > @@ -481,6 +481,7 @@ struct binder_priority {
> > >   * @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
> > >   */
> > > @@ -510,6 +511,7 @@ struct binder_proc {
> > >       struct binder_context *context;
> > >       spinlock_t inner_lock;
> > >       spinlock_t outer_lock;
> > > +     struct dentry *binderfs_entry;
> > >  };
> > >
> > >  enum {
> > > @@ -5347,6 +5349,8 @@ 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);
> > > @@ -5368,11 +5372,14 @@ static int binder_open(struct inode *nodp, struct file *filp)
> > >       }
> > >
> > >       /* 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);
> > >
> > > @@ -5403,6 +5410,27 @@ 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 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;
> >
> > You are sure that you don't want to fail the open, when the debug file
> > cannot be created in the binderfs instance? I'm not objecting at all, I
> > just want to make sure that this is the semantics you want because it
> > would be easy to differentiate between the non-fail-debugfs and the new
> > binderfs case.
>
> I don't think we should fail the open, but it would be nice to have
> some indication that it failed -- maybe a pr_warn() ?

Thanks for taking a look Christian and Todd! The reason I do not fail
binder_open() on an error here is because once the file has been
created for a process, if the same process invokes binder_open() again
from a different context, the binderfs_create_file() call would fail
with the EEXIST error code. This is expected behaviour since the log
file is shared between all contexts of a process(same as the behaviour
of the file in debugfs today). I can add a pr_warn() statement in v2
as Todd suggested so that the failure would be logged.

> >
> > > +
> > > +     }
> > > +
> > >       return 0;
> > >  }
> > >
> > > @@ -5442,6 +5470,12 @@ 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;
> > > diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
> > > index b9be42d9464c..bd47f7f72075 100644
> > > --- a/drivers/android/binder_internal.h
> > > +++ b/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
> > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
> > > index dc25a7d759c9..c386a3738290 100644
> > > --- a/drivers/android/binderfs.c
> > > +++ b/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;
> > > @@ -535,7 +504,22 @@ static struct dentry *binderfs_create_dentry(struct dentry *dir,
> > >       return dentry;
> > >  }
> > >
> > > -static struct dentry *binderfs_create_file(struct dentry *dir, const char *name,
> > > +void binderfs_remove_file(struct dentry *dentry)
> > > +{
> > > +     struct inode *dir;
> > > +
> > > +     dir = d_inode(dentry->d_parent);
> > > +     inode_lock(dir);
> > > +     if (simple_positive(dentry)) {
> > > +             dget(dentry);
> > > +             simple_unlink(dir, dentry);
> > > +             d_delete(dentry);
> > > +             dput(dentry);
> > > +     }
> > > +     inode_unlock(dir);
> > > +}
> > > +
> > > +struct dentry *binderfs_create_file(struct dentry *dir, const char *name,
> > >                                   const struct file_operations *fops,
> > >                                   void *data)
> > >  {
> > > @@ -604,7 +588,8 @@ static struct dentry *binderfs_create_dir(struct dentry *parent,
> > >
> > >  static int init_binder_logs(struct super_block *sb)
> > >  {
> > > -     struct dentry *binder_logs_root_dir, *file_dentry;
> > > +     struct dentry *binder_logs_root_dir, *file_dentry, *proc_log_dir;
> > > +     struct binderfs_info *info;
> > >       int ret = 0;
> > >
> > >       binder_logs_root_dir = binderfs_create_dir(sb->s_root,
> > > @@ -648,8 +633,18 @@ static int init_binder_logs(struct super_block *sb)
> > >                                          "failed_transaction_log",
> > >                                          &binder_transaction_log_fops,
> > >                                          &binder_transaction_log_failed);
> > > -     if (IS_ERR(file_dentry))
> > > +     if (IS_ERR(file_dentry)) {
> > >               ret = PTR_ERR(file_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;
> > > --
> > > 2.23.0.187.g17f5b7556c-goog
> > >
> >
> > --
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> >