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Subject[RESEND PATCH v3 1/2] binder: Add default binder devices through binderfs when configured
Date
From: Hridya Valsaraju <hridya@google.com>

Currently, since each binderfs instance needs its own
private binder devices, every time a binderfs instance is
mounted, all the default binder devices need to be created
via the BINDER_CTL_ADD IOCTL. This patch aims to
add a solution to automatically create the default binder
devices for each binderfs instance that gets mounted.
To achieve this goal, when CONFIG_ANDROID_BINDERFS is set,
the default binder devices specified by CONFIG_ANDROID_BINDER_DEVICES
are created in each binderfs instance instead of global devices
being created by the binder driver.

Co-developed-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20190808222727.132744-2-hridya@google.com
---
drivers/android/binder.c | 5 +++--
drivers/android/binder_internal.h | 2 ++
drivers/android/binderfs.c | 23 ++++++++++++++++++++---
3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index dc1c83eafc22..ef2d3e582368 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -122,7 +122,7 @@ static uint32_t binder_debug_mask = BINDER_DEBUG_USER_ERROR |
BINDER_DEBUG_FAILED_TRANSACTION | BINDER_DEBUG_DEAD_TRANSACTION;
module_param_named(debug_mask, binder_debug_mask, uint, 0644);

-static char *binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
+char *binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
module_param_named(devices, binder_devices_param, charp, 0444);

static DECLARE_WAIT_QUEUE_HEAD(binder_user_error_wait);
@@ -6131,7 +6131,8 @@ static int __init binder_init(void)
&transaction_log_fops);
}

- if (strcmp(binder_devices_param, "") != 0) {
+ if (!IS_ENABLED(CONFIG_ANDROID_BINDERFS) &&
+ strcmp(binder_devices_param, "") != 0) {
/*
* Copy the module_parameter string, because we don't want to
* tokenize it in-place.
diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
index 045b3e42d98b..fe8c745dc8e0 100644
--- a/drivers/android/binder_internal.h
+++ b/drivers/android/binder_internal.h
@@ -37,6 +37,8 @@ struct binder_device {

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);
#else
diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index e773f45d19d9..aee46dd1be91 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -186,8 +186,7 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
req->major = MAJOR(binderfs_dev);
req->minor = minor;

- ret = copy_to_user(userp, req, sizeof(*req));
- if (ret) {
+ if (userp && copy_to_user(userp, req, sizeof(*req))) {
ret = -EFAULT;
goto err;
}
@@ -467,6 +466,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
int ret;
struct binderfs_info *info;
struct inode *inode = NULL;
+ struct binderfs_device device_info = { 0 };
+ const char *name;
+ size_t len;

sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
@@ -521,7 +523,22 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
if (!sb->s_root)
return -ENOMEM;

- return binderfs_binder_ctl_create(sb);
+ ret = binderfs_binder_ctl_create(sb);
+ if (ret)
+ return ret;
+
+ name = binder_devices_param;
+ for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
+ strscpy(device_info.name, name, len + 1);
+ ret = binderfs_binder_device_create(inode, NULL, &device_info);
+ if (ret)
+ return ret;
+ name += len;
+ if (*name == ',')
+ name++;
+ }
+
+ return 0;
}

static struct dentry *binderfs_mount(struct file_system_type *fs_type,
--
2.23.0
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