UBUNTU: SAUCE: binder: turn into module

The Android binder driver needs to become a module for the sake of shipping
Anbox. To do this we need to export the following functions since binder is
currently still using them:

- security_binder_set_context_mgr()
- security_binder_transaction()
- security_binder_transfer_binder()
- security_binder_transfer_file()
- can_nice()
- __close_fd_get_file()
- mmput_async()
- task_work_add()
- map_kernel_range_noflush()
- get_vm_area()
- zap_page_range()
- put_ipc_ns()
- get_ipc_ns_exported()
- show_init_ipc_ns()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
[ saf: fix additional reference to init_ipc_ns from 5.0-rc6 ]
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

drivers/android/Kconfig

@@ -9,7 +9,7 @@ config ANDROID
 if ANDROID
 
 config ANDROID_BINDER_IPC
-	bool "Android Binder IPC Driver"
+	tristate "Android Binder IPC Driver"
 	depends on MMU
 	default n
 	---help---
@@ -21,8 +21,8 @@ config ANDROID_BINDER_IPC
 	  between said processes.
 
 config ANDROID_BINDERFS
-	bool "Android Binderfs filesystem"
-	depends on ANDROID_BINDER_IPC
+	tristate "Android Binderfs filesystem"
+	depends on (ANDROID_BINDER_IPC=y) || (ANDROID_BINDER_IPC=m && m)
 	default n
 	---help---
 	  Binderfs is a pseudo-filesystem for the Android Binder IPC driver

drivers/android/Makefile

@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only
 ccflags-y += -I$(src)			# needed for trace events
 
-obj-$(CONFIG_ANDROID_BINDERFS)		+= binderfs.o
-obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o binder_alloc.o
-obj-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o
+binder_linux-y := binder.o binder_alloc.o
+obj-$(CONFIG_ANDROID_BINDER_IPC) += binder_linux.o
+binder_linux-$(CONFIG_ANDROID_BINDERFS) += binderfs.o
+binder_linux-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o
+
+# binder-$(CONFIG_ANDROID_BINDER_IPC) := binder.o binder_alloc.o
+# binder-$(CONFIG_ANDROID_BINDERFS) += binderfs.o

drivers/android/binder.c

@@ -6182,9 +6182,20 @@ err_alloc_device_names_failed:
 	return ret;
 }
 
-device_initcall(binder_init);
+module_init(binder_init);
+/*
+ * binder will have no exit function since binderfs instances can be mounted
+ * multiple times and also in user namespaces finding and destroying them all
+ * is not feasible without introducing insane locking. Just ignoring existing
+ * instances on module unload also wouldn't work since we would loose track of
+ * what major numer was dynamically allocated and also what minor numbers are
+ * already given out. So this would get us into all kinds of issues with device
+ * number reuse. So simply don't allow unloading unless we are forced to do so.
+ */
+
+MODULE_AUTHOR("Google, Inc.");
+MODULE_DESCRIPTION("Driver for Android binder device");
+MODULE_LICENSE("GPL v2");
 
 #define CREATE_TRACE_POINTS
 #include "binder_trace.h"
-
-MODULE_LICENSE("GPL v2");

drivers/android/binder_alloc.h

@@ -6,6 +6,7 @@
 #ifndef _LINUX_BINDER_ALLOC_H
 #define _LINUX_BINDER_ALLOC_H
 
+#include <linux/kconfig.h>
 #include <linux/rbtree.h>
 #include <linux/list.h>
 #include <linux/mm.h>
@@ -105,7 +106,7 @@ struct binder_alloc {
 	size_t pages_high;
 };
 
-#ifdef CONFIG_ANDROID_BINDER_IPC_SELFTEST
+#if IS_ENABLED(CONFIG_ANDROID_BINDER_IPC_SELFTEST)
 void binder_selftest_alloc(struct binder_alloc *alloc);
 #else
 static inline void binder_selftest_alloc(struct binder_alloc *alloc) {}

drivers/android/binder_internal.h

@@ -5,6 +5,7 @@
 
 #include <linux/export.h>
 #include <linux/fs.h>
+#include <linux/kconfig.h>
 #include <linux/list.h>
 #include <linux/miscdevice.h>
 #include <linux/mutex.h>
@@ -73,7 +74,7 @@ extern const struct file_operations binder_fops;
 
 extern char *binder_devices_param;
 
-#ifdef CONFIG_ANDROID_BINDERFS
+#if IS_ENABLED(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,
@@ -94,7 +95,7 @@ static inline struct dentry *binderfs_create_file(struct dentry *dir,
 static inline void binderfs_remove_file(struct dentry *dentry) {}
 #endif
 
-#ifdef CONFIG_ANDROID_BINDERFS
+#if IS_ENABLED(CONFIG_ANDROID_BINDERFS)
 extern int __init init_binderfs(void);
 #else
 static inline int __init init_binderfs(void)

drivers/android/binderfs.c

@@ -109,7 +109,7 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	struct super_block *sb = ref_inode->i_sb;
 	struct binderfs_info *info = sb->s_fs_info;
 #if defined(CONFIG_IPC_NS)
-	bool use_reserve = (info->ipc_ns == &init_ipc_ns);
+	bool use_reserve = (info->ipc_ns == show_init_ipc_ns());
 #else
 	bool use_reserve = true;
 #endif
@@ -405,7 +405,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	struct dentry *root = sb->s_root;
 	struct binderfs_info *info = sb->s_fs_info;
 #if defined(CONFIG_IPC_NS)
-	bool use_reserve = (info->ipc_ns == &init_ipc_ns);
+	bool use_reserve = (info->ipc_ns == show_init_ipc_ns());
 #else
 	bool use_reserve = true;
 #endif
@@ -683,7 +683,7 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
 		return -ENOMEM;
 	info = sb->s_fs_info;
 
-	info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
+	info->ipc_ns = get_ipc_ns_exported(current->nsproxy->ipc_ns);
 
 	ret = binderfs_parse_mount_opts(data, &info->mount_opts);
 	if (ret)

fs/file.c

@@ -669,6 +669,7 @@ out_unlock:
 	*res = NULL;
 	return -ENOENT;
 }
+EXPORT_SYMBOL(__close_fd_get_file);
 
 void do_close_on_exec(struct files_struct *files)
 {

include/linux/ipc_namespace.h

@@ -119,6 +119,9 @@ extern int mq_init_ns(struct ipc_namespace *ns);
 static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
 #endif
 
+extern struct ipc_namespace *get_ipc_ns_exported(struct ipc_namespace *ns);
+extern struct ipc_namespace *show_init_ipc_ns(void);
+
 #if defined(CONFIG_IPC_NS)
 extern struct ipc_namespace *copy_ipcs(unsigned long flags,
 	struct user_namespace *user_ns, struct ipc_namespace *ns);

ipc/namespace.c

@@ -152,6 +152,23 @@ void put_ipc_ns(struct ipc_namespace *ns)
 		free_ipc_ns(ns);
 	}
 }
+EXPORT_SYMBOL(put_ipc_ns);
+
+struct ipc_namespace *get_ipc_ns_exported(struct ipc_namespace *ns)
+{
+	return get_ipc_ns(ns);
+}
+EXPORT_SYMBOL(get_ipc_ns_exported);
+
+struct ipc_namespace *show_init_ipc_ns(void)
+{
+#if defined(CONFIG_IPC_NS)
+	return &init_ipc_ns;
+#else
+	return NULL;
+#endif
+}
+EXPORT_SYMBOL(show_init_ipc_ns);
 
 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 {

kernel/fork.c

@@ -1122,6 +1122,7 @@ void mmput_async(struct mm_struct *mm)
 		schedule_work(&mm->async_put_work);
 	}
 }
+EXPORT_SYMBOL(mmput_async);
 #endif
 
 /**

kernel/sched/core.c

@@ -4559,6 +4559,7 @@ int can_nice(const struct task_struct *p, const int nice)
 	return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
 		capable(CAP_SYS_NICE));
 }
+EXPORT_SYMBOL(can_nice);
 
 #ifdef __ARCH_WANT_SYS_NICE
 

kernel/task_work.c

@@ -40,6 +40,7 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
 		set_notify_resume(task);
 	return 0;
 }
+EXPORT_SYMBOL(task_work_add);
 
 /**
  * task_work_cancel - cancel a pending work added by task_work_add()

mm/memory.c

@@ -1340,6 +1340,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
 	mmu_notifier_invalidate_range_end(&range);
 	tlb_finish_mmu(&tlb, start, range.end);
 }
+EXPORT_SYMBOL(zap_page_range);
 
 /**
  * zap_page_range_single - remove user pages in a given range

mm/vmalloc.c

@@ -1963,6 +1963,7 @@ int map_kernel_range_noflush(unsigned long addr, unsigned long size,
 {
 	return vmap_page_range_noflush(addr, addr + size, prot, pages);
 }
+EXPORT_SYMBOL(map_kernel_range_noflush);
 
 /**
  * unmap_kernel_range_noflush - unmap kernel VM area
@@ -2104,6 +2105,7 @@ struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
 				  NUMA_NO_NODE, GFP_KERNEL,
 				  __builtin_return_address(0));
 }
+EXPORT_SYMBOL(get_vm_area);
 
 struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
 				const void *caller)

security/security.c

@@ -674,24 +674,28 @@ int security_binder_set_context_mgr(struct task_struct *mgr)
 {
 	return call_int_hook(binder_set_context_mgr, 0, mgr);
 }
+EXPORT_SYMBOL(security_binder_set_context_mgr);
 
 int security_binder_transaction(struct task_struct *from,
 				struct task_struct *to)
 {
 	return call_int_hook(binder_transaction, 0, from, to);
 }
+EXPORT_SYMBOL(security_binder_transaction);
 
 int security_binder_transfer_binder(struct task_struct *from,
 				    struct task_struct *to)
 {
 	return call_int_hook(binder_transfer_binder, 0, from, to);
 }
+EXPORT_SYMBOL(security_binder_transfer_binder);
 
 int security_binder_transfer_file(struct task_struct *from,
 				  struct task_struct *to, struct file *file)
 {
 	return call_int_hook(binder_transfer_file, 0, from, to, file);
 }
+EXPORT_SYMBOL(security_binder_transfer_file);
 
 int security_ptrace_access_check(struct task_struct *child, unsigned int mode)
 {