um: hostfs: define our own API boundary

Instead of exporting the set of functions provided by
glibc that are needed for hostfs_user.c, just build that
into the kernel image whenever hostfs is built, and then
export _those_ functions cleanly, to be independent of
the libc implementation.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/os-Linux/user_syms.c

@@ -34,81 +34,11 @@ EXPORT_SYMBOL(memset);
 
 EXPORT_SYMBOL(printf);
 
-/* Here, instead, I can provide a fake prototype. Yes, someone cares: genksyms.
- * However, the modules will use the CRC defined *here*, no matter if it is
- * good; so the versions of these symbols will always match
- */
-#define EXPORT_SYMBOL_PROTO(sym)       \
-	int sym(void) __weak; \
-	EXPORT_SYMBOL(sym);
-
-extern void readdir64(void) __attribute__((weak));
-EXPORT_SYMBOL(readdir64);
-extern void truncate64(void) __attribute__((weak));
-EXPORT_SYMBOL(truncate64);
-
 #ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
 EXPORT_SYMBOL(vsyscall_ehdr);
 EXPORT_SYMBOL(vsyscall_end);
 #endif
 
-EXPORT_SYMBOL_PROTO(__errno_location);
-
-EXPORT_SYMBOL_PROTO(access);
-EXPORT_SYMBOL_PROTO(open);
-EXPORT_SYMBOL_PROTO(open64);
-EXPORT_SYMBOL_PROTO(close);
-EXPORT_SYMBOL_PROTO(read);
-EXPORT_SYMBOL_PROTO(write);
-EXPORT_SYMBOL_PROTO(dup2);
-EXPORT_SYMBOL_PROTO(__xstat);
-EXPORT_SYMBOL_PROTO(__lxstat);
-EXPORT_SYMBOL_PROTO(__lxstat64);
-EXPORT_SYMBOL_PROTO(__fxstat64);
-EXPORT_SYMBOL_PROTO(lseek);
-EXPORT_SYMBOL_PROTO(lseek64);
-EXPORT_SYMBOL_PROTO(chown);
-EXPORT_SYMBOL_PROTO(fchown);
-EXPORT_SYMBOL_PROTO(truncate);
-EXPORT_SYMBOL_PROTO(ftruncate64);
-EXPORT_SYMBOL_PROTO(utime);
-EXPORT_SYMBOL_PROTO(utimes);
-EXPORT_SYMBOL_PROTO(futimes);
-EXPORT_SYMBOL_PROTO(chmod);
-EXPORT_SYMBOL_PROTO(fchmod);
-EXPORT_SYMBOL_PROTO(rename);
-EXPORT_SYMBOL_PROTO(__xmknod);
-
-EXPORT_SYMBOL_PROTO(symlink);
-EXPORT_SYMBOL_PROTO(link);
-EXPORT_SYMBOL_PROTO(unlink);
-EXPORT_SYMBOL_PROTO(readlink);
-
-EXPORT_SYMBOL_PROTO(mkdir);
-EXPORT_SYMBOL_PROTO(rmdir);
-EXPORT_SYMBOL_PROTO(opendir);
-EXPORT_SYMBOL_PROTO(readdir);
-EXPORT_SYMBOL_PROTO(closedir);
-EXPORT_SYMBOL_PROTO(seekdir);
-EXPORT_SYMBOL_PROTO(telldir);
-
-EXPORT_SYMBOL_PROTO(ioctl);
-
-EXPORT_SYMBOL_PROTO(pread64);
-EXPORT_SYMBOL_PROTO(pwrite64);
-
-EXPORT_SYMBOL_PROTO(statfs);
-EXPORT_SYMBOL_PROTO(statfs64);
-
-EXPORT_SYMBOL_PROTO(getuid);
-
-EXPORT_SYMBOL_PROTO(fsync);
-EXPORT_SYMBOL_PROTO(fdatasync);
-
-EXPORT_SYMBOL_PROTO(lstat64);
-EXPORT_SYMBOL_PROTO(fstat64);
-EXPORT_SYMBOL_PROTO(mknod);
-
 /* Export symbols used by GCC for the stack protector. */
 extern void __stack_smash_handler(void *) __attribute__((weak));
 EXPORT_SYMBOL(__stack_smash_handler);

fs/Makefile

@@ -124,7 +124,7 @@ obj-$(CONFIG_9P_FS)		+= 9p/
 obj-$(CONFIG_AFS_FS)		+= afs/
 obj-$(CONFIG_NILFS2_FS)		+= nilfs2/
 obj-$(CONFIG_BEFS_FS)		+= befs/
-obj-$(CONFIG_HOSTFS)		+= hostfs/
+obj-y				+= hostfs/
 obj-$(CONFIG_CACHEFILES)	+= cachefiles/
 obj-$(CONFIG_DEBUG_FS)		+= debugfs/
 obj-$(CONFIG_TRACING)		+= tracefs/

fs/hostfs/Makefile

@@ -3,9 +3,11 @@
 # Licensed under the GPL
 #
 
-hostfs-objs := hostfs_kern.o hostfs_user.o
+hostfs-objs := hostfs_kern.o
 
-obj-y :=
+hostfs-builtin-$(CONFIG_HOSTFS) += hostfs_user.o hostfs_user_exp.o
+
+obj-y := $(hostfs-builtin-y) $(hostfs-builtin-m)
 obj-$(CONFIG_HOSTFS) += hostfs.o
 
 include $(srctree)/arch/um/scripts/Makefile.rules

fs/hostfs/hostfs_user_exp.c

+#include <linux/module.h>
+#include "hostfs.h"
+
+EXPORT_SYMBOL_GPL(stat_file);
+EXPORT_SYMBOL_GPL(access_file);
+EXPORT_SYMBOL_GPL(open_file);
+EXPORT_SYMBOL_GPL(open_dir);
+EXPORT_SYMBOL_GPL(seek_dir);
+EXPORT_SYMBOL_GPL(read_dir);
+EXPORT_SYMBOL_GPL(read_file);
+EXPORT_SYMBOL_GPL(write_file);
+EXPORT_SYMBOL_GPL(lseek_file);
+EXPORT_SYMBOL_GPL(fsync_file);
+EXPORT_SYMBOL_GPL(replace_file);
+EXPORT_SYMBOL_GPL(close_file);
+EXPORT_SYMBOL_GPL(close_dir);
+EXPORT_SYMBOL_GPL(file_create);
+EXPORT_SYMBOL_GPL(set_attr);
+EXPORT_SYMBOL_GPL(make_symlink);
+EXPORT_SYMBOL_GPL(unlink_file);
+EXPORT_SYMBOL_GPL(do_mkdir);
+EXPORT_SYMBOL_GPL(hostfs_do_rmdir);
+EXPORT_SYMBOL_GPL(do_mknod);
+EXPORT_SYMBOL_GPL(link_file);
+EXPORT_SYMBOL_GPL(hostfs_do_readlink);
+EXPORT_SYMBOL_GPL(rename_file);
+EXPORT_SYMBOL_GPL(rename2_file);
+EXPORT_SYMBOL_GPL(do_statfs);