linux-kernel - [RFC PATCH 24/35] syscalls: do not call sys

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Date:   Sun, 11 Mar 2018 11:55:46 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     linux-kernel@...r.kernel.org, luto@...nel.org,
        torvalds@...ux-foundation.org, mingo@...nel.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Subject: [RFC PATCH 24/35] syscalls: do not call sys_unlink() within the kernel

CC: Al Viro <viro@...iv.linux.org.uk>
CC: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
---
 include/linux/syscalls.h | 10 ++++++++++
 init/do_mounts.h         |  2 +-
 init/do_mounts_initrd.c  |  4 ++--
 init/do_mounts_rd.c      |  2 +-
 init/initramfs.c         |  4 ++--
 5 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 5b17c3c64a52..452be95ab9ca 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -963,4 +963,14 @@ int ksys_chdir(const char __user *filename);
 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 			 unsigned int flags);
 
+/*
+ * The following kernel syscall equivalents are just wrappers to fs-internal
+ * functions. Therefore, provide stubs to be inlined at the callsites.
+ */
+extern long do_unlinkat(int dfd, struct filename *name);
+static inline long ksys_unlink(const char __user *pathname)
+{
+	return do_unlinkat(AT_FDCWD, getname(pathname));
+}
+
 #endif
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 5b05c8f93f47..401f90ee1eeb 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -16,7 +16,7 @@ extern int root_mountflags;
 
 static inline int create_dev(char *name, dev_t dev)
 {
-	sys_unlink(name);
+	ksys_unlink(name);
 	return sys_mknod(name, S_IFBLK|0600, new_encode_dev(dev));
 }
 
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index c19d9070134e..784576b633fd 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -128,11 +128,11 @@ bool __init initrd_load(void)
 		 * mounted in the normal path.
 		 */
 		if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
-			sys_unlink("/initrd.image");
+			ksys_unlink("/initrd.image");
 			handle_initrd();
 			return true;
 		}
 	}
-	sys_unlink("/initrd.image");
+	ksys_unlink("/initrd.image");
 	return false;
 }
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 2d365c398ccc..5b69056f610a 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -288,7 +288,7 @@ int __init rd_load_image(char *from)
 	sys_close(out_fd);
 out:
 	kfree(buf);
-	sys_unlink("/dev/ram");
+	ksys_unlink("/dev/ram");
 	return res;
 }
 
diff --git a/init/initramfs.c b/init/initramfs.c
index 6f972df15bf2..08eb551168a8 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -319,7 +319,7 @@ static void __init clean_path(char *path, umode_t fmode)
 		if (S_ISDIR(st.mode))
 			sys_rmdir(path);
 		else
-			sys_unlink(path);
+			ksys_unlink(path);
 	}
 }
 
@@ -591,7 +591,7 @@ static void __init clean_rootfs(void)
 				if (S_ISDIR(st.mode))
 					sys_rmdir(dirp->d_name);
 				else
-					sys_unlink(dirp->d_name);
+					ksys_unlink(dirp->d_name);
 			}
 
 			num -= dirp->d_reclen;
-- 
2.16.2