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Subject[PATCH 072/109] fs: add ksys_unlink() wrapper; remove in-kernel calls to sys_unlink()
Date
Using this wrapper allows us to avoid the in-kernel calls to the
sys_unlink() syscall. The ksys_ prefix denotes that this function is meant
s a drop-in replacement for the syscall. In particular, it uses the same
calling convention as sys_unlink().

In the near future, all callers of ksys_unlink() should be converted to
call do_unlinkat() directly or, at least, to operate on regular kernel
pointers.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---
include/linux/syscalls.h | 11 +++++++++++
init/do_mounts.h | 2 +-
init/do_mounts_initrd.c | 4 ++--
init/do_mounts_rd.c | 2 +-
init/initramfs.c | 4 ++--
5 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 090645b48447..7cbfb41e666b 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -954,4 +954,15 @@ int ksys_chroot(const char __user *filename);
ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
int ksys_chdir(const char __user *filename);

+/*
+ * 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 83f396d30b9a..e9e9e1c67d31 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;
--
2.16.3
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