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Subject[PATCH 085/109] fs: add ksys_getdents64() helper; remove in-kernel calls to sys_getdents64()
Date
Using this helper allows us to avoid the in-kernel calls to the
sys_getdents64() syscall. The ksys_ prefix denotes that this function
is meant as a drop-in replacement for the syscall. In particular, it
uses the same calling convention as sys_getdents64().

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: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---
fs/readdir.c | 11 +++++++++--
include/linux/syscalls.h | 2 ++
init/initramfs.c | 4 ++--
3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/fs/readdir.c b/fs/readdir.c
index 1b83b0ad183b..d97f548e6323 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -292,8 +292,8 @@ static int filldir64(struct dir_context *ctx, const char *name, int namlen,
return -EFAULT;
}

-SYSCALL_DEFINE3(getdents64, unsigned int, fd,
- struct linux_dirent64 __user *, dirent, unsigned int, count)
+int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent,
+ unsigned int count)
{
struct fd f;
struct linux_dirent64 __user * lastdirent;
@@ -326,6 +326,13 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd,
return error;
}

+
+SYSCALL_DEFINE3(getdents64, unsigned int, fd,
+ struct linux_dirent64 __user *, dirent, unsigned int, count)
+{
+ return ksys_getdents64(fd, dirent, count);
+}
+
#ifdef CONFIG_COMPAT
struct compat_old_linux_dirent {
compat_ulong_t d_ino;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index f9df17dcec1c..c056aff6d7ad 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -955,6 +955,8 @@ ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
int ksys_chdir(const char __user *filename);
int ksys_fchmod(unsigned int fd, umode_t mode);
int ksys_fchown(unsigned int fd, uid_t user, gid_t group);
+int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent,
+ unsigned int count);

/*
* The following kernel syscall equivalents are just wrappers to fs-internal
diff --git a/init/initramfs.c b/init/initramfs.c
index 5f2ff1d2370e..13643c46ebab 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -579,7 +579,7 @@ static void __init clean_rootfs(void)
}

dirp = buf;
- num = sys_getdents64(fd, dirp, BUF_SIZE);
+ num = ksys_getdents64(fd, dirp, BUF_SIZE);
while (num > 0) {
while (num > 0) {
struct kstat st;
@@ -599,7 +599,7 @@ static void __init clean_rootfs(void)
}
dirp = buf;
memset(buf, 0, BUF_SIZE);
- num = sys_getdents64(fd, dirp, BUF_SIZE);
+ num = ksys_getdents64(fd, dirp, BUF_SIZE);
}

ksys_close(fd);
--
2.16.3
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