lkml.org 
[lkml]   [2018]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 070/109] fs: add ksys_write() helper; remove in-kernel calls to sys_write()
Date
Using this helper allows us to avoid the in-kernel calls to the sys_write()
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_write().

In the near future, the do_mounts / initramfs callers of ksys_write()
should be converted to use filp_open() and vfs_write() instead.

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>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---
arch/s390/kernel/compat_linux.c | 2 +-
fs/read_write.c | 9 +++++++--
include/linux/syscalls.h | 1 +
init/do_mounts_rd.c | 4 ++--
init/initramfs.c | 2 +-
5 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index 79b7a3438d54..5a9cfde5fc28 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -468,7 +468,7 @@ COMPAT_SYSCALL_DEFINE3(s390_write, unsigned int, fd, const char __user *, buf, c
if ((compat_ssize_t) count < 0)
return -EINVAL;

- return sys_write(fd, buf, count);
+ return ksys_write(fd, buf, count);
}

/*
diff --git a/fs/read_write.c b/fs/read_write.c
index f8547b82dfb3..8e8f0b4f52e2 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -578,8 +578,7 @@ SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)
return ret;
}

-SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
- size_t, count)
+ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count)
{
struct fd f = fdget_pos(fd);
ssize_t ret = -EBADF;
@@ -595,6 +594,12 @@ SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
return ret;
}

+SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
+ size_t, count)
+{
+ return ksys_write(fd, buf, count);
+}
+
SYSCALL_DEFINE4(pread64, unsigned int, fd, char __user *, buf,
size_t, count, loff_t, pos)
{
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 920a0db1871d..80524faa9664 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -951,5 +951,6 @@ int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
int ksys_umount(char __user *name, int flags);
int ksys_dup(unsigned int fildes);
int ksys_chroot(const char __user *filename);
+ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);

#endif
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 99e0b649fc0e..2d365c398ccc 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -270,7 +270,7 @@ int __init rd_load_image(char *from)
printk("Loading disk #%d... ", disk);
}
sys_read(in_fd, buf, BLOCK_SIZE);
- sys_write(out_fd, buf, BLOCK_SIZE);
+ ksys_write(out_fd, buf, BLOCK_SIZE);
#if !defined(CONFIG_S390)
if (!(i % 16)) {
pr_cont("%c\b", rotator[rotate & 0x3]);
@@ -317,7 +317,7 @@ static long __init compr_fill(void *buf, unsigned long len)

static long __init compr_flush(void *window, unsigned long outcnt)
{
- long written = sys_write(crd_outfd, window, outcnt);
+ long written = ksys_write(crd_outfd, window, outcnt);
if (written != outcnt) {
if (decompress_error == 0)
printk(KERN_ERR
diff --git a/init/initramfs.c b/init/initramfs.c
index 7e99a0038942..6f972df15bf2 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -27,7 +27,7 @@ static ssize_t __init xwrite(int fd, const char *p, size_t count)

/* sys_write only can write MAX_RW_COUNT aka 2G-4K bytes at most */
while (count) {
- ssize_t rv = sys_write(fd, p, count);
+ ssize_t rv = ksys_write(fd, p, count);

if (rv < 0) {
if (rv == -EINTR || rv == -EAGAIN)
--
2.16.3
\
 
 \ /
  Last update: 2018-03-29 13:55    [W:0.396 / U:1.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site