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fs: add ksys_write() helper; remove in-kernel calls to sys_write()

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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>
This commit is contained in:
Dominik Brodowski 2018-03-11 11:34:41 +01:00
parent a16fe33ab5
commit e7a3e8b2ed
5 changed files with 12 additions and 6 deletions
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2
arch/s390/kernel/compat_linux.c
View file

@ -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);
}
/*

9
fs/read_write.c
View file

@ -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)
{

1
include/linux/syscalls.h
View file

@ -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

4
init/do_mounts_rd.c
View file

@ -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

2
init/initramfs.c
View file

@ -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)