Commit e7a3e8b2 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent a16fe33a

arch/s390/kernel/compat_linux.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}



/*

fs/read_write.c

+7 −2
Original line number Diff line number Diff line
@@ -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)

{

include/linux/syscalls.h

+1 −0
Original line number Diff line number Diff line
@@ -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

init/do_mounts_rd.c

+2 −2
Original line number Diff line number Diff line
@@ -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

init/initramfs.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

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