Commit 3ce4a7bf authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

fs: add ksys_read() helper; remove in-kernel calls to sys_read() 

Using this helper allows us to avoid the in-kernel calls to the
sys_read() 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_read().

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 76847e43

arch/s390/kernel/compat_linux.c

+1 −1
Original line number Diff line number Diff line
@@ -460,7 +460,7 @@ COMPAT_SYSCALL_DEFINE3(s390_read, unsigned int, fd, char __user *, buf, compat_s 
	if ((compat_ssize_t) count < 0)

		return -EINVAL; 



	return sys_read(fd, buf, count);

	return ksys_read(fd, buf, count);

}



COMPAT_SYSCALL_DEFINE3(s390_write, unsigned int, fd, const char __user *, buf, compat_size_t, count)

fs/read_write.c

+6 −1
Original line number Diff line number Diff line
@@ -568,7 +568,7 @@ static inline void file_pos_write(struct file *file, loff_t pos) 
	file->f_pos = pos;

}



SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)

ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count)

{

	struct fd f = fdget_pos(fd);

	ssize_t ret = -EBADF;
@@ -583,6 +583,11 @@ SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count) 
	return ret;

}



SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)

{

	return ksys_read(fd, buf, count);

}



ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count)

{

	struct fd f = fdget_pos(fd);

include/linux/syscalls.h

+1 −0
Original line number Diff line number Diff line
@@ -959,6 +959,7 @@ int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent, 
		    unsigned int count);

int ksys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg);

off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence);

ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count);



/*

 * The following kernel syscall equivalents are just wrappers to fs-internal

init/do_mounts.c

+1 −1
Original line number Diff line number Diff line
@@ -500,7 +500,7 @@ void __init change_floppy(char *fmt, ...) 
		ksys_ioctl(fd, TCGETS, (long)&termios);

		termios.c_lflag &= ~ICANON;

		ksys_ioctl(fd, TCSETSF, (long)&termios);

		sys_read(fd, &c, 1);

		ksys_read(fd, &c, 1);

		termios.c_lflag |= ICANON;

		ksys_ioctl(fd, TCSETSF, (long)&termios);

		ksys_close(fd);

init/do_mounts_rd.c

+5 −5
Original line number Diff line number Diff line
@@ -91,7 +91,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) 
	 * Read block 0 to test for compressed kernel

	 */

	ksys_lseek(fd, start_block * BLOCK_SIZE, 0);

	sys_read(fd, buf, size);

	ksys_read(fd, buf, size);



	*decompressor = decompress_method(buf, size, &compress_name);

	if (compress_name) {
@@ -137,7 +137,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) 
	 * Read 512 bytes further to check if cramfs is padded

	 */

	ksys_lseek(fd, start_block * BLOCK_SIZE + 0x200, 0);

	sys_read(fd, buf, size);

	ksys_read(fd, buf, size);



	if (cramfsb->magic == CRAMFS_MAGIC) {

		printk(KERN_NOTICE
@@ -151,7 +151,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) 
	 * Read block 1 to test for minix and ext2 superblock

	 */

	ksys_lseek(fd, (start_block+1) * BLOCK_SIZE, 0);

	sys_read(fd, buf, size);

	ksys_read(fd, buf, size);



	/* Try minix */

	if (minixsb->s_magic == MINIX_SUPER_MAGIC ||
@@ -269,7 +269,7 @@ int __init rd_load_image(char *from) 
			}

			printk("Loading disk #%d... ", disk);

		}

		sys_read(in_fd, buf, BLOCK_SIZE);

		ksys_read(in_fd, buf, BLOCK_SIZE);

		ksys_write(out_fd, buf, BLOCK_SIZE);

#if !defined(CONFIG_S390)

		if (!(i % 16)) {
@@ -307,7 +307,7 @@ static int crd_infd, crd_outfd; 


static long __init compr_fill(void *buf, unsigned long len)

{

	long r = sys_read(crd_infd, buf, len);

	long r = ksys_read(crd_infd, buf, len);

	if (r < 0)

		printk(KERN_ERR "RAMDISK: error while reading compressed data");

	else if (r == 0)

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