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

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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: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-13 21:56:26 +01:00
parent 76847e4344
commit 3ce4a7bf66
5 changed files with 14 additions and 8 deletions
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2
arch/s390/kernel/compat_linux.c
View File

@ -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)

7
fs/read_write.c
View File

@ -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);

1
include/linux/syscalls.h
View File

@ -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

2
init/do_mounts.c
View File

@ -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);

10
init/do_mounts_rd.c
View File

@ -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)