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.ga17...@light.dominikbrodowski.net Cc: Alexander Viro <v...@zeniv.linux.org.uk> Cc: linux-s...@vger.kernel.org Signed-off-by: Dominik Brodowski <li...@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
