Using this helper allows us to avoid the in-kernel calls to the sys_lseek() 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_lseek().
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> Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net> --- fs/read_write.c | 9 +++++++-- include/linux/syscalls.h | 1 + init/do_mounts_rd.c | 8 ++++---- 3 files changed, 12 insertions(+), 6 deletions(-) diff --git a/fs/read_write.c b/fs/read_write.c index 8e8f0b4f52e2..b38b008a078e 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -301,7 +301,7 @@ loff_t vfs_llseek(struct file *file, loff_t offset, int whence) } EXPORT_SYMBOL(vfs_llseek); -SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence) +off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence) { off_t retval; struct fd f = fdget_pos(fd); @@ -319,10 +319,15 @@ SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence) return retval; } +SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence) +{ + return ksys_lseek(fd, offset, whence); +} + #ifdef CONFIG_COMPAT COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence) { - return sys_lseek(fd, offset, whence); + return ksys_lseek(fd, offset, whence); } #endif diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 5a959efd8fb7..0f24e5334569 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -958,6 +958,7 @@ int ksys_fchown(unsigned int fd, uid_t user, gid_t group); 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); /* * The following kernel syscall equivalents are just wrappers to fs-internal diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c index 4dafaed5736f..13e54148c0e0 100644 --- a/init/do_mounts_rd.c +++ b/init/do_mounts_rd.c @@ -90,7 +90,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) /* * Read block 0 to test for compressed kernel */ - sys_lseek(fd, start_block * BLOCK_SIZE, 0); + ksys_lseek(fd, start_block * BLOCK_SIZE, 0); sys_read(fd, buf, size); *decompressor = decompress_method(buf, size, &compress_name); @@ -136,7 +136,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) /* * Read 512 bytes further to check if cramfs is padded */ - sys_lseek(fd, start_block * BLOCK_SIZE + 0x200, 0); + ksys_lseek(fd, start_block * BLOCK_SIZE + 0x200, 0); sys_read(fd, buf, size); if (cramfsb->magic == CRAMFS_MAGIC) { @@ -150,7 +150,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) /* * Read block 1 to test for minix and ext2 superblock */ - sys_lseek(fd, (start_block+1) * BLOCK_SIZE, 0); + ksys_lseek(fd, (start_block+1) * BLOCK_SIZE, 0); sys_read(fd, buf, size); /* Try minix */ @@ -178,7 +178,7 @@ identify_ramdisk_image(int fd, int start_block, decompress_fn *decompressor) start_block); done: - sys_lseek(fd, start_block * BLOCK_SIZE, 0); + ksys_lseek(fd, start_block * BLOCK_SIZE, 0); kfree(buf); return nblocks; } -- 2.16.3
