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fs: add ksys_dup{,3}() helper; remove in-kernel calls to sys_dup{,3}()
Using ksys_dup() and ksys_dup3() as helper functions allows us to avoid the in-kernel calls to the sys_dup() and sys_dup3() syscalls. The ksys_ prefix denotes that these functions are meant as a drop-in replacement for the syscalls. In particular, they use the same calling convention as sys_dup{,3}(). In the near future, the fs-external callers of ksys_dup{,3}() should be converted to call do_dup2() directly. Then, ksys_dup{,3}() can be moved within sys_dup{,3}() again. 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>
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commit
c7248321a3
16
fs/file.c
16
fs/file.c
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@ -870,7 +870,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
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return err;
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}
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SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
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static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
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{
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int err = -EBADF;
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struct file *file;
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@ -904,6 +904,11 @@ SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
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return err;
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}
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SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
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{
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return ksys_dup3(oldfd, newfd, flags);
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}
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SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
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{
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if (unlikely(newfd == oldfd)) { /* corner case */
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@ -916,10 +921,10 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
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rcu_read_unlock();
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return retval;
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}
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return sys_dup3(oldfd, newfd, 0);
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return ksys_dup3(oldfd, newfd, 0);
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}
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SYSCALL_DEFINE1(dup, unsigned int, fildes)
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int ksys_dup(unsigned int fildes)
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{
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int ret = -EBADF;
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struct file *file = fget_raw(fildes);
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@ -934,6 +939,11 @@ SYSCALL_DEFINE1(dup, unsigned int, fildes)
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return ret;
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}
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SYSCALL_DEFINE1(dup, unsigned int, fildes)
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{
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return ksys_dup(fildes);
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}
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int f_dupfd(unsigned int from, struct file *file, unsigned flags)
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{
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int err;
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@ -949,5 +949,6 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
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int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
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unsigned long flags, void __user *data);
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int ksys_umount(char __user *name, int flags);
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int ksys_dup(unsigned int fildes);
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#endif
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@ -39,8 +39,8 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new)
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sys_unshare(CLONE_FS | CLONE_FILES);
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/* stdin/stdout/stderr for /linuxrc */
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sys_open("/dev/console", O_RDWR, 0);
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sys_dup(0);
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sys_dup(0);
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ksys_dup(0);
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ksys_dup(0);
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/* move initrd over / and chdir/chroot in initrd root */
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sys_chdir("/root");
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ksys_mount(".", "/", NULL, MS_MOVE, NULL);
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@ -1077,8 +1077,8 @@ static noinline void __init kernel_init_freeable(void)
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if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
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pr_err("Warning: unable to open an initial console.\n");
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(void) sys_dup(0);
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(void) sys_dup(0);
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(void) ksys_dup(0);
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(void) ksys_dup(0);
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/*
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* check if there is an early userspace init. If yes, let it do all
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* the work
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