fs: add ksys_chdir() helper; remove in-kernel calls to sys_chdir()
Using this helper allows us to avoid the in-kernel calls to the sys_chdir() 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_chdir(). 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: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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@ -386,7 +386,7 @@ static int devtmpfsd(void *p)
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*err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
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if (*err)
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goto out;
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sys_chdir("/.."); /* will traverse into overmounted root */
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ksys_chdir("/.."); /* will traverse into overmounted root */
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ksys_chroot(".");
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complete(&setup_done);
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while (1) {
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@ -431,7 +431,7 @@ SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
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return sys_faccessat(AT_FDCWD, filename, mode);
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}
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SYSCALL_DEFINE1(chdir, const char __user *, filename)
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int ksys_chdir(const char __user *filename)
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{
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struct path path;
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int error;
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@ -457,6 +457,11 @@ out:
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return error;
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}
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SYSCALL_DEFINE1(chdir, const char __user *, filename)
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{
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return ksys_chdir(filename);
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}
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SYSCALL_DEFINE1(fchdir, unsigned int, fd)
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{
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struct fd f = fdget_raw(fd);
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@ -952,5 +952,6 @@ int ksys_umount(char __user *name, int flags);
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int ksys_dup(unsigned int fildes);
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int ksys_chroot(const char __user *filename);
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ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
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int ksys_chdir(const char __user *filename);
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#endif
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@ -367,7 +367,7 @@ static int __init do_mount_root(char *name, char *fs, int flags, void *data)
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if (err)
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return err;
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sys_chdir("/root");
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ksys_chdir("/root");
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s = current->fs->pwd.dentry->d_sb;
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ROOT_DEV = s->s_dev;
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printk(KERN_INFO
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@ -42,7 +42,7 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new)
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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_chdir("/root");
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ksys_mount(".", "/", NULL, MS_MOVE, NULL);
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ksys_chroot(".");
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sys_setsid();
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@ -61,7 +61,7 @@ static void __init handle_initrd(void)
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/* mount initrd on rootfs' /root */
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mount_block_root("/dev/root.old", root_mountflags & ~MS_RDONLY);
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sys_mkdir("/old", 0700);
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sys_chdir("/old");
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ksys_chdir("/old");
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/* try loading default modules from initrd */
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load_default_modules();
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@ -86,11 +86,11 @@ static void __init handle_initrd(void)
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ksys_chroot("..");
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if (new_decode_dev(real_root_dev) == Root_RAM0) {
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sys_chdir("/old");
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ksys_chdir("/old");
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return;
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}
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sys_chdir("/");
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ksys_chdir("/");
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ROOT_DEV = new_decode_dev(real_root_dev);
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mount_root();
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