kernel: add ksys_unshare() helper; remove in-kernel calls to sys_unshare()
Using this helper allows us to avoid the in-kernel calls to the sys_unshare() 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_unshare(). 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> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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@ -380,7 +380,7 @@ static int devtmpfsd(void *p)
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{
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char options[] = "mode=0755";
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int *err = p;
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*err = sys_unshare(CLONE_NEWNS);
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*err = ksys_unshare(CLONE_NEWNS);
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if (*err)
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goto out;
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*err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
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@ -961,6 +961,7 @@ int ksys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg);
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off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence);
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ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count);
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void ksys_sync(void);
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int ksys_unshare(unsigned long unshare_flags);
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/*
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* The following kernel syscall equivalents are just wrappers to fs-internal
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@ -36,7 +36,7 @@ __setup("noinitrd", no_initrd);
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static int init_linuxrc(struct subprocess_info *info, struct cred *new)
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{
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sys_unshare(CLONE_FS | CLONE_FILES);
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ksys_unshare(CLONE_FS | CLONE_FILES);
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/* stdin/stdout/stderr for /linuxrc */
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ksys_open("/dev/console", O_RDWR, 0);
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ksys_dup(0);
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@ -2354,7 +2354,7 @@ static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp
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* constructed. Here we are modifying the current, active,
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* task_struct.
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*/
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SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
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int ksys_unshare(unsigned long unshare_flags)
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{
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struct fs_struct *fs, *new_fs = NULL;
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struct files_struct *fd, *new_fd = NULL;
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@ -2470,6 +2470,11 @@ bad_unshare_out:
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return err;
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}
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SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
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{
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return ksys_unshare(unshare_flags);
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}
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/*
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* Helper to unshare the files of the current task.
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* We don't want to expose copy_files internals to
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