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kernel: add ksys_setsid() helper; remove in-kernel call to sys_setsid()

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Using this helper allows us to avoid the in-kernel call to the
sys_setsid() 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_setsid().

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>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-16 12:36:06 +01:00
parent 9b32105ec6
commit e2aaa9f423
3 changed files with 8 additions and 2 deletions
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1
include/linux/syscalls.h
View File

@ -962,6 +962,7 @@ off_t ksys_lseek(unsigned int fd, off_t offset, unsigned int whence);
ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count);
void ksys_sync(void);
int ksys_unshare(unsigned long unshare_flags);
int ksys_setsid(void);
/*
* The following kernel syscall equivalents are just wrappers to fs-internal

2
init/do_mounts_initrd.c
View File

@ -45,7 +45,7 @@ static int init_linuxrc(struct subprocess_info *info, struct cred *new)
ksys_chdir("/root");
ksys_mount(".", "/", NULL, MS_MOVE, NULL);
ksys_chroot(".");
sys_setsid();
ksys_setsid();
return 0;
}

7
kernel/sys.c
View File

@ -1150,7 +1150,7 @@ static void set_special_pids(struct pid *pid)
change_pid(curr, PIDTYPE_PGID, pid);
}
SYSCALL_DEFINE0(setsid)
int ksys_setsid(void)
{
struct task_struct *group_leader = current->group_leader;
struct pid *sid = task_pid(group_leader);
@ -1183,6 +1183,11 @@ out:
return err;
}
SYSCALL_DEFINE0(setsid)
{
return ksys_setsid();
}
DECLARE_RWSEM(uts_sem);
#ifdef COMPAT_UTS_MACHINE