Unverified Commit cad6967a authored by Christian Brauner's avatar Christian Brauner
Browse files

fork: introduce kernel_clone() 

The old _do_fork() helper doesn't follow naming conventions of in-kernel
helpers for syscalls. The process creation cleanup in [1] didn't change the
name to something more reasonable mainly because _do_fork() was used in quite a
few places. So sending this as a separate series seemed the better strategy.

This commit does two things:
1. renames _do_fork() to kernel_clone() but keeps _do_fork() as a simple static
   inline wrapper around kernel_clone().
2. Changes the return type from long to pid_t. This aligns kernel_thread() and
   kernel_clone(). Also, the return value from kernel_clone that is surfaced in
   fork(), vfork(), clone(), and clone3() is taken from pid_vrn() which returns
   a pid_t too.

Follow-up patches will switch each caller of _do_fork() and each place where it
is referenced over to kernel_clone(). After all these changes are done, we can
remove _do_fork() completely and will only be left with kernel_clone().

[1]: 9ba27414 ("Merge tag 'fork-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux"

)

Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200819104655.436656-2-christian.brauner@ubuntu.com
parent 9123e3a7

include/linux/sched/task.h

+5 −1
Original line number Diff line number Diff line
@@ -83,7 +83,11 @@ extern void do_group_exit(int); 
extern void exit_files(struct task_struct *);

extern void exit_itimers(struct signal_struct *);



extern long _do_fork(struct kernel_clone_args *kargs);

extern pid_t kernel_clone(struct kernel_clone_args *kargs);

static inline long _do_fork(struct kernel_clone_args *kargs)

{

	return kernel_clone(kargs);

}

struct task_struct *fork_idle(int);

struct mm_struct *copy_init_mm(void);

extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);

kernel/fork.c

+8 −8
Original line number Diff line number Diff line
@@ -2384,14 +2384,14 @@ struct mm_struct *copy_init_mm(void) 
 *

 * args->exit_signal is expected to be checked for sanity by the caller.

 */

long _do_fork(struct kernel_clone_args *args)

pid_t kernel_clone(struct kernel_clone_args *args)

{

	u64 clone_flags = args->flags;

	struct completion vfork;

	struct pid *pid;

	struct task_struct *p;

	int trace = 0;

	long nr;

	pid_t nr;



	/*

	 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
@@ -2477,7 +2477,7 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 
		.stack_size	= (unsigned long)arg,

	};



	return _do_fork(&args);

	return kernel_clone(&args);

}



#ifdef __ARCH_WANT_SYS_FORK
@@ -2488,7 +2488,7 @@ SYSCALL_DEFINE0(fork) 
		.exit_signal = SIGCHLD,

	};



	return _do_fork(&args);

	return kernel_clone(&args);

#else

	/* can not support in nommu mode */

	return -EINVAL;
@@ -2504,7 +2504,7 @@ SYSCALL_DEFINE0(vfork) 
		.exit_signal	= SIGCHLD,

	};



	return _do_fork(&args);

	return kernel_clone(&args);

}

#endif
@@ -2542,7 +2542,7 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, 
		.tls		= tls,

	};



	return _do_fork(&args);

	return kernel_clone(&args);

}

#endif
@@ -2700,7 +2700,7 @@ SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size) 
	if (!clone3_args_valid(&kargs))

		return -EINVAL;



	return _do_fork(&kargs);

	return kernel_clone(&kargs);

}

#endif
@@ -2863,7 +2863,7 @@ int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, 
/*

 * unshare allows a process to 'unshare' part of the process

 * context which was originally shared using clone.  copy_*

 * functions used by _do_fork() cannot be used here directly

 * functions used by kernel_clone() cannot be used here directly

 * because they modify an inactive task_struct that is being

 * constructed. Here we are modifying the current, active,

 * task_struct.

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