Merge tag 'for-linus-20191003' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull clone3/pidfd fixes from Christian Brauner:
 "This contains a couple of fixes:

   - Fix pidfd selftest compilation (Shuah Kahn)

     Due to a false linking instruction in the Makefile compilation for
     the pidfd selftests would fail on some systems.

   - Fix compilation for glibc on RISC-V systems (Seth Forshee)

     In some scenarios linux/uapi/linux/sched.h is included where
     __ASSEMBLY__ is defined causing a build failure because struct
     clone_args was not guarded by an #ifndef __ASSEMBLY__.

   - Add missing clone3() and struct clone_args kernel-doc (Christian Brauner)

     clone3() and struct clone_args were missing kernel-docs. (The goal
     is to use kernel-doc for any function or type where it's worth it.)
     For struct clone_args this also contains a comment about the fact
     that it's versioned by size"

* tag 'for-linus-20191003' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  sched: add kernel-doc for struct clone_args
  fork: add kernel-doc for clone3
  selftests: pidfd: Fix undefined reference to pthread_create()
  sched: Add __ASSEMBLY__ guards around struct clone_args

Author: torvalds

include/uapi/linux/sched.h

@@ -33,8 +33,31 @@
 #define CLONE_NEWNET		0x40000000	/* New network namespace */
 #define CLONE_IO		0x80000000	/* Clone io context */
 
-/*
- * Arguments for the clone3 syscall
+#ifndef __ASSEMBLY__
+/**
+ * struct clone_args - arguments for the clone3 syscall
+ * @flags:       Flags for the new process as listed above.
+ *               All flags are valid except for CSIGNAL and
+ *               CLONE_DETACHED.
+ * @pidfd:       If CLONE_PIDFD is set, a pidfd will be
+ *               returned in this argument.
+ * @child_tid:   If CLONE_CHILD_SETTID is set, the TID of the
+ *               child process will be returned in the child's
+ *               memory.
+ * @parent_tid:  If CLONE_PARENT_SETTID is set, the TID of
+ *               the child process will be returned in the
+ *               parent's memory.
+ * @exit_signal: The exit_signal the parent process will be
+ *               sent when the child exits.
+ * @stack:       Specify the location of the stack for the
+ *               child process.
+ * @stack_size:  The size of the stack for the child process.
+ * @tls:         If CLONE_SETTLS is set, the tls descriptor
+ *               is set to tls.
+ *
+ * The structure is versioned by size and thus extensible.
+ * New struct members must go at the end of the struct and
+ * must be properly 64bit aligned.
  */
 struct clone_args {
 	__aligned_u64 flags;
@@ -46,6 +69,7 @@ struct clone_args {
 	__aligned_u64 stack_size;
 	__aligned_u64 tls;
 };
+#endif
 
 /*
  * Scheduling policies

kernel/fork.c

@@ -2604,6 +2604,17 @@ static bool clone3_args_valid(const struct kernel_clone_args *kargs)
 	return true;
 }
 
+/**
+ * clone3 - create a new process with specific properties
+ * @uargs: argument structure
+ * @size:  size of @uargs
+ *
+ * clone3() is the extensible successor to clone()/clone2().
+ * It takes a struct as argument that is versioned by its size.
+ *
+ * Return: On success, a positive PID for the child process.
+ *         On error, a negative errno number.
+ */
 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
 {
 	int err;

tools/testing/selftests/pidfd/Makefile

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
-CFLAGS += -g -I../../../../usr/include/ -lpthread
+CFLAGS += -g -I../../../../usr/include/ -pthread
 
 TEST_GEN_PROGS := pidfd_test pidfd_open_test pidfd_poll_test pidfd_wait