[PATCH v5 1/5] Add an internal wrapper for clone, clone2 and clone3

["H.J. Lu" <hjl.tools@gmail.com>]

The clone3 system call provides a superset of the functionality of clone
and clone2.  It also provides a number of API improve ments, including
the ability to specify the size of the child's stack area which can be
used by kernel to compute the shadow stack size when allocating the
shadow stack.  Add:

extern int __clone_internal (struct clone_args *__cl_args,
			     int (*__func) (void *__arg), void *__arg);

to provide an abstract interface for clone, clone2 and clone3.

1. Add cast_to_pointer to cast an integer to void * pointer.
2. Simplify stack management for thread creation by passing both stack
base and size to create_thread.
3. Consolidate clone vs clone2 differences into a single file.
4. Use only __clone_internal to clone a thread.
5. Call __clone3 if HAVE_CLONE3_WAPPER is defined.  If __clone3 returns
-1 with ENOSYS, fall back to clone or clone2.
6. Enable the public clone3 wrapper in the future after it has been
added to all targets.

Tested with build-many-glibcs.py.
---
 include/clone_internal.h                  | 14 ++++
 include/libc-pointer-arith.h              |  3 +
 sysdeps/unix/sysv/linux/Makefile          |  4 +-
 sysdeps/unix/sysv/linux/clone-internal.c  | 97 +++++++++++++++++++++++
 sysdeps/unix/sysv/linux/clone-offsets.sym |  5 ++
 sysdeps/unix/sysv/linux/clone3.c          |  1 +
 sysdeps/unix/sysv/linux/clone3.h          | 55 +++++++++++++
 sysdeps/unix/sysv/linux/createthread.c    | 25 +++---
 sysdeps/unix/sysv/linux/spawni.c          | 26 +++---
 9 files changed, 202 insertions(+), 28 deletions(-)
 create mode 100644 include/clone_internal.h
 create mode 100644 sysdeps/unix/sysv/linux/clone-internal.c
 create mode 100644 sysdeps/unix/sysv/linux/clone-offsets.sym
 create mode 100644 sysdeps/unix/sysv/linux/clone3.c
 create mode 100644 sysdeps/unix/sysv/linux/clone3.h

diff --git a/include/clone_internal.h b/include/clone_internal.h
new file mode 100644
index 0000000000..124f7ba169
--- /dev/null
+++ b/include/clone_internal.h
@@ -0,0 +1,14 @@
+#ifndef _CLONE3_H
+#include_next <clone3.h>
+
+extern __typeof (clone3) __clone3;
+
+/* The internal wrapper of clone and clone3.  */
+extern __typeof (clone3) __clone_internal;
+
+#ifndef _ISOMAC
+libc_hidden_proto (__clone3)
+libc_hidden_proto (__clone_internal)
+#endif
+
+#endif
diff --git a/include/libc-pointer-arith.h b/include/libc-pointer-arith.h
index 72e722c5aa..04ba537617 100644
--- a/include/libc-pointer-arith.h
+++ b/include/libc-pointer-arith.h
@@ -37,6 +37,9 @@
 /* Cast an integer or a pointer VAL to integer with proper type.  */
 # define cast_to_integer(val) ((__integer_if_pointer_type (val)) (val))
 
+/* Cast an integer VAL to void * pointer.  */
+# define cast_to_pointer(val) ((void *) (uintptr_t) (val))
+
 /* Align a value by rounding down to closest size.
    e.g. Using size of 4096, we get this behavior:
 	{4095, 4096, 4097} = {0, 4096, 4096}.  */
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index fb155cf856..7c1f32b84d 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -54,6 +54,8 @@ CFLAGS-malloc.c += -DMORECORE_CLEARS=2
 endif
 
 ifeq ($(subdir),misc)
+gen-as-const-headers += clone-offsets.sym
+
 sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
 		   setfsuid setfsgid epoll_pwait signalfd \
 		   eventfd eventfd_read eventfd_write prlimit \
@@ -64,7 +66,7 @@ sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
 		   time64-support pselect32 \
 		   xstat fxstat lxstat xstat64 fxstat64 lxstat64 \
 		   fxstatat fxstatat64 \
-		   xmknod xmknodat
+		   xmknod xmknodat clone3 clone-internal
 
 CFLAGS-gethostid.c = -fexceptions
 CFLAGS-tee.c = -fexceptions -fasynchronous-unwind-tables
diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
new file mode 100644
index 0000000000..c357b0ac14
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/clone-internal.c
@@ -0,0 +1,97 @@
+/* The internal wrapper of clone and clone3.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <stddef.h>
+#include <errno.h>
+#include <sched.h>
+#include <clone_internal.h>
+#include <libc-pointer-arith.h>	/* For cast_to_pointer.  */
+#include <stackinfo.h>		/* For _STACK_GROWS_{UP,DOWN}.  */
+
+#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
+#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
+#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
+
+#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+#define offsetofend(TYPE, MEMBER) \
+  (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
+
+_Static_assert (__alignof(struct clone_args) == 8,
+		"__alignof(struct clone_args) != 8");
+_Static_assert (offsetofend(struct clone_args, tls) == CLONE_ARGS_SIZE_VER0,
+		"offsetofend(struct clone_args, tls) != CLONE_ARGS_SIZE_VER0");
+_Static_assert (offsetofend(struct clone_args, set_tid_size) == CLONE_ARGS_SIZE_VER1,
+		"offsetofend(struct clone_args, set_tid_size) != CLONE_ARGS_SIZE_VER1");
+_Static_assert (offsetofend(struct clone_args, cgroup) == CLONE_ARGS_SIZE_VER2,
+		"offsetofend(struct clone_args, cgroup) != CLONE_ARGS_SIZE_VER2");
+_Static_assert (sizeof(struct clone_args) == CLONE_ARGS_SIZE_VER2,
+		"sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2");
+
+int
+__clone_internal (struct clone_args *cl_args,
+		  int (*func) (void *arg), void *arg)
+{
+  int ret;
+#ifdef HAVE_CLONE3_WAPPER
+  /* Try clone3 first.  */
+  int saved_errno = errno;
+  ret = __clone3 (cl_args, func, arg);
+  if (ret != -1 || errno != ENOSYS)
+    return ret;
+
+  /* NB: Restore errno since errno may be checked against non-zero
+     return value.  */
+  __set_errno (saved_errno);
+#else
+    /* Check invalid arguments.  */
+  if (cl_args == NULL || func == NULL)
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+#endif
+
+  /* Map clone3 arguments to clone arguments.  NB: No need to check
+     invalid clone3 specific bits since this is an internal function.  */
+  int flags = cl_args->flags | cl_args->exit_signal;
+  void *stack = cast_to_pointer (cl_args->stack);
+
+#ifdef __ia64__
+  ret = __clone2 (func, stack, cl_args->stack_size,
+		  flags, arg,
+		  cast_to_pointer (cl_args->parent_tid),
+		  cast_to_pointer (cl_args->tls),
+		  cast_to_pointer (cl_args->child_tid));
+#else
+# if !_STACK_GROWS_DOWN && !_STACK_GROWS_UP
+#  error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
+# endif
+
+# if _STACK_GROWS_DOWN
+  stack += cl_args->stack_size;
+# endif
+  ret = __clone (func, stack, flags, arg,
+		 cast_to_pointer (cl_args->parent_tid),
+		 cast_to_pointer (cl_args->tls),
+		 cast_to_pointer (cl_args->child_tid));
+#endif
+  return ret;
+}
+
+libc_hidden_def (__clone_internal)
diff --git a/sysdeps/unix/sysv/linux/clone-offsets.sym b/sysdeps/unix/sysv/linux/clone-offsets.sym
new file mode 100644
index 0000000000..d767e49fc8
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/clone-offsets.sym
@@ -0,0 +1,5 @@
+#include <clone3.h>
+
+--
+
+CLONE_ARGS_SIZE			sizeof (struct clone_args)
diff --git a/sysdeps/unix/sysv/linux/clone3.c b/sysdeps/unix/sysv/linux/clone3.c
new file mode 100644
index 0000000000..de963ef89d
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/clone3.c
@@ -0,0 +1 @@
+/* An empty placeholder.  */
diff --git a/sysdeps/unix/sysv/linux/clone3.h b/sysdeps/unix/sysv/linux/clone3.h
new file mode 100644
index 0000000000..a222948d55
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/clone3.h
@@ -0,0 +1,55 @@
+/* The wrapper of clone3.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _CLONE3_H
+#define _CLONE3_H	1
+
+#include <features.h>
+#include <stdint.h>
+
+__BEGIN_DECLS
+
+struct clone_args
+{
+  uint64_t flags;	 /* Flags bit mask.  */
+  uint64_t pidfd;	 /* Where to store PID file descriptor
+			    (pid_t *).  */
+  uint64_t child_tid;	 /* Where to store child TID, in child's memory
+			    (pid_t *).  */
+  uint64_t parent_tid;	 /* Where to store child TID, in parent's memory
+			    (int *). */
+  uint64_t exit_signal;	 /* Signal to deliver to parent on child
+			    termination */
+  uint64_t stack;	 /* The lowest address of stack.  */
+  uint64_t stack_size;	 /* Size of stack.  */
+  uint64_t tls;		 /* Location of new TLS.  */
+  uint64_t set_tid;	 /* Pointer to a pid_t array
+			    (since Linux 5.5).  */
+  uint64_t set_tid_size; /* Number of elements in set_tid
+			    (since Linux 5.5). */
+  uint64_t cgroup;	 /* File descriptor for target cgroup
+			    of child (since Linux 5.7).  */
+} __attribute__ ((aligned (8)));
+
+/* The wrapper of clone3.  */
+extern int clone3 (struct clone_args *__cl_args,
+		   int (*__func) (void *__arg), void *__arg);
+
+__END_DECLS
+
+#endif /* clone3.h */
diff --git a/sysdeps/unix/sysv/linux/createthread.c b/sysdeps/unix/sysv/linux/createthread.c
index bc3409b326..406c73ba00 100644
--- a/sysdeps/unix/sysv/linux/createthread.c
+++ b/sysdeps/unix/sysv/linux/createthread.c
@@ -25,15 +25,10 @@
 #include <ldsodefs.h>
 #include <tls.h>
 #include <stdint.h>
+#include <clone_internal.h>
 
 #include <arch-fork.h>
 
-#ifdef __NR_clone2
-# define ARCH_CLONE __clone2
-#else
-# define ARCH_CLONE __clone
-#endif
-
 /* See the comments in pthread_create.c for the requirements for these
    two macros and the create_thread function.  */
 
@@ -47,7 +42,8 @@ static int start_thread (void *arg) __attribute__ ((noreturn));
 
 static int
 create_thread (struct pthread *pd, const struct pthread_attr *attr,
-	       bool *stopped_start, STACK_VARIABLES_PARMS, bool *thread_ran)
+	       bool *stopped_start, void *stackaddr, size_t stacksize,
+	       bool *thread_ran)
 {
   /* Determine whether the newly created threads has to be started
      stopped since we have to set the scheduling parameters or set the
@@ -100,9 +96,18 @@ create_thread (struct pthread *pd, const struct pthread_attr *attr,
 
   TLS_DEFINE_INIT_TP (tp, pd);
 
-  if (__glibc_unlikely (ARCH_CLONE (&start_thread, STACK_VARIABLES_ARGS,
-				    clone_flags, pd, &pd->tid, tp, &pd->tid)
-			== -1))
+  struct clone_args args =
+    {
+      .flags = clone_flags,
+      .pidfd = (uintptr_t) &pd->tid,
+      .parent_tid = (uintptr_t) &pd->tid,
+      .child_tid = (uintptr_t) &pd->tid,
+      .stack = (uintptr_t) stackaddr,
+      .stack_size = stacksize,
+      .tls = (uintptr_t) tp,
+    };
+  int ret = __clone_internal (&args, &start_thread, pd);
+  if (__glibc_unlikely (ret == -1))
     return errno;
 
   /* It's started now, so if we fail below, we'll have to cancel it
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index 501f8fbccd..fd29858cf5 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -31,6 +31,7 @@
 #include <dl-sysdep.h>
 #include <libc-pointer-arith.h>
 #include <ldsodefs.h>
+#include <clone_internal.h>
 #include "spawn_int.h"
 
 /* The Linux implementation of posix_spawn{p} uses the clone syscall directly
@@ -59,21 +60,6 @@
    normal program exit with the exit code 127.  */
 #define SPAWN_ERROR	127
 
-#ifdef __ia64__
-# define CLONE(__fn, __stackbase, __stacksize, __flags, __args) \
-  __clone2 (__fn, __stackbase, __stacksize, __flags, __args, 0, 0, 0)
-#else
-# define CLONE(__fn, __stack, __stacksize, __flags, __args) \
-  __clone (__fn, __stack, __flags, __args)
-#endif
-
-/* Since ia64 wants the stackbase w/clone2, re-use the grows-up macro.  */
-#if _STACK_GROWS_UP || defined (__ia64__)
-# define STACK(__stack, __stack_size) (__stack)
-#elif _STACK_GROWS_DOWN
-# define STACK(__stack, __stack_size) (__stack + __stack_size)
-#endif
-
 
 struct posix_spawn_args
 {
@@ -378,8 +364,14 @@ __spawnix (pid_t * pid, const char *file,
      need for CLONE_SETTLS.  Although parent and child share the same TLS
      namespace, there will be no concurrent access for TLS variables (errno
      for instance).  */
-  new_pid = CLONE (__spawni_child, STACK (stack, stack_size), stack_size,
-		   CLONE_VM | CLONE_VFORK | SIGCHLD, &args);
+  struct clone_args clone_args =
+    {
+      .flags = CLONE_VM | CLONE_VFORK,
+      .exit_signal = SIGCHLD,
+      .stack = (uintptr_t) stack,
+      .stack_size = stack_size,
+    };
+  new_pid = __clone_internal (&clone_args, __spawni_child, &args);
 
   /* It needs to collect the case where the auxiliary process was created
      but failed to execute the file (due either any preparation step or
-- 
2.31.1