[PATCH 0/7] Optimize posix_spawn signal setup with clone3

[PATCH 0/7] Optimize posix_spawn signal setup with clone3

[Adhemerval Zanella]

Currently posix_spawn has to issue at least NSIG sigaction syscalls
to obtain current signal disposition and more if there are not
either SIG_IGN or SIG_DFL.  The clone3 CLONE_CLEAR_SIGHAND reset
all signal handlers of the child not set to SIG_IGN to SIG_DFL, thus
allowing to skip the preparation phase.

The exception is the signals defined by posix_spawnattr_setsigdefault
when POSIX_SPAWN_SETSIGDEF is set, since they can be SIG_IGN.

The patchset also adds clone3 implementation for aarch64, powerpc64,
s390x, and riscv.

Adhemerval Zanella (7):
  linux: Do set signal handler if it is already SIG_DFL
  linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn
  powerpc64le: Add the clone3 wrapper
  aarch64: Add the clone3 wrapper
  s390x: Add the clone3 wrapper
  riscv: Add the clone3 wrapper
  Linux: optimize clone3 internal usage

 include/clone_internal.h                      |  10 +
 posix/Makefile                                |   3 +-
 posix/tst-spawn7.c                            | 177 ++++++++++++++++++
 sysdeps/unix/sysv/linux/aarch64/clone3.S      |  90 +++++++++
 sysdeps/unix/sysv/linux/aarch64/sysdep.h      |   2 +
 sysdeps/unix/sysv/linux/clone-internal.c      |  61 ++++--
 sysdeps/unix/sysv/linux/clone3.h              |   6 +
 sysdeps/unix/sysv/linux/kernel-features.h     |   8 +
 .../sysv/linux/powerpc/powerpc64/clone3.S     | 145 ++++++++++++++
 sysdeps/unix/sysv/linux/powerpc/sysdep.h      |   1 +
 sysdeps/unix/sysv/linux/riscv/clone3.S        |  83 ++++++++
 sysdeps/unix/sysv/linux/riscv/sysdep.h        |   1 +
 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S |  84 +++++++++
 sysdeps/unix/sysv/linux/s390/sysdep.h         |   1 +
 sysdeps/unix/sysv/linux/spawni.c              |  33 +++-
 15 files changed, 679 insertions(+), 26 deletions(-)
 create mode 100644 posix/tst-spawn7.c
 create mode 100644 sysdeps/unix/sysv/linux/aarch64/clone3.S
 create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
 create mode 100644 sysdeps/unix/sysv/linux/riscv/clone3.S
 create mode 100644 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S

-- 
2.34.1

[PATCH 1/7] linux: Do set signal handler if it is already SIG_DFL

[Adhemerval Zanella]

There is no need to issue another sigaction is the disposition is
already SIG_DFL.

Checked on x86_64-linux-gnu.
---
 sysdeps/unix/sysv/linux/spawni.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index ee843a2247..65ee03c804 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -129,7 +129,7 @@ __spawni_child (void *arguments)
 	  else
 	    {
 	      __libc_sigaction (sig, 0, &sa);
-	      if (sa.sa_handler == SIG_IGN)
+	      if (sa.sa_handler == SIG_IGN || sa.sa_handler == SIG_DFL)
 		continue;
 	      sa.sa_handler = SIG_DFL;
 	    }
-- 
2.34.1

[PATCH 2/7] linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn

[Adhemerval Zanella]

The clone3 flag resets all signal handlers of the child not set to
SIG_IGN to SIG_DFL.  It allows to skip most of the sigaction calls
to setup child signal handling, where previously a posix_spawn
has to issue 2 times NSIG sigaction calls (one to obtain the current
disposition and another to set either SIG_DFL or SIG_IGN).

The expection is POSIX_SPAWN_SETSIGDEF the child still setup the
signal for the case the disposition is SIG_IGN.

It also need to handle the fallback where clone3 is not available,
to set the fallback in child.  This is done by splitting of
__clone_internal_fallback from __clone_internal.

Checked on x86_64-linux-gnu.
---
 include/clone_internal.h                 |   5 +
 posix/Makefile                           |   3 +-
 posix/tst-spawn7.c                       | 177 +++++++++++++++++++++++
 sysdeps/unix/sysv/linux/clone-internal.c |  38 +++--
 sysdeps/unix/sysv/linux/clone3.h         |   6 +
 sysdeps/unix/sysv/linux/spawni.c         |  31 ++--
 6 files changed, 235 insertions(+), 25 deletions(-)
 create mode 100644 posix/tst-spawn7.c

diff --git a/include/clone_internal.h b/include/clone_internal.h
index 4b23ef33ce..320640e64b 100644
--- a/include/clone_internal.h
+++ b/include/clone_internal.h
@@ -7,6 +7,11 @@ extern __typeof (clone3) __clone3;
    -1 with ENOSYS, fall back to clone or clone2.  */
 extern int __clone_internal (struct clone_args *__cl_args,
 			     int (*__func) (void *__arg), void *__arg);
+/* The fallback code which calls clone/clone2 based on clone3 arguments.  */
+extern int __clone_internal_fallback (struct clone_args *__cl_args,
+				      int (*__func) (void *__arg),
+				      void *__arg)
+     attribute_hidden;
 
 #ifndef _ISOMAC
 libc_hidden_proto (__clone3)
diff --git a/posix/Makefile b/posix/Makefile
index d1df7c27cb..7887eb1c8b 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -109,7 +109,7 @@ tests		:= test-errno tstgetopt testfnm runtests runptests \
 		   tst-glob-tilde test-ssize-max tst-spawn4 bug-regex37 \
 		   bug-regex38 tst-regcomp-truncated tst-spawn-chdir \
 		   tst-wordexp-nocmd tst-execveat tst-spawn5 \
-		   tst-sched_getaffinity tst-spawn6
+		   tst-sched_getaffinity tst-spawn6 tst-spawn7
 
 # Test for the glob symbol version that was replaced in glibc 2.27.
 ifeq ($(have-GLIBC_2.26)$(build-shared),yesyes)
@@ -291,6 +291,7 @@ tst-spawn-ARGS = -- $(host-test-program-cmd)
 tst-spawn-static-ARGS = $(tst-spawn-ARGS)
 tst-spawn5-ARGS = -- $(host-test-program-cmd)
 tst-spawn6-ARGS = -- $(host-test-program-cmd)
+tst-spawn7-ARGS = -- $(host-test-program-cmd)
 tst-dir-ARGS = `pwd` `cd $(common-objdir)/$(subdir); pwd` `cd $(common-objdir); pwd` $(objpfx)tst-dir
 tst-chmod-ARGS = $(objdir)
 tst-vfork3-ARGS = --test-dir=$(objpfx)
diff --git a/posix/tst-spawn7.c b/posix/tst-spawn7.c
new file mode 100644
index 0000000000..4b920bf08e
--- /dev/null
+++ b/posix/tst-spawn7.c
@@ -0,0 +1,177 @@
+/* Tests for posix_spawn signal handling.
+   Copyright (C) 2022 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <getopt.h>
+#include <spawn.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/xsignal.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+/* Nonzero if the program gets called via `exec'.  */
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+static int restart;
+
+/* Hold the four initial argument used to respawn the process, plus
+   the extra '--direct' and '--restart', the check type, and a final NULL.  */
+static char *spargs[8];
+static int check_type_argc;
+
+/* Called on process re-execution.  */
+_Noreturn static void
+handle_restart (int argc, char *argv[])
+{
+  assert (argc == 1);
+
+  if (strcmp (argv[0], "SIG_DFL") == 0)
+    {
+      for (int i = 1; i < NSIG; i++)
+	{
+	  struct sigaction sa;
+	  int r = sigaction (i, NULL, &sa);
+	  /* Skip internal signals (such as SIGCANCEL).  */
+	  if (r == -1)
+	    continue;
+	  TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL);
+	}
+    }
+  else if (strcmp (argv[0], "SIG_IGN") == 0)
+    {
+      for (int i = 1; i < NSIG; i++)
+	{
+	  struct sigaction sa;
+	  int r = sigaction (i, NULL, &sa);
+	  /* Skip internal signals (such as SIGCANCEL).  */
+	  if (r == -1)
+	    continue;
+	  if (i == SIGUSR1 || i == SIGUSR2)
+	    TEST_VERIFY_EXIT (sa.sa_handler == SIG_IGN);
+	  else
+	    TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL);
+	}
+    }
+
+  exit (EXIT_SUCCESS);
+}
+
+static void
+spawn_signal_test (const char *type, const posix_spawnattr_t *attr)
+{
+  spargs[check_type_argc] = (char*) type;
+
+  pid_t pid;
+  int status;
+
+  TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, attr, spargs, environ), 0);
+  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
+  TEST_VERIFY (WIFEXITED (status));
+  TEST_VERIFY (!WIFSIGNALED (status));
+  TEST_COMPARE (WEXITSTATUS (status), 0);
+}
+
+static void
+dummy_sa_handler (int)
+{
+}
+
+static void
+do_test_signals (void)
+{
+  {
+    /* Check if all signals handler are set to SIG_DFL on spawned process.  */
+    spawn_signal_test ("SIG_DFL", NULL);
+  }
+
+  {
+    /* Same as before, but set SIGUSR1 and SIGUSR2.  */
+    struct sigaction sa = { 0 };
+    sa.sa_handler = dummy_sa_handler;
+    xsigaction (SIGUSR1, &sa, NULL);
+    xsigaction (SIGUSR2, &sa, NULL);
+    spawn_signal_test ("SIG_DFL", NULL);
+  }
+
+  {
+    /* Check if SIG_IGN is keep as is.  */
+    struct sigaction sa = { 0 };
+    sa.sa_handler = SIG_IGN;
+    xsigaction (SIGUSR1, &sa, NULL);
+    xsigaction (SIGUSR2, &sa, NULL);
+    spawn_signal_test ("SIG_IGN", NULL);
+  }
+
+  {
+    /* Check if SIG_IGN handlers are set to SIG_DFL.  */
+    posix_spawnattr_t attr;
+    posix_spawnattr_init (&attr);
+    sigset_t mask;
+    sigemptyset (&mask);
+    sigaddset (&mask, SIGUSR1);
+    sigaddset (&mask, SIGUSR2);
+    posix_spawnattr_setsigdefault (&attr, &mask);
+    posix_spawnattr_setflags (&attr, POSIX_SPAWN_SETSIGDEF);
+    spawn_signal_test ("SIG_DFL", &attr);
+    posix_spawnattr_destroy (&attr);
+  }
+}
+
+static int
+do_test (int argc, char *argv[])
+{
+  /* We must have either:
+
+     - one or four parameters if called initially:
+       + argv[1]: path for ld.so        optional
+       + argv[2]: "--library-path"      optional
+       + argv[3]: the library path      optional
+       + argv[4]: the application name
+
+     - six parameters left if called through re-execution:
+       + argv[1]: the application name
+       + argv[2]: check SIG_IGN
+
+     * When built with --enable-hardcoded-path-in-tests or issued without
+       using the loader directly.  */
+
+  if (restart)
+    /* Ignore the application name. */
+    handle_restart (argc - 1, &argv[1]);
+
+  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
+
+  int i;
+
+  for (i = 0; i < argc - 1; i++)
+    spargs[i] = argv[i + 1];
+  spargs[i++] = (char *) "--direct";
+  spargs[i++] = (char *) "--restart";
+  check_type_argc = i++;
+  spargs[i] = NULL;
+
+
+  do_test_signals ();
+
+  return 0;
+}
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
index a71effcbd3..d9eb254ffb 100644
--- a/sysdeps/unix/sysv/linux/clone-internal.c
+++ b/sysdeps/unix/sysv/linux/clone-internal.c
@@ -44,27 +44,15 @@ _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)
+__clone_internal_fallback (struct clone_args *cl_args,
+			   int (*func) (void *arg), void *arg)
 {
-  int ret;
-#ifdef HAVE_CLONE3_WRAPPER
-  /* Try clone3 first.  */
-  int saved_errno = errno;
-  ret = __clone3 (cl_args, sizeof (*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);
-#endif
-
   /* Map clone3 arguments to clone arguments.  NB: No need to check
      invalid clone3 specific bits in flags nor exit_signal since this
      is an internal function.  */
   int flags = cl_args->flags | cl_args->exit_signal;
   void *stack = cast_to_pointer (cl_args->stack);
+  int ret;
 
 #ifdef __ia64__
   ret = __clone2 (func, stack, cl_args->stack_size,
@@ -88,4 +76,24 @@ __clone_internal (struct clone_args *cl_args,
   return ret;
 }
 
+
+int
+__clone_internal (struct clone_args *cl_args,
+		  int (*func) (void *arg), void *arg)
+{
+#ifdef HAVE_CLONE3_WRAPPER
+  /* Try clone3 first.  */
+  int saved_errno = errno;
+  int ret = __clone3 (cl_args, sizeof (*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);
+#endif
+
+  return __clone_internal_fallback (cl_args, func, arg);
+}
+
 libc_hidden_def (__clone_internal)
diff --git a/sysdeps/unix/sysv/linux/clone3.h b/sysdeps/unix/sysv/linux/clone3.h
index 889014a6a9..a150363f89 100644
--- a/sysdeps/unix/sysv/linux/clone3.h
+++ b/sysdeps/unix/sysv/linux/clone3.h
@@ -25,6 +25,12 @@
 
 __BEGIN_DECLS
 
+/* Flags for the clone3 syscall.  */
+#define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and
+					      reset to SIG_DFL.  */
+#define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given
+					    the right permissions.  */
+
 /* The unsigned 64-bit and 8-byte aligned integer type.  */
 typedef __U64_TYPE __aligned_uint64_t __attribute__ ((__aligned__ (8)));
 
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index 65ee03c804..5251b4c602 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -66,6 +66,7 @@ struct posix_spawn_args
   ptrdiff_t argc;
   char *const *envp;
   int xflags;
+  bool use_clone3;
   int err;
 };
 
@@ -104,12 +105,11 @@ __spawni_child (void *arguments)
   const posix_spawnattr_t *restrict attr = args->attr;
   const posix_spawn_file_actions_t *file_actions = args->fa;
 
-  /* The child must ensure that no signal handler are enabled because it shared
-     memory with parent, so the signal disposition must be either SIG_DFL or
-     SIG_IGN.  It does by iterating over all signals and although it could
-     possibly be more optimized (by tracking which signal potentially have a
-     signal handler), it might requires system specific solutions (since the
-     sigset_t data type can be very different on different architectures).  */
+  /* The child must ensure that no signal handler are enabled because it
+     shared memory with parent, so the signal disposition must be either
+     SIG_DFL or SIG_IGN.  If clone3/CLONE_CLEAR_SIGHAND is used, there is
+     only need to set the defined signals to SIG_DFL if POSIX_SPAWN_SETSIGDEF
+     is used; otherwise, the code iterates over all signals.  */
   struct sigaction sa;
   memset (&sa, '\0', sizeof (sa));
 
@@ -122,7 +122,7 @@ __spawni_child (void *arguments)
 	{
 	  sa.sa_handler = SIG_DFL;
 	}
-      else if (__sigismember (&hset, sig))
+      else if (!args->use_clone3 && __sigismember (&hset, sig))
 	{
 	  if (is_internal_signal (sig))
 	    sa.sa_handler = SIG_IGN;
@@ -382,12 +382,25 @@ __spawnix (pid_t * pid, const char *file,
      for instance).  */
   struct clone_args clone_args =
     {
-      .flags = CLONE_VM | CLONE_VFORK,
+      /* No supported flags like CLONE_CLEAR_SIGHAND will be cleared up by
+	 __clone_internal_fallback.  */
+      .flags = CLONE_CLEAR_SIGHAND | CLONE_VM | CLONE_VFORK,
       .exit_signal = SIGCHLD,
       .stack = (uintptr_t) stack,
       .stack_size = stack_size,
     };
-  new_pid = __clone_internal (&clone_args, __spawni_child, &args);
+#ifdef HAVE_CLONE3_WRAPPER
+  args.use_clone3 = true;
+  new_pid = __clone3 (&clone_args, sizeof (clone_args), __spawni_child,
+		      &args);
+  /* clone3 was added on 5.3 and CLONE_CLEAR_SIGHAND on 5.5.  */
+  if (new_pid == -1 && (errno == ENOSYS || errno == EINVAL))
+#endif
+    {
+      args.use_clone3 = false;
+      new_pid = __clone_internal_fallback (&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
-- 
2.34.1

[PATCH 3/7] powerpc64le: Add the clone3 wrapper

[Adhemerval Zanella]

It follows the internal signature:

  extern int clone3 (struct clone_args *__cl_args, size_t __size,
 int (*__func) (void *__arg), void *__arg);

And x86_64 semantics to return EINVAL if either cl_args or func
is NULL.  The stack is 16-byte aligned prior executing func.

Checked on powerpc64le-linux-gnu.
---
 .../sysv/linux/powerpc/powerpc64/clone3.S     | 145 ++++++++++++++++++
 sysdeps/unix/sysv/linux/powerpc/sysdep.h      |   1 +
 2 files changed, 146 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S

diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
new file mode 100644
index 0000000000..a7461a3a42
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
@@ -0,0 +1,145 @@
+/* The clone3 syscall wrapper.  Linux/powerpc64 version.
+   Copyright (C) 2022 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>
+#define _ERRNO_H        1
+#include <bits/errno.h>
+
+/* The userland implementation is:
+   int clone3 (struct clone_args *cl_args, size_t size,
+               int (*func)(void *arg), void *arg);
+
+   the kernel entry is:
+   int clone3 (struct clone_args *cl_args, size_t size);
+
+   The parameters are passed in registers from userland:
+   r3: cl_args
+   r4: size
+   r5: func
+   r6: arg  */
+
+        .text
+ENTRY(__clone3)
+	CALL_MCOUNT 4
+
+	/* Sanity checks args.  */
+	cmpdi	cr0, r3, 0
+	cmpdi	cr1, r5, 0
+	cror	cr0*4+eq, cr1*4+eq, cr0*4+eq
+	beq	cr0,L(badargs)
+
+	/* Save some regs in the "red zone".  */
+#ifdef USE_PPC_SCV
+	std	r28, -24(r1)
+	cfi_offset (r28, -24)
+#endif
+	std	r29, -16(r1)
+	std	r30, -8(r1)
+	cfi_offset (r29, -16)
+	cfi_offset (r30, -8)
+
+	/* Save fn and args across syscall.  */
+	mr	r30, r5		/* Function.  */
+	mr	r29, r6		/* Arguments.  */
+
+	/* End FDE now, because in the child the unwind info will be
+	   wrong.  */
+	cfi_endproc
+
+	/* Do the system call, the kernel expects:
+	   r0: system call numer
+	   r3: cl_args
+	   r4: size  */
+	li	r0, SYS_ify(clone3)
+#ifdef USE_PPC_SCV
+	CHECK_SCV_SUPPORT r28 0f
+	/* This is equivalent to DO_CALL_SCV, but we cannot use the macro here
+	   because it uses CFI directives and we just called cfi_endproc.  */
+	mflr 	r9
+	std 	r9, FRAME_LR_SAVE(r1)
+	.machine "push"
+	.machine "power9"
+	scv 	0
+	.machine "pop"
+	ld 	r9, FRAME_LR_SAVE(r1)
+	mtlr 	r9
+
+	/* When using scv, error is indicated by negative r3.  */
+	cmpdi	cr1, r3, 0
+	b	1f
+#endif
+0:      DO_CALL_SC
+
+	/* With sc, error is indicated by cr0.SO.  */
+	cmpdi	cr1, r3, 0
+	crandc	cr1*4+eq, cr1*4+eq, cr0*4+so
+
+1:	bne-	cr1,L(parent)
+
+	/* Child, load the function and arguments.  */
+
+	/* Align stack.  */
+	rldicr	r1, r1, 0, 59
+
+	std	r2, FRAME_TOC_SAVE(r1)
+	PPC64_LOAD_FUNCPTR r30
+	mr	r3, r29
+	bctrl
+	ld	r2, FRAME_TOC_SAVE(r1)
+
+	li	r0, SYS_ify(exit)
+	DO_CALL_SC
+	/* We won't ever get here but provide a nop so that the linker
+	   will insert a toc adjusting stub if necessary.  */
+	nop
+
+L(badargs):
+	cfi_startproc
+	li	r3, EINVAL
+	TAIL_CALL_SYSCALL_ERROR
+
+L(parent):
+	/* Check if svc is available.  */
+	cmpdi cr1, r28, 0
+
+	/* Parent.  Restore registers & return.  */
+#ifdef USE_PPC_SCV
+	cfi_offset (r28, -24)
+	ld	r28, -24(r1)
+	cfi_restore (r28)
+#endif
+	cfi_offset (r29,-16)
+	cfi_offset (r30,-8)
+	ld	r29, -16(r1)
+	ld	r30, -8(r1)
+	cfi_restore (r29)
+	cfi_restore (r30)
+
+#ifdef USE_PPC_SCV
+	beq	cr1, 0f
+	RET_SCV
+	b	1f
+#endif
+0:	RET_SC
+1:	TAIL_CALL_SYSCALL_ERROR
+
+PSEUDO_END (__clone3)
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
index 4fb135aa8d..b86951207d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
+++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
@@ -246,6 +246,7 @@
 #if defined(__PPC64__) || defined(__powerpc64__)
 #define HAVE_CLOCK_GETRES64_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME64_VSYSCALL	"__kernel_clock_gettime"
+#define HAVE_CLONE3_WRAPPER		1
 #else
 #define HAVE_CLOCK_GETRES_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME_VSYSCALL	"__kernel_clock_gettime"
-- 
2.34.1

[PATCH 4/7] aarch64: Add the clone3 wrapper

[Adhemerval Zanella]

It follow the internal signature:

  extern int clone3 (struct clone_args *__cl_args, size_t __size,
 int (*__func) (void *__arg), void *__arg);

And x86_64 semantics to return EINVAL if either cl_args or func
is NULL.  The stack is 16-byte aligned prior executing func.

Checked on aarch64-linux-gnu.
---
 sysdeps/unix/sysv/linux/aarch64/clone3.S | 90 ++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/aarch64/sysdep.h |  2 +
 2 files changed, 92 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/aarch64/clone3.S

diff --git a/sysdeps/unix/sysv/linux/aarch64/clone3.S b/sysdeps/unix/sysv/linux/aarch64/clone3.S
new file mode 100644
index 0000000000..dba93430eb
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/clone3.S
@@ -0,0 +1,90 @@
+/* The clone3 syscall wrapper.  Linux/aarch64 version.
+   Copyright (C) 2022 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>
+#define _ERRNO_H        1
+#include <bits/errno.h>
+
+/* The userland implementation is:
+   int clone3 (struct clone_args *cl_args, size_t size,
+               int (*func)(void *arg), void *arg);
+
+   the kernel entry is:
+   int clone3 (struct clone_args *cl_args, size_t size);
+
+   The parameters are passed in registers from userland:
+   x0: cl_args
+   x1: size
+   x2: func
+   x3: arg  */
+
+        .text
+ENTRY(__clone3)
+	PTR_ARG (0)
+	PTR_ARG (1)
+	PTR_ARG (3)
+	PTR_ARG (4)
+	/* Save args for the child.  */
+	mov	x10, x0		/* cl_args  */
+	mov	x11, x2		/* func	 */
+	mov	x12, x3		/* args  */
+
+	/* Sanity check args.  */
+	mov	x0, #-EINVAL
+	cbz	x10, .Lsyscall_error	/* No NULL cl_args pointer.  */
+	cbz	x2, .Lsyscall_error	/* No NULL function pointer.  */
+
+	/* Do the system call, the kernel expects:
+	   x8: system call number
+	   x0: cl_args
+	   x1: size  */
+	mov	x0, x10
+	mov	x8, #SYS_ify(clone3)
+	svc	0x0
+
+	cmp	x0, #0
+	beq	thread_start
+	blt	.Lsyscall_error
+	RET
+PSEUDO_END (__clone3)
+
+	.align 4
+	.type thread_start, %function
+thread_start:
+	cfi_startproc
+	cfi_undefined (x30)
+	mov	x29, 0
+
+	/* Align sp.  */
+	mov	x0, sp
+	and	x0, x0, -16
+	mov	sp, x0
+
+	/* Pick the function arg and execute.  */
+	mov	x0, x12
+	blr	x11
+
+	/* We are done, pass the return value through x0.  */
+	mov	x8, #SYS_ify(exit)
+	svc	0x0
+	cfi_endproc
+	.size thread_start, .-thread_start
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
diff --git a/sysdeps/unix/sysv/linux/aarch64/sysdep.h b/sysdeps/unix/sysv/linux/aarch64/sysdep.h
index f1853e012f..42bb22f5e6 100644
--- a/sysdeps/unix/sysv/linux/aarch64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/aarch64/sysdep.h
@@ -164,6 +164,8 @@
 # define HAVE_CLOCK_GETTIME64_VSYSCALL	"__kernel_clock_gettime"
 # define HAVE_GETTIMEOFDAY_VSYSCALL	"__kernel_gettimeofday"
 
+# define HAVE_CLONE3_WRAPPER		1
+
 # undef INTERNAL_SYSCALL_RAW
 # define INTERNAL_SYSCALL_RAW(name, nr, args...)		\
   ({ long _sys_result;						\
-- 
2.34.1

[PATCH 5/7] s390x: Add the clone3 wrapper

[Adhemerval Zanella]

It follows the internal signature:

  extern int clone3 (struct clone_args *__cl_args, size_t __size,
 int (*__func) (void *__arg), void *__arg);

And x86_64 semantics to return EINVAL if either cl_args or func
is NULL.  The stack is 16-byte aligned prior executing func.

Checked on s390x-linux-gnu.
---
 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S | 84 +++++++++++++++++++
 sysdeps/unix/sysv/linux/s390/sysdep.h         |  1 +
 2 files changed, 85 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S

diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
new file mode 100644
index 0000000000..d338acfc9c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
@@ -0,0 +1,84 @@
+/* The clone3 syscall wrapper.  Linux/s390x version.
+   Copyright (C) 2022 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>
+#define _ERRNO_H        1
+#include <bits/errno.h>
+
+/* The userland implementation is:
+   int clone3 (struct clone_args *cl_args, size_t size,
+               int (*func)(void *arg), void *arg);
+
+   the kernel entry is:
+   int clone3 (struct clone_args *cl_args, size_t size);
+
+   The parameters are passed in registers from userland:
+   r2: cl_args
+   r3: size
+   r4: func
+   r5: arg  */
+
+        .text
+ENTRY(__clone3)
+	stg	%r6, 48(%r15)
+
+	/* Sanity check args.  */
+	ltgr	%r2, %r2
+	je	error
+	ltgr	%r6, %r4
+	je	error
+
+	/* Do the system call, the kernel expects:
+	   r1: system call number
+	   r2: cl_args
+	   r3: size  */
+	lghi	%r1, SYS_ify(clone3)
+	svc	0
+	ltgr	%r2,%r2			/* check return code */
+	jz	thread_start
+	lg	%r6, 48(%r15)
+	jgm	SYSCALL_ERROR_LABEL
+	br	%r14
+error:
+	lghi	%r2,-EINVAL
+	jg	SYSCALL_ERROR_LABEL
+PSEUDO_END (__clone3)
+
+	.align 4
+	.type thread_start, %function
+thread_start:
+	cfi_startproc
+	/* Mark r14 as undefined in order to stop unwinding here.  */
+	cfi_undefined (r14)
+
+	/* Align stack.  */
+	nill    %r15, 0xfff0
+
+	/* func is in gpr 6, arg in gpr 5.  */
+	lgr	%r2, %r5
+	aghi	%r15, -160
+	xc	0(8,%r15),0(%r15)
+	basr	%r14, %r6
+
+	DO_CALL (exit, 1)
+	cfi_endproc
+	.size thread_start, .-thread_start
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
diff --git a/sysdeps/unix/sysv/linux/s390/sysdep.h b/sysdeps/unix/sysv/linux/s390/sysdep.h
index 930d7efe03..366c797ef1 100644
--- a/sysdeps/unix/sysv/linux/s390/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/sysdep.h
@@ -72,6 +72,7 @@
 #ifdef __s390x__
 #define HAVE_CLOCK_GETRES64_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME64_VSYSCALL	"__kernel_clock_gettime"
+#define HAVE_CLONE3_WRAPPER		1
 #else
 #define HAVE_CLOCK_GETRES_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME_VSYSCALL	"__kernel_clock_gettime"
-- 
2.34.1

[PATCH 6/7] riscv: Add the clone3 wrapper

[Adhemerval Zanella]

It follows the internal signature:

  extern int clone3 (struct clone_args *__cl_args, size_t __size,
 int (*__func) (void *__arg), void *__arg);

And x86_64 semantics to return EINVAL if either cl_args or func
is NULL.  The stack is 16-byte aligned prior executing func.

Checked on riscv64-linux-gnu-rv64imafdc-lp64d.
---
 sysdeps/unix/sysv/linux/riscv/clone3.S | 83 ++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/riscv/sysdep.h |  1 +
 2 files changed, 84 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/riscv/clone3.S

diff --git a/sysdeps/unix/sysv/linux/riscv/clone3.S b/sysdeps/unix/sysv/linux/riscv/clone3.S
new file mode 100644
index 0000000000..1e6e807aa0
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/clone3.S
@@ -0,0 +1,83 @@
+/* The clone3 syscall wrapper.  Linux/RISC-V version.
+   Copyright (C) 2022 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 <asm/errno.h>
+#include <sys/asm.h>
+#include <sysdep.h>
+
+/* The userland implementation is:
+   int clone3 (struct clone_args *cl_args, size_t size,
+               int (*func)(void *arg), void *arg);
+
+   the kernel entry is:
+   int clone3 (struct clone_args *cl_args, size_t size);
+
+   The parameters are passed in registers from userland:
+   a0: cl_args
+   a1: size
+   a2: func
+   a3: arg  */
+
+        .text
+ENTRY(__clone3)
+	/* Sanity check args.  */
+	beqz	a0, L(invalid)	/* No NULL cl_args pointer.  */
+	beqz	a2, L(invalid)  /* No NULL function pointer.  */
+
+	/* Do the system call, the kernel expects:
+	   a7: system call number
+	   a0: cl_args
+	   a1: size  */
+	li	a7, __NR_clone3
+	scall
+
+	bltz	a0, L(error)
+	beqz	a0, L(thread_start)
+
+	ret
+
+L(invalid):
+	li	a0, -EINVAL
+L(error):
+	tail	__syscall_error
+END (__clone3)
+
+ENTRY(__thread_start_clone3)
+L(thread_start):
+	/* Terminate call stack by noting ra is undefined.  Use a dummy
+	   .cfi_label to force starting the FDE.  */
+	.cfi_label .Ldummy
+	cfi_undefined (ra)
+
+	/* Align stack to a 128-bit boundary as per RISC-V ABI.  */
+	andi		sp, sp, ALMASK
+
+	/* Restore the arg for user's function and call the user's
+	   function.  */
+	mv		a1, a2	/* Function pointer.  */
+	mv		a0, a3	/* Argument pointer.  */
+	jalr		a1
+
+	/* Call exit with the function's return value.  */
+	li		a7, __NR_exit
+	scall
+END(__thread_start_clone3)
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
diff --git a/sysdeps/unix/sysv/linux/riscv/sysdep.h b/sysdeps/unix/sysv/linux/riscv/sysdep.h
index 9b03b10567..57523dc7b7 100644
--- a/sysdeps/unix/sysv/linux/riscv/sysdep.h
+++ b/sysdeps/unix/sysv/linux/riscv/sysdep.h
@@ -150,6 +150,7 @@
 
 /* RV32 does not support the gettime VDSO syscalls.  */
 # endif
+# define HAVE_CLONE3_WRAPPER		1
 
 /* List of system calls which are supported as vsyscalls (for RV32 and
    RV64).  */
-- 
2.34.1

[PATCH 7/7] Linux: optimize clone3 internal usage

[Adhemerval Zanella]

Now that clone3 is used on more architectures, add an optimization
to avoid calling when glibc detects that it is no supported by the
kernel.  It also adds __ASSUME_CLONE3, which allows skip this
optimization and issue clone3 syscall directly.

It does not handle the the small window between 5.3 and 5.5 for
posix_spawn (CLONE_CLEAR_SIGHAND was added in 5.5).

Checked on x86_64-linux-gnu.
---
 include/clone_internal.h                  |  5 +++++
 sysdeps/unix/sysv/linux/clone-internal.c  | 25 ++++++++++++++++++++++-
 sysdeps/unix/sysv/linux/kernel-features.h |  8 ++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/include/clone_internal.h b/include/clone_internal.h
index 320640e64b..71c52211c7 100644
--- a/include/clone_internal.h
+++ b/include/clone_internal.h
@@ -7,6 +7,11 @@ extern __typeof (clone3) __clone3;
    -1 with ENOSYS, fall back to clone or clone2.  */
 extern int __clone_internal (struct clone_args *__cl_args,
 			     int (*__func) (void *__arg), void *__arg);
+/* clone3 wrapper that avoid issuing the syscall once clone3 fails with
+   ENOSYS.  */
+extern int __clone3_internal (struct clone_args *cl_args,
+			      int (*func) (void *args), void *arg)
+     attribute_hidden;
 /* The fallback code which calls clone/clone2 based on clone3 arguments.  */
 extern int __clone_internal_fallback (struct clone_args *__cl_args,
 				      int (*__func) (void *__arg),
diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
index d9eb254ffb..7e20d02025 100644
--- a/sysdeps/unix/sysv/linux/clone-internal.c
+++ b/sysdeps/unix/sysv/linux/clone-internal.c
@@ -76,6 +76,29 @@ __clone_internal_fallback (struct clone_args *cl_args,
   return ret;
 }
 
+int
+__clone3_internal (struct clone_args *cl_args, int (*func) (void *args),
+		   void *arg)
+{
+#ifdef HAVE_CLONE3_WRAPPER
+# if __ASSUME_CLONE3
+  return __clone3 (cl_args, sizeof (*cl_args), func, arg);
+# else
+  static int clone3_supported = 1;
+  if (atomic_load_relaxed (&clone3_supported) == 1)
+    {
+      int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
+      if (ret != -1 || errno != ENOSYS)
+	return ret;
+
+      atomic_store_relaxed (&clone3_supported, 0);
+    }
+# endif
+#endif
+  __set_errno (ENOSYS);
+  return -1;
+}
+
 
 int
 __clone_internal (struct clone_args *cl_args,
@@ -84,7 +107,7 @@ __clone_internal (struct clone_args *cl_args,
 #ifdef HAVE_CLONE3_WRAPPER
   /* Try clone3 first.  */
   int saved_errno = errno;
-  int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
+  int ret = __clone3_internal (cl_args, func, arg);
   if (ret != -1 || errno != ENOSYS)
     return ret;
 
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 74adc3956b..496c7f34cb 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -236,4 +236,12 @@
 # define __ASSUME_FUTEX_LOCK_PI2 0
 #endif
 
+/* The clone3 system call was introduced across all architectures
+   in Linux 5.3.  */
+#if __LINUX_KERNEL_VERSION >= 0x050300
+# define __ASSUME_CLONE3 1
+#else
+# define __ASSUME_CLONE3 0
+#endif
+
 #endif /* kernel-features.h */
-- 
2.34.1