linux: Use waitid on wait4 if __NR_wait4 is not defined

If the wait4 syscall is not avaliable (such as y2038 safe 32-bit
systems) it uses waitid syscall instead.  For full support we need
the 5.4+ kernel as that allows a pid of 0 with the P_PGID idtype.

Co-authored-by: Alistair Francis <alistair.francis@wdc.com>

2 files changed, 84 insertions, 1 deletions

diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index 603e517ca6..5f1352ad43 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -67,7 +67,6 @@ swapoff		-	swapoff		i:s	__swapoff	swapoff
 unshare		EXTRA	unshare		i:i	unshare
 uselib		EXTRA	uselib		i:s	__compat_uselib	uselib@GLIBC_2.0:GLIBC_2.23
 utime		-	utime		i:sP	utime
-wait4		-	wait4		i:iWiP	__wait4		wait4
 
 chown		-	chown		i:sii	__libc_chown	__chown chown
 
diff --git a/sysdeps/unix/sysv/linux/wait4.c b/sysdeps/unix/sysv/linux/wait4.c
new file mode 100644
index 0000000000..c722753819
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/wait4.c
@@ -0,0 +1,84 @@
+/* Linux wait4 syscall implementation.
+   Copyright (C) 2019 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 <sys/wait.h>
+#include <sys/resource.h>
+#include <sysdep-cancel.h>
+
+__pid_t
+__wait4 (__pid_t pid, int *stat_loc, int options, struct rusage *usage)
+{
+#if __NR_wait4
+   return SYSCALL_CANCEL (wait4, pid, stat_loc, options, usage);
+#else
+  idtype_t idtype = P_PID;
+
+  if (pid < -1)
+    {
+      idtype = P_PGID;
+      pid *= -1;
+    }
+  else if (pid == -1)
+    {
+      idtype = P_ALL;
+    }
+  else if (pid == 0)
+    {
+      /* Linux Kernels 5.4 support pid 0 with P_PGID to specify wait on
+       * the current PID's group. Earlier kernels will return -EINVAL.
+       */
+      idtype = P_PGID;
+    }
+
+  options |= WEXITED;
+
+  siginfo_t infop;
+  if (SYSCALL_CANCEL (waitid, idtype, pid, &infop, options, usage) < 0)
+    return -1;
+
+  if (stat_loc)
+    {
+      *stat_loc = 0;
+      switch (infop.si_code)
+        {
+        case CLD_EXITED:
+          *stat_loc = W_EXITCODE (infop.si_status, 0);
+          break;
+        case CLD_DUMPED:
+          *stat_loc = WCOREDUMP (infop.si_signo);
+          /* Fallthrough */
+        case CLD_KILLED:
+          *stat_loc |= infop.si_status;
+          break;
+        case CLD_TRAPPED:
+        case CLD_STOPPED:
+          *stat_loc = W_STOPCODE (infop.si_status);
+          break;
+        case CLD_CONTINUED:
+          *stat_loc = 0xffff;
+          break;
+	default:
+	  *stat_loc = 0;
+	  break;
+        }
+    }
+
+  return infop.si_pid;
+#endif
+}
+weak_alias (__wait4, wait4)