[PATCH v2] sysdeps/wait: Use the waitid syscall if required

[Alistair Francis <alistair dot francis at wdc dot com>]

If the waitpid and wait4 syscalls aren't avaliable (such as y2038 safe
32-bit systems) let us use the waitid syscall isntead.

Unfortunately waitid is substantially differnt to waitpid and wait4, so
the conversion ends up being complex.

For full support we need the 5.4+ kernel as that allows a pid of 0 with
the P_PGID idtype.

This change also removes the wait4 syscall from syscalls.list and
replaces it with a __wait4() implementation.
---
This was patch was runtime tested with RV32 and RV64
It was build tested using the ./scripts/build-many-glibcs.py script.

 include/sys/wait.h                         |  3 +-
 sysdeps/unix/sysv/linux/syscalls.list      |  1 -
 sysdeps/unix/sysv/linux/wait.c             | 41 +++++++++-
 sysdeps/unix/sysv/linux/wait4.c            | 87 ++++++++++++++++++++++
 sysdeps/unix/sysv/linux/waitpid.c          | 59 ++++++++++++++-
 sysdeps/unix/sysv/linux/waitpid_nocancel.c | 56 +++++++++++++-
 6 files changed, 239 insertions(+), 8 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/wait4.c

diff --git a/include/sys/wait.h b/include/sys/wait.h
index 5ac9cd6ca6b..fab0e17f7d5 100644
--- a/include/sys/wait.h
+++ b/include/sys/wait.h
@@ -13,7 +13,6 @@ extern __pid_t __wait (int *__stat_loc);
 extern __pid_t __wait3 (int *__stat_loc,
 			int __options, struct rusage * __usage);
 extern __pid_t __wait4 (__pid_t __pid, int *__stat_loc,
-			int __options, struct rusage *__usage)
-			attribute_hidden;
+			int __options, struct rusage *__usage);
 #endif
 #endif
diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
index e374f97b5f8..31f1d258fe1 100644
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -69,7 +69,6 @@ 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/wait.c b/sysdeps/unix/sysv/linux/wait.c
index c2385c752e2..28a27af8135 100644
--- a/sysdeps/unix/sysv/linux/wait.c
+++ b/sysdeps/unix/sysv/linux/wait.c
@@ -26,9 +26,44 @@
 pid_t
 __libc_wait (int *stat_loc)
 {
-  pid_t result = SYSCALL_CANCEL (wait4, WAIT_ANY, stat_loc, 0,
-				 (struct rusage *) NULL);
-  return result;
+#ifdef __NR_wait4
+  return SYSCALL_CANCEL (wait4, WAIT_ANY, stat_loc, 0,
+                         (struct rusage *) NULL);
+#else
+  siginfo_t infop;
+  __pid_t ret;
+
+  ret = SYSCALL_CANCEL (waitid, P_ALL, 0, &infop, WEXITED, NULL);
+
+  if (ret < 0)
+      return ret;
+
+  if (stat_loc)
+    {
+      *stat_loc = 0;
+      switch (infop.si_code)
+      {
+        case CLD_EXITED:
+            *stat_loc = infop.si_status << 8;
+            break;
+        case CLD_DUMPED:
+            *stat_loc = 0x80;
+            /* Fallthrough */
+        case CLD_KILLED:
+            *stat_loc |= infop.si_status;
+            break;
+        case CLD_TRAPPED:
+        case CLD_STOPPED:
+            *stat_loc = infop.si_status << 8 | 0x7f;
+            break;
+        case CLD_CONTINUED:
+            *stat_loc = 0xffff;
+            break;
+      }
+    }
+
+  return infop.si_pid;
+#endif
 }
 
 weak_alias (__libc_wait, __wait)
diff --git a/sysdeps/unix/sysv/linux/wait4.c b/sysdeps/unix/sysv/linux/wait4.c
new file mode 100644
index 00000000000..6d6fea34f9a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/wait4.c
@@ -0,0 +1,87 @@
+/* Linux wait4 syscall implementation.
+   Copyright (C) 1991-2019 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 <errno.h>
+#include <sys/resource.h>
+#include <stddef.h>
+
+__pid_t
+__wait4 (__pid_t pid, int *stat_loc, int options,
+         struct rusage *usage)
+{
+#ifdef __NR_wait4
+  return INLINE_SYSCALL_CALL (wait4, pid, stat_loc, options, usage);
+#else
+  __pid_t ret;
+  idtype_t idtype = P_PID;
+  siginfo_t infop;
+
+  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;
+
+  ret = INLINE_SYSCALL_CALL (waitid, idtype, pid, &infop, options, usage);
+
+  if (ret < 0)
+      return ret;
+
+  if (stat_loc)
+    {
+      *stat_loc = 0;
+      switch (infop.si_code)
+      {
+        case CLD_EXITED:
+            *stat_loc = infop.si_status << 8;
+            break;
+        case CLD_DUMPED:
+            *stat_loc = 0x80;
+            /* Fallthrough */
+        case CLD_KILLED:
+            *stat_loc |= infop.si_status;
+            break;
+        case CLD_TRAPPED:
+        case CLD_STOPPED:
+            *stat_loc = infop.si_status << 8 | 0x7f;
+            break;
+        case CLD_CONTINUED:
+            *stat_loc = 0xffff;
+            break;
+      }
+    }
+
+  return infop.si_pid;
+#endif
+}
+
+weak_alias (__wait4, wait4)
diff --git a/sysdeps/unix/sysv/linux/waitpid.c b/sysdeps/unix/sysv/linux/waitpid.c
index d35aac01bcc..a02275c3ff5 100644
--- a/sysdeps/unix/sysv/linux/waitpid.c
+++ b/sysdeps/unix/sysv/linux/waitpid.c
@@ -20,14 +20,71 @@
 #include <sysdep-cancel.h>
 #include <stdlib.h>
 #include <sys/wait.h>
+#include <unistd.h>
 
 __pid_t
 __waitpid (__pid_t pid, int *stat_loc, int options)
 {
 #ifdef __NR_waitpid
   return SYSCALL_CANCEL (waitpid, pid, stat_loc, options);
-#else
+#elif defined(__NR_wait4)
   return SYSCALL_CANCEL (wait4, pid, stat_loc, options, NULL);
+#else
+  __pid_t ret;
+  idtype_t idtype = P_PID;
+  siginfo_t infop;
+
+  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;
+
+  ret = SYSCALL_CANCEL (waitid, idtype, pid, &infop, options, NULL);
+
+  if (ret < 0)
+    {
+      return ret;
+    }
+
+  if (stat_loc)
+    {
+      *stat_loc = 0;
+      switch (infop.si_code)
+        {
+        case CLD_EXITED:
+            *stat_loc = infop.si_status << 8;
+            break;
+        case CLD_DUMPED:
+            *stat_loc = 0x80;
+            /* Fallthrough */
+        case CLD_KILLED:
+            *stat_loc |= infop.si_status;
+            break;
+        case CLD_TRAPPED:
+        case CLD_STOPPED:
+            *stat_loc = infop.si_status << 8 | 0x7f;
+            break;
+        case CLD_CONTINUED:
+            *stat_loc = 0xffff;
+            break;
+        }
+    }
+
+  return infop.si_pid;
 #endif
 }
 libc_hidden_def (__waitpid)
diff --git a/sysdeps/unix/sysv/linux/waitpid_nocancel.c b/sysdeps/unix/sysv/linux/waitpid_nocancel.c
index 3697c6b938c..59b07c5f73d 100644
--- a/sysdeps/unix/sysv/linux/waitpid_nocancel.c
+++ b/sysdeps/unix/sysv/linux/waitpid_nocancel.c
@@ -27,8 +27,62 @@ __waitpid_nocancel (__pid_t pid, int *stat_loc, int options)
 {
 #ifdef __NR_waitpid
   return INLINE_SYSCALL_CALL (waitpid, pid, stat_loc, options);
-#else
+#elif defined (__NR_wait4)
   return INLINE_SYSCALL_CALL (wait4, pid, stat_loc, options, NULL);
+#else
+  __pid_t ret;
+  idtype_t idtype = P_PID;
+  siginfo_t infop;
+
+  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;
+
+  ret = INLINE_SYSCALL_CALL (waitid, idtype, pid, &infop, options, NULL);
+
+  if (ret < 0)
+      return ret;
+
+  if (stat_loc)
+    {
+      *stat_loc = 0;
+      switch (infop.si_code)
+        {
+        case CLD_EXITED:
+            *stat_loc = infop.si_status << 8;
+            break;
+        case CLD_DUMPED:
+            *stat_loc = 0x80;
+            /* Fallthrough */
+        case CLD_KILLED:
+            *stat_loc |= infop.si_status;
+            break;
+        case CLD_TRAPPED:
+        case CLD_STOPPED:
+            *stat_loc = infop.si_status << 8 | 0x7f;
+            break;
+        case CLD_CONTINUED:
+            *stat_loc = 0xffff;
+            break;
+        }
+    }
+
+  return infop.si_pid;
 #endif
 }
 libc_hidden_def (__waitpid_nocancel)
-- 
2.23.0