Linux/Alpha: don't use timeval32 system calls.

Linux/Alpha has two versions of several system call wrappers that take
or return data of type "struct timeval" (possibly nested inside a
larger structure).  The GLIBC_2.0 version is a compat symbol that
calls __NR_osf_foo or __NR_old_foo and uses a struct timeval with a
32-bit tv_sec field.  The GLIBC_2.1 version is used for current code,
calls __NR_foo, and uses a struct timeval with a 64-bit tv_sec field.

This patch changes all of the compat symbols of this type to be
wrappers around their GLIBC_2.1 counterparts; the compatibility system
calls will no longer be used.  It serves as a proposal for part of how
we do the transition to 64-bit time_t on systems that currently use
32-bit time_t:

 * The patched glibc will NOT use system calls that involve 32-bit
   time_t to implement its compatibility symbols.  This will make both
   our lives and the kernel maintainers' lives easier.  The primary
   argument I've seen against it is that the kernel could warn about
   uses of the old system calls, helping people find old binaries that
   need to be recompiled.  I think there are several other ways we
   could accomplish this, e.g. scripts to scan the filesystem for
   binaries with references to the old symbol versions, or issuing
   diagnostics ourselves.

 * The compat symbols do NOT report failure after the Y2038 deadline.
   An earlier revision of this patch had them return -1 and set errno
   to EOVERFLOW, but Adhemerval pointed out that many of them have
   already performed side effects at the point where we discover the
   overflow, so that would break more than it fixes.  Also, we don't
   want people to be _checking_ for EOVERFLOW from these functions; we
   want them to recompile with 64-bit time_t.  So it's not actually
   useful for them to report failure to the calling code.

 * What they do do, when they encounter overflow, is saturate the
   overflowed "struct timeval"(s): tv_sec is set to INT32_MAX and
   tv_nsec is set to 999999.  That means time stops advancing for
   programs with 32-bit time_t when they reach the deadline.  That's
   obviously going to break stuff, but I think wrapping around is
   probably going to break _more_ stuff.  I'd be interested to hear
   arguments against, if anyone has one.

The new header file tv32-compat.h is currently Alpha-specific but I
mean for it to be reused to aid in writing wrappers for all affected
architectures.  I only put it in sysdeps/unix/sysv/linux/alpha for now
because I haven't checked whether the various "foo32" structures it
defines agree with the ABI for ports other than Linux/Alpha.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/alpha/osf_wait4.c b/sysdeps/unix/sysv/linux/alpha/osf_wait4.c
new file mode 100644
index 0000000000..e8db554660
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/alpha/osf_wait4.c
@@ -0,0 +1,41 @@
+/* wait4 -- wait for process to change state.  Linux/Alpha/tv32 version.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <shlib-compat.h>
+
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
+
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <sys/wait.h>
+#include <tv32-compat.h>
+
+pid_t
+attribute_compat_text_section
+__wait4_tv32 (pid_t pid, int *status, int options, struct rusage32 *usage32)
+{
+  struct rusage usage64;
+  pid_t child = __wait4 (pid, status, options, &usage64);
+
+  if (child >= 0 && usage32 != NULL)
+    rusage64_to_rusage32 (usage32, &usage64);
+  return child;
+}
+
+compat_symbol (libc, __wait4_tv32, wait4, GLIBC_2_0);
+#endif