Linux: Remove <sys/sysctl.h> and the sysctl function

Linux 5.5 remove the system call in commit
61a47c1ad3a4dc6882f01ebdc88138ac62d0df03 ("Linux: Remove
<sys/sysctl.h>").  Therefore, the compat function is just a stub that
sets ENOSYS.

Due to SHLIB_COMPAT, new ports will not add the sysctl function anymore
automatically.

x32 already lacks the sysctl function, so an empty sysctl.c file is
used to suppress it.  Otherwise, a new compat symbol would be added.

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

14 files changed, 51 insertions, 277 deletions

diff --git a/NEWS b/NEWS
index 3cf738adfb..2424fecdc0 100644
--- a/NEWS
+++ b/NEWS
@@ -16,7 +16,11 @@ Major new features:
 
 Deprecated and removed features, and other changes affecting compatibility:
 
-  [Add deprecations, removals and changes affecting compatibility here]
+* The deprecated <sys/sysctl.h> header and the sysctl function have been
+  removed.  To support old binaries, the sysctl function continues to
+  exist as a compatibility symbol (on those architectures which had it),
+  but always fails with ENOSYS.  This reflects the removal of the system
+  call from all architectures, starting with Linux 5.5.
 
 Changes to build and runtime requirements:
 
diff --git a/include/sys/sysctl.h b/include/sys/sysctl.h
deleted file mode 100644
index fa102aa226..0000000000
--- a/include/sys/sysctl.h
+++ /dev/null
@@ -1,3 +0,0 @@
-#ifndef _SYS_SYSCTL_H
-#include_next <sys/sysctl.h>
-#endif  /* _SYS_SYSCTL_H */
diff --git a/manual/sysinfo.texi b/manual/sysinfo.texi
index 4beee0129b..4ca4555443 100644
--- a/manual/sysinfo.texi
+++ b/manual/sysinfo.texi
@@ -14,7 +14,6 @@ can make changes.
 * Platform Type::               Determining operating system and basic
                                   machine type
 * Filesystem Handling::         Controlling/querying mounts
-* System Parameters::           Getting and setting various system parameters
 @end menu
 
 To get information on parameters of the system that are built into the
@@ -1107,146 +1106,3 @@ to zeroes.  It is more widely available than @code{umount2} but since it
 lacks the possibility to forcefully unmount a filesystem is deprecated
 when @code{umount2} is also available.
 @end deftypefun
-
-
-
-@node System Parameters
-@section System Parameters
-
-This section describes the @code{sysctl} function, which gets and sets
-a variety of system parameters.
-
-The symbols used in this section are declared in the file @file{sys/sysctl.h}.
-
-@deftypefun int sysctl (int *@var{names}, int @var{nlen}, void *@var{oldval}, size_t *@var{oldlenp}, void *@var{newval}, size_t @var{newlen})
-@standards{BSD, sys/sysctl.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-@c Direct syscall, Linux only.
-
-@code{sysctl} gets or sets a specified system parameter.  There are so
-many of these parameters that it is not practical to list them all here,
-but here are some examples:
-
-@itemize @bullet
-@item network domain name
-@item paging parameters
-@item network Address Resolution Protocol timeout time
-@item maximum number of files that may be open
-@item root filesystem device
-@item when kernel was built
-@end itemize
-
-The set of available parameters depends on the kernel configuration and
-can change while the system is running, particularly when you load and
-unload loadable kernel modules.
-
-The system parameters with which @code{sysctl} is concerned are arranged
-in a hierarchical structure like a hierarchical filesystem.  To identify
-a particular parameter, you specify a path through the structure in a
-way analogous to specifying the pathname of a file.  Each component of
-the path is specified by an integer and each of these integers has a
-macro defined for it by @file{sys/sysctl.h}.  @var{names} is the path, in
-the form of an array of integers.  Each component of the path is one
-element of the array, in order.  @var{nlen} is the number of components
-in the path.
-
-For example, the first component of the path for all the paging
-parameters is the value @code{CTL_VM}.  For the free page thresholds, the
-second component of the path is @code{VM_FREEPG}.  So to get the free
-page threshold values, make @var{names} an array containing the two
-elements @code{CTL_VM} and @code{VM_FREEPG} and make @var{nlen} = 2.
-
-
-The format of the value of a parameter depends on the parameter.
-Sometimes it is an integer; sometimes it is an ASCII string; sometimes
-it is an elaborate structure.  In the case of the free page thresholds
-used in the example above, the parameter value is a structure containing
-several integers.
-
-In any case, you identify a place to return the parameter's value with
-@var{oldval} and specify the amount of storage available at that
-location as *@var{oldlenp}.  *@var{oldlenp} does double duty because it
-is also the output location that contains the actual length of the
-returned value.
-
-If you don't want the parameter value returned, specify a null pointer
-for @var{oldval}.
-
-To set the parameter, specify the address and length of the new value
-as @var{newval} and @var{newlen}.  If you don't want to set the parameter,
-specify a null pointer as @var{newval}.
-
-If you get and set a parameter in the same @code{sysctl} call, the value
-returned is the value of the parameter before it was set.
-
-Each system parameter has a set of permissions similar to the
-permissions for a file (including the permissions on directories in its
-path) that determine whether you may get or set it.  For the purposes of
-these permissions, every parameter is considered to be owned by the
-superuser and Group 0 so processes with that effective uid or gid may
-have more access to system parameters.  Unlike with files, the superuser
-does not invariably have full permission to all system parameters, because
-some of them are designed not to be changed ever.
-
-
-@code{sysctl} returns a zero return value if it succeeds.  Otherwise, it
-returns @code{-1} and sets @code{errno} appropriately.  Besides the
-failures that apply to all system calls, the following are the
-@code{errno} codes for all possible failures:
-
-@table @code
-@item EPERM
-The process is not permitted to access one of the components of the
-path of the system parameter or is not permitted to access the system parameter
-itself in the way (read or write) that it requested.
-@c There is some indication in the Linux 2.2 code that the code is trying to
-@c return EACCES here, but the EACCES value never actually makes it to the
-@c user.
-@item ENOTDIR
-There is no system parameter corresponding to @var{name}.
-@item EFAULT
-@var{oldval} is not null, which means the process wanted to read the parameter,
-but *@var{oldlenp} is zero, so there is no place to return it.
-@item EINVAL
-@itemize @bullet
-@item
-The process attempted to set a system parameter to a value that is not valid
-for that parameter.
-@item
-The space provided for the return of the system parameter is not the right
-size for that parameter.
-@end itemize
-@item ENOMEM
-This value may be returned instead of the more correct @code{EINVAL} in some
-cases where the space provided for the return of the system parameter is too
-small.
-
-@end table
-
-@end deftypefun
-
-If you have a Linux kernel with the @code{proc} filesystem, you can get
-and set most of the same parameters by reading and writing to files in
-the @code{sys} directory of the @code{proc} filesystem.  In the @code{sys}
-directory, the directory structure represents the hierarchical structure
-of the parameters.  E.g. you can display the free page thresholds with
-@smallexample
-cat /proc/sys/vm/freepages
-@end smallexample
-@c In Linux, the sysctl() and /proc instances of the parameter are created
-@c together.  The proc filesystem accesses the same data structure as
-@c sysctl(), which has special fields in it for /proc.  But it is still
-@c possible to create a sysctl-only parameter.
-
-Some more traditional and more widely available, though less general,
-@glibcadj{} functions for getting and setting some of the same system
-parameters are:
-
-@itemize @bullet
-@item
-@code{getdomainname}, @code{setdomainname}
-@item
-@code{gethostname}, @code{sethostname} (@xref{Host Identification}.)
-@item
-@code{uname} (@xref{Platform Type}.)
-@end itemize
diff --git a/scripts/check-installed-headers.sh b/scripts/check-installed-headers.sh
index f70340f098..aab56cf405 100644
--- a/scripts/check-installed-headers.sh
+++ b/scripts/check-installed-headers.sh
@@ -74,11 +74,6 @@ for header in "$@"; do
         (finclude/*)
             continue;;
 
-	# sys/sysctl.h produces a deprecation warning and therefore
-	# fails compilation with -Werror.
-	(sys/sysctl.h)
-	    continue;;
-
         # sys/vm86.h is "unsupported on x86-64" and errors out on that target.
         (sys/vm86.h)
             case "$is_x86_64" in
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 60dc5cf9e5..089a4899d5 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -54,9 +54,7 @@ CFLAGS-malloc.c += -DMORECORE_CLEARS=2
 endif
 
 ifeq ($(subdir),misc)
-include $(firstword $(wildcard $(sysdirs:=/sysctl.mk)))
-
-sysdep_routines += adjtimex clone umount umount2 readahead \
+sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
 		   setfsuid setfsgid epoll_pwait signalfd \
 		   eventfd eventfd_read eventfd_write prlimit \
 		   personality epoll_wait tee vmsplice splice \
@@ -71,7 +69,7 @@ CFLAGS-open_by_handle_at.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sync_file_range.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-tst-writev.c += "-DARTIFICIAL_LIMIT=(0x80000000-sysconf(_SC_PAGESIZE))"
 
-sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
+sysdep_headers += sys/mount.h sys/acct.h \
 		  sys/klog.h \
 		  sys/user.h sys/prctl.h \
 		  sys/kd.h sys/soundcard.h sys/vt.h \
@@ -81,7 +79,7 @@ sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
 		  bits/a.out.h sys/inotify.h sys/signalfd.h sys/eventfd.h \
 		  sys/timerfd.h sys/fanotify.h bits/eventfd.h bits/inotify.h \
 		  bits/signalfd.h bits/timerfd.h bits/epoll.h \
-		  bits/socket_type.h bits/syscall.h bits/sysctl.h \
+		  bits/socket_type.h bits/syscall.h \
 		  bits/mman-linux.h bits/mman-shared.h bits/ptrace-shared.h \
 		  bits/siginfo-arch.h bits/siginfo-consts-arch.h \
 		  bits/procfs.h bits/procfs-id.h bits/procfs-extra.h \
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index d385085c61..9a58dda9f2 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -177,6 +177,8 @@ libc {
   GLIBC_2.30 {
     getdents64; gettid; tgkill;
   }
+  GLIBC_2.32 {
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;
diff --git a/sysdeps/unix/sysv/linux/bits/sysctl.h b/sysdeps/unix/sysv/linux/bits/sysctl.h
deleted file mode 100644
index 81447b2f74..0000000000
--- a/sysdeps/unix/sysv/linux/bits/sysctl.h
+++ /dev/null
@@ -1 +0,0 @@
-/* Empty file.  */
diff --git a/sysdeps/unix/sysv/linux/x86/bits/sysctl.h b/sysdeps/unix/sysv/linux/microblaze/sysctl.c
index 873a2af109..d35dd8ef1e 100644
--- a/sysdeps/unix/sysv/linux/x86/bits/sysctl.h
+++ b/sysdeps/unix/sysv/linux/microblaze/sysctl.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2012-2020 Free Software Foundation, Inc.
+/* sysctl function stub.  microblaze version.
+   Copyright (C) 2020 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
@@ -15,6 +16,14 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#if defined __x86_64__ && defined __ILP32__
-# error "sysctl system call is unsupported in x32 kernel"
+/* microblaze is special because it has an ABI baseline of 2.18, but
+   still includes the __sysctl symbol.  */
+
+#ifdef SHARED
+
+# include <sysdeps/unix/sysv/linux/sysctl.c>
+
+strong_alias (___sysctl, ___sysctl2)
+compat_symbol (libc, ___sysctl2, __sysctl, GLIBC_2_2);
+
 #endif
diff --git a/sysdeps/unix/sysv/linux/generic/sysctl.c b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/sysctl.c
index e7d5a3cf93..25203e4aa4 100644
--- a/sysdeps/unix/sysv/linux/generic/sysctl.c
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/sysctl.c
@@ -1,6 +1,6 @@
-/* Copyright (C) 2011-2020 Free Software Foundation, Inc.
+/* sysctl function stub.  powerpc64le version.
+   Copyright (C) 2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
-   Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -13,20 +13,17 @@
    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
+   License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
+/* powerpc64le is special because it has an ABI baseline of 2.17, but
+   still includes the __sysctl symbol.  */
 
-#include <sysdep.h>
-#include <sys/syscall.h>
+#ifdef SHARED
 
-/* This deprecated syscall is no longer used (replaced with /proc/sys).  */
-int
-sysctl (int *name, int nlen, void *oldval, size_t *oldlenp,
-        void *newval, size_t newlen)
-{
-  __set_errno (ENOSYS);
-  return -1;
-}
-stub_warning (sysctl)
+# include <sysdeps/unix/sysv/linux/sysctl.c>
+
+strong_alias (___sysctl, ___sysctl2)
+compat_symbol (libc, ___sysctl2, __sysctl, GLIBC_2_2);
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/sys/sysctl.h b/sysdeps/unix/sysv/linux/sys/sysctl.h
deleted file mode 100644
index 1ead597244..0000000000
--- a/sysdeps/unix/sysv/linux/sys/sysctl.h
+++ /dev/null
@@ -1,76 +0,0 @@
-/* Copyright (C) 1996-2020 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	_SYS_SYSCTL_H
-#define	_SYS_SYSCTL_H	1
-
-#warning "The <sys/sysctl.h> header is deprecated and will be removed."
-
-#include <features.h>
-#define __need_size_t
-#include <stddef.h>
-/* Prevent more kernel headers than necessary to be included.  */
-#ifndef _LINUX_KERNEL_H
-# define _LINUX_KERNEL_H	1
-# define __undef_LINUX_KERNEL_H
-#endif
-#ifndef _LINUX_TYPES_H
-# define _LINUX_TYPES_H		1
-# define __undef_LINUX_TYPES_H
-#endif
-#ifndef _LINUX_LIST_H
-# define _LINUX_LIST_H		1
-# define __undef_LINUX_LIST_H
-#endif
-#ifndef __LINUX_COMPILER_H
-# define __LINUX_COMPILER_H	1
-# define __user
-# define __undef__LINUX_COMPILER_H
-#endif
-
-#include <linux/sysctl.h>
-
-#ifdef __undef_LINUX_KERNEL_H
-# undef _LINUX_KERNEL_H
-# undef __undef_LINUX_KERNEL_H
-#endif
-#ifdef __undef_LINUX_TYPES_H
-# undef _LINUX_TYPES_H
-# undef __undef_LINUX_TYPES_H
-#endif
-#ifdef __undef_LINUX_LIST_H
-# undef _LINUX_LIST_H
-# undef __undef_LINUX_LIST_H
-#endif
-#ifdef __undef__LINUX_COMPILER_H
-# undef __LINUX_COMPILER_H
-# undef __user
-# undef __undef__LINUX_COMPILER_H
-#endif
-
-#include <bits/sysctl.h>
-
-__BEGIN_DECLS
-
-/* Read or write system parameters.  */
-extern int sysctl (int *__name, int __nlen, void *__oldval,
-		   size_t *__oldlenp, void *__newval, size_t __newlen) __THROW
-  __attribute_deprecated__;
-
-__END_DECLS
-
-#endif	/* _SYS_SYSCTL_H */
diff --git a/sysdeps/unix/sysv/linux/sysctl.c b/sysdeps/unix/sysv/linux/sysctl.c
index 5ea8be8da1..389b958226 100644
--- a/sysdeps/unix/sysv/linux/sysctl.c
+++ b/sysdeps/unix/sysv/linux/sysctl.c
@@ -1,4 +1,4 @@
-/* Read or write system information.  Linux version.
+/* sysctl function stub.
    Copyright (C) 1996-2020 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -17,25 +17,20 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <errno.h>
-#include <linux/sysctl.h>
+#include <shlib-compat.h>
 
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-int
-__sysctl (int *name, int nlen, void *oldval, size_t *oldlenp,
-	  void *newval, size_t newlen)
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_32)
+int attribute_compat_text_section
+___sysctl (int *name, int nlen, void *oldval, size_t *oldlenp,
+           void *newval, size_t newlen)
 {
-  struct __sysctl_args args =
-  {
-    .name = name,
-    .nlen = nlen,
-    .oldval = oldval,
-    .oldlenp = oldlenp,
-    .newval = newval,
-    .newlen = newlen
-  };
-
-  return INLINE_SYSCALL (_sysctl, 1, &args);
+  __set_errno (ENOSYS);
+  return -1;
 }
-weak_alias (__sysctl, sysctl)
+compat_symbol (libc, ___sysctl, sysctl, GLIBC_2_0);
+
+# if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
+strong_alias (___sysctl, ___sysctl2)
+compat_symbol (libc, ___sysctl2, __sysctl, GLIBC_2_2);
+# endif
+#endif
diff --git a/sysdeps/unix/sysv/linux/sysctl.mk b/sysdeps/unix/sysv/linux/sysctl.mk
deleted file mode 100644
index 8d04d12e25..0000000000
--- a/sysdeps/unix/sysv/linux/sysctl.mk
+++ /dev/null
@@ -1,3 +0,0 @@
-# sysctl system call has been deprecated.  It is provided for backward
-# compatility.  New target shouldn't add it (see x86_64/x32/sysctl.mk).
-sysdep_routines += sysctl
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.c b/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.c
new file mode 100644
index 0000000000..88f2f741cf
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.c
@@ -0,0 +1,2 @@
+/* Despite the old base symbol version, x32 does not have a sysctl
+   function.  */
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.mk b/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.mk
deleted file mode 100644
index da018fe624..0000000000
--- a/sysdeps/unix/sysv/linux/x86_64/x32/sysctl.mk
+++ /dev/null
@@ -1 +0,0 @@
-# X32 doesn't support sysctl.