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>

1 files changed, 0 insertions, 144 deletions

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