Section (2) s390_guarded_storage
Name
s390_guarded_storage — operations with z/Architecture guarded storage facility
Synopsis
#include <asm/guarded_storage.h>
int
s390_guarded_storage( |
int command, |
struct gs_cb *gs_cb) ; |
DESCRIPTION
The s390_guarded_storage
()
system call enables the use of the Guarded Storage Facility
(a z/Architecture-specific feature) for user-space
processes.
The guarded storage facility is a hardware feature that allows marking up to 64 memory regions (as of z14) as guarded; reading a pointer with a newly introduced Load Guarded (LGG) or Load Logical and Shift Guarded (LLGFSG) instructions will cause a range check on the loaded value and invoke a (previously set up) user-space handler if one of the guarded regions is affected.
The command
argument indicates which function to perform. The following
commands are supported:
GS_ENABLE
-
Enable the guarded storage facility for the calling task. The initial content of the guarded storage control block will be all zeros. After enablement, user-space code can use the Load Guarded Storage Controls (LGSC) instruction (or the
load_gs_cb
() function wrapper provided in theasm/guarded_storage.h
header) to load an arbitrary control block. While a task is enabled, the kernel will save and restore the calling content of the guarded storage registers on context switch. GS_DISABLE
-
Disables the use of the guarded storage facility for the calling task. The kernel will cease to save and restore the content of the guarded storage registers, the task-specific content of these registers is lost.
GS_SET_BC_CB
-
Set a broadcast guarded storage control block to the one provided in the
gs_cb
argument. This is called per thread and associates a specific guarded storage control block with the calling task. This control block will be used in the broadcast commandGS_BROADCAST
. GS_CLEAR_BC_CB
-
Clears the broadcast guarded storage control block. The guarded storage control block will no longer have the association established by the
GS_SET_BC_CB
command. GS_BROADCAST
-
Sends a broadcast to all thread siblings of the calling task. Every sibling that has established a broadcast guarded storage control block will load this control block and will be enabled for guarded storage. The broadcast guarded storage control block is consumed; a second broadcast without a refresh of the stored control block with
GS_SET_BC_CB
will not have any effect.
The gs_cb
argument
specifies the address of a guarded storage control block
structure and is currently used only by the GS_SET_BC_CB
command; all other
aforementioned commands ignore this argument.
RETURN VALUE
On success, the return value of s390_guarded_storage
() is 0.
On error, −1 is returned, and errno
is set appropriately.
ERRORS
- EFAULT
-
command
wasGS_SET_BC_CB
and the copying of the guarded storage control block structure pointed by thegs_cb
argument has failed. - EINVAL
-
The value provided in the
command
argument was not valid. - ENOMEM
-
command
was one ofGS_ENABLE
orGS_SET_BC_CB
, and the allocation of a new guarded storage control block has failed. - EOPNOTSUPP
-
The guarded storage facility is not supported by the hardware.
CONFORMING TO
This Linux-specific system call is available only on the s390 architecture.
The guarded storage facility is available beginning with System z14.
NOTES
Glibc does not provide a wrapper for this system call, use syscall(2) to call it.
The description of the guarded storage facility along with related instructions and Guarded Storage Control Block and Guarded Storage Event Parameter List structure layouts is available in z/Architecture Principles of Operations beginning from the twelfth edition.
The gs_cb
structure has a field gsepla
(Guarded Storage Event
Parameter List Address), which is a user-space pointer to a
Guarded Storage Event Parameter List structure (that contains
the address of the aforementioned event handler in the
gseha
field), and
its layout is available as a gs_epl
structure type
definition in the asm/guarded_storage.h
header.
COLOPHON
This page is part of release 5.04 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
Copyright (C) 2018 Eugene Syromyatnikov <evgsyrgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |