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SYNOPSIS top

#include <asm/guarded_storage.h>/* Definition ofGS_*constants */#include <sys/syscall.h>/* Definition ofSYS_*constants */#include <unistd.h>int syscall(SYS_s390_guarded_storage, intcommand,struct gs_cb *gs_cb);Note: glibc provides no wrapper fors390_guarded_storage(), necessitating the use ofsyscall(2).

DESCRIPTION top

Thes390_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. Thecommand 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 theload_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 thegs_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 theGS_SET_BC_CBcommand.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 withGS_SET_BC_CBwill not have any effect. Thegs_cb argument specifies the address of a guarded storage control block structure and is currently used only by theGS_SET_BC_CBcommand; all other aforementioned commands ignore this argument.

ERRORS top

EFAULTcommand wasGS_SET_BC_CBand the copying of the guarded storage control block structure pointed by thegs_cb argument has failed.EINVALThe value provided in thecommand argument was not valid.ENOMEMcommand was one ofGS_ENABLEorGS_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.

NOTES top

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. Thegs_cb structure has a fieldgsepla (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 thegseha field), and its layout is available as ags_eplstructure type definition in theasm/guarded_storage.h header.

COLOPHON top

This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17s390_guarded_storage(2)

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