s390_guarded_storage(2) — Linux manual page


s390_guarded_storage(2)    System Calls Manual   s390_guarded_storage(2)

NAME         top

       s390_guarded_storage - operations with z/Architecture guarded
       storage facility

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <asm/guarded_storage.h> /* Definition of GS_* constants */
       #include <sys/syscall.h>         /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_s390_guarded_storage, int command,
                   struct gs_cb *gs_cb);

       Note: glibc provides no wrapper for s390_guarded_storage(),
       necessitating the use of syscall(2).

DESCRIPTION         top

       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:

              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 the
              asm/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.

              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.

              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 command GS_BROADCAST.

              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.

              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         top

       On success, the return value of s390_guarded_storage() is 0.

       On error, -1 is returned, and errno is set to indicate the error.

ERRORS         top

       EFAULT command was GS_SET_BC_CB and the copying of the guarded
              storage control block structure pointed by the gs_cb
              argument has failed.

       EINVAL The value provided in the command argument was not valid.

       ENOMEM command was one of GS_ENABLE or GS_SET_BC_CB, and the
              allocation of a new guarded storage control block has

              The guarded storage facility is not supported by the

STANDARDS         top

       Linux on s390.

HISTORY         top

       Linux 4.12.  System z14.

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.

       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.

SEE ALSO         top


COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02        s390_guarded_storage(2)

Pages that refer to this page: syscalls(2)