Section (2) s390_guarded_storage
s390_guarded_storage — operations with z/Architecture guarded storage facility
|struct gs_cb *gs_cb
system call enables the use of the Guarded Storage Facility
(a z/Architecture-specific feature) for user-space
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.
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.hheader) 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_cbargument. 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
Clears the broadcast guarded storage control block. The guarded storage control block will no longer have the association established by the
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_CBwill not have any effect.
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.
On success, the return value of
s390_guarded_storage() is 0.
On error, −1 is returned, and
errno is set appropriately.
GS_SET_BC_CBand the copying of the guarded storage control block structure pointed by the
gs_cbargument has failed.
The value provided in the
commandargument was not valid.
commandwas one of
GS_SET_BC_CB, and the allocation of a new guarded storage control block has failed.
The guarded storage facility is not supported by the hardware.
This Linux-specific system call is available only on the s390 architecture.
The guarded storage facility is available beginning with System z14.
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.
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
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Copyright (C) 2018 Eugene Syromyatnikov <evgsyrgmail.com>
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