S390_GUARDED_STORAGE(2) System Calls Manual S390_GUARDED_STORAGE(2)
s390_guarded_storage - operations with z/Architecture guarded storage
int s390_guarded_storage(int command, struct gs_cb *gs_cb);
The s390_guarded_storage() 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.
The command argument indicates which function to perform. The follow-
ing 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_stor-
age.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 pro-
vided in the gs_cb argument. This is called per thread and as-
sociates a specific guarded storage control block with the call-
ing task. This control block will be used in the broadcast com-
Clears the broadcast guarded storage control block. The guarded
storage control block will no longer have the association estab-
lished 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.
On success, the return value of s390_guarded_storage() is 0.
On error, -1 is returned, and errno is set appropriately.
EFAULT command was GS_SET_BC_CB and the copying of the guarded storage
control block structure pointed by the gs_cb argument has
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 failed.
The guarded storage facility is not supported by the hardware.
This system call is available since Linux 4.12.
This Linux-specific system call is available only on the s390 architec-
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 in-
structions and Guarded Storage Control Block and Guarded Storage Event
Parameter List structure layouts is available in "z/Architecture Prin-
ciples 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 aforemen-
tioned event handler in the gseha field), and its layout is available
as a gs_epl structure type definition in the asm/guarded_storage.h
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Linux Programmer's Manual 2019-03-06 S390_GUARDED_STORAGE(2)
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