Section: System Calls (2)
s390_guarded_storage - operations with z/Architecture guarded storage facility
int s390_guarded_storage(int command, struct gs_cb *gs_cb);
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.
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
function wrapper provided in the
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
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
will not have any effect.
argument specifies the address of a guarded storage control block structure
and is currently used only by the
command; all other aforementioned commands ignore this argument.
On success, the return value of
On error, -1 is returned, and
is set appropriately.
and the copying of the guarded storage control block structure pointed by the
argument has failed.
The value provided in the
argument was not valid.
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 architecture.
The guarded storage facility is available beginning with System z14.
Glibc does not provide a wrapper for this system call, use
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
(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
field), and its layout is available as a
structure type definition in the
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