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 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
- 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
- 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.
argument specifies the address of a guarded storage control
block structure and is currently used only by the GS_SET_BC_CB
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.
- command was GS_SET_BC_CB and the copying of the guarded
storage control block structure pointed by the gs_cb argument has
- The value provided in the command argument was not valid.
- 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 architecture.
The guarded storage facility is available beginning with System z14.
Glibc does not provide a wrapper for this system call, use syscall
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