1S390_GUARDED_STORAGE(2) System Calls Manual S390_GUARDED_STORAGE(2)
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6 s390_guarded_storage - operations with z/Architecture guarded storage
7 facility
8
10 #include <asm/guarded_storage.h>
11 int s390_guarded_storage(int command, struct gs_cb *gs_cb);
13
15 The s390_guarded_storage() system call enables the use of the Guarded
16 Storage Facility (a z/Architecture-specific feature) for user-space
17 processes.
18 The guarded storage facility is a hardware feature that allows marking
20 up to 64 memory regions (as of z14) as guarded; reading a pointer with
21 a newly introduced "Load Guarded" (LGG) or "Load Logical and Shift
22 Guarded" (LLGFSG) instructions will cause a range check on the loaded
23 value and invoke a (previously set up) user-space handler if one of the
24 guarded regions is affected.
25 The command argument indicates which function to perform. The follow‐
27 ing commands are supported:
28 GS_ENABLE
30 Enable the guarded storage facility for the calling task. The
31 initial content of the guarded storage control block will be all
32 zeros. After enablement, user-space code can use the "Load
33 Guarded Storage Controls" (LGSC) instruction (or the
34 load_gs_cb() function wrapper provided in the asm/guarded_stor‐
35 age.h header) to load an arbitrary control block. While a task
36 is enabled, the kernel will save and restore the calling content
37 of the guarded storage registers on context switch.
38 GS_DISABLE
40 Disables the use of the guarded storage facility for the calling
41 task. The kernel will cease to save and restore the content of
42 the guarded storage registers, the task-specific content of
43 these registers is lost.
44 GS_SET_BC_CB
46 Set a broadcast guarded storage control block to the one pro‐
47 vided in the gs_cb argument. This is called per thread and as‐
48 sociates a specific guarded storage control block with the call‐
49 ing task. This control block will be used in the broadcast com‐
50 mand GS_BROADCAST.
51 GS_CLEAR_BC_CB
53 Clears the broadcast guarded storage control block. The guarded
54 storage control block will no longer have the association estab‐
55 lished by the GS_SET_BC_CB command.
56 GS_BROADCAST
58 Sends a broadcast to all thread siblings of the calling task.
59 Every sibling that has established a broadcast guarded storage
60 control block will load this control block and will be enabled
61 for guarded storage. The broadcast guarded storage control
62 block is consumed; a second broadcast without a refresh of the
63 stored control block with GS_SET_BC_CB will not have any effect.
64 The gs_cb argument specifies the address of a guarded storage control
66 block structure and is currently used only by the GS_SET_BC_CB command;
67 all other aforementioned commands ignore this argument.
68
70 On success, the return value of s390_guarded_storage() is 0.
71 On error, -1 is returned, and errno is set appropriately.
73
75 EFAULT command was GS_SET_BC_CB and the copying of the guarded storage
76 control block structure pointed by the gs_cb argument has
77 failed.
78 EINVAL The value provided in the command argument was not valid.
80 ENOMEM command was one of GS_ENABLE or GS_SET_BC_CB, and the allocation
82 of a new guarded storage control block has failed.
83 EOPNOTSUPP
85 The guarded storage facility is not supported by the hardware.
86
88 This system call is available since Linux 4.12.
89
91 This Linux-specific system call is available only on the s390 architec‐
92 ture.
93 The guarded storage facility is available beginning with System z14.
95
97 Glibc does not provide a wrapper for this system call, use syscall(2)
98 to call it.
99 The description of the guarded storage facility along with related
101 instructions and Guarded Storage Control Block and Guarded Storage
102 Event Parameter List structure layouts is available in "z/Architecture
103 Principles of Operations" beginning from the twelfth edition.
104 The gs_cb structure has a field gsepla (Guarded Storage Event Parameter
106 List Address), which is a user-space pointer to a Guarded Storage Event
107 Parameter List structure (that contains the address of the aforemen‐
108 tioned event handler in the gseha field), and its layout is available
109 as a gs_epl structure type definition in the asm/guarded_storage.h
110 header.
111
113 syscall(2)
114
116 This page is part of release 5.02 of the Linux man-pages project. A
117 description of the project, information about reporting bugs, and the
118 latest version of this page, can be found at
119 https://www.kernel.org/doc/man-pages/.
120Linux Programmer's Manual 2019-03-06 S390_GUARDED_STORAGE(2)