xref: /openbmc/linux/arch/um/Kconfig (revision e3211e41) 
1# SPDX-License-Identifier: GPL-2.0
2
3menu "UML-specific options"
4
5config UML
6	bool
7	default y
8	select ARCH_EPHEMERAL_INODES
9	select ARCH_HAS_KCOV
10	select ARCH_NO_PREEMPT
11	select HAVE_ARCH_AUDITSYSCALL
12	select HAVE_ARCH_SECCOMP_FILTER
13	select HAVE_ASM_MODVERSIONS
14	select HAVE_UID16
15	select HAVE_FUTEX_CMPXCHG if FUTEX
16	select HAVE_DEBUG_KMEMLEAK
17	select HAVE_DEBUG_BUGVERBOSE
18	select NO_DMA
19	select GENERIC_IRQ_SHOW
20	select GENERIC_CPU_DEVICES
21	select HAVE_GCC_PLUGINS
22	select SET_FS
23	select TTY # Needed for line.c
24
25config MMU
26	bool
27	default y
28
29config NO_IOMEM
30	def_bool y
31
32config ISA
33	bool
34
35config SBUS
36	bool
37
38config TRACE_IRQFLAGS_SUPPORT
39	bool
40	default y
41
42config LOCKDEP_SUPPORT
43	bool
44	default y
45
46config STACKTRACE_SUPPORT
47	bool
48	default y
49	select STACKTRACE
50
51config GENERIC_CALIBRATE_DELAY
52	bool
53	default y
54
55config HZ
56	int
57	default 100
58
59config NR_CPUS
60	int
61	range 1 1
62	default 1
63
64source "arch/$(HEADER_ARCH)/um/Kconfig"
65
66config MAY_HAVE_RUNTIME_DEPS
67        bool
68
69config STATIC_LINK
70	bool "Force a static link"
71	depends on CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS || !MAY_HAVE_RUNTIME_DEPS
72	help
73	  This option gives you the ability to force a static link of UML.
74	  Normally, UML is linked as a shared binary.  This is inconvenient for
75	  use in a chroot jail.  So, if you intend to run UML inside a chroot,
76	  you probably want to say Y here.
77	  Additionally, this option enables using higher memory spaces (up to
78	  2.75G) for UML.
79
80	  NOTE: This option is incompatible with some networking features which
81	  depend on features that require being dynamically loaded (like NSS).
82
83config LD_SCRIPT_STATIC
84	bool
85	default y
86	depends on STATIC_LINK
87
88config LD_SCRIPT_DYN
89	bool
90	default y
91	depends on !LD_SCRIPT_STATIC
92	select MODULE_REL_CRCS if MODVERSIONS
93
94config HOSTFS
95	tristate "Host filesystem"
96	help
97	  While the User-Mode Linux port uses its own root file system for
98	  booting and normal file access, this module lets the UML user
99	  access files stored on the host.  It does not require any
100	  network connection between the Host and UML.  An example use of
101	  this might be:
102
103	  mount none /tmp/fromhost -t hostfs -o /tmp/umlshare
104
105	  where /tmp/fromhost is an empty directory inside UML and
106	  /tmp/umlshare is a directory on the host with files the UML user
107	  wishes to access.
108
109	  For more information, see
110	  <http://user-mode-linux.sourceforge.net/hostfs.html>.
111
112	  If you'd like to be able to work with files stored on the host,
113	  say Y or M here; otherwise say N.
114
115config MCONSOLE
116	bool "Management console"
117	depends on PROC_FS
118	default y
119	help
120	  The user mode linux management console is a low-level interface to
121	  the kernel, somewhat like the i386 SysRq interface.  Since there is
122	  a full-blown operating system running under every user mode linux
123	  instance, there is much greater flexibility possible than with the
124	  SysRq mechanism.
125
126	  If you answer 'Y' to this option, to use this feature, you need the
127	  mconsole client (called uml_mconsole) which is present in CVS in
128	  2.4.5-9um and later (path /tools/mconsole), and is also in the
129	  distribution RPM package in 2.4.6 and later.
130
131	  It is safe to say 'Y' here.
132
133config MAGIC_SYSRQ
134	bool "Magic SysRq key"
135	depends on MCONSOLE
136	help
137	  If you say Y here, you will have some control over the system even
138	  if the system crashes for example during kernel debugging (e.g., you
139	  will be able to flush the buffer cache to disk, reboot the system
140	  immediately or dump some status information). A key for each of the
141	  possible requests is provided.
142
143	  This is the feature normally accomplished by pressing a key
144	  while holding SysRq (Alt+PrintScreen).
145
146	  On UML, this is accomplished by sending a "sysrq" command with
147	  mconsole, followed by the letter for the requested command.
148
149	  The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y
150	  unless you really know what this hack does.
151
152config KERNEL_STACK_ORDER
153	int "Kernel stack size order"
154	default 2 if 64BIT
155	range 2 10 if 64BIT
156	default 1 if !64BIT
157	help
158	  This option determines the size of UML kernel stacks.  They will
159	  be 1 << order pages.  The default is OK unless you're running Valgrind
160	  on UML, in which case, set this to 3.
161	  It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on
162	  older (pre-2017) CPUs. It is not recommended on newer CPUs due to the
163	  increase in the size of the state which needs to be saved when handling
164	  signals.
165
166config MMAPPER
167	tristate "iomem emulation driver"
168	help
169	  This driver allows a host file to be used as emulated IO memory inside
170	  UML.
171
172config PGTABLE_LEVELS
173	int
174	default 3 if 3_LEVEL_PGTABLES
175	default 2
176
177config UML_TIME_TRAVEL_SUPPORT
178	bool
179	prompt "Support time-travel mode (e.g. for test execution)"
180	# inf-cpu mode is incompatible with the benchmarking
181	depends on !RAID6_PQ_BENCHMARK
182	depends on !SMP
183	help
184	  Enable this option to support time travel inside the UML instance.
185
186	  After enabling this option, two modes are accessible at runtime
187	  (selected by the kernel command line), see the kernel's command-
188	  line help for more details.
189
190	  It is safe to say Y, but you probably don't need this.
191
192endmenu
193
194source "arch/um/drivers/Kconfig"
195
196config ARCH_SUSPEND_POSSIBLE
197	def_bool y
198
199source "kernel/power/Kconfig"
200