xref: /openbmc/linux/arch/um/Kconfig (revision cc1e6315)
1# SPDX-License-Identifier: GPL-2.0
2
3menu "UML-specific options"
4
5config UML
6	bool
7	default y
8	select ARCH_HAS_KCOV
9	select ARCH_NO_PREEMPT
10	select HAVE_ARCH_AUDITSYSCALL
11	select HAVE_ARCH_SECCOMP_FILTER
12	select HAVE_UID16
13	select HAVE_FUTEX_CMPXCHG if FUTEX
14	select HAVE_DEBUG_KMEMLEAK
15	select GENERIC_IRQ_SHOW
16	select GENERIC_CPU_DEVICES
17	select GENERIC_CLOCKEVENTS
18	select HAVE_GCC_PLUGINS
19	select TTY # Needed for line.c
20
21config MMU
22	bool
23	default y
24
25config NO_IOMEM
26	def_bool y
27
28config ISA
29	bool
30
31config SBUS
32	bool
33
34config PCI
35	bool
36
37config PCMCIA
38	bool
39
40config TRACE_IRQFLAGS_SUPPORT
41	bool
42	default y
43
44config LOCKDEP_SUPPORT
45	bool
46	default y
47
48config STACKTRACE_SUPPORT
49	bool
50	default y
51	select STACKTRACE
52
53config GENERIC_CALIBRATE_DELAY
54	bool
55	default y
56
57config HZ
58	int
59	default 100
60
61config NR_CPUS
62	int
63	range 1 1
64	default 1
65
66source "arch/$(HEADER_ARCH)/um/Kconfig"
67
68config STATIC_LINK
69	bool "Force a static link"
70	default n
71	help
72	  This option gives you the ability to force a static link of UML.
73	  Normally, UML is linked as a shared binary.  This is inconvenient for
74	  use in a chroot jail.  So, if you intend to run UML inside a chroot,
75	  you probably want to say Y here.
76	  Additionally, this option enables using higher memory spaces (up to
77	  2.75G) for UML.
78
79config LD_SCRIPT_STATIC
80	bool
81	default y
82	depends on STATIC_LINK
83
84config LD_SCRIPT_DYN
85	bool
86	default y
87	depends on !LD_SCRIPT_STATIC
88        select MODULE_REL_CRCS if MODVERSIONS
89
90config HOSTFS
91	tristate "Host filesystem"
92	help
93          While the User-Mode Linux port uses its own root file system for
94          booting and normal file access, this module lets the UML user
95          access files stored on the host.  It does not require any
96          network connection between the Host and UML.  An example use of
97          this might be:
98
99          mount none /tmp/fromhost -t hostfs -o /tmp/umlshare
100
101          where /tmp/fromhost is an empty directory inside UML and
102          /tmp/umlshare is a directory on the host with files the UML user
103          wishes to access.
104
105          For more information, see
106          <http://user-mode-linux.sourceforge.net/hostfs.html>.
107
108          If you'd like to be able to work with files stored on the host,
109          say Y or M here; otherwise say N.
110
111config MCONSOLE
112	bool "Management console"
113	depends on PROC_FS
114	default y
115	help
116          The user mode linux management console is a low-level interface to
117          the kernel, somewhat like the i386 SysRq interface.  Since there is
118          a full-blown operating system running under every user mode linux
119          instance, there is much greater flexibility possible than with the
120          SysRq mechanism.
121
122          If you answer 'Y' to this option, to use this feature, you need the
123          mconsole client (called uml_mconsole) which is present in CVS in
124          2.4.5-9um and later (path /tools/mconsole), and is also in the
125          distribution RPM package in 2.4.6 and later.
126
127          It is safe to say 'Y' here.
128
129config MAGIC_SYSRQ
130	bool "Magic SysRq key"
131	depends on MCONSOLE
132	help
133	  If you say Y here, you will have some control over the system even
134	  if the system crashes for example during kernel debugging (e.g., you
135	  will be able to flush the buffer cache to disk, reboot the system
136	  immediately or dump some status information). A key for each of the
137	  possible requests is provided.
138
139	  This is the feature normally accomplished by pressing a key
140	  while holding SysRq (Alt+PrintScreen).
141
142	  On UML, this is accomplished by sending a "sysrq" command with
143	  mconsole, followed by the letter for the requested command.
144
145	  The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y
146	  unless you really know what this hack does.
147
148config KERNEL_STACK_ORDER
149	int "Kernel stack size order"
150	default 1 if 64BIT
151	range 1 10 if 64BIT
152	default 0 if !64BIT
153	help
154	  This option determines the size of UML kernel stacks.  They will
155	  be 1 << order pages.  The default is OK unless you're running Valgrind
156	  on UML, in which case, set this to 3.
157
158config MMAPPER
159	tristate "iomem emulation driver"
160	help
161	  This driver allows a host file to be used as emulated IO memory inside
162	  UML.
163
164config NO_DMA
165	def_bool y
166
167config PGTABLE_LEVELS
168	int
169	default 3 if 3_LEVEL_PGTABLES
170	default 2
171
172config SECCOMP
173	def_bool y
174	prompt "Enable seccomp to safely compute untrusted bytecode"
175	---help---
176	  This kernel feature is useful for number crunching applications
177	  that may need to compute untrusted bytecode during their
178	  execution. By using pipes or other transports made available to
179	  the process as file descriptors supporting the read/write
180	  syscalls, it's possible to isolate those applications in
181	  their own address space using seccomp. Once seccomp is
182	  enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
183	  and the task is only allowed to execute a few safe syscalls
184	  defined by each seccomp mode.
185
186	  If unsure, say Y.
187
188endmenu
189
190source "arch/um/drivers/Kconfig"
191