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 HAVE_DEBUG_BUGVERBOSE 16 select GENERIC_IRQ_SHOW 17 select GENERIC_CPU_DEVICES 18 select GENERIC_CLOCKEVENTS 19 select HAVE_GCC_PLUGINS 20 select TTY # Needed for line.c 21 22config MMU 23 bool 24 default y 25 26config NO_IOMEM 27 def_bool y 28 29config ISA 30 bool 31 32config SBUS 33 bool 34 35config TRACE_IRQFLAGS_SUPPORT 36 bool 37 default y 38 39config LOCKDEP_SUPPORT 40 bool 41 default y 42 43config STACKTRACE_SUPPORT 44 bool 45 default y 46 select STACKTRACE 47 48config GENERIC_CALIBRATE_DELAY 49 bool 50 default y 51 52config HZ 53 int 54 default 100 55 56config NR_CPUS 57 int 58 range 1 1 59 default 1 60 61source "arch/$(HEADER_ARCH)/um/Kconfig" 62 63config STATIC_LINK 64 bool "Force a static link" 65 default n 66 help 67 This option gives you the ability to force a static link of UML. 68 Normally, UML is linked as a shared binary. This is inconvenient for 69 use in a chroot jail. So, if you intend to run UML inside a chroot, 70 you probably want to say Y here. 71 Additionally, this option enables using higher memory spaces (up to 72 2.75G) for UML. 73 74config LD_SCRIPT_STATIC 75 bool 76 default y 77 depends on STATIC_LINK 78 79config LD_SCRIPT_DYN 80 bool 81 default y 82 depends on !LD_SCRIPT_STATIC 83 select MODULE_REL_CRCS if MODVERSIONS 84 85config HOSTFS 86 tristate "Host filesystem" 87 help 88 While the User-Mode Linux port uses its own root file system for 89 booting and normal file access, this module lets the UML user 90 access files stored on the host. It does not require any 91 network connection between the Host and UML. An example use of 92 this might be: 93 94 mount none /tmp/fromhost -t hostfs -o /tmp/umlshare 95 96 where /tmp/fromhost is an empty directory inside UML and 97 /tmp/umlshare is a directory on the host with files the UML user 98 wishes to access. 99 100 For more information, see 101 <http://user-mode-linux.sourceforge.net/hostfs.html>. 102 103 If you'd like to be able to work with files stored on the host, 104 say Y or M here; otherwise say N. 105 106config MCONSOLE 107 bool "Management console" 108 depends on PROC_FS 109 default y 110 help 111 The user mode linux management console is a low-level interface to 112 the kernel, somewhat like the i386 SysRq interface. Since there is 113 a full-blown operating system running under every user mode linux 114 instance, there is much greater flexibility possible than with the 115 SysRq mechanism. 116 117 If you answer 'Y' to this option, to use this feature, you need the 118 mconsole client (called uml_mconsole) which is present in CVS in 119 2.4.5-9um and later (path /tools/mconsole), and is also in the 120 distribution RPM package in 2.4.6 and later. 121 122 It is safe to say 'Y' here. 123 124config MAGIC_SYSRQ 125 bool "Magic SysRq key" 126 depends on MCONSOLE 127 help 128 If you say Y here, you will have some control over the system even 129 if the system crashes for example during kernel debugging (e.g., you 130 will be able to flush the buffer cache to disk, reboot the system 131 immediately or dump some status information). A key for each of the 132 possible requests is provided. 133 134 This is the feature normally accomplished by pressing a key 135 while holding SysRq (Alt+PrintScreen). 136 137 On UML, this is accomplished by sending a "sysrq" command with 138 mconsole, followed by the letter for the requested command. 139 140 The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y 141 unless you really know what this hack does. 142 143config KERNEL_STACK_ORDER 144 int "Kernel stack size order" 145 default 2 if 64BIT 146 range 2 10 if 64BIT 147 default 1 if !64BIT 148 help 149 This option determines the size of UML kernel stacks. They will 150 be 1 << order pages. The default is OK unless you're running Valgrind 151 on UML, in which case, set this to 3. 152 It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on 153 older (pre-2017) CPUs. It is not recommended on newer CPUs due to the 154 increase in the size of the state which needs to be saved when handling 155 signals. 156 157config MMAPPER 158 tristate "iomem emulation driver" 159 help 160 This driver allows a host file to be used as emulated IO memory inside 161 UML. 162 163config NO_DMA 164 def_bool y 165 166config PGTABLE_LEVELS 167 int 168 default 3 if 3_LEVEL_PGTABLES 169 default 2 170 171config SECCOMP 172 def_bool y 173 prompt "Enable seccomp to safely compute untrusted bytecode" 174 ---help--- 175 This kernel feature is useful for number crunching applications 176 that may need to compute untrusted bytecode during their 177 execution. By using pipes or other transports made available to 178 the process as file descriptors supporting the read/write 179 syscalls, it's possible to isolate those applications in 180 their own address space using seccomp. Once seccomp is 181 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled 182 and the task is only allowed to execute a few safe syscalls 183 defined by each seccomp mode. 184 185 If unsure, say Y. 186 187config UML_TIME_TRAVEL_SUPPORT 188 bool 189 prompt "Support time-travel mode (e.g. for test execution)" 190 help 191 Enable this option to support time travel inside the UML instance. 192 193 After enabling this option, two modes are accessible at runtime 194 (selected by the kernel command line), see the kernel's command- 195 line help for more details. 196 197 It is safe to say Y, but you probably don't need this. 198 199endmenu 200 201source "arch/um/drivers/Kconfig" 202