1# SPDX-License-Identifier: GPL-2.0 2 3menu "UML-specific options" 4 5config UML 6 bool 7 default y 8 select ARCH_HAS_CPU_FINALIZE_INIT 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 HAVE_COPY_THREAD_TLS 19 select GENERIC_IRQ_SHOW 20 select GENERIC_CPU_DEVICES 21 select GENERIC_CLOCKEVENTS 22 select HAVE_GCC_PLUGINS 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 STATIC_LINK 67 bool "Force a static link" 68 default n 69 help 70 This option gives you the ability to force a static link of UML. 71 Normally, UML is linked as a shared binary. This is inconvenient for 72 use in a chroot jail. So, if you intend to run UML inside a chroot, 73 you probably want to say Y here. 74 Additionally, this option enables using higher memory spaces (up to 75 2.75G) for UML. 76 77config LD_SCRIPT_STATIC 78 bool 79 default y 80 depends on STATIC_LINK 81 82config LD_SCRIPT_DYN 83 bool 84 default y 85 depends on !LD_SCRIPT_STATIC 86 select MODULE_REL_CRCS if MODVERSIONS 87 88config LD_SCRIPT_DYN_RPATH 89 bool "set rpath in the binary" if EXPERT 90 default y 91 depends on LD_SCRIPT_DYN 92 help 93 Add /lib (and /lib64 for 64-bit) to the linux binary's rpath 94 explicitly. 95 96 You may need to turn this off if compiling for nix systems 97 that have their libraries in random /nix directories and 98 might otherwise unexpected use libraries from /lib or /lib64 99 instead of the desired ones. 100 101config HOSTFS 102 tristate "Host filesystem" 103 help 104 While the User-Mode Linux port uses its own root file system for 105 booting and normal file access, this module lets the UML user 106 access files stored on the host. It does not require any 107 network connection between the Host and UML. An example use of 108 this might be: 109 110 mount none /tmp/fromhost -t hostfs -o /tmp/umlshare 111 112 where /tmp/fromhost is an empty directory inside UML and 113 /tmp/umlshare is a directory on the host with files the UML user 114 wishes to access. 115 116 For more information, see 117 <http://user-mode-linux.sourceforge.net/hostfs.html>. 118 119 If you'd like to be able to work with files stored on the host, 120 say Y or M here; otherwise say N. 121 122config MCONSOLE 123 bool "Management console" 124 depends on PROC_FS 125 default y 126 help 127 The user mode linux management console is a low-level interface to 128 the kernel, somewhat like the i386 SysRq interface. Since there is 129 a full-blown operating system running under every user mode linux 130 instance, there is much greater flexibility possible than with the 131 SysRq mechanism. 132 133 If you answer 'Y' to this option, to use this feature, you need the 134 mconsole client (called uml_mconsole) which is present in CVS in 135 2.4.5-9um and later (path /tools/mconsole), and is also in the 136 distribution RPM package in 2.4.6 and later. 137 138 It is safe to say 'Y' here. 139 140config MAGIC_SYSRQ 141 bool "Magic SysRq key" 142 depends on MCONSOLE 143 help 144 If you say Y here, you will have some control over the system even 145 if the system crashes for example during kernel debugging (e.g., you 146 will be able to flush the buffer cache to disk, reboot the system 147 immediately or dump some status information). A key for each of the 148 possible requests is provided. 149 150 This is the feature normally accomplished by pressing a key 151 while holding SysRq (Alt+PrintScreen). 152 153 On UML, this is accomplished by sending a "sysrq" command with 154 mconsole, followed by the letter for the requested command. 155 156 The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y 157 unless you really know what this hack does. 158 159config KERNEL_STACK_ORDER 160 int "Kernel stack size order" 161 default 2 if 64BIT 162 range 2 10 if 64BIT 163 default 1 if !64BIT 164 help 165 This option determines the size of UML kernel stacks. They will 166 be 1 << order pages. The default is OK unless you're running Valgrind 167 on UML, in which case, set this to 3. 168 It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on 169 older (pre-2017) CPUs. It is not recommended on newer CPUs due to the 170 increase in the size of the state which needs to be saved when handling 171 signals. 172 173config MMAPPER 174 tristate "iomem emulation driver" 175 help 176 This driver allows a host file to be used as emulated IO memory inside 177 UML. 178 179config NO_DMA 180 def_bool y 181 182config PGTABLE_LEVELS 183 int 184 default 3 if 3_LEVEL_PGTABLES 185 default 2 186 187config SECCOMP 188 def_bool y 189 prompt "Enable seccomp to safely compute untrusted bytecode" 190 ---help--- 191 This kernel feature is useful for number crunching applications 192 that may need to compute untrusted bytecode during their 193 execution. By using pipes or other transports made available to 194 the process as file descriptors supporting the read/write 195 syscalls, it's possible to isolate those applications in 196 their own address space using seccomp. Once seccomp is 197 enabled via prctl(PR_SET_SECCOMP), it cannot be disabled 198 and the task is only allowed to execute a few safe syscalls 199 defined by each seccomp mode. 200 201 If unsure, say Y. 202 203config UML_TIME_TRAVEL_SUPPORT 204 bool 205 prompt "Support time-travel mode (e.g. for test execution)" 206 help 207 Enable this option to support time travel inside the UML instance. 208 209 After enabling this option, two modes are accessible at runtime 210 (selected by the kernel command line), see the kernel's command- 211 line help for more details. 212 213 It is safe to say Y, but you probably don't need this. 214 215endmenu 216 217source "arch/um/drivers/Kconfig" 218