# SPDX-License-Identifier: GPL-2.0 menu "UML-specific options" config UML bool default y select ARCH_HAS_KCOV select ARCH_NO_PREEMPT select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_SECCOMP_FILTER select HAVE_UID16 select HAVE_FUTEX_CMPXCHG if FUTEX select HAVE_DEBUG_KMEMLEAK select HAVE_DEBUG_BUGVERBOSE select GENERIC_IRQ_SHOW select GENERIC_CPU_DEVICES select GENERIC_CLOCKEVENTS select HAVE_GCC_PLUGINS select TTY # Needed for line.c config MMU bool default y config NO_IOMEM def_bool y config ISA bool config SBUS bool config TRACE_IRQFLAGS_SUPPORT bool default y config LOCKDEP_SUPPORT bool default y config STACKTRACE_SUPPORT bool default y select STACKTRACE config GENERIC_CALIBRATE_DELAY bool default y config HZ int default 100 config NR_CPUS int range 1 1 default 1 source "arch/$(HEADER_ARCH)/um/Kconfig" config STATIC_LINK bool "Force a static link" default n help This option gives you the ability to force a static link of UML. Normally, UML is linked as a shared binary. This is inconvenient for use in a chroot jail. So, if you intend to run UML inside a chroot, you probably want to say Y here. Additionally, this option enables using higher memory spaces (up to 2.75G) for UML. config LD_SCRIPT_STATIC bool default y depends on STATIC_LINK config LD_SCRIPT_DYN bool default y depends on !LD_SCRIPT_STATIC select MODULE_REL_CRCS if MODVERSIONS config HOSTFS tristate "Host filesystem" help While the User-Mode Linux port uses its own root file system for booting and normal file access, this module lets the UML user access files stored on the host. It does not require any network connection between the Host and UML. An example use of this might be: mount none /tmp/fromhost -t hostfs -o /tmp/umlshare where /tmp/fromhost is an empty directory inside UML and /tmp/umlshare is a directory on the host with files the UML user wishes to access. For more information, see <http://user-mode-linux.sourceforge.net/hostfs.html>. If you'd like to be able to work with files stored on the host, say Y or M here; otherwise say N. config MCONSOLE bool "Management console" depends on PROC_FS default y help The user mode linux management console is a low-level interface to the kernel, somewhat like the i386 SysRq interface. Since there is a full-blown operating system running under every user mode linux instance, there is much greater flexibility possible than with the SysRq mechanism. If you answer 'Y' to this option, to use this feature, you need the mconsole client (called uml_mconsole) which is present in CVS in 2.4.5-9um and later (path /tools/mconsole), and is also in the distribution RPM package in 2.4.6 and later. It is safe to say 'Y' here. config MAGIC_SYSRQ bool "Magic SysRq key" depends on MCONSOLE help If you say Y here, you will have some control over the system even if the system crashes for example during kernel debugging (e.g., you will be able to flush the buffer cache to disk, reboot the system immediately or dump some status information). A key for each of the possible requests is provided. This is the feature normally accomplished by pressing a key while holding SysRq (Alt+PrintScreen). On UML, this is accomplished by sending a "sysrq" command with mconsole, followed by the letter for the requested command. The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y unless you really know what this hack does. config KERNEL_STACK_ORDER int "Kernel stack size order" default 2 if 64BIT range 2 10 if 64BIT default 1 if !64BIT help This option determines the size of UML kernel stacks. They will be 1 << order pages. The default is OK unless you're running Valgrind on UML, in which case, set this to 3. It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on older (pre-2017) CPUs. It is not recommended on newer CPUs due to the increase in the size of the state which needs to be saved when handling signals. config MMAPPER tristate "iomem emulation driver" help This driver allows a host file to be used as emulated IO memory inside UML. config NO_DMA def_bool y config PGTABLE_LEVELS int default 3 if 3_LEVEL_PGTABLES default 2 config SECCOMP def_bool y prompt "Enable seccomp to safely compute untrusted bytecode" ---help--- This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their execution. By using pipes or other transports made available to the process as file descriptors supporting the read/write syscalls, it's possible to isolate those applications in their own address space using seccomp. Once seccomp is enabled via prctl(PR_SET_SECCOMP), it cannot be disabled and the task is only allowed to execute a few safe syscalls defined by each seccomp mode. If unsure, say Y. endmenu source "arch/um/drivers/Kconfig"