xref: /linux/arch/um/Kconfig (revision 399ead3a6d76cbdd29a716660db5c84a314dab70)

# SPDX-License-Identifier: GPL-2.0

menu "UML-specific options"

config UML
	bool
	default y
	select ARCH_DISABLE_KASAN_INLINE if STATIC_LINK
	select ARCH_NEEDS_DEFER_KASAN if STATIC_LINK
	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
	select ARCH_HAS_CACHE_LINE_SIZE
	select ARCH_HAS_CPU_FINALIZE_INIT
	select ARCH_HAS_FORTIFY_SOURCE
	select ARCH_HAS_GCOV_PROFILE_ALL
	select ARCH_HAS_KCOV
	select ARCH_HAS_STRNCPY_FROM_USER
	select ARCH_HAS_STRNLEN_USER
	select ARCH_HAS_STRICT_KERNEL_RWX
	select HAVE_ARCH_AUDITSYSCALL
	select HAVE_ARCH_KASAN if X86_64
	select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
	select HAVE_ARCH_SECCOMP_FILTER
	select HAVE_ASM_MODVERSIONS
	select HAVE_UID16
	select HAVE_DEBUG_KMEMLEAK
	select HAVE_DEBUG_BUGVERBOSE
	select HAVE_PAGE_SIZE_4KB
	select NO_DMA if !UML_DMA_EMULATION
	select OF_EARLY_FLATTREE if OF
	select GENERIC_IRQ_SHOW
	select GENERIC_CPU_DEVICES
	select GENERIC_SMP_IDLE_THREAD
	select HAVE_GCC_PLUGINS
	select ARCH_SUPPORTS_LTO_CLANG
	select ARCH_SUPPORTS_LTO_CLANG_THIN
	select TRACE_IRQFLAGS_SUPPORT
	select TTY # Needed for line.c
	select HAVE_ARCH_VMAP_STACK
	select HAVE_RUST
	select ARCH_HAS_UBSAN
	select HAVE_ARCH_TRACEHOOK
	select HAVE_SYSCALL_TRACEPOINTS
	select THREAD_INFO_IN_TASK
	select SPARSE_IRQ

config MMU
	bool
	default y

config UML_DMA_EMULATION
	bool

config NO_IOMEM
	bool "disable IOMEM" if EXPERT
	depends on !INDIRECT_IOMEM
	default y

config UML_IOMEM_EMULATION
	bool
	select INDIRECT_IOMEM
	select GENERIC_PCI_IOMAP

config ISA
	bool

config SBUS
	bool

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 UML_SUBARCH_SUPPORTS_SMP
	bool

config SMP
	bool "Symmetric multi-processing support"
	default n
	depends on UML_SUBARCH_SUPPORTS_SMP
	help
	  This option enables UML SMP support.

	  With this enabled, users can tell UML to start multiple virtual
	  processors. Each virtual processor is represented as a separate
	  host thread.

	  In UML, kthreads and normal threads (when running in kernel mode)
	  can be scheduled and executed simultaneously on different virtual
	  processors. However, the userspace code of normal threads still
	  runs within their respective single-threaded stubs.

	  That is, SMP support is available both within the kernel and
	  across different processes, but remains limited within threads
	  of the same process in userspace.

config NR_CPUS_RANGE_BEGIN
	int
	default 1 if !SMP
	default 2

config NR_CPUS_RANGE_END
	int
	default 1 if !SMP
	default 64

config NR_CPUS_DEFAULT
	int
	default 1 if !SMP
	default 2

config NR_CPUS
	int "Maximum number of CPUs" if SMP
	range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END
	default NR_CPUS_DEFAULT

source "arch/$(HEADER_ARCH)/um/Kconfig"

config MAY_HAVE_RUNTIME_DEPS
	bool

config STATIC_LINK
	bool "Force a static link"
	depends on !MAY_HAVE_RUNTIME_DEPS
	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.

	  NOTE: This option is incompatible with some networking features which
	  depend on features that require being dynamically loaded (like NSS).

config LD_SCRIPT_STATIC
	bool
	default y
	depends on STATIC_LINK

config LD_SCRIPT_DYN
	bool
	default y
	depends on !LD_SCRIPT_STATIC

config LD_SCRIPT_DYN_RPATH
	bool "set rpath in the binary" if EXPERT
	default y
	depends on LD_SCRIPT_DYN
	help
	  Add /lib (and /lib64 for 64-bit) to the linux binary's rpath
	  explicitly.

	  You may need to turn this off if compiling for nix systems
	  that have their libraries in random /nix directories and
	  might otherwise unexpected use libraries from /lib or /lib64
	  instead of the desired ones.

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 PGTABLE_LEVELS
	int
	default 4 if 64BIT
	default 2 if !64BIT

config UML_TIME_TRAVEL_SUPPORT
	bool
	prompt "Support time-travel mode (e.g. for test execution)"
	# inf-cpu mode is incompatible with the benchmarking
	depends on !RAID6_PQ_BENCHMARK
	depends on !SMP
	help
	  Enable this option to support time travel inside the UML instance.

	  After enabling this option, two modes are accessible at runtime
	  (selected by the kernel command line), see the kernel's command-
	  line help for more details.

	  It is safe to say Y, but you probably don't need this.

config UML_MAX_USERSPACE_ITERATIONS
	int
	prompt "Maximum number of unscheduled userspace iterations"
	default 10000
	depends on UML_TIME_TRAVEL_SUPPORT
	help
	  In UML inf-cpu and ext time-travel mode userspace can run without being
	  interrupted. This will eventually overwhelm the kernel and create OOM
	  situations (mainly RCU not running). This setting specifies the number
	  of kernel/userspace switches (minor/major page fault, signal or syscall)
	  for the same userspace thread before the sched_clock is advanced by a
	  jiffie to trigger scheduling.

	  Setting it to zero disables the feature.

config KASAN_SHADOW_OFFSET
	hex
	depends on KASAN
	default 0x100000000000
	help
	  This is the offset at which the ~16TB of shadow memory is
	  mapped and used by KASAN for memory debugging. This can be any
	  address that has at least KASAN_SHADOW_SIZE (total address space divided
	  by 8) amount of space so that the KASAN shadow memory does not conflict
	  with anything. The default is 0x100000000000, which works even if mem is
	  set to a large value. On low-memory systems, try 0x7fff8000, as it fits
	  into the immediate of most instructions, improving performance.

endmenu

source "arch/um/drivers/Kconfig"

config ARCH_SUSPEND_POSSIBLE
	def_bool y
	depends on !SMP

menu "Power management options"

source "kernel/power/Kconfig"

endmenu