arch/um/Kconfig.um

   1 # SPDX-License-Identifier: GPL-2.0
   2 config STATIC_LINK
   3         bool "Force a static link"
   4         default n
   5         help
   6           This option gives you the ability to force a static link of UML.
   7           Normally, UML is linked as a shared binary.  This is inconvenient for
   8           use in a chroot jail.  So, if you intend to run UML inside a chroot,
   9           you probably want to say Y here.
  10           Additionally, this option enables using higher memory spaces (up to
  11           2.75G) for UML.
  12
  13 source "mm/Kconfig"
  14
  15 config LD_SCRIPT_STATIC
  16         bool
  17         default y
  18         depends on STATIC_LINK
  19
  20 config LD_SCRIPT_DYN
  21         bool
  22         default y
  23         depends on !LD_SCRIPT_STATIC
  24         select MODULE_REL_CRCS if MODVERSIONS
  25
  26 source "fs/Kconfig.binfmt"
  27
  28 config HOSTFS
  29         tristate "Host filesystem"
  30         help
  31           While the User-Mode Linux port uses its own root file system for
  32           booting and normal file access, this module lets the UML user
  33           access files stored on the host.  It does not require any
  34           network connection between the Host and UML.  An example use of
  35           this might be:
  36
  37           mount none /tmp/fromhost -t hostfs -o /tmp/umlshare
  38
  39           where /tmp/fromhost is an empty directory inside UML and
  40           /tmp/umlshare is a directory on the host with files the UML user
  41           wishes to access.
  42
  43           For more information, see
  44           <http://user-mode-linux.sourceforge.net/hostfs.html>.
  45
  46           If you'd like to be able to work with files stored on the host,
  47           say Y or M here; otherwise say N.
  48
  49 config MCONSOLE
  50         bool "Management console"
  51         depends on PROC_FS
  52         default y
  53         help
  54           The user mode linux management console is a low-level interface to
  55           the kernel, somewhat like the i386 SysRq interface.  Since there is
  56           a full-blown operating system running under every user mode linux
  57           instance, there is much greater flexibility possible than with the
  58           SysRq mechanism.
  59
  60           If you answer 'Y' to this option, to use this feature, you need the
  61           mconsole client (called uml_mconsole) which is present in CVS in
  62           2.4.5-9um and later (path /tools/mconsole), and is also in the
  63           distribution RPM package in 2.4.6 and later.
  64
  65           It is safe to say 'Y' here.
  66
  67 config MAGIC_SYSRQ
  68         bool "Magic SysRq key"
  69         depends on MCONSOLE
  70         help
  71           If you say Y here, you will have some control over the system even
  72           if the system crashes for example during kernel debugging (e.g., you
  73           will be able to flush the buffer cache to disk, reboot the system
  74           immediately or dump some status information). A key for each of the
  75           possible requests is provided.
  76
  77           This is the feature normally accomplished by pressing a key
  78           while holding SysRq (Alt+PrintScreen).
  79
  80           On UML, this is accomplished by sending a "sysrq" command with
  81           mconsole, followed by the letter for the requested command.
  82
  83           The keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
  84           unless you really know what this hack does.
  85
  86 config KERNEL_STACK_ORDER
  87         int "Kernel stack size order"
  88         default 1 if 64BIT
  89         range 1 10 if 64BIT
  90         default 0 if !64BIT
  91         help
  92           This option determines the size of UML kernel stacks.  They will
  93           be 1 << order pages.  The default is OK unless you're running Valgrind
  94           on UML, in which case, set this to 3.
  95
  96 config MMAPPER
  97         tristate "iomem emulation driver"
  98         help
  99           This driver allows a host file to be used as emulated IO memory inside
 100           UML.
 101
 102 config NO_DMA
 103         def_bool y
 104
 105 config PGTABLE_LEVELS
 106         int
 107         default 3 if 3_LEVEL_PGTABLES
 108         default 2
 109
 110 config SECCOMP
 111         def_bool y
 112         prompt "Enable seccomp to safely compute untrusted bytecode"
 113         ---help---
 114           This kernel feature is useful for number crunching applications
 115           that may need to compute untrusted bytecode during their
 116           execution. By using pipes or other transports made available to
 117           the process as file descriptors supporting the read/write
 118           syscalls, it's possible to isolate those applications in
 119           their own address space using seccomp. Once seccomp is
 120           enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
 121           and the task is only allowed to execute a few safe syscalls
 122           defined by each seccomp mode.
 123
 124           If unsure, say Y.