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linux/arch/um/Kconfig
Paolo 'Blaisorblade' Giarrusso b2670eacfb [PATCH] uml: use DEFCONFIG_LIST to avoid reading host's config 
This should make sure that, for UML, host's configuration files are not
considered, which avoids various pains to the user.  Our dependency are such
that the obtained Kconfig will be valid and will lead to successful
compilation - however they cannot prevent an user from disabling any boot
device, and if an option is not set in the read .config (say
/boot/config-XXX), with make menuconfig ARCH=um, it is not set.  This always
disables UBD and all console I/O channels, which leads to non-working UML
kernels, so this bothers users - especially now, since it will happen on
almost every machine (/boot/config-`uname -r` exists almost on every machine).
 It can be workarounded with make defconfig ARCH=um, but it is non-obvious and
can be avoided, so please _do_ merge this patch.

Given the existence of options, it could be interesting to implement
(additionally) "option required" - with it, Kconfig will refuse reading a
.config file (from wherever it comes) if the given option is not set.  With
this, one could mark with it the option characteristic of the given
architecture (it was an old proposal of Roman Zippel, when I pointed out our
problem):

config UML
	option required
	default y

However this should be further discussed:
*) for x86, it must support constructs like:

==arch/i386/Kconfig==
config 64BIT
	option required
	default n
where Kconfig must require that CONFIG_64BIT is disabled or not present in the
read .config.

*) do we want to do such checks only for the starting defconfig or also for
   .config? Which leads to:
*) I may want to port a x86_64 .config to x86 and viceversa, or even among more
   different archs. Should that be allowed, and in which measure (the user may
   force skipping the check for a .config or it is only given a warning by
   default)?

Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: <kbuild-devel@lists.sourceforge.net>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-20 10:26:36 -07:00

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config DEFCONFIG_LIST
string
option defconfig_list
default "arch/$ARCH/defconfig"
# UML uses the generic IRQ sugsystem
config GENERIC_HARDIRQS
bool
default y
config UML
bool
default y
config MMU
bool
default y
mainmenu "Linux/Usermode Kernel Configuration"
config ISA
bool
config SBUS
bool
config PCI
bool
config PCMCIA
bool
# Yet to do!
config TRACE_IRQFLAGS_SUPPORT
bool
default n
config LOCKDEP_SUPPORT
bool
default y
config STACKTRACE_SUPPORT
bool
default y
config GENERIC_CALIBRATE_DELAY
bool
default y
# Used in kernel/irq/manage.c and include/linux/irq.h
config IRQ_RELEASE_METHOD
bool
default y
menu "UML-specific options"
config MODE_TT
bool "Tracing thread support (DEPRECATED)"
default n
depends on BROKEN
help
This option controls whether tracing thread support is compiled
into UML. This option is largely obsolete, given that skas0 provides
skas security and performance without needing to patch the host.
It is safe to say 'N' here; saying 'Y' may cause additional problems
with the resulting binary even if you run UML in SKAS mode, and running
in TT mode is strongly *NOT RECOMMENDED*.
config STATIC_LINK
bool "Force a static link"
default n
depends on !MODE_TT
help
If CONFIG_MODE_TT is disabled, then this option gives you the ability
to force a static link of UML. Normally, if only skas mode is built
in to UML, it will be linked as a shared binary. This is inconvenient
for use in a chroot jail. So, if you intend to run UML inside a
chroot, and you disable CONFIG_MODE_TT, you probably want to say Y
here.
Additionally, this option enables using higher memory spaces (up to
2.75G) for UML - disabling CONFIG_MODE_TT and enabling this option leads
to best results for this.
config KERNEL_HALF_GIGS
int "Kernel address space size (in .5G units)"
default "1"
depends on MODE_TT
help
This determines the amount of address space that UML will allocate for
its own, measured in half Gigabyte units. The default is 1.
Change this only if you need to boot UML with an unusually large amount
of physical memory.
config MODE_SKAS
bool "Separate Kernel Address Space support" if MODE_TT
default y
help
This option controls whether skas (separate kernel address space)
support is compiled in.
Unless you have specific needs to use TT mode (which applies almost only
to developers), you should say Y here.
SKAS mode will make use of the SKAS3 patch if it is applied on the host
(and your UML will run in SKAS3 mode), but if no SKAS patch is applied
on the host it will run in SKAS0 mode, which is anyway faster than TT
mode.
source "arch/um/Kconfig.arch"
source "mm/Kconfig"
config LD_SCRIPT_STATIC
bool
default y
depends on MODE_TT || STATIC_LINK
config LD_SCRIPT_DYN
bool
default y
depends on !LD_SCRIPT_STATIC
config NET
bool "Networking support"
help
Unless you really know what you are doing, you should say Y here.
The reason is that some programs need kernel networking support even
when running on a stand-alone machine that isn't connected to any
other computer. If you are upgrading from an older kernel, you
should consider updating your networking tools too because changes
in the kernel and the tools often go hand in hand. The tools are
contained in the package net-tools, the location and version number
of which are given in <file:Documentation/Changes>.
For a general introduction to Linux networking, it is highly
recommended to read the NET-HOWTO, available from
<http://www.tldp.org/docs.html#howto>.
source "fs/Kconfig.binfmt"
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 HPPFS
tristate "HoneyPot ProcFS (EXPERIMENTAL)"
depends on EXPERIMENTAL
help
hppfs (HoneyPot ProcFS) is a filesystem which allows UML /proc
entries to be overridden, removed, or fabricated from the host.
Its purpose is to allow a UML to appear to be a physical machine
by removing or changing anything in /proc which gives away the
identity of a UML.
See <http://user-mode-linux.sf.net/hppfs.html> for more information.
You only need this if you are setting up a UML honeypot. Otherwise,
it is safe to say 'N' here.
config MCONSOLE
bool "Management console"
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/sysrq.txt>. Don't say Y
unless you really know what this hack does.
config SMP
bool "Symmetric multi-processing support (EXPERIMENTAL)"
default n
#SMP_BROKEN is for x86_64.
depends on MODE_TT && EXPERIMENTAL && (!SMP_BROKEN || (BROKEN && SMP_BROKEN))
help
This option enables UML SMP support.
It is NOT related to having a real SMP box. Not directly, at least.
UML implements virtual SMP by allowing as many processes to run
simultaneously on the host as there are virtual processors configured.
Obviously, if the host is a uniprocessor, those processes will
timeshare, but, inside UML, will appear to be running simultaneously.
If the host is a multiprocessor, then UML processes may run
simultaneously, depending on the host scheduler.
This, however, is supported only in TT mode. So, if you use the SKAS
patch on your host, switching to TT mode and enabling SMP usually gives
you worse performances.
Also, since the support for SMP has been under-developed, there could
be some bugs being exposed by enabling SMP.
If you don't know what to do, say N.
config NR_CPUS
int "Maximum number of CPUs (2-32)"
range 2 32
depends on SMP
default "32"
config NEST_LEVEL
int "Nesting level"
default "0"
help
This is set to the number of layers of UMLs that this UML will be run
in. Normally, this is zero, meaning that it will run directly on the
host. Setting it to one will build a UML that can run inside a UML
that is running on the host. Generally, if you intend this UML to run
inside another UML, set CONFIG_NEST_LEVEL to one more than the host
UML.
Note that if the hosting UML has its CONFIG_KERNEL_HALF_GIGS set to
greater than one, then the guest UML should have its CONFIG_NEST_LEVEL
set to the host's CONFIG_NEST_LEVEL + CONFIG_KERNEL_HALF_GIGS.
Only change this if you are running nested UMLs.
config HIGHMEM
bool "Highmem support (EXPERIMENTAL)"
depends on !64BIT && EXPERIMENTAL
default n
help
This was used to allow UML to run with big amounts of memory.
Currently it is unstable, so if unsure say N.
To use big amounts of memory, it is recommended to disable TT mode (i.e.
CONFIG_MODE_TT) and enable static linking (i.e. CONFIG_STATIC_LINK) -
this should allow the guest to use up to 2.75G of memory.
config KERNEL_STACK_ORDER
int "Kernel stack size order"
default 2
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.
config UML_REAL_TIME_CLOCK
bool "Real-time Clock"
default y
help
This option makes UML time deltas match wall clock deltas. This should
normally be enabled. The exception would be if you are debugging with
UML and spend long times with UML stopped at a breakpoint. In this
case, when UML is restarted, it will call the timer enough times to make
up for the time spent at the breakpoint. This could result in a
noticeable lag. If this is a problem, then disable this option.
endmenu
source "init/Kconfig"
source "drivers/block/Kconfig"
source "arch/um/Kconfig.char"
source "drivers/base/Kconfig"
source "net/Kconfig"
source "arch/um/Kconfig.net"
source "drivers/net/Kconfig"
source "drivers/connector/Kconfig"
source "fs/Kconfig"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"
menu "SCSI support"
depends on BROKEN
config SCSI
tristate "SCSI support"
# This gives us free_dma, which scsi.c wants.
config GENERIC_ISA_DMA
bool
depends on SCSI
default y
source "arch/um/Kconfig.scsi"
endmenu
source "drivers/md/Kconfig"
if BROKEN
source "drivers/mtd/Kconfig"
endif
#This is just to shut up some Kconfig warnings, so no prompt.
config INPUT
bool
default n
source "arch/um/Kconfig.debug"
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