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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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065038706f
Sometimes it can be useful to run with "time travel" inside the UML instance, for example for testing. For example, some tests for the wireless subsystem and userspace are based on hwsim, a virtual wireless adapter. Some tests can take a long time to run because they e.g. wait for 120 seconds to elapse for some regulatory checks. This obviously goes faster if it need not actually wait that long, but time inside the test environment just "bumps up" when there's nothing to do. Add CONFIG_UML_TIME_TRAVEL_SUPPORT to enable code to support such modes at runtime, selected on the command line: * just "time-travel", in which time inside the UML instance can move faster than real time, if there's nothing to do * "time-travel=inf-cpu" in which time also moves slower and any CPU processing takes no time at all, which allows to implement consistent behaviour regardless of host CPU load (or speed) or debug overhead. An additional "time-travel-start=<seconds>" parameter is also supported in this case to start the wall clock at this time (in unix epoch). With this enabled, the test mentioned above goes from a runtime of about 140 seconds (with startup overhead and all) to being CPU bound and finishing in 15 seconds (on my slow laptop). Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Richard Weinberger <richard@nod.at>
201 lines
5.3 KiB
Text
201 lines
5.3 KiB
Text
# SPDX-License-Identifier: GPL-2.0
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menu "UML-specific options"
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config UML
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bool
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default y
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select ARCH_HAS_KCOV
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select ARCH_NO_PREEMPT
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select HAVE_ARCH_AUDITSYSCALL
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select HAVE_ARCH_SECCOMP_FILTER
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select HAVE_UID16
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select HAVE_FUTEX_CMPXCHG if FUTEX
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select HAVE_DEBUG_KMEMLEAK
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select HAVE_DEBUG_BUGVERBOSE
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select GENERIC_IRQ_SHOW
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select GENERIC_CPU_DEVICES
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select GENERIC_CLOCKEVENTS
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select HAVE_GCC_PLUGINS
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select TTY # Needed for line.c
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config MMU
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bool
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default y
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config NO_IOMEM
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def_bool y
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config ISA
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bool
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config SBUS
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bool
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config TRACE_IRQFLAGS_SUPPORT
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bool
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default y
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config LOCKDEP_SUPPORT
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bool
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default y
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config STACKTRACE_SUPPORT
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bool
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default y
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select STACKTRACE
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config GENERIC_CALIBRATE_DELAY
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bool
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default y
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config HZ
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int
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default 100
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config NR_CPUS
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int
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range 1 1
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default 1
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source "arch/$(HEADER_ARCH)/um/Kconfig"
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config STATIC_LINK
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bool "Force a static link"
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default n
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help
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This option gives you the ability to force a static link of UML.
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Normally, UML is linked as a shared binary. This is inconvenient for
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use in a chroot jail. So, if you intend to run UML inside a chroot,
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you probably want to say Y here.
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Additionally, this option enables using higher memory spaces (up to
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2.75G) for UML.
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config LD_SCRIPT_STATIC
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bool
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default y
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depends on STATIC_LINK
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config LD_SCRIPT_DYN
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bool
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default y
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depends on !LD_SCRIPT_STATIC
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select MODULE_REL_CRCS if MODVERSIONS
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config HOSTFS
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tristate "Host filesystem"
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help
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While the User-Mode Linux port uses its own root file system for
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booting and normal file access, this module lets the UML user
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access files stored on the host. It does not require any
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network connection between the Host and UML. An example use of
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this might be:
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mount none /tmp/fromhost -t hostfs -o /tmp/umlshare
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where /tmp/fromhost is an empty directory inside UML and
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/tmp/umlshare is a directory on the host with files the UML user
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wishes to access.
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For more information, see
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<http://user-mode-linux.sourceforge.net/hostfs.html>.
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If you'd like to be able to work with files stored on the host,
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say Y or M here; otherwise say N.
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config MCONSOLE
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bool "Management console"
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depends on PROC_FS
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default y
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help
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The user mode linux management console is a low-level interface to
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the kernel, somewhat like the i386 SysRq interface. Since there is
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a full-blown operating system running under every user mode linux
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instance, there is much greater flexibility possible than with the
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SysRq mechanism.
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If you answer 'Y' to this option, to use this feature, you need the
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mconsole client (called uml_mconsole) which is present in CVS in
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2.4.5-9um and later (path /tools/mconsole), and is also in the
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distribution RPM package in 2.4.6 and later.
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It is safe to say 'Y' here.
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config MAGIC_SYSRQ
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bool "Magic SysRq key"
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depends on MCONSOLE
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help
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If you say Y here, you will have some control over the system even
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if the system crashes for example during kernel debugging (e.g., you
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will be able to flush the buffer cache to disk, reboot the system
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immediately or dump some status information). A key for each of the
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possible requests is provided.
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This is the feature normally accomplished by pressing a key
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while holding SysRq (Alt+PrintScreen).
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On UML, this is accomplished by sending a "sysrq" command with
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mconsole, followed by the letter for the requested command.
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The keys are documented in <file:Documentation/admin-guide/sysrq.rst>. Don't say Y
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unless you really know what this hack does.
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config KERNEL_STACK_ORDER
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int "Kernel stack size order"
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default 2 if 64BIT
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range 2 10 if 64BIT
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default 1 if !64BIT
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help
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This option determines the size of UML kernel stacks. They will
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be 1 << order pages. The default is OK unless you're running Valgrind
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on UML, in which case, set this to 3.
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It is possible to reduce the stack to 1 for 64BIT and 0 for 32BIT on
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older (pre-2017) CPUs. It is not recommended on newer CPUs due to the
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increase in the size of the state which needs to be saved when handling
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signals.
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config MMAPPER
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tristate "iomem emulation driver"
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help
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This driver allows a host file to be used as emulated IO memory inside
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UML.
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config NO_DMA
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def_bool y
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config PGTABLE_LEVELS
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int
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default 3 if 3_LEVEL_PGTABLES
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default 2
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config SECCOMP
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def_bool y
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prompt "Enable seccomp to safely compute untrusted bytecode"
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---help---
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This kernel feature is useful for number crunching applications
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that may need to compute untrusted bytecode during their
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execution. By using pipes or other transports made available to
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the process as file descriptors supporting the read/write
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syscalls, it's possible to isolate those applications in
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their own address space using seccomp. Once seccomp is
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enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
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and the task is only allowed to execute a few safe syscalls
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defined by each seccomp mode.
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If unsure, say Y.
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config UML_TIME_TRAVEL_SUPPORT
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bool
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prompt "Support time-travel mode (e.g. for test execution)"
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help
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Enable this option to support time travel inside the UML instance.
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After enabling this option, two modes are accessible at runtime
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(selected by the kernel command line), see the kernel's command-
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line help for more details.
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It is safe to say Y, but you probably don't need this.
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endmenu
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source "arch/um/drivers/Kconfig"
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