6d98ca7364
So Ingo finally did figure out why UML broke with this option: UML passes gcc the -fno-unit-at-a-time flag, and apparently that wreaks havoc with gcc's inlining. We could turn off -fno-unit-at-a-time for UML for gcc4+ (which is what x86 does), but there's bad blood about this whole option, and it does show that the thing is just fragile as heck. So let tempers cool, and disable the thing, and we can revisit the decision later. Cc: Adrian Bunk <bunk@kernel.org> Cc: David Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
273 lines
7.7 KiB
Plaintext
273 lines
7.7 KiB
Plaintext
menu "Kernel hacking"
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config TRACE_IRQFLAGS_SUPPORT
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def_bool y
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source "lib/Kconfig.debug"
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config NONPROMISC_DEVMEM
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bool "Disable promiscuous /dev/mem"
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help
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The /dev/mem file by default only allows userspace access to PCI
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space and the BIOS code and data regions. This is sufficient for
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dosemu and X and all common users of /dev/mem. With this config
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option, you allow userspace access to all of memory, including
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kernel and userspace memory. Accidental access to this is
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obviously disasterous, but specific access can be used by people
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debugging the kernel.
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config EARLY_PRINTK
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bool "Early printk" if EMBEDDED
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default y
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help
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Write kernel log output directly into the VGA buffer or to a serial
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port.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. For normal operation
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it is not recommended because it looks ugly and doesn't cooperate
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with klogd/syslogd or the X server. You should normally N here,
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unless you want to debug such a crash.
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config DEBUG_STACKOVERFLOW
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bool "Check for stack overflows"
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depends on DEBUG_KERNEL
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help
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This option will cause messages to be printed if free stack space
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drops below a certain limit.
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config DEBUG_STACK_USAGE
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bool "Stack utilization instrumentation"
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depends on DEBUG_KERNEL
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help
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Enables the display of the minimum amount of free stack which each
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task has ever had available in the sysrq-T and sysrq-P debug output.
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This option will slow down process creation somewhat.
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config DEBUG_PAGEALLOC
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bool "Debug page memory allocations"
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depends on DEBUG_KERNEL
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help
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Unmap pages from the kernel linear mapping after free_pages().
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This results in a large slowdown, but helps to find certain types
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of memory corruptions.
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config DEBUG_PER_CPU_MAPS
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bool "Debug access to per_cpu maps"
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depends on DEBUG_KERNEL
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depends on X86_64_SMP
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default n
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help
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Say Y to verify that the per_cpu map being accessed has
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been setup. Adds a fair amount of code to kernel memory
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and decreases performance.
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Say N if unsure.
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config X86_PTDUMP
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bool "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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select DEBUG_FS
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help
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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If in doubt, say "N"
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config DEBUG_RODATA
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bool "Write protect kernel read-only data structures"
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default y
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depends on DEBUG_KERNEL
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help
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Mark the kernel read-only data as write-protected in the pagetables,
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in order to catch accidental (and incorrect) writes to such const
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data. This is recommended so that we can catch kernel bugs sooner.
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If in doubt, say "Y".
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config DIRECT_GBPAGES
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bool "Enable gbpages-mapped kernel pagetables"
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depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64
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help
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Enable gigabyte pages support (if the CPU supports it). This can
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improve the kernel's performance a tiny bit by reducing TLB
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pressure.
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This is experimental code.
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If in doubt, say "N".
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config DEBUG_RODATA_TEST
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bool "Testcase for the DEBUG_RODATA feature"
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depends on DEBUG_RODATA
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help
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This option enables a testcase for the DEBUG_RODATA
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feature as well as for the change_page_attr() infrastructure.
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If in doubt, say "N"
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config DEBUG_NX_TEST
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tristate "Testcase for the NX non-executable stack feature"
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depends on DEBUG_KERNEL && m
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help
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This option enables a testcase for the CPU NX capability
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and the software setup of this feature.
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If in doubt, say "N"
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config 4KSTACKS
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bool "Use 4Kb for kernel stacks instead of 8Kb"
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depends on X86_32
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help
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If you say Y here the kernel will use a 4Kb stacksize for the
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kernel stack attached to each process/thread. This facilitates
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running more threads on a system and also reduces the pressure
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on the VM subsystem for higher order allocations. This option
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will also use IRQ stacks to compensate for the reduced stackspace.
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config X86_FIND_SMP_CONFIG
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def_bool y
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depends on X86_LOCAL_APIC || X86_VOYAGER
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depends on X86_32
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config X86_MPPARSE
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def_bool y
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depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64
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config DOUBLEFAULT
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default y
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bool "Enable doublefault exception handler" if EMBEDDED
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depends on X86_32
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help
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This option allows trapping of rare doublefault exceptions that
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would otherwise cause a system to silently reboot. Disabling this
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option saves about 4k and might cause you much additional grey
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hair.
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config IOMMU_DEBUG
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bool "Enable IOMMU debugging"
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depends on GART_IOMMU && DEBUG_KERNEL
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depends on X86_64
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help
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Force the IOMMU to on even when you have less than 4GB of
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memory and add debugging code. On overflow always panic. And
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allow to enable IOMMU leak tracing. Can be disabled at boot
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time with iommu=noforce. This will also enable scatter gather
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list merging. Currently not recommended for production
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code. When you use it make sure you have a big enough
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IOMMU/AGP aperture. Most of the options enabled by this can
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be set more finegrained using the iommu= command line
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options. See Documentation/x86_64/boot-options.txt for more
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details.
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config IOMMU_LEAK
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bool "IOMMU leak tracing"
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depends on DEBUG_KERNEL
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depends on IOMMU_DEBUG
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help
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Add a simple leak tracer to the IOMMU code. This is useful when you
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are debugging a buggy device driver that leaks IOMMU mappings.
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#
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# IO delay types:
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#
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config IO_DELAY_TYPE_0X80
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int
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default "0"
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config IO_DELAY_TYPE_0XED
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int
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default "1"
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config IO_DELAY_TYPE_UDELAY
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int
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default "2"
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config IO_DELAY_TYPE_NONE
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int
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default "3"
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choice
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prompt "IO delay type"
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default IO_DELAY_0X80
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config IO_DELAY_0X80
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bool "port 0x80 based port-IO delay [recommended]"
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help
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This is the traditional Linux IO delay used for in/out_p.
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It is the most tested hence safest selection here.
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config IO_DELAY_0XED
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bool "port 0xed based port-IO delay"
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help
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Use port 0xed as the IO delay. This frees up port 0x80 which is
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often used as a hardware-debug port.
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config IO_DELAY_UDELAY
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bool "udelay based port-IO delay"
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help
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Use udelay(2) as the IO delay method. This provides the delay
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while not having any side-effect on the IO port space.
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config IO_DELAY_NONE
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bool "no port-IO delay"
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help
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No port-IO delay. Will break on old boxes that require port-IO
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delay for certain operations. Should work on most new machines.
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endchoice
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if IO_DELAY_0X80
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0X80
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endif
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if IO_DELAY_0XED
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0XED
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endif
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if IO_DELAY_UDELAY
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_UDELAY
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endif
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if IO_DELAY_NONE
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_NONE
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endif
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config DEBUG_BOOT_PARAMS
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bool "Debug boot parameters"
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depends on DEBUG_KERNEL
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depends on DEBUG_FS
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help
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This option will cause struct boot_params to be exported via debugfs.
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config CPA_DEBUG
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bool "CPA self-test code"
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depends on DEBUG_KERNEL
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help
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Do change_page_attr() self-tests every 30 seconds.
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config OPTIMIZE_INLINING
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bool "Allow gcc to uninline functions marked 'inline'"
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depends on BROKEN
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help
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This option determines if the kernel forces gcc to inline the functions
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developers have marked 'inline'. Doing so takes away freedom from gcc to
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do what it thinks is best, which is desirable for the gcc 3.x series of
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compilers. The gcc 4.x series have a rewritten inlining algorithm and
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disabling this option will generate a smaller kernel there. Hopefully
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this algorithm is so good that allowing gcc4 to make the decision can
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become the default in the future, until then this option is there to
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test gcc for this.
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endmenu
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