Edit File: Kconfig.debug
menu "Kernel hacking" config TRACE_IRQFLAGS_SUPPORT def_bool y source "lib/Kconfig.debug" config EARLY_PRINTK_USB bool config STRICT_DEVMEM bool "Filter access to /dev/mem" ---help--- If this option is disabled, you allow userspace (root) access to all of memory, including kernel and userspace memory. Accidental access to this is obviously disastrous, but specific access can be used by people debugging the kernel. Note that with PAT support enabled, even in this case there are restrictions on /dev/mem use due to the cache aliasing requirements. If this option is switched on, the /dev/mem file only allows userspace access to PCI space and the BIOS code and data regions. This is sufficient for dosemu and X and all common users of /dev/mem. If in doubt, say Y. config X86_VERBOSE_BOOTUP bool "Enable verbose x86 bootup info messages" default y ---help--- Enables the informational output from the decompression stage (e.g. bzImage) of the boot. If you disable this you will still see errors. Disable this if you want silent bootup. config EARLY_PRINTK bool "Early printk" if EXPERT default y ---help--- Write kernel log output directly into the VGA buffer or to a serial port. This is useful for kernel debugging when your machine crashes very early before the console code is initialized. For normal operation it is not recommended because it looks ugly and doesn't cooperate with klogd/syslogd or the X server. You should normally say N here, unless you want to debug such a crash. config EARLY_PRINTK_INTEL_MID bool "Early printk for Intel MID platform support" depends on EARLY_PRINTK && X86_INTEL_MID config EARLY_PRINTK_DBGP bool "Early printk via EHCI debug port" depends on EARLY_PRINTK && PCI select EARLY_PRINTK_USB ---help--- Write kernel log output directly into the EHCI debug port. This is useful for kernel debugging when your machine crashes very early before the console code is initialized. For normal operation it is not recommended because it looks ugly and doesn't cooperate with klogd/syslogd or the X server. You should normally say N here, unless you want to debug such a crash. You need usb debug device. config DEBUG_STACKOVERFLOW bool "Check for stack overflows" depends on DEBUG_KERNEL ---help--- Say Y here if you want to check the overflows of kernel, IRQ and exception stacks. This option will cause messages of the stacks in detail when free stack space drops below a certain limit. If in doubt, say "N". config EARLY_PRINTK_EFI bool "Early printk via the EFI framebuffer" depends on EFI && EARLY_PRINTK select FONT_SUPPORT ---help--- Write kernel log output directly into the EFI framebuffer. This is useful for kernel debugging when your machine crashes very early before the console code is initialized. config EARLY_PRINTK_USB_XDBC bool "Early printk via the xHCI debug port" depends on EARLY_PRINTK && PCI select EARLY_PRINTK_USB ---help--- Write kernel log output directly into the xHCI debug port. One use for this feature is kernel debugging, for example when your machine crashes very early before the regular console code is initialized. Other uses include simpler, lockless logging instead of a full-blown printk console driver + klogd. For normal production environments this is normally not recommended, because it doesn't feed events into klogd/syslogd and doesn't try to print anything on the screen. You should normally say N here, unless you want to debug early crashes or need a very simple printk logging facility. config MCSAFE_TEST def_bool n config X86_PTDUMP bool "Export kernel pagetable layout to userspace via debugfs" depends on DEBUG_KERNEL select DEBUG_FS ---help--- Say Y here if you want to show the kernel pagetable layout in a debugfs file. This information is only useful for kernel developers who are working in architecture specific areas of the kernel. It is probably not a good idea to enable this feature in a production kernel. If in doubt, say "N" config EFI_PGT_DUMP bool "Dump the EFI pagetable" depends on EFI && X86_PTDUMP ---help--- Enable this if you want to dump the EFI page table before enabling virtual mode. This can be used to debug miscellaneous issues with the mapping of the EFI runtime regions into that table. config DEBUG_RODATA bool "Write protect kernel read-only data structures" default y depends on DEBUG_KERNEL ---help--- Mark the kernel read-only data as write-protected in the pagetables, in order to catch accidental (and incorrect) writes to such const data. This is recommended so that we can catch kernel bugs sooner. If in doubt, say "Y". config DEBUG_RODATA_TEST bool "Testcase for the DEBUG_RODATA feature" depends on DEBUG_RODATA default y ---help--- This option enables a testcase for the DEBUG_RODATA feature as well as for the change_page_attr() infrastructure. If in doubt, say "N" config DEBUG_SET_MODULE_RONX bool "Set loadable kernel module data as NX and text as RO" depends on MODULES ---help--- This option helps catch unintended modifications to loadable kernel module's text and read-only data. It also prevents execution of module data. Such protection may interfere with run-time code patching and dynamic kernel tracing - and they might also protect against certain classes of kernel exploits. If in doubt, say "N". config DOUBLEFAULT default y bool "Enable doublefault exception handler" if EXPERT depends on X86_32 ---help--- This option allows trapping of rare doublefault exceptions that would otherwise cause a system to silently reboot. Disabling this option saves about 4k and might cause you much additional grey hair. config DEBUG_TLBFLUSH bool "Set upper limit of TLB entries to flush one-by-one" depends on DEBUG_KERNEL ---help--- X86-only for now. This option allows the user to tune the amount of TLB entries the kernel flushes one-by-one instead of doing a full TLB flush. In certain situations, the former is cheaper. This is controlled by the tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it to -1, the code flushes the whole TLB unconditionally. Otherwise, for positive values of it, the kernel will use single TLB entry invalidating instructions according to the following formula: flush_entries <= active_tlb_entries / 2^tlb_flushall_shift If in doubt, say "N". config IOMMU_DEBUG bool "Enable IOMMU debugging" depends on GART_IOMMU && DEBUG_KERNEL depends on X86_64 ---help--- Force the IOMMU to on even when you have less than 4GB of memory and add debugging code. On overflow always panic. And allow to enable IOMMU leak tracing. Can be disabled at boot time with iommu=noforce. This will also enable scatter gather list merging. Currently not recommended for production code. When you use it make sure you have a big enough IOMMU/AGP aperture. Most of the options enabled by this can be set more finegrained using the iommu= command line options. See Documentation/x86/x86_64/boot-options.txt for more details. config IOMMU_STRESS bool "Enable IOMMU stress-test mode" ---help--- This option disables various optimizations in IOMMU related code to do real stress testing of the IOMMU code. This option will cause a performance drop and should only be enabled for testing. config IOMMU_LEAK bool "IOMMU leak tracing" depends on IOMMU_DEBUG && DMA_API_DEBUG ---help--- Add a simple leak tracer to the IOMMU code. This is useful when you are debugging a buggy device driver that leaks IOMMU mappings. config HAVE_MMIOTRACE_SUPPORT def_bool y config X86_DECODER_SELFTEST bool "x86 instruction decoder selftest" depends on DEBUG_KERNEL && KPROBES ---help--- Perform x86 instruction decoder selftests at build time. This option is useful for checking the sanity of x86 instruction decoder code. If unsure, say "N". # # IO delay types: # config IO_DELAY_TYPE_0X80 int default "0" config IO_DELAY_TYPE_0XED int default "1" config IO_DELAY_TYPE_UDELAY int default "2" config IO_DELAY_TYPE_NONE int default "3" choice prompt "IO delay type" default IO_DELAY_0X80 config IO_DELAY_0X80 bool "port 0x80 based port-IO delay [recommended]" ---help--- This is the traditional Linux IO delay used for in/out_p. It is the most tested hence safest selection here. config IO_DELAY_0XED bool "port 0xed based port-IO delay" ---help--- Use port 0xed as the IO delay. This frees up port 0x80 which is often used as a hardware-debug port. config IO_DELAY_UDELAY bool "udelay based port-IO delay" ---help--- Use udelay(2) as the IO delay method. This provides the delay while not having any side-effect on the IO port space. config IO_DELAY_NONE bool "no port-IO delay" ---help--- No port-IO delay. Will break on old boxes that require port-IO delay for certain operations. Should work on most new machines. endchoice if IO_DELAY_0X80 config DEFAULT_IO_DELAY_TYPE int default IO_DELAY_TYPE_0X80 endif if IO_DELAY_0XED config DEFAULT_IO_DELAY_TYPE int default IO_DELAY_TYPE_0XED endif if IO_DELAY_UDELAY config DEFAULT_IO_DELAY_TYPE int default IO_DELAY_TYPE_UDELAY endif if IO_DELAY_NONE config DEFAULT_IO_DELAY_TYPE int default IO_DELAY_TYPE_NONE endif config DEBUG_BOOT_PARAMS bool "Debug boot parameters" depends on DEBUG_KERNEL depends on DEBUG_FS ---help--- This option will cause struct boot_params to be exported via debugfs. config CPA_DEBUG bool "CPA self-test code" depends on DEBUG_KERNEL ---help--- Do change_page_attr() self-tests every 30 seconds. config OPTIMIZE_INLINING bool "Allow gcc to uninline functions marked 'inline'" ---help--- This option determines if the kernel forces gcc to inline the functions developers have marked 'inline'. Doing so takes away freedom from gcc to do what it thinks is best, which is desirable for the gcc 3.x series of compilers. The gcc 4.x series have a rewritten inlining algorithm and enabling this option will generate a smaller kernel there. Hopefully this algorithm is so good that allowing gcc 4.x and above to make the decision will become the default in the future. Until then this option is there to test gcc for this. If unsure, say N. config DEBUG_NMI_SELFTEST bool "NMI Selftest" depends on DEBUG_KERNEL && X86_LOCAL_APIC ---help--- Enabling this option turns on a quick NMI selftest to verify that the NMI behaves correctly. This might help diagnose strange hangs that rely on NMI to function properly. If unsure, say N. endmenu