1menu "Kernel hacking" 2 3config TRACE_IRQFLAGS_SUPPORT 4 def_bool y 5 6source "lib/Kconfig.debug" 7 8config NONPROMISC_DEVMEM 9 bool "Disable promiscuous /dev/mem" 10 help 11 The /dev/mem file by default only allows userspace access to PCI 12 space and the BIOS code and data regions. This is sufficient for 13 dosemu and X and all common users of /dev/mem. With this config 14 option, you allow userspace access to all of memory, including 15 kernel and userspace memory. Accidental access to this is 16 obviously disasterous, but specific access can be used by people 17 debugging the kernel. 18 19config EARLY_PRINTK 20 bool "Early printk" if EMBEDDED 21 default y 22 help 23 Write kernel log output directly into the VGA buffer or to a serial 24 port. 25 26 This is useful for kernel debugging when your machine crashes very 27 early before the console code is initialized. For normal operation 28 it is not recommended because it looks ugly and doesn't cooperate 29 with klogd/syslogd or the X server. You should normally N here, 30 unless you want to debug such a crash. 31 32config DEBUG_STACKOVERFLOW 33 bool "Check for stack overflows" 34 depends on DEBUG_KERNEL 35 help 36 This option will cause messages to be printed if free stack space 37 drops below a certain limit. 38 39config DEBUG_STACK_USAGE 40 bool "Stack utilization instrumentation" 41 depends on DEBUG_KERNEL 42 help 43 Enables the display of the minimum amount of free stack which each 44 task has ever had available in the sysrq-T and sysrq-P debug output. 45 46 This option will slow down process creation somewhat. 47 48config DEBUG_PAGEALLOC 49 bool "Debug page memory allocations" 50 depends on DEBUG_KERNEL 51 help 52 Unmap pages from the kernel linear mapping after free_pages(). 53 This results in a large slowdown, but helps to find certain types 54 of memory corruptions. 55 56config DEBUG_PER_CPU_MAPS 57 bool "Debug access to per_cpu maps" 58 depends on DEBUG_KERNEL 59 depends on X86_64_SMP 60 default n 61 help 62 Say Y to verify that the per_cpu map being accessed has 63 been setup. Adds a fair amount of code to kernel memory 64 and decreases performance. 65 66 Say N if unsure. 67 68config X86_PTDUMP 69 bool "Export kernel pagetable layout to userspace via debugfs" 70 depends on DEBUG_KERNEL 71 select DEBUG_FS 72 help 73 Say Y here if you want to show the kernel pagetable layout in a 74 debugfs file. This information is only useful for kernel developers 75 who are working in architecture specific areas of the kernel. 76 It is probably not a good idea to enable this feature in a production 77 kernel. 78 If in doubt, say "N" 79 80config DEBUG_RODATA 81 bool "Write protect kernel read-only data structures" 82 default y 83 depends on DEBUG_KERNEL 84 help 85 Mark the kernel read-only data as write-protected in the pagetables, 86 in order to catch accidental (and incorrect) writes to such const 87 data. This is recommended so that we can catch kernel bugs sooner. 88 If in doubt, say "Y". 89 90config DIRECT_GBPAGES 91 bool "Enable gbpages-mapped kernel pagetables" 92 depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64 93 help 94 Enable gigabyte pages support (if the CPU supports it). This can 95 improve the kernel's performance a tiny bit by reducing TLB 96 pressure. 97 98 This is experimental code. 99 100 If in doubt, say "N". 101 102config DEBUG_RODATA_TEST 103 bool "Testcase for the DEBUG_RODATA feature" 104 depends on DEBUG_RODATA 105 help 106 This option enables a testcase for the DEBUG_RODATA 107 feature as well as for the change_page_attr() infrastructure. 108 If in doubt, say "N" 109 110config DEBUG_NX_TEST 111 tristate "Testcase for the NX non-executable stack feature" 112 depends on DEBUG_KERNEL && m 113 help 114 This option enables a testcase for the CPU NX capability 115 and the software setup of this feature. 116 If in doubt, say "N" 117 118config 4KSTACKS 119 bool "Use 4Kb for kernel stacks instead of 8Kb" 120 depends on X86_32 121 default y 122 help 123 If you say Y here the kernel will use a 4Kb stacksize for the 124 kernel stack attached to each process/thread. This facilitates 125 running more threads on a system and also reduces the pressure 126 on the VM subsystem for higher order allocations. This option 127 will also use IRQ stacks to compensate for the reduced stackspace. 128 129config X86_FIND_SMP_CONFIG 130 def_bool y 131 depends on X86_LOCAL_APIC || X86_VOYAGER 132 depends on X86_32 133 134config X86_MPPARSE 135 def_bool y 136 depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64 137 138config DOUBLEFAULT 139 default y 140 bool "Enable doublefault exception handler" if EMBEDDED 141 depends on X86_32 142 help 143 This option allows trapping of rare doublefault exceptions that 144 would otherwise cause a system to silently reboot. Disabling this 145 option saves about 4k and might cause you much additional grey 146 hair. 147 148config IOMMU_DEBUG 149 bool "Enable IOMMU debugging" 150 depends on GART_IOMMU && DEBUG_KERNEL 151 depends on X86_64 152 help 153 Force the IOMMU to on even when you have less than 4GB of 154 memory and add debugging code. On overflow always panic. And 155 allow to enable IOMMU leak tracing. Can be disabled at boot 156 time with iommu=noforce. This will also enable scatter gather 157 list merging. Currently not recommended for production 158 code. When you use it make sure you have a big enough 159 IOMMU/AGP aperture. Most of the options enabled by this can 160 be set more finegrained using the iommu= command line 161 options. See Documentation/x86_64/boot-options.txt for more 162 details. 163 164config IOMMU_LEAK 165 bool "IOMMU leak tracing" 166 depends on DEBUG_KERNEL 167 depends on IOMMU_DEBUG 168 help 169 Add a simple leak tracer to the IOMMU code. This is useful when you 170 are debugging a buggy device driver that leaks IOMMU mappings. 171 172# 173# IO delay types: 174# 175 176config IO_DELAY_TYPE_0X80 177 int 178 default "0" 179 180config IO_DELAY_TYPE_0XED 181 int 182 default "1" 183 184config IO_DELAY_TYPE_UDELAY 185 int 186 default "2" 187 188config IO_DELAY_TYPE_NONE 189 int 190 default "3" 191 192choice 193 prompt "IO delay type" 194 default IO_DELAY_0X80 195 196config IO_DELAY_0X80 197 bool "port 0x80 based port-IO delay [recommended]" 198 help 199 This is the traditional Linux IO delay used for in/out_p. 200 It is the most tested hence safest selection here. 201 202config IO_DELAY_0XED 203 bool "port 0xed based port-IO delay" 204 help 205 Use port 0xed as the IO delay. This frees up port 0x80 which is 206 often used as a hardware-debug port. 207 208config IO_DELAY_UDELAY 209 bool "udelay based port-IO delay" 210 help 211 Use udelay(2) as the IO delay method. This provides the delay 212 while not having any side-effect on the IO port space. 213 214config IO_DELAY_NONE 215 bool "no port-IO delay" 216 help 217 No port-IO delay. Will break on old boxes that require port-IO 218 delay for certain operations. Should work on most new machines. 219 220endchoice 221 222if IO_DELAY_0X80 223config DEFAULT_IO_DELAY_TYPE 224 int 225 default IO_DELAY_TYPE_0X80 226endif 227 228if IO_DELAY_0XED 229config DEFAULT_IO_DELAY_TYPE 230 int 231 default IO_DELAY_TYPE_0XED 232endif 233 234if IO_DELAY_UDELAY 235config DEFAULT_IO_DELAY_TYPE 236 int 237 default IO_DELAY_TYPE_UDELAY 238endif 239 240if IO_DELAY_NONE 241config DEFAULT_IO_DELAY_TYPE 242 int 243 default IO_DELAY_TYPE_NONE 244endif 245 246config DEBUG_BOOT_PARAMS 247 bool "Debug boot parameters" 248 depends on DEBUG_KERNEL 249 depends on DEBUG_FS 250 help 251 This option will cause struct boot_params to be exported via debugfs. 252 253config CPA_DEBUG 254 bool "CPA self-test code" 255 depends on DEBUG_KERNEL 256 help 257 Do change_page_attr() self-tests every 30 seconds. 258 259endmenu 260