1menu "Kernel hacking" 2 3config TRACE_IRQFLAGS_SUPPORT 4 def_bool y 5 6source "lib/Kconfig.debug" 7 8config STRICT_DEVMEM 9 bool "Filter access to /dev/mem" 10 ---help--- 11 If this option is disabled, you allow userspace (root) access to all 12 of memory, including kernel and userspace memory. Accidental 13 access to this is obviously disastrous, but specific access can 14 be used by people debugging the kernel. Note that with PAT support 15 enabled, even in this case there are restrictions on /dev/mem 16 use due to the cache aliasing requirements. 17 18 If this option is switched on, the /dev/mem file only allows 19 userspace access to PCI space and the BIOS code and data regions. 20 This is sufficient for dosemu and X and all common users of 21 /dev/mem. 22 23 If in doubt, say Y. 24 25config X86_VERBOSE_BOOTUP 26 bool "Enable verbose x86 bootup info messages" 27 default y 28 ---help--- 29 Enables the informational output from the decompression stage 30 (e.g. bzImage) of the boot. If you disable this you will still 31 see errors. Disable this if you want silent bootup. 32 33config EARLY_PRINTK 34 bool "Early printk" if EMBEDDED 35 default y 36 ---help--- 37 Write kernel log output directly into the VGA buffer or to a serial 38 port. 39 40 This is useful for kernel debugging when your machine crashes very 41 early before the console code is initialized. For normal operation 42 it is not recommended because it looks ugly and doesn't cooperate 43 with klogd/syslogd or the X server. You should normally N here, 44 unless you want to debug such a crash. 45 46config EARLY_PRINTK_DBGP 47 bool "Early printk via EHCI debug port" 48 default n 49 depends on EARLY_PRINTK && PCI 50 ---help--- 51 Write kernel log output directly into the EHCI debug port. 52 53 This is useful for kernel debugging when your machine crashes very 54 early before the console code is initialized. For normal operation 55 it is not recommended because it looks ugly and doesn't cooperate 56 with klogd/syslogd or the X server. You should normally N here, 57 unless you want to debug such a crash. You need usb debug device. 58 59config DEBUG_STACKOVERFLOW 60 bool "Check for stack overflows" 61 depends on DEBUG_KERNEL 62 ---help--- 63 This option will cause messages to be printed if free stack space 64 drops below a certain limit. 65 66config DEBUG_STACK_USAGE 67 bool "Stack utilization instrumentation" 68 depends on DEBUG_KERNEL 69 ---help--- 70 Enables the display of the minimum amount of free stack which each 71 task has ever had available in the sysrq-T and sysrq-P debug output. 72 73 This option will slow down process creation somewhat. 74 75config DEBUG_PER_CPU_MAPS 76 bool "Debug access to per_cpu maps" 77 depends on DEBUG_KERNEL 78 depends on SMP 79 default n 80 ---help--- 81 Say Y to verify that the per_cpu map being accessed has 82 been setup. Adds a fair amount of code to kernel memory 83 and decreases performance. 84 85 Say N if unsure. 86 87config X86_PTDUMP 88 bool "Export kernel pagetable layout to userspace via debugfs" 89 depends on DEBUG_KERNEL 90 select DEBUG_FS 91 ---help--- 92 Say Y here if you want to show the kernel pagetable layout in a 93 debugfs file. This information is only useful for kernel developers 94 who are working in architecture specific areas of the kernel. 95 It is probably not a good idea to enable this feature in a production 96 kernel. 97 If in doubt, say "N" 98 99config DEBUG_RODATA 100 bool "Write protect kernel read-only data structures" 101 default y 102 depends on DEBUG_KERNEL 103 ---help--- 104 Mark the kernel read-only data as write-protected in the pagetables, 105 in order to catch accidental (and incorrect) writes to such const 106 data. This is recommended so that we can catch kernel bugs sooner. 107 If in doubt, say "Y". 108 109config DEBUG_RODATA_TEST 110 bool "Testcase for the DEBUG_RODATA feature" 111 depends on DEBUG_RODATA 112 default y 113 ---help--- 114 This option enables a testcase for the DEBUG_RODATA 115 feature as well as for the change_page_attr() infrastructure. 116 If in doubt, say "N" 117 118config DEBUG_NX_TEST 119 tristate "Testcase for the NX non-executable stack feature" 120 depends on DEBUG_KERNEL && m 121 ---help--- 122 This option enables a testcase for the CPU NX capability 123 and the software setup of this feature. 124 If in doubt, say "N" 125 126config 4KSTACKS 127 bool "Use 4Kb for kernel stacks instead of 8Kb" 128 depends on X86_32 129 ---help--- 130 If you say Y here the kernel will use a 4Kb stacksize for the 131 kernel stack attached to each process/thread. This facilitates 132 running more threads on a system and also reduces the pressure 133 on the VM subsystem for higher order allocations. This option 134 will also use IRQ stacks to compensate for the reduced stackspace. 135 136config DOUBLEFAULT 137 default y 138 bool "Enable doublefault exception handler" if EMBEDDED 139 depends on X86_32 140 ---help--- 141 This option allows trapping of rare doublefault exceptions that 142 would otherwise cause a system to silently reboot. Disabling this 143 option saves about 4k and might cause you much additional grey 144 hair. 145 146config IOMMU_DEBUG 147 bool "Enable IOMMU debugging" 148 depends on GART_IOMMU && DEBUG_KERNEL 149 depends on X86_64 150 ---help--- 151 Force the IOMMU to on even when you have less than 4GB of 152 memory and add debugging code. On overflow always panic. And 153 allow to enable IOMMU leak tracing. Can be disabled at boot 154 time with iommu=noforce. This will also enable scatter gather 155 list merging. Currently not recommended for production 156 code. When you use it make sure you have a big enough 157 IOMMU/AGP aperture. Most of the options enabled by this can 158 be set more finegrained using the iommu= command line 159 options. See Documentation/x86_64/boot-options.txt for more 160 details. 161 162config IOMMU_STRESS 163 bool "Enable IOMMU stress-test mode" 164 ---help--- 165 This option disables various optimizations in IOMMU related 166 code to do real stress testing of the IOMMU code. This option 167 will cause a performance drop and should only be enabled for 168 testing. 169 170config IOMMU_LEAK 171 bool "IOMMU leak tracing" 172 depends on IOMMU_DEBUG && DMA_API_DEBUG 173 ---help--- 174 Add a simple leak tracer to the IOMMU code. This is useful when you 175 are debugging a buggy device driver that leaks IOMMU mappings. 176 177config X86_DS_SELFTEST 178 bool "DS selftest" 179 default y 180 depends on DEBUG_KERNEL 181 depends on X86_DS 182 ---help--- 183 Perform Debug Store selftests at boot time. 184 If in doubt, say "N". 185 186config HAVE_MMIOTRACE_SUPPORT 187 def_bool y 188 189config X86_DECODER_SELFTEST 190 bool "x86 instruction decoder selftest" 191 depends on DEBUG_KERNEL && KPROBES 192 ---help--- 193 Perform x86 instruction decoder selftests at build time. 194 This option is useful for checking the sanity of x86 instruction 195 decoder code. 196 If unsure, say "N". 197 198# 199# IO delay types: 200# 201 202config IO_DELAY_TYPE_0X80 203 int 204 default "0" 205 206config IO_DELAY_TYPE_0XED 207 int 208 default "1" 209 210config IO_DELAY_TYPE_UDELAY 211 int 212 default "2" 213 214config IO_DELAY_TYPE_NONE 215 int 216 default "3" 217 218choice 219 prompt "IO delay type" 220 default IO_DELAY_0X80 221 222config IO_DELAY_0X80 223 bool "port 0x80 based port-IO delay [recommended]" 224 ---help--- 225 This is the traditional Linux IO delay used for in/out_p. 226 It is the most tested hence safest selection here. 227 228config IO_DELAY_0XED 229 bool "port 0xed based port-IO delay" 230 ---help--- 231 Use port 0xed as the IO delay. This frees up port 0x80 which is 232 often used as a hardware-debug port. 233 234config IO_DELAY_UDELAY 235 bool "udelay based port-IO delay" 236 ---help--- 237 Use udelay(2) as the IO delay method. This provides the delay 238 while not having any side-effect on the IO port space. 239 240config IO_DELAY_NONE 241 bool "no port-IO delay" 242 ---help--- 243 No port-IO delay. Will break on old boxes that require port-IO 244 delay for certain operations. Should work on most new machines. 245 246endchoice 247 248if IO_DELAY_0X80 249config DEFAULT_IO_DELAY_TYPE 250 int 251 default IO_DELAY_TYPE_0X80 252endif 253 254if IO_DELAY_0XED 255config DEFAULT_IO_DELAY_TYPE 256 int 257 default IO_DELAY_TYPE_0XED 258endif 259 260if IO_DELAY_UDELAY 261config DEFAULT_IO_DELAY_TYPE 262 int 263 default IO_DELAY_TYPE_UDELAY 264endif 265 266if IO_DELAY_NONE 267config DEFAULT_IO_DELAY_TYPE 268 int 269 default IO_DELAY_TYPE_NONE 270endif 271 272config DEBUG_BOOT_PARAMS 273 bool "Debug boot parameters" 274 depends on DEBUG_KERNEL 275 depends on DEBUG_FS 276 ---help--- 277 This option will cause struct boot_params to be exported via debugfs. 278 279config CPA_DEBUG 280 bool "CPA self-test code" 281 depends on DEBUG_KERNEL 282 ---help--- 283 Do change_page_attr() self-tests every 30 seconds. 284 285config OPTIMIZE_INLINING 286 bool "Allow gcc to uninline functions marked 'inline'" 287 ---help--- 288 This option determines if the kernel forces gcc to inline the functions 289 developers have marked 'inline'. Doing so takes away freedom from gcc to 290 do what it thinks is best, which is desirable for the gcc 3.x series of 291 compilers. The gcc 4.x series have a rewritten inlining algorithm and 292 enabling this option will generate a smaller kernel there. Hopefully 293 this algorithm is so good that allowing gcc 4.x and above to make the 294 decision will become the default in the future. Until then this option 295 is there to test gcc for this. 296 297 If unsure, say N. 298 299config DEBUG_STRICT_USER_COPY_CHECKS 300 bool "Strict copy size checks" 301 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 302 ---help--- 303 Enabling this option turns a certain set of sanity checks for user 304 copy operations into compile time failures. 305 306 The copy_from_user() etc checks are there to help test if there 307 are sufficient security checks on the length argument of 308 the copy operation, by having gcc prove that the argument is 309 within bounds. 310 311 If unsure, or if you run an older (pre 4.4) gcc, say N. 312 313endmenu 314