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