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 EXPERT 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_MRST 47 bool "Early printk for MRST platform support" 48 depends on EARLY_PRINTK && X86_MRST 49 50config EARLY_PRINTK_DBGP 51 bool "Early printk via EHCI debug port" 52 depends on EARLY_PRINTK && PCI 53 ---help--- 54 Write kernel log output directly into the EHCI debug port. 55 56 This is useful for kernel debugging when your machine crashes very 57 early before the console code is initialized. For normal operation 58 it is not recommended because it looks ugly and doesn't cooperate 59 with klogd/syslogd or the X server. You should normally N here, 60 unless you want to debug such a crash. You need usb debug device. 61 62config DEBUG_STACKOVERFLOW 63 bool "Check for stack overflows" 64 depends on DEBUG_KERNEL 65 ---help--- 66 This option will cause messages to be printed if free stack space 67 drops below a certain limit. 68 69config DEBUG_STACK_USAGE 70 bool "Stack utilization instrumentation" 71 depends on DEBUG_KERNEL 72 ---help--- 73 Enables the display of the minimum amount of free stack which each 74 task has ever had available in the sysrq-T and sysrq-P debug output. 75 76 This option will slow down process creation somewhat. 77 78config DEBUG_PER_CPU_MAPS 79 bool "Debug access to per_cpu maps" 80 depends on DEBUG_KERNEL 81 depends on SMP 82 ---help--- 83 Say Y to verify that the per_cpu map being accessed has 84 been setup. Adds a fair amount of code to kernel memory 85 and decreases performance. 86 87 Say N if unsure. 88 89config X86_PTDUMP 90 bool "Export kernel pagetable layout to userspace via debugfs" 91 depends on DEBUG_KERNEL 92 select DEBUG_FS 93 ---help--- 94 Say Y here if you want to show the kernel pagetable layout in a 95 debugfs file. This information is only useful for kernel developers 96 who are working in architecture specific areas of the kernel. 97 It is probably not a good idea to enable this feature in a production 98 kernel. 99 If in doubt, say "N" 100 101config DEBUG_RODATA 102 bool "Write protect kernel read-only data structures" 103 default y 104 depends on DEBUG_KERNEL 105 ---help--- 106 Mark the kernel read-only data as write-protected in the pagetables, 107 in order to catch accidental (and incorrect) writes to such const 108 data. This is recommended so that we can catch kernel bugs sooner. 109 If in doubt, say "Y". 110 111config DEBUG_RODATA_TEST 112 bool "Testcase for the DEBUG_RODATA feature" 113 depends on DEBUG_RODATA 114 default y 115 ---help--- 116 This option enables a testcase for the DEBUG_RODATA 117 feature as well as for the change_page_attr() infrastructure. 118 If in doubt, say "N" 119 120config DEBUG_SET_MODULE_RONX 121 bool "Set loadable kernel module data as NX and text as RO" 122 depends on MODULES 123 ---help--- 124 This option helps catch unintended modifications to loadable 125 kernel module's text and read-only data. It also prevents execution 126 of module data. Such protection may interfere with run-time code 127 patching and dynamic kernel tracing - and they might also protect 128 against certain classes of kernel exploits. 129 If in doubt, say "N". 130 131config DEBUG_NX_TEST 132 tristate "Testcase for the NX non-executable stack feature" 133 depends on DEBUG_KERNEL && m 134 ---help--- 135 This option enables a testcase for the CPU NX capability 136 and the software setup of this feature. 137 If in doubt, say "N" 138 139config DOUBLEFAULT 140 default y 141 bool "Enable doublefault exception handler" if EXPERT 142 depends on X86_32 143 ---help--- 144 This option allows trapping of rare doublefault exceptions that 145 would otherwise cause a system to silently reboot. Disabling this 146 option saves about 4k and might cause you much additional grey 147 hair. 148 149config IOMMU_DEBUG 150 bool "Enable IOMMU debugging" 151 depends on GART_IOMMU && DEBUG_KERNEL 152 depends on X86_64 153 ---help--- 154 Force the IOMMU to on even when you have less than 4GB of 155 memory and add debugging code. On overflow always panic. And 156 allow to enable IOMMU leak tracing. Can be disabled at boot 157 time with iommu=noforce. This will also enable scatter gather 158 list merging. Currently not recommended for production 159 code. When you use it make sure you have a big enough 160 IOMMU/AGP aperture. Most of the options enabled by this can 161 be set more finegrained using the iommu= command line 162 options. See Documentation/x86_64/boot-options.txt for more 163 details. 164 165config IOMMU_STRESS 166 bool "Enable IOMMU stress-test mode" 167 ---help--- 168 This option disables various optimizations in IOMMU related 169 code to do real stress testing of the IOMMU code. This option 170 will cause a performance drop and should only be enabled for 171 testing. 172 173config IOMMU_LEAK 174 bool "IOMMU leak tracing" 175 depends on IOMMU_DEBUG && DMA_API_DEBUG 176 ---help--- 177 Add a simple leak tracer to the IOMMU code. This is useful when you 178 are debugging a buggy device driver that leaks IOMMU mappings. 179 180config HAVE_MMIOTRACE_SUPPORT 181 def_bool y 182 183config X86_DECODER_SELFTEST 184 bool "x86 instruction decoder selftest" 185 depends on DEBUG_KERNEL && KPROBES 186 ---help--- 187 Perform x86 instruction decoder selftests at build time. 188 This option is useful for checking the sanity of x86 instruction 189 decoder code. 190 If unsure, say "N". 191 192# 193# IO delay types: 194# 195 196config IO_DELAY_TYPE_0X80 197 int 198 default "0" 199 200config IO_DELAY_TYPE_0XED 201 int 202 default "1" 203 204config IO_DELAY_TYPE_UDELAY 205 int 206 default "2" 207 208config IO_DELAY_TYPE_NONE 209 int 210 default "3" 211 212choice 213 prompt "IO delay type" 214 default IO_DELAY_0X80 215 216config IO_DELAY_0X80 217 bool "port 0x80 based port-IO delay [recommended]" 218 ---help--- 219 This is the traditional Linux IO delay used for in/out_p. 220 It is the most tested hence safest selection here. 221 222config IO_DELAY_0XED 223 bool "port 0xed based port-IO delay" 224 ---help--- 225 Use port 0xed as the IO delay. This frees up port 0x80 which is 226 often used as a hardware-debug port. 227 228config IO_DELAY_UDELAY 229 bool "udelay based port-IO delay" 230 ---help--- 231 Use udelay(2) as the IO delay method. This provides the delay 232 while not having any side-effect on the IO port space. 233 234config IO_DELAY_NONE 235 bool "no port-IO delay" 236 ---help--- 237 No port-IO delay. Will break on old boxes that require port-IO 238 delay for certain operations. Should work on most new machines. 239 240endchoice 241 242if IO_DELAY_0X80 243config DEFAULT_IO_DELAY_TYPE 244 int 245 default IO_DELAY_TYPE_0X80 246endif 247 248if IO_DELAY_0XED 249config DEFAULT_IO_DELAY_TYPE 250 int 251 default IO_DELAY_TYPE_0XED 252endif 253 254if IO_DELAY_UDELAY 255config DEFAULT_IO_DELAY_TYPE 256 int 257 default IO_DELAY_TYPE_UDELAY 258endif 259 260if IO_DELAY_NONE 261config DEFAULT_IO_DELAY_TYPE 262 int 263 default IO_DELAY_TYPE_NONE 264endif 265 266config DEBUG_BOOT_PARAMS 267 bool "Debug boot parameters" 268 depends on DEBUG_KERNEL 269 depends on DEBUG_FS 270 ---help--- 271 This option will cause struct boot_params to be exported via debugfs. 272 273config CPA_DEBUG 274 bool "CPA self-test code" 275 depends on DEBUG_KERNEL 276 ---help--- 277 Do change_page_attr() self-tests every 30 seconds. 278 279config OPTIMIZE_INLINING 280 bool "Allow gcc to uninline functions marked 'inline'" 281 ---help--- 282 This option determines if the kernel forces gcc to inline the functions 283 developers have marked 'inline'. Doing so takes away freedom from gcc to 284 do what it thinks is best, which is desirable for the gcc 3.x series of 285 compilers. The gcc 4.x series have a rewritten inlining algorithm and 286 enabling this option will generate a smaller kernel there. Hopefully 287 this algorithm is so good that allowing gcc 4.x and above to make the 288 decision will become the default in the future. Until then this option 289 is there to test gcc for this. 290 291 If unsure, say N. 292 293config DEBUG_STRICT_USER_COPY_CHECKS 294 bool "Strict copy size checks" 295 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 296 ---help--- 297 Enabling this option turns a certain set of sanity checks for user 298 copy operations into compile time failures. 299 300 The copy_from_user() etc checks are there to help test if there 301 are sufficient security checks on the length argument of 302 the copy operation, by having gcc prove that the argument is 303 within bounds. 304 305 If unsure, or if you run an older (pre 4.4) gcc, say N. 306 307endmenu 308