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_INTEL_MID 47 bool "Early printk for Intel MID platform support" 48 depends on EARLY_PRINTK && X86_INTEL_MID 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 Say Y here if you want to check the overflows of kernel, IRQ 67 and exception stacks. This option will cause messages of the 68 stacks in detail when free stack space drops below a certain 69 limit. 70 If in doubt, say "N". 71 72config X86_PTDUMP 73 bool "Export kernel pagetable layout to userspace via debugfs" 74 depends on DEBUG_KERNEL 75 select DEBUG_FS 76 ---help--- 77 Say Y here if you want to show the kernel pagetable layout in a 78 debugfs file. This information is only useful for kernel developers 79 who are working in architecture specific areas of the kernel. 80 It is probably not a good idea to enable this feature in a production 81 kernel. 82 If in doubt, say "N" 83 84config DEBUG_RODATA 85 bool "Write protect kernel read-only data structures" 86 default y 87 depends on DEBUG_KERNEL 88 ---help--- 89 Mark the kernel read-only data as write-protected in the pagetables, 90 in order to catch accidental (and incorrect) writes to such const 91 data. This is recommended so that we can catch kernel bugs sooner. 92 If in doubt, say "Y". 93 94config DEBUG_RODATA_TEST 95 bool "Testcase for the DEBUG_RODATA feature" 96 depends on DEBUG_RODATA 97 default y 98 ---help--- 99 This option enables a testcase for the DEBUG_RODATA 100 feature as well as for the change_page_attr() infrastructure. 101 If in doubt, say "N" 102 103config DEBUG_SET_MODULE_RONX 104 bool "Set loadable kernel module data as NX and text as RO" 105 depends on MODULES 106 ---help--- 107 This option helps catch unintended modifications to loadable 108 kernel module's text and read-only data. It also prevents execution 109 of module data. Such protection may interfere with run-time code 110 patching and dynamic kernel tracing - and they might also protect 111 against certain classes of kernel exploits. 112 If in doubt, say "N". 113 114config DEBUG_NX_TEST 115 tristate "Testcase for the NX non-executable stack feature" 116 depends on DEBUG_KERNEL && m 117 ---help--- 118 This option enables a testcase for the CPU NX capability 119 and the software setup of this feature. 120 If in doubt, say "N" 121 122config DOUBLEFAULT 123 default y 124 bool "Enable doublefault exception handler" if EXPERT 125 depends on X86_32 126 ---help--- 127 This option allows trapping of rare doublefault exceptions that 128 would otherwise cause a system to silently reboot. Disabling this 129 option saves about 4k and might cause you much additional grey 130 hair. 131 132config IOMMU_DEBUG 133 bool "Enable IOMMU debugging" 134 depends on GART_IOMMU && DEBUG_KERNEL 135 depends on X86_64 136 ---help--- 137 Force the IOMMU to on even when you have less than 4GB of 138 memory and add debugging code. On overflow always panic. And 139 allow to enable IOMMU leak tracing. Can be disabled at boot 140 time with iommu=noforce. This will also enable scatter gather 141 list merging. Currently not recommended for production 142 code. When you use it make sure you have a big enough 143 IOMMU/AGP aperture. Most of the options enabled by this can 144 be set more finegrained using the iommu= command line 145 options. See Documentation/x86/x86_64/boot-options.txt for more 146 details. 147 148config IOMMU_STRESS 149 bool "Enable IOMMU stress-test mode" 150 ---help--- 151 This option disables various optimizations in IOMMU related 152 code to do real stress testing of the IOMMU code. This option 153 will cause a performance drop and should only be enabled for 154 testing. 155 156config IOMMU_LEAK 157 bool "IOMMU leak tracing" 158 depends on IOMMU_DEBUG && DMA_API_DEBUG 159 ---help--- 160 Add a simple leak tracer to the IOMMU code. This is useful when you 161 are debugging a buggy device driver that leaks IOMMU mappings. 162 163config HAVE_MMIOTRACE_SUPPORT 164 def_bool y 165 166config X86_DECODER_SELFTEST 167 bool "x86 instruction decoder selftest" 168 depends on DEBUG_KERNEL && KPROBES 169 ---help--- 170 Perform x86 instruction decoder selftests at build time. 171 This option is useful for checking the sanity of x86 instruction 172 decoder code. 173 If unsure, say "N". 174 175# 176# IO delay types: 177# 178 179config IO_DELAY_TYPE_0X80 180 int 181 default "0" 182 183config IO_DELAY_TYPE_0XED 184 int 185 default "1" 186 187config IO_DELAY_TYPE_UDELAY 188 int 189 default "2" 190 191config IO_DELAY_TYPE_NONE 192 int 193 default "3" 194 195choice 196 prompt "IO delay type" 197 default IO_DELAY_0X80 198 199config IO_DELAY_0X80 200 bool "port 0x80 based port-IO delay [recommended]" 201 ---help--- 202 This is the traditional Linux IO delay used for in/out_p. 203 It is the most tested hence safest selection here. 204 205config IO_DELAY_0XED 206 bool "port 0xed based port-IO delay" 207 ---help--- 208 Use port 0xed as the IO delay. This frees up port 0x80 which is 209 often used as a hardware-debug port. 210 211config IO_DELAY_UDELAY 212 bool "udelay based port-IO delay" 213 ---help--- 214 Use udelay(2) as the IO delay method. This provides the delay 215 while not having any side-effect on the IO port space. 216 217config IO_DELAY_NONE 218 bool "no port-IO delay" 219 ---help--- 220 No port-IO delay. Will break on old boxes that require port-IO 221 delay for certain operations. Should work on most new machines. 222 223endchoice 224 225if IO_DELAY_0X80 226config DEFAULT_IO_DELAY_TYPE 227 int 228 default IO_DELAY_TYPE_0X80 229endif 230 231if IO_DELAY_0XED 232config DEFAULT_IO_DELAY_TYPE 233 int 234 default IO_DELAY_TYPE_0XED 235endif 236 237if IO_DELAY_UDELAY 238config DEFAULT_IO_DELAY_TYPE 239 int 240 default IO_DELAY_TYPE_UDELAY 241endif 242 243if IO_DELAY_NONE 244config DEFAULT_IO_DELAY_TYPE 245 int 246 default IO_DELAY_TYPE_NONE 247endif 248 249config DEBUG_BOOT_PARAMS 250 bool "Debug boot parameters" 251 depends on DEBUG_KERNEL 252 depends on DEBUG_FS 253 ---help--- 254 This option will cause struct boot_params to be exported via debugfs. 255 256config CPA_DEBUG 257 bool "CPA self-test code" 258 depends on DEBUG_KERNEL 259 ---help--- 260 Do change_page_attr() self-tests every 30 seconds. 261 262config OPTIMIZE_INLINING 263 bool "Allow gcc to uninline functions marked 'inline'" 264 ---help--- 265 This option determines if the kernel forces gcc to inline the functions 266 developers have marked 'inline'. Doing so takes away freedom from gcc to 267 do what it thinks is best, which is desirable for the gcc 3.x series of 268 compilers. The gcc 4.x series have a rewritten inlining algorithm and 269 enabling this option will generate a smaller kernel there. Hopefully 270 this algorithm is so good that allowing gcc 4.x and above to make the 271 decision will become the default in the future. Until then this option 272 is there to test gcc for this. 273 274 If unsure, say N. 275 276config DEBUG_STRICT_USER_COPY_CHECKS 277 bool "Strict copy size checks" 278 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 279 ---help--- 280 Enabling this option turns a certain set of sanity checks for user 281 copy operations into compile time failures. 282 283 The copy_from_user() etc checks are there to help test if there 284 are sufficient security checks on the length argument of 285 the copy operation, by having gcc prove that the argument is 286 within bounds. 287 288 If unsure, or if you run an older (pre 4.4) gcc, say N. 289 290config DEBUG_NMI_SELFTEST 291 bool "NMI Selftest" 292 depends on DEBUG_KERNEL && X86_LOCAL_APIC 293 ---help--- 294 Enabling this option turns on a quick NMI selftest to verify 295 that the NMI behaves correctly. 296 297 This might help diagnose strange hangs that rely on NMI to 298 function properly. 299 300 If unsure, say N. 301 302endmenu 303