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 EARLY_PRINTK_EFI 63 bool "Early printk via the EFI framebuffer" 64 depends on EFI && EARLY_PRINTK 65 select FONT_SUPPORT 66 ---help--- 67 Write kernel log output directly into the EFI framebuffer. 68 69 This is useful for kernel debugging when your machine crashes very 70 early before the console code is initialized. 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 ---help--- 126 This option allows trapping of rare doublefault exceptions that 127 would otherwise cause a system to silently reboot. Disabling this 128 option saves about 4k and might cause you much additional grey 129 hair. 130 131config DEBUG_TLBFLUSH 132 bool "Set upper limit of TLB entries to flush one-by-one" 133 depends on DEBUG_KERNEL 134 ---help--- 135 136 X86-only for now. 137 138 This option allows the user to tune the amount of TLB entries the 139 kernel flushes one-by-one instead of doing a full TLB flush. In 140 certain situations, the former is cheaper. This is controlled by the 141 tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it 142 to -1, the code flushes the whole TLB unconditionally. Otherwise, 143 for positive values of it, the kernel will use single TLB entry 144 invalidating instructions according to the following formula: 145 146 flush_entries <= active_tlb_entries / 2^tlb_flushall_shift 147 148 If in doubt, say "N". 149 150config IOMMU_DEBUG 151 bool "Enable IOMMU debugging" 152 depends on GART_IOMMU && DEBUG_KERNEL 153 depends on X86_64 154 ---help--- 155 Force the IOMMU to on even when you have less than 4GB of 156 memory and add debugging code. On overflow always panic. And 157 allow to enable IOMMU leak tracing. Can be disabled at boot 158 time with iommu=noforce. This will also enable scatter gather 159 list merging. Currently not recommended for production 160 code. When you use it make sure you have a big enough 161 IOMMU/AGP aperture. Most of the options enabled by this can 162 be set more finegrained using the iommu= command line 163 options. See Documentation/x86/x86_64/boot-options.txt for more 164 details. 165 166config IOMMU_STRESS 167 bool "Enable IOMMU stress-test mode" 168 ---help--- 169 This option disables various optimizations in IOMMU related 170 code to do real stress testing of the IOMMU code. This option 171 will cause a performance drop and should only be enabled for 172 testing. 173 174config IOMMU_LEAK 175 bool "IOMMU leak tracing" 176 depends on IOMMU_DEBUG && DMA_API_DEBUG 177 ---help--- 178 Add a simple leak tracer to the IOMMU code. This is useful when you 179 are debugging a buggy device driver that leaks IOMMU mappings. 180 181config HAVE_MMIOTRACE_SUPPORT 182 def_bool y 183 184config X86_DECODER_SELFTEST 185 bool "x86 instruction decoder selftest" 186 depends on DEBUG_KERNEL && KPROBES 187 depends on !COMPILE_TEST 188 ---help--- 189 Perform x86 instruction decoder selftests at build time. 190 This option is useful for checking the sanity of x86 instruction 191 decoder code. 192 If unsure, say "N". 193 194# 195# IO delay types: 196# 197 198config IO_DELAY_TYPE_0X80 199 int 200 default "0" 201 202config IO_DELAY_TYPE_0XED 203 int 204 default "1" 205 206config IO_DELAY_TYPE_UDELAY 207 int 208 default "2" 209 210config IO_DELAY_TYPE_NONE 211 int 212 default "3" 213 214choice 215 prompt "IO delay type" 216 default IO_DELAY_0X80 217 218config IO_DELAY_0X80 219 bool "port 0x80 based port-IO delay [recommended]" 220 ---help--- 221 This is the traditional Linux IO delay used for in/out_p. 222 It is the most tested hence safest selection here. 223 224config IO_DELAY_0XED 225 bool "port 0xed based port-IO delay" 226 ---help--- 227 Use port 0xed as the IO delay. This frees up port 0x80 which is 228 often used as a hardware-debug port. 229 230config IO_DELAY_UDELAY 231 bool "udelay based port-IO delay" 232 ---help--- 233 Use udelay(2) as the IO delay method. This provides the delay 234 while not having any side-effect on the IO port space. 235 236config IO_DELAY_NONE 237 bool "no port-IO delay" 238 ---help--- 239 No port-IO delay. Will break on old boxes that require port-IO 240 delay for certain operations. Should work on most new machines. 241 242endchoice 243 244if IO_DELAY_0X80 245config DEFAULT_IO_DELAY_TYPE 246 int 247 default IO_DELAY_TYPE_0X80 248endif 249 250if IO_DELAY_0XED 251config DEFAULT_IO_DELAY_TYPE 252 int 253 default IO_DELAY_TYPE_0XED 254endif 255 256if IO_DELAY_UDELAY 257config DEFAULT_IO_DELAY_TYPE 258 int 259 default IO_DELAY_TYPE_UDELAY 260endif 261 262if IO_DELAY_NONE 263config DEFAULT_IO_DELAY_TYPE 264 int 265 default IO_DELAY_TYPE_NONE 266endif 267 268config DEBUG_BOOT_PARAMS 269 bool "Debug boot parameters" 270 depends on DEBUG_KERNEL 271 depends on DEBUG_FS 272 ---help--- 273 This option will cause struct boot_params to be exported via debugfs. 274 275config CPA_DEBUG 276 bool "CPA self-test code" 277 depends on DEBUG_KERNEL 278 ---help--- 279 Do change_page_attr() self-tests every 30 seconds. 280 281config OPTIMIZE_INLINING 282 bool "Allow gcc to uninline functions marked 'inline'" 283 ---help--- 284 This option determines if the kernel forces gcc to inline the functions 285 developers have marked 'inline'. Doing so takes away freedom from gcc to 286 do what it thinks is best, which is desirable for the gcc 3.x series of 287 compilers. The gcc 4.x series have a rewritten inlining algorithm and 288 enabling this option will generate a smaller kernel there. Hopefully 289 this algorithm is so good that allowing gcc 4.x and above to make the 290 decision will become the default in the future. Until then this option 291 is there to test gcc for this. 292 293 If unsure, say N. 294 295config DEBUG_NMI_SELFTEST 296 bool "NMI Selftest" 297 depends on DEBUG_KERNEL && X86_LOCAL_APIC 298 ---help--- 299 Enabling this option turns on a quick NMI selftest to verify 300 that the NMI behaves correctly. 301 302 This might help diagnose strange hangs that rely on NMI to 303 function properly. 304 305 If unsure, say N. 306 307config X86_DEBUG_STATIC_CPU_HAS 308 bool "Debug alternatives" 309 depends on DEBUG_KERNEL 310 ---help--- 311 This option causes additional code to be generated which 312 fails if static_cpu_has() is used before alternatives have 313 run. 314 315 If unsure, say N. 316 317endmenu 318