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 EFI_PGT_DUMP 85 bool "Dump the EFI pagetable" 86 depends on EFI && X86_PTDUMP 87 ---help--- 88 Enable this if you want to dump the EFI page table before 89 enabling virtual mode. This can be used to debug miscellaneous 90 issues with the mapping of the EFI runtime regions into that 91 table. 92 93config DEBUG_RODATA 94 bool "Write protect kernel read-only data structures" 95 default y 96 depends on DEBUG_KERNEL 97 ---help--- 98 Mark the kernel read-only data as write-protected in the pagetables, 99 in order to catch accidental (and incorrect) writes to such const 100 data. This is recommended so that we can catch kernel bugs sooner. 101 If in doubt, say "Y". 102 103config DEBUG_RODATA_TEST 104 bool "Testcase for the DEBUG_RODATA feature" 105 depends on DEBUG_RODATA 106 default y 107 ---help--- 108 This option enables a testcase for the DEBUG_RODATA 109 feature as well as for the change_page_attr() infrastructure. 110 If in doubt, say "N" 111 112config DEBUG_SET_MODULE_RONX 113 bool "Set loadable kernel module data as NX and text as RO" 114 depends on MODULES 115 ---help--- 116 This option helps catch unintended modifications to loadable 117 kernel module's text and read-only data. It also prevents execution 118 of module data. Such protection may interfere with run-time code 119 patching and dynamic kernel tracing - and they might also protect 120 against certain classes of kernel exploits. 121 If in doubt, say "N". 122 123config DEBUG_NX_TEST 124 tristate "Testcase for the NX non-executable stack feature" 125 depends on DEBUG_KERNEL && m 126 ---help--- 127 This option enables a testcase for the CPU NX capability 128 and the software setup of this feature. 129 If in doubt, say "N" 130 131config DOUBLEFAULT 132 default y 133 bool "Enable doublefault exception handler" if EXPERT 134 ---help--- 135 This option allows trapping of rare doublefault exceptions that 136 would otherwise cause a system to silently reboot. Disabling this 137 option saves about 4k and might cause you much additional grey 138 hair. 139 140config DEBUG_TLBFLUSH 141 bool "Set upper limit of TLB entries to flush one-by-one" 142 depends on DEBUG_KERNEL 143 ---help--- 144 145 X86-only for now. 146 147 This option allows the user to tune the amount of TLB entries the 148 kernel flushes one-by-one instead of doing a full TLB flush. In 149 certain situations, the former is cheaper. This is controlled by the 150 tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it 151 to -1, the code flushes the whole TLB unconditionally. Otherwise, 152 for positive values of it, the kernel will use single TLB entry 153 invalidating instructions according to the following formula: 154 155 flush_entries <= active_tlb_entries / 2^tlb_flushall_shift 156 157 If in doubt, say "N". 158 159config IOMMU_DEBUG 160 bool "Enable IOMMU debugging" 161 depends on GART_IOMMU && DEBUG_KERNEL 162 depends on X86_64 163 ---help--- 164 Force the IOMMU to on even when you have less than 4GB of 165 memory and add debugging code. On overflow always panic. And 166 allow to enable IOMMU leak tracing. Can be disabled at boot 167 time with iommu=noforce. This will also enable scatter gather 168 list merging. Currently not recommended for production 169 code. When you use it make sure you have a big enough 170 IOMMU/AGP aperture. Most of the options enabled by this can 171 be set more finegrained using the iommu= command line 172 options. See Documentation/x86/x86_64/boot-options.txt for more 173 details. 174 175config IOMMU_STRESS 176 bool "Enable IOMMU stress-test mode" 177 ---help--- 178 This option disables various optimizations in IOMMU related 179 code to do real stress testing of the IOMMU code. This option 180 will cause a performance drop and should only be enabled for 181 testing. 182 183config IOMMU_LEAK 184 bool "IOMMU leak tracing" 185 depends on IOMMU_DEBUG && DMA_API_DEBUG 186 ---help--- 187 Add a simple leak tracer to the IOMMU code. This is useful when you 188 are debugging a buggy device driver that leaks IOMMU mappings. 189 190config HAVE_MMIOTRACE_SUPPORT 191 def_bool y 192 193config X86_DECODER_SELFTEST 194 bool "x86 instruction decoder selftest" 195 depends on DEBUG_KERNEL && KPROBES 196 depends on !COMPILE_TEST 197 ---help--- 198 Perform x86 instruction decoder selftests at build time. 199 This option is useful for checking the sanity of x86 instruction 200 decoder code. 201 If unsure, say "N". 202 203# 204# IO delay types: 205# 206 207config IO_DELAY_TYPE_0X80 208 int 209 default "0" 210 211config IO_DELAY_TYPE_0XED 212 int 213 default "1" 214 215config IO_DELAY_TYPE_UDELAY 216 int 217 default "2" 218 219config IO_DELAY_TYPE_NONE 220 int 221 default "3" 222 223choice 224 prompt "IO delay type" 225 default IO_DELAY_0X80 226 227config IO_DELAY_0X80 228 bool "port 0x80 based port-IO delay [recommended]" 229 ---help--- 230 This is the traditional Linux IO delay used for in/out_p. 231 It is the most tested hence safest selection here. 232 233config IO_DELAY_0XED 234 bool "port 0xed based port-IO delay" 235 ---help--- 236 Use port 0xed as the IO delay. This frees up port 0x80 which is 237 often used as a hardware-debug port. 238 239config IO_DELAY_UDELAY 240 bool "udelay based port-IO delay" 241 ---help--- 242 Use udelay(2) as the IO delay method. This provides the delay 243 while not having any side-effect on the IO port space. 244 245config IO_DELAY_NONE 246 bool "no port-IO delay" 247 ---help--- 248 No port-IO delay. Will break on old boxes that require port-IO 249 delay for certain operations. Should work on most new machines. 250 251endchoice 252 253if IO_DELAY_0X80 254config DEFAULT_IO_DELAY_TYPE 255 int 256 default IO_DELAY_TYPE_0X80 257endif 258 259if IO_DELAY_0XED 260config DEFAULT_IO_DELAY_TYPE 261 int 262 default IO_DELAY_TYPE_0XED 263endif 264 265if IO_DELAY_UDELAY 266config DEFAULT_IO_DELAY_TYPE 267 int 268 default IO_DELAY_TYPE_UDELAY 269endif 270 271if IO_DELAY_NONE 272config DEFAULT_IO_DELAY_TYPE 273 int 274 default IO_DELAY_TYPE_NONE 275endif 276 277config DEBUG_BOOT_PARAMS 278 bool "Debug boot parameters" 279 depends on DEBUG_KERNEL 280 depends on DEBUG_FS 281 ---help--- 282 This option will cause struct boot_params to be exported via debugfs. 283 284config CPA_DEBUG 285 bool "CPA self-test code" 286 depends on DEBUG_KERNEL 287 ---help--- 288 Do change_page_attr() self-tests every 30 seconds. 289 290config OPTIMIZE_INLINING 291 bool "Allow gcc to uninline functions marked 'inline'" 292 ---help--- 293 This option determines if the kernel forces gcc to inline the functions 294 developers have marked 'inline'. Doing so takes away freedom from gcc to 295 do what it thinks is best, which is desirable for the gcc 3.x series of 296 compilers. The gcc 4.x series have a rewritten inlining algorithm and 297 enabling this option will generate a smaller kernel there. Hopefully 298 this algorithm is so good that allowing gcc 4.x and above to make the 299 decision will become the default in the future. Until then this option 300 is there to test gcc for this. 301 302 If unsure, say N. 303 304config DEBUG_NMI_SELFTEST 305 bool "NMI Selftest" 306 depends on DEBUG_KERNEL && X86_LOCAL_APIC 307 ---help--- 308 Enabling this option turns on a quick NMI selftest to verify 309 that the NMI behaves correctly. 310 311 This might help diagnose strange hangs that rely on NMI to 312 function properly. 313 314 If unsure, say N. 315 316config X86_DEBUG_STATIC_CPU_HAS 317 bool "Debug alternatives" 318 depends on DEBUG_KERNEL 319 ---help--- 320 This option causes additional code to be generated which 321 fails if static_cpu_has() is used before alternatives have 322 run. 323 324 If unsure, say N. 325 326endmenu 327