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