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 EMBEDDED 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_DBGP 47 bool "Early printk via EHCI debug port" 48 default n 49 depends on EARLY_PRINTK && PCI 50 ---help--- 51 Write kernel log output directly into the EHCI debug port. 52 53 This is useful for kernel debugging when your machine crashes very 54 early before the console code is initialized. For normal operation 55 it is not recommended because it looks ugly and doesn't cooperate 56 with klogd/syslogd or the X server. You should normally N here, 57 unless you want to debug such a crash. You need usb debug device. 58 59config DEBUG_STACKOVERFLOW 60 bool "Check for stack overflows" 61 depends on DEBUG_KERNEL 62 ---help--- 63 This option will cause messages to be printed if free stack space 64 drops below a certain limit. 65 66config DEBUG_STACK_USAGE 67 bool "Stack utilization instrumentation" 68 depends on DEBUG_KERNEL 69 ---help--- 70 Enables the display of the minimum amount of free stack which each 71 task has ever had available in the sysrq-T and sysrq-P debug output. 72 73 This option will slow down process creation somewhat. 74 75config DEBUG_PER_CPU_MAPS 76 bool "Debug access to per_cpu maps" 77 depends on DEBUG_KERNEL 78 depends on SMP 79 default n 80 ---help--- 81 Say Y to verify that the per_cpu map being accessed has 82 been setup. Adds a fair amount of code to kernel memory 83 and decreases performance. 84 85 Say N if unsure. 86 87config X86_PTDUMP 88 bool "Export kernel pagetable layout to userspace via debugfs" 89 depends on DEBUG_KERNEL 90 select DEBUG_FS 91 ---help--- 92 Say Y here if you want to show the kernel pagetable layout in a 93 debugfs file. This information is only useful for kernel developers 94 who are working in architecture specific areas of the kernel. 95 It is probably not a good idea to enable this feature in a production 96 kernel. 97 If in doubt, say "N" 98 99config DEBUG_RODATA 100 bool "Write protect kernel read-only data structures" 101 default y 102 depends on DEBUG_KERNEL 103 ---help--- 104 Mark the kernel read-only data as write-protected in the pagetables, 105 in order to catch accidental (and incorrect) writes to such const 106 data. This is recommended so that we can catch kernel bugs sooner. 107 If in doubt, say "Y". 108 109config DEBUG_RODATA_TEST 110 bool "Testcase for the DEBUG_RODATA feature" 111 depends on DEBUG_RODATA 112 default y 113 ---help--- 114 This option enables a testcase for the DEBUG_RODATA 115 feature as well as for the change_page_attr() infrastructure. 116 If in doubt, say "N" 117 118config DEBUG_NX_TEST 119 tristate "Testcase for the NX non-executable stack feature" 120 depends on DEBUG_KERNEL && m 121 ---help--- 122 This option enables a testcase for the CPU NX capability 123 and the software setup of this feature. 124 If in doubt, say "N" 125 126config 4KSTACKS 127 bool "Use 4Kb for kernel stacks instead of 8Kb" 128 depends on X86_32 129 ---help--- 130 If you say Y here the kernel will use a 4Kb stacksize for the 131 kernel stack attached to each process/thread. This facilitates 132 running more threads on a system and also reduces the pressure 133 on the VM subsystem for higher order allocations. This option 134 will also use IRQ stacks to compensate for the reduced stackspace. 135 136config DOUBLEFAULT 137 default y 138 bool "Enable doublefault exception handler" if EMBEDDED 139 depends on X86_32 140 ---help--- 141 This option allows trapping of rare doublefault exceptions that 142 would otherwise cause a system to silently reboot. Disabling this 143 option saves about 4k and might cause you much additional grey 144 hair. 145 146config IOMMU_DEBUG 147 bool "Enable IOMMU debugging" 148 depends on GART_IOMMU && DEBUG_KERNEL 149 depends on X86_64 150 ---help--- 151 Force the IOMMU to on even when you have less than 4GB of 152 memory and add debugging code. On overflow always panic. And 153 allow to enable IOMMU leak tracing. Can be disabled at boot 154 time with iommu=noforce. This will also enable scatter gather 155 list merging. Currently not recommended for production 156 code. When you use it make sure you have a big enough 157 IOMMU/AGP aperture. Most of the options enabled by this can 158 be set more finegrained using the iommu= command line 159 options. See Documentation/x86_64/boot-options.txt for more 160 details. 161 162config IOMMU_LEAK 163 bool "IOMMU leak tracing" 164 depends on DEBUG_KERNEL 165 depends on IOMMU_DEBUG 166 ---help--- 167 Add a simple leak tracer to the IOMMU code. This is useful when you 168 are debugging a buggy device driver that leaks IOMMU mappings. 169 170config HAVE_MMIOTRACE_SUPPORT 171 def_bool y 172 173# 174# IO delay types: 175# 176 177config IO_DELAY_TYPE_0X80 178 int 179 default "0" 180 181config IO_DELAY_TYPE_0XED 182 int 183 default "1" 184 185config IO_DELAY_TYPE_UDELAY 186 int 187 default "2" 188 189config IO_DELAY_TYPE_NONE 190 int 191 default "3" 192 193choice 194 prompt "IO delay type" 195 default IO_DELAY_0X80 196 197config IO_DELAY_0X80 198 bool "port 0x80 based port-IO delay [recommended]" 199 ---help--- 200 This is the traditional Linux IO delay used for in/out_p. 201 It is the most tested hence safest selection here. 202 203config IO_DELAY_0XED 204 bool "port 0xed based port-IO delay" 205 ---help--- 206 Use port 0xed as the IO delay. This frees up port 0x80 which is 207 often used as a hardware-debug port. 208 209config IO_DELAY_UDELAY 210 bool "udelay based port-IO delay" 211 ---help--- 212 Use udelay(2) as the IO delay method. This provides the delay 213 while not having any side-effect on the IO port space. 214 215config IO_DELAY_NONE 216 bool "no port-IO delay" 217 ---help--- 218 No port-IO delay. Will break on old boxes that require port-IO 219 delay for certain operations. Should work on most new machines. 220 221endchoice 222 223if IO_DELAY_0X80 224config DEFAULT_IO_DELAY_TYPE 225 int 226 default IO_DELAY_TYPE_0X80 227endif 228 229if IO_DELAY_0XED 230config DEFAULT_IO_DELAY_TYPE 231 int 232 default IO_DELAY_TYPE_0XED 233endif 234 235if IO_DELAY_UDELAY 236config DEFAULT_IO_DELAY_TYPE 237 int 238 default IO_DELAY_TYPE_UDELAY 239endif 240 241if IO_DELAY_NONE 242config DEFAULT_IO_DELAY_TYPE 243 int 244 default IO_DELAY_TYPE_NONE 245endif 246 247config DEBUG_BOOT_PARAMS 248 bool "Debug boot parameters" 249 depends on DEBUG_KERNEL 250 depends on DEBUG_FS 251 ---help--- 252 This option will cause struct boot_params to be exported via debugfs. 253 254config CPA_DEBUG 255 bool "CPA self-test code" 256 depends on DEBUG_KERNEL 257 ---help--- 258 Do change_page_attr() self-tests every 30 seconds. 259 260config OPTIMIZE_INLINING 261 bool "Allow gcc to uninline functions marked 'inline'" 262 ---help--- 263 This option determines if the kernel forces gcc to inline the functions 264 developers have marked 'inline'. Doing so takes away freedom from gcc to 265 do what it thinks is best, which is desirable for the gcc 3.x series of 266 compilers. The gcc 4.x series have a rewritten inlining algorithm and 267 enabling this option will generate a smaller kernel there. Hopefully 268 this algorithm is so good that allowing gcc 4.x and above to make the 269 decision will become the default in the future. Until then this option 270 is there to test gcc for this. 271 272 If unsure, say N. 273 274endmenu 275