1menu "Kernel hacking" 2 3config TRACE_IRQFLAGS_SUPPORT 4 def_bool y 5 6source "lib/Kconfig.debug" 7 8config NONPROMISC_DEVMEM 9 bool "Disable promiscuous /dev/mem" 10 help 11 The /dev/mem file by default only allows userspace access to PCI 12 space and the BIOS code and data regions. This is sufficient for 13 dosemu and X and all common users of /dev/mem. With this config 14 option, you allow userspace access to all of memory, including 15 kernel and userspace memory. Accidental access to this is 16 obviously disasterous, but specific access can be used by people 17 debugging the kernel. 18 19config EARLY_PRINTK 20 bool "Early printk" if EMBEDDED 21 default y 22 help 23 Write kernel log output directly into the VGA buffer or to a serial 24 port. 25 26 This is useful for kernel debugging when your machine crashes very 27 early before the console code is initialized. For normal operation 28 it is not recommended because it looks ugly and doesn't cooperate 29 with klogd/syslogd or the X server. You should normally N here, 30 unless you want to debug such a crash. 31 32config DEBUG_STACKOVERFLOW 33 bool "Check for stack overflows" 34 depends on DEBUG_KERNEL 35 help 36 This option will cause messages to be printed if free stack space 37 drops below a certain limit. 38 39config DEBUG_STACK_USAGE 40 bool "Stack utilization instrumentation" 41 depends on DEBUG_KERNEL 42 help 43 Enables the display of the minimum amount of free stack which each 44 task has ever had available in the sysrq-T and sysrq-P debug output. 45 46 This option will slow down process creation somewhat. 47 48config DEBUG_PAGEALLOC 49 bool "Debug page memory allocations" 50 depends on DEBUG_KERNEL 51 help 52 Unmap pages from the kernel linear mapping after free_pages(). 53 This results in a large slowdown, but helps to find certain types 54 of memory corruptions. 55 56config DEBUG_PER_CPU_MAPS 57 bool "Debug access to per_cpu maps" 58 depends on DEBUG_KERNEL 59 depends on X86_64_SMP 60 default n 61 help 62 Say Y to verify that the per_cpu map being accessed has 63 been setup. Adds a fair amount of code to kernel memory 64 and decreases performance. 65 66 Say N if unsure. 67 68config X86_PTDUMP 69 bool "Export kernel pagetable layout to userspace via debugfs" 70 depends on DEBUG_KERNEL 71 select DEBUG_FS 72 help 73 Say Y here if you want to show the kernel pagetable layout in a 74 debugfs file. This information is only useful for kernel developers 75 who are working in architecture specific areas of the kernel. 76 It is probably not a good idea to enable this feature in a production 77 kernel. 78 If in doubt, say "N" 79 80config DEBUG_RODATA 81 bool "Write protect kernel read-only data structures" 82 default y 83 depends on DEBUG_KERNEL 84 help 85 Mark the kernel read-only data as write-protected in the pagetables, 86 in order to catch accidental (and incorrect) writes to such const 87 data. This is recommended so that we can catch kernel bugs sooner. 88 If in doubt, say "Y". 89 90config DIRECT_GBPAGES 91 bool "Enable gbpages-mapped kernel pagetables" 92 depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64 93 help 94 Enable gigabyte pages support (if the CPU supports it). This can 95 improve the kernel's performance a tiny bit by reducing TLB 96 pressure. 97 98 This is experimental code. 99 100 If in doubt, say "N". 101 102config DEBUG_RODATA_TEST 103 bool "Testcase for the DEBUG_RODATA feature" 104 depends on DEBUG_RODATA 105 help 106 This option enables a testcase for the DEBUG_RODATA 107 feature as well as for the change_page_attr() infrastructure. 108 If in doubt, say "N" 109 110config DEBUG_NX_TEST 111 tristate "Testcase for the NX non-executable stack feature" 112 depends on DEBUG_KERNEL && m 113 help 114 This option enables a testcase for the CPU NX capability 115 and the software setup of this feature. 116 If in doubt, say "N" 117 118config 4KSTACKS 119 bool "Use 4Kb for kernel stacks instead of 8Kb" 120 depends on X86_32 121 help 122 If you say Y here the kernel will use a 4Kb stacksize for the 123 kernel stack attached to each process/thread. This facilitates 124 running more threads on a system and also reduces the pressure 125 on the VM subsystem for higher order allocations. This option 126 will also use IRQ stacks to compensate for the reduced stackspace. 127 128config X86_FIND_SMP_CONFIG 129 def_bool y 130 depends on X86_LOCAL_APIC || X86_VOYAGER 131 depends on X86_32 132 133config X86_MPPARSE 134 def_bool y 135 depends on (X86_32 && (X86_LOCAL_APIC && !X86_VISWS)) || X86_64 136 137config DOUBLEFAULT 138 default y 139 bool "Enable doublefault exception handler" if EMBEDDED 140 depends on X86_32 141 help 142 This option allows trapping of rare doublefault exceptions that 143 would otherwise cause a system to silently reboot. Disabling this 144 option saves about 4k and might cause you much additional grey 145 hair. 146 147config IOMMU_DEBUG 148 bool "Enable IOMMU debugging" 149 depends on GART_IOMMU && DEBUG_KERNEL 150 depends on X86_64 151 help 152 Force the IOMMU to on even when you have less than 4GB of 153 memory and add debugging code. On overflow always panic. And 154 allow to enable IOMMU leak tracing. Can be disabled at boot 155 time with iommu=noforce. This will also enable scatter gather 156 list merging. Currently not recommended for production 157 code. When you use it make sure you have a big enough 158 IOMMU/AGP aperture. Most of the options enabled by this can 159 be set more finegrained using the iommu= command line 160 options. See Documentation/x86_64/boot-options.txt for more 161 details. 162 163config IOMMU_LEAK 164 bool "IOMMU leak tracing" 165 depends on DEBUG_KERNEL 166 depends on IOMMU_DEBUG 167 help 168 Add a simple leak tracer to the IOMMU code. This is useful when you 169 are debugging a buggy device driver that leaks IOMMU mappings. 170 171# 172# IO delay types: 173# 174 175config IO_DELAY_TYPE_0X80 176 int 177 default "0" 178 179config IO_DELAY_TYPE_0XED 180 int 181 default "1" 182 183config IO_DELAY_TYPE_UDELAY 184 int 185 default "2" 186 187config IO_DELAY_TYPE_NONE 188 int 189 default "3" 190 191choice 192 prompt "IO delay type" 193 default IO_DELAY_0X80 194 195config IO_DELAY_0X80 196 bool "port 0x80 based port-IO delay [recommended]" 197 help 198 This is the traditional Linux IO delay used for in/out_p. 199 It is the most tested hence safest selection here. 200 201config IO_DELAY_0XED 202 bool "port 0xed based port-IO delay" 203 help 204 Use port 0xed as the IO delay. This frees up port 0x80 which is 205 often used as a hardware-debug port. 206 207config IO_DELAY_UDELAY 208 bool "udelay based port-IO delay" 209 help 210 Use udelay(2) as the IO delay method. This provides the delay 211 while not having any side-effect on the IO port space. 212 213config IO_DELAY_NONE 214 bool "no port-IO delay" 215 help 216 No port-IO delay. Will break on old boxes that require port-IO 217 delay for certain operations. Should work on most new machines. 218 219endchoice 220 221if IO_DELAY_0X80 222config DEFAULT_IO_DELAY_TYPE 223 int 224 default IO_DELAY_TYPE_0X80 225endif 226 227if IO_DELAY_0XED 228config DEFAULT_IO_DELAY_TYPE 229 int 230 default IO_DELAY_TYPE_0XED 231endif 232 233if IO_DELAY_UDELAY 234config DEFAULT_IO_DELAY_TYPE 235 int 236 default IO_DELAY_TYPE_UDELAY 237endif 238 239if IO_DELAY_NONE 240config DEFAULT_IO_DELAY_TYPE 241 int 242 default IO_DELAY_TYPE_NONE 243endif 244 245config DEBUG_BOOT_PARAMS 246 bool "Debug boot parameters" 247 depends on DEBUG_KERNEL 248 depends on DEBUG_FS 249 help 250 This option will cause struct boot_params to be exported via debugfs. 251 252config CPA_DEBUG 253 bool "CPA self-test code" 254 depends on DEBUG_KERNEL 255 help 256 Do change_page_attr() self-tests every 30 seconds. 257 258config OPTIMIZE_INLINING 259 bool "Allow gcc to uninline functions marked 'inline'" 260 depends on BROKEN 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 disabling this option will generate a smaller kernel there. Hopefully 267 this algorithm is so good that allowing gcc4 to make the decision can 268 become the default in the future, until then this option is there to 269 test gcc for this. 270 271endmenu 272 273