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_PAGEALLOC 76 bool "Debug page memory allocations" 77 depends on DEBUG_KERNEL 78 help 79 Unmap pages from the kernel linear mapping after free_pages(). 80 This results in a large slowdown, but helps to find certain types 81 of memory corruptions. 82 83config DEBUG_PER_CPU_MAPS 84 bool "Debug access to per_cpu maps" 85 depends on DEBUG_KERNEL 86 depends on X86_SMP 87 default n 88 help 89 Say Y to verify that the per_cpu map being accessed has 90 been setup. Adds a fair amount of code to kernel memory 91 and decreases performance. 92 93 Say N if unsure. 94 95config X86_PTDUMP 96 bool "Export kernel pagetable layout to userspace via debugfs" 97 depends on DEBUG_KERNEL 98 select DEBUG_FS 99 help 100 Say Y here if you want to show the kernel pagetable layout in a 101 debugfs file. This information is only useful for kernel developers 102 who are working in architecture specific areas of the kernel. 103 It is probably not a good idea to enable this feature in a production 104 kernel. 105 If in doubt, say "N" 106 107config DEBUG_RODATA 108 bool "Write protect kernel read-only data structures" 109 default y 110 depends on DEBUG_KERNEL 111 help 112 Mark the kernel read-only data as write-protected in the pagetables, 113 in order to catch accidental (and incorrect) writes to such const 114 data. This is recommended so that we can catch kernel bugs sooner. 115 If in doubt, say "Y". 116 117config DIRECT_GBPAGES 118 bool "Enable gbpages-mapped kernel pagetables" 119 depends on DEBUG_KERNEL && EXPERIMENTAL && X86_64 120 help 121 Enable gigabyte pages support (if the CPU supports it). This can 122 improve the kernel's performance a tiny bit by reducing TLB 123 pressure. 124 125 This is experimental code. 126 127 If in doubt, say "N". 128 129config DEBUG_RODATA_TEST 130 bool "Testcase for the DEBUG_RODATA feature" 131 depends on DEBUG_RODATA 132 help 133 This option enables a testcase for the DEBUG_RODATA 134 feature as well as for the change_page_attr() infrastructure. 135 If in doubt, say "N" 136 137config DEBUG_NX_TEST 138 tristate "Testcase for the NX non-executable stack feature" 139 depends on DEBUG_KERNEL && m 140 help 141 This option enables a testcase for the CPU NX capability 142 and the software setup of this feature. 143 If in doubt, say "N" 144 145config 4KSTACKS 146 bool "Use 4Kb for kernel stacks instead of 8Kb" 147 depends on X86_32 148 help 149 If you say Y here the kernel will use a 4Kb stacksize for the 150 kernel stack attached to each process/thread. This facilitates 151 running more threads on a system and also reduces the pressure 152 on the VM subsystem for higher order allocations. This option 153 will also use IRQ stacks to compensate for the reduced stackspace. 154 155config DOUBLEFAULT 156 default y 157 bool "Enable doublefault exception handler" if EMBEDDED 158 depends on X86_32 159 help 160 This option allows trapping of rare doublefault exceptions that 161 would otherwise cause a system to silently reboot. Disabling this 162 option saves about 4k and might cause you much additional grey 163 hair. 164 165config IOMMU_DEBUG 166 bool "Enable IOMMU debugging" 167 depends on GART_IOMMU && DEBUG_KERNEL 168 depends on X86_64 169 help 170 Force the IOMMU to on even when you have less than 4GB of 171 memory and add debugging code. On overflow always panic. And 172 allow to enable IOMMU leak tracing. Can be disabled at boot 173 time with iommu=noforce. This will also enable scatter gather 174 list merging. Currently not recommended for production 175 code. When you use it make sure you have a big enough 176 IOMMU/AGP aperture. Most of the options enabled by this can 177 be set more finegrained using the iommu= command line 178 options. See Documentation/x86_64/boot-options.txt for more 179 details. 180 181config IOMMU_LEAK 182 bool "IOMMU leak tracing" 183 depends on DEBUG_KERNEL 184 depends on IOMMU_DEBUG 185 help 186 Add a simple leak tracer to the IOMMU code. This is useful when you 187 are debugging a buggy device driver that leaks IOMMU mappings. 188 189config MMIOTRACE_HOOKS 190 bool 191 192config MMIOTRACE 193 bool "Memory mapped IO tracing" 194 depends on DEBUG_KERNEL && PCI 195 select TRACING 196 select MMIOTRACE_HOOKS 197 help 198 Mmiotrace traces Memory Mapped I/O access and is meant for 199 debugging and reverse engineering. It is called from the ioremap 200 implementation and works via page faults. Tracing is disabled by 201 default and can be enabled at run-time. 202 203 See Documentation/tracers/mmiotrace.txt. 204 If you are not helping to develop drivers, say N. 205 206config MMIOTRACE_TEST 207 tristate "Test module for mmiotrace" 208 depends on MMIOTRACE && m 209 help 210 This is a dumb module for testing mmiotrace. It is very dangerous 211 as it will write garbage to IO memory starting at a given address. 212 However, it should be safe to use on e.g. unused portion of VRAM. 213 214 Say N, unless you absolutely know what you are doing. 215 216# 217# IO delay types: 218# 219 220config IO_DELAY_TYPE_0X80 221 int 222 default "0" 223 224config IO_DELAY_TYPE_0XED 225 int 226 default "1" 227 228config IO_DELAY_TYPE_UDELAY 229 int 230 default "2" 231 232config IO_DELAY_TYPE_NONE 233 int 234 default "3" 235 236choice 237 prompt "IO delay type" 238 default IO_DELAY_0X80 239 240config IO_DELAY_0X80 241 bool "port 0x80 based port-IO delay [recommended]" 242 help 243 This is the traditional Linux IO delay used for in/out_p. 244 It is the most tested hence safest selection here. 245 246config IO_DELAY_0XED 247 bool "port 0xed based port-IO delay" 248 help 249 Use port 0xed as the IO delay. This frees up port 0x80 which is 250 often used as a hardware-debug port. 251 252config IO_DELAY_UDELAY 253 bool "udelay based port-IO delay" 254 help 255 Use udelay(2) as the IO delay method. This provides the delay 256 while not having any side-effect on the IO port space. 257 258config IO_DELAY_NONE 259 bool "no port-IO delay" 260 help 261 No port-IO delay. Will break on old boxes that require port-IO 262 delay for certain operations. Should work on most new machines. 263 264endchoice 265 266if IO_DELAY_0X80 267config DEFAULT_IO_DELAY_TYPE 268 int 269 default IO_DELAY_TYPE_0X80 270endif 271 272if IO_DELAY_0XED 273config DEFAULT_IO_DELAY_TYPE 274 int 275 default IO_DELAY_TYPE_0XED 276endif 277 278if IO_DELAY_UDELAY 279config DEFAULT_IO_DELAY_TYPE 280 int 281 default IO_DELAY_TYPE_UDELAY 282endif 283 284if IO_DELAY_NONE 285config DEFAULT_IO_DELAY_TYPE 286 int 287 default IO_DELAY_TYPE_NONE 288endif 289 290config DEBUG_BOOT_PARAMS 291 bool "Debug boot parameters" 292 depends on DEBUG_KERNEL 293 depends on DEBUG_FS 294 help 295 This option will cause struct boot_params to be exported via debugfs. 296 297config CPA_DEBUG 298 bool "CPA self-test code" 299 depends on DEBUG_KERNEL 300 help 301 Do change_page_attr() self-tests every 30 seconds. 302 303config OPTIMIZE_INLINING 304 bool "Allow gcc to uninline functions marked 'inline'" 305 help 306 This option determines if the kernel forces gcc to inline the functions 307 developers have marked 'inline'. Doing so takes away freedom from gcc to 308 do what it thinks is best, which is desirable for the gcc 3.x series of 309 compilers. The gcc 4.x series have a rewritten inlining algorithm and 310 disabling this option will generate a smaller kernel there. Hopefully 311 this algorithm is so good that allowing gcc4 to make the decision can 312 become the default in the future, until then this option is there to 313 test gcc for this. 314 315 If unsure, say N. 316 317endmenu 318 319