menu "Kernel hacking" source "lib/Kconfig.debug" config DEBUG_STACKOVERFLOW bool "Check for stack overflows" depends on DEBUG_KERNEL help This option will cause messages to be printed if free stack space drops below a certain limit. config DEBUG_STACK_USAGE bool "Enable stack utilization instrumentation" depends on DEBUG_KERNEL help Enables the display of the minimum amount of free stack which each task has ever had available in the sysrq-T output. This option will slow down process creation somewhat. config HAVE_ARCH_KGDB def_bool y config DEBUG_VERBOSE bool "Verbose fault messages" default y select PRINTK help When a program crashes due to an exception, or the kernel detects an internal error, the kernel can print a not so brief message explaining what the problem was. This debugging information is useful to developers and kernel hackers when tracking down problems, but mostly meaningless to other people. This is always helpful for debugging but serves no purpose on a production system. Most people should say N here. config DEBUG_MMRS bool "Generate Blackfin MMR tree" select DEBUG_FS help Create a tree of Blackfin MMRs via the debugfs tree. If you enable this, you will find all MMRs laid out in the /sys/kernel/debug/blackfin/ directory where you can read/write MMRs directly from userspace. This is obviously just a debug feature. config DEBUG_HWERR bool "Hardware error interrupt debugging" depends on DEBUG_KERNEL help When enabled, the hardware error interrupt is never disabled, and will happen immediately when an error condition occurs. This comes at a slight cost in code size, but is necessary if you are getting hardware error interrupts and need to know where they are coming from. config EXACT_HWERR bool "Try to make Hardware errors exact" depends on DEBUG_HWERR help By default, the Blackfin hardware errors are not exact - the error be reported multiple cycles after the error happens. This delay can cause the wrong application, or even the kernel to receive a signal to be killed. If you are getting HW errors in your system, try turning this on to ensure they are at least comming from the proper thread. On production systems, it is safe (and a small optimization) to say N. config DEBUG_DOUBLEFAULT bool "Debug Double Faults" default n help If an exception is caused while executing code within the exception handler, the NMI handler, the reset vector, or in emulator mode, a double fault occurs. On the Blackfin, this is a unrecoverable event. You have two options: - RESET exactly when double fault occurs. The excepting instruction address is stored in RETX, where the next kernel boot will print it out. - Print debug message. This is much more error prone, although easier to handle. It is error prone since: - The excepting instruction is not committed. - All writebacks from the instruction are prevented. - The generated exception is not taken. - The EXCAUSE field is updated with an unrecoverable event The only way to check this is to see if EXCAUSE contains the unrecoverable event value at every exception return. By selecting this option, you are skipping over the faulting instruction, and hoping things stay together enough to print out a debug message. This does add a little kernel code, but is the only method to debug double faults - if unsure say "Y" choice prompt "Double Fault Failure Method" default DEBUG_DOUBLEFAULT_PRINT depends on DEBUG_DOUBLEFAULT config DEBUG_DOUBLEFAULT_PRINT bool "Print" config DEBUG_DOUBLEFAULT_RESET bool "Reset" endchoice config DEBUG_ICACHE_CHECK bool "Check Instruction cache coherency" depends on DEBUG_KERNEL depends on DEBUG_HWERR help Say Y here if you are getting weird unexplained errors. This will ensure that icache is what SDRAM says it should be by doing a byte wise comparison between SDRAM and instruction cache. This also relocates the irq_panic() function to L1 memory, (which is un-cached). config DEBUG_HUNT_FOR_ZERO bool "Catch NULL pointer reads/writes" default y help Say Y here to catch reads/writes to anywhere in the memory range from 0x0000 - 0x0FFF (the first 4k) of memory. This is useful in catching common programming errors such as NULL pointer dereferences. Misbehaving applications will be killed (generate a SEGV) while the kernel will trigger a panic. Enabling this option will take up an extra entry in CPLB table. Otherwise, there is no extra overhead. config DEBUG_BFIN_HWTRACE_ON bool "Turn on Blackfin's Hardware Trace" default y help All Blackfins include a Trace Unit which stores a history of the last 16 changes in program flow taken by the program sequencer. The history allows the user to recreate the program sequencer’s recent path. This can be handy when an application dies - we print out the execution path of how it got to the offending instruction. By turning this off, you may save a tiny amount of power. choice prompt "Omit loop Tracing" default DEBUG_BFIN_HWTRACE_COMPRESSION_OFF depends on DEBUG_BFIN_HWTRACE_ON help The trace buffer can be configured to omit recording of changes in program flow that match either the last entry or one of the last two entries. Omitting one of these entries from the record prevents the trace buffer from overflowing because of any sort of loop (for, do while, etc) in the program. Because zero-overhead Hardware loops are not recorded in the trace buffer, this feature can be used to prevent trace overflow from loops that are nested four deep. config DEBUG_BFIN_HWTRACE_COMPRESSION_OFF bool "Trace all Loops" help The trace buffer records all changes of flow config DEBUG_BFIN_HWTRACE_COMPRESSION_ONE bool "Compress single-level loops" help The trace buffer does not record single loops - helpful if trace is spinning on a while or do loop. config DEBUG_BFIN_HWTRACE_COMPRESSION_TWO bool "Compress two-level loops" help The trace buffer does not record loops two levels deep. Helpful if the trace is spinning in a nested loop endchoice config DEBUG_BFIN_HWTRACE_COMPRESSION int depends on DEBUG_BFIN_HWTRACE_ON default 0 if DEBUG_BFIN_HWTRACE_COMPRESSION_OFF default 1 if DEBUG_BFIN_HWTRACE_COMPRESSION_ONE default 2 if DEBUG_BFIN_HWTRACE_COMPRESSION_TWO config DEBUG_BFIN_HWTRACE_EXPAND bool "Expand Trace Buffer greater than 16 entries" depends on DEBUG_BFIN_HWTRACE_ON default n help By selecting this option, every time the 16 hardware entries in the Blackfin's HW Trace buffer are full, the kernel will move them into a software buffer, for dumping when there is an issue. This has a great impact on performance, (an interrupt every 16 change of flows) and should normally be turned off, except in those nasty debugging sessions config DEBUG_BFIN_HWTRACE_EXPAND_LEN int "Size of Trace buffer (in power of 2k)" range 0 4 depends on DEBUG_BFIN_HWTRACE_EXPAND default 1 help This sets the size of the software buffer that the trace information is kept in. 0 for (2^0) 1k, or 256 entries, 1 for (2^1) 2k, or 512 entries, 2 for (2^2) 4k, or 1024 entries, 3 for (2^3) 8k, or 2048 entries, 4 for (2^4) 16k, or 4096 entries config DEBUG_BFIN_NO_KERN_HWTRACE bool "Turn off hwtrace in CPLB handlers" depends on DEBUG_BFIN_HWTRACE_ON default y help The CPLB error handler contains a lot of flow changes which can quickly fill up the hardware trace buffer. When debugging crashes, the hardware trace may indicate that the problem lies in kernel space when in reality an application is buggy. Say Y here to disable hardware tracing in some known "jumpy" pieces of code so that the trace buffer will extend further back. config EARLY_PRINTK bool "Early printk" default n select SERIAL_CORE_CONSOLE help This option enables special console drivers which allow the kernel to print messages very early in the bootup process. This is useful for kernel debugging when your machine crashes very early before the console code is initialized. After enabling this feature, you must add "earlyprintk=serial,uart0,57600" to the command line (bootargs). It is safe to say Y here in all cases, as all of this lives in the init section and is thrown away after the kernel boots completely. config CPLB_INFO bool "Display the CPLB information" help Display the CPLB information via /proc/cplbinfo. config ACCESS_CHECK bool "Check the user pointer address" default y help Usually the pointer transfer from user space is checked to see if its address is in the kernel space. Say N here to disable that check to improve the performance. config BFIN_ISRAM_SELF_TEST bool "isram boot self tests" default n help Run some self tests of the isram driver code at boot. endmenu