kernel_optimize_test/arch/blackfin/Kconfig.debug

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.

endmenu