ARM: 7073/1: debug: augment DEBUG_LL Kconfig help to clarify behaviour

[mirror_ubuntu-eoan-kernel.git] / arch / arm / Kconfig.debug

menu "Kernel hacking"

source "lib/Kconfig.debug"

config STRICT_DEVMEM
	bool "Filter access to /dev/mem"
	depends on MMU
	---help---
	  If this option is disabled, you allow userspace (root) access to all
	  of memory, including kernel and userspace memory. Accidental
	  access to this is obviously disastrous, but specific access can
	  be used by people debugging the kernel.

	  If this option is switched on, the /dev/mem file only allows
	  userspace access to memory mapped peripherals.

          If in doubt, say Y.

# RMK wants arm kernels compiled with frame pointers or stack unwinding.
# If you know what you are doing and are willing to live without stack
# traces, you can get a slightly smaller kernel by setting this option to
# n, but then RMK will have to kill you ;).
config FRAME_POINTER
	bool
	depends on !THUMB2_KERNEL
	default y if !ARM_UNWIND || FUNCTION_GRAPH_TRACER
	help
	  If you say N here, the resulting kernel will be slightly smaller and
	  faster. However, if neither FRAME_POINTER nor ARM_UNWIND are enabled,
	  when a problem occurs with the kernel, the information that is
	  reported is severely limited.

config ARM_UNWIND
	bool "Enable stack unwinding support (EXPERIMENTAL)"
	depends on AEABI && EXPERIMENTAL
	default y
	help
	  This option enables stack unwinding support in the kernel
	  using the information automatically generated by the
	  compiler. The resulting kernel image is slightly bigger but
	  the performance is not affected. Currently, this feature
	  only works with EABI compilers. If unsure say Y.

config OLD_MCOUNT
	bool
	depends on FUNCTION_TRACER && FRAME_POINTER
	default y

config DEBUG_USER
	bool "Verbose user fault messages"
	help
	  When a user program crashes due to an exception, the kernel can
	  print a brief message explaining what the problem was. This is
	  sometimes helpful for debugging but serves no purpose on a
	  production system. Most people should say N here.

	  In addition, you need to pass user_debug=N on the kernel command
	  line to enable this feature.  N consists of the sum of:

	      1 - undefined instruction events
	      2 - system calls
	      4 - invalid data aborts
	      8 - SIGSEGV faults
	     16 - SIGBUS faults

# These options are only for real kernel hackers who want to get their hands dirty.
config DEBUG_LL
	bool "Kernel low-level debugging functions (read help!)"
	depends on DEBUG_KERNEL
	help
	  Say Y here to include definitions of printascii, printch, printhex
	  in the kernel.  This is helpful if you are debugging code that
	  executes before the console is initialized.

	  Note that selecting this option will limit the kernel to a single
	  UART definition, as specified below. Attempting to boot the kernel
	  image on a different platform *will not work*, so this option should
	  not be enabled for kernels that are intended to be portable.

choice
	prompt "Kernel low-level debugging port"
	depends on DEBUG_LL

	config DEBUG_DC21285_PORT
		bool "Kernel low-level debugging messages via footbridge serial port"
		depends on FOOTBRIDGE
		help
		  Say Y here if you want the debug print routines to direct
		  their output to the serial port in the DC21285 (Footbridge).
		  Saying N will cause the debug messages to appear on the first
		  16550 serial port.

	config DEBUG_CLPS711X_UART2
		bool "Kernel low-level debugging messages via UART2"
		depends on ARCH_CLPS711X
		help
		  Say Y here if you want the debug print routines to direct
		  their output to the second serial port on these devices.
		  Saying N will cause the debug messages to appear on the first
		  serial port.

endchoice

config EARLY_PRINTK
	bool "Early printk"
	depends on DEBUG_LL
	help
	  Say Y here if you want to have an early console using the
	  kernel low-level debugging functions. Add earlyprintk to your
	  kernel parameters to enable this console.

config DEBUG_ICEDCC
	bool "Kernel low-level debugging via EmbeddedICE DCC channel"
	depends on DEBUG_LL
	help
	  Say Y here if you want the debug print routines to direct their
	  output to the EmbeddedICE macrocell's DCC channel using
	  co-processor 14. This is known to work on the ARM9 style ICE
	  channel and on the XScale with the PEEDI.

	  It does include a timeout to ensure that the system does not
	  totally freeze when there is nothing connected to read.

config OC_ETM
	bool "On-chip ETM and ETB"
	select ARM_AMBA
	help
	  Enables the on-chip embedded trace macrocell and embedded trace
	  buffer driver that will allow you to collect traces of the
	  kernel code.

config DEBUG_S3C_UART
	depends on PLAT_SAMSUNG
	int "S3C UART to use for low-level debug"
	default "0"
	help
	  Choice for UART for kernel low-level using S3C UARTS,
	  should be between zero and two. The port must have been
	  initialised by the boot-loader before use.

	  The uncompressor code port configuration is now handled
	  by CONFIG_S3C_LOWLEVEL_UART_PORT.

endmenu