s390/debug: add early tracing support

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Debug areas can currently only be used after s390dbf initialization
which occurs as a postcore_initcall. This is too late for tracing
earlier code such as that related to console_init().

This patch introduces a macro for defining a statically initialized
debug area that can be used to trace very early code. The macro is made
available for built-in code only because modules are never running
during early boot.

Example usage:

1. Define static debug area:

  DEFINE_STATIC_DEBUG_INFO(my_debug, "my_debug", 4, 1, 16,
			   &debug_hex_ascii_view);

2. Add trace entry:

  debug_event(&my_debug, 0, "DATA", 4);

Note: The debug area is automatically registered in debugfs during boot.
      A driver must not call any of the debug_register()/_unregister()
      functions on a static debug_info_t!

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

...

This commit is contained in:

Peter Oberparleiter 2021-08-13 15:05:04 +02:00 • committed by Heiko Carstens

parent 9372a82892

commit d72541f945

2 changed files with 151 additions and 0 deletions

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96

arch/s390/include/asm/debug.h

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55

arch/s390/kernel/debug.c

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