mm: add a basic debugging framework for memory initialisation

Boot initialisation is very complex, with significant numbers of
architecture-specific routines, hooks and code ordering.  While significant
amounts of the initialisation is architecture-independent, it trusts the data
received from the architecture layer.  This is a mistake, and has resulted in
a number of difficult-to-diagnose bugs.

This patchset adds some validation and tracing to memory initialisation.  It
also introduces a few basic defensive measures.  The validation code can be
explicitly disabled for embedded systems.

This patch:

Add additional debugging and verification code for memory initialisation.

Once enabled, the verification checks are always run and when required
additional debugging information may be outputted via a mminit_loglevel=
command-line parameter.

The verification code is placed in a new file mm/mm_init.c.  Ideally other mm
initialisation code will be moved here over time.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 47e7d8794fc..5e20ccb5a73 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1225,6 +1225,14 @@ and is between 256 and 4096 characters. It is defined in the file
 
         mga=            [HW,DRM]
 
+        mminit_loglevel=
+                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
+                        parameter allows control of the logging verbosity for
+                        the additional memory initialisation checks. A value
+                        of 0 disables mminit logging and a level of 4 will
+                        log everything. Information is printed at KERN_DEBUG
+                        so loglevel=8 may also need to be specified.
+
         mousedev.tap_time=
                         [MOUSE] Maximum time between finger touching and
                         leaving touchpad surface for touch to be considered