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, 27 insertions, 0 deletions

diff --git a/mm/internal.h b/mm/internal.h
index 0034e947e4bc..a7ee05253294 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -59,4 +59,31 @@ static inline unsigned long page_order(struct page *page)
 #define __paginginit __init
 #endif
 
+/* Memory initialisation debug and verification */
+enum mminit_level {
+        MMINIT_WARNING,
+        MMINIT_VERIFY,
+        MMINIT_TRACE
+};
+
+#ifdef CONFIG_DEBUG_MEMORY_INIT
+
+extern int mminit_loglevel;
+
+#define mminit_dprintk(level, prefix, fmt, arg...) \
+do { \
+        if (level < mminit_loglevel) { \
+                printk(level <= MMINIT_WARNING ? KERN_WARNING : KERN_DEBUG); \
+                printk(KERN_CONT "mminit::" prefix " " fmt, ##arg); \
+        } \
+} while (0)
+
+#else
+
+static inline void mminit_dprintk(enum mminit_level level,
+                                const char *prefix, const char *fmt, ...)
+{
+}
+
+#endif /* CONFIG_DEBUG_MEMORY_INIT */
 #endif