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>

6 files changed, 79 insertions, 9 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 47e7d8794fc6..5e20ccb5a736 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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 882c51048993..e1d4764435ed 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -505,6 +505,18 @@ config DEBUG_WRITECOUNT
 
           If unsure, say N.
 
+config DEBUG_MEMORY_INIT
+        bool "Debug memory initialisation" if EMBEDDED
+        default !EMBEDDED
+        help
+          Enable this for additional checks during memory initialisation.
+          The sanity checks verify aspects of the VM such as the memory model
+          and other information provided by the architecture. Verbose
+          information will be printed at KERN_DEBUG loglevel depending
+          on the mminit_loglevel= command-line option.
+
+          If unsure, say Y
+
 config DEBUG_LIST
         bool "Debug linked list manipulation"
         depends on DEBUG_KERNEL
diff --git a/mm/Makefile b/mm/Makefile
index 18c143b3c46c..4bbc8f094ff0 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_TMPFS_POSIX_ACL) += shmem_acl.o
 obj-$(CONFIG_TINY_SHMEM) += tiny-shmem.o
 obj-$(CONFIG_SLOB) += slob.o
 obj-$(CONFIG_SLAB) += slab.o
+obj-$(CONFIG_DEBUG_MEMORY_INIT) += mm_init.o
 obj-$(CONFIG_SLUB) += slub.o
 obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
 obj-$(CONFIG_FS_XIP) += filemap_xip.o
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
diff --git a/mm/mm_init.c b/mm/mm_init.c
new file mode 100644
index 000000000000..c01d8dfec817
--- /dev/null
+++ b/mm/mm_init.c
@@ -0,0 +1,18 @@
+/*
+ * mm_init.c - Memory initialisation verification and debugging
+ *
+ * Copyright 2008 IBM Corporation, 2008
+ * Author Mel Gorman <mel@csn.ul.ie>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+int __meminitdata mminit_loglevel;
+
+static __init int set_mminit_loglevel(char *str)
+{
+        get_option(&str, &mminit_loglevel);
+        return 0;
+}
+early_param("mminit_loglevel", set_mminit_loglevel);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 79ac4afc908c..0908352ba727 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2975,7 +2975,8 @@ void __init sparse_memory_present_with_active_regions(int nid)
 void __init push_node_boundaries(unsigned int nid,
                 unsigned long start_pfn, unsigned long end_pfn)
 {
-        printk(KERN_DEBUG "Entering push_node_boundaries(%u, %lu, %lu)\n",
+        mminit_dprintk(MMINIT_TRACE, "zoneboundary",
+                        "Entering push_node_boundaries(%u, %lu, %lu)\n",
                         nid, start_pfn, end_pfn);
 
         /* Initialise the boundary for this node if necessary */
@@ -2993,7 +2994,8 @@ void __init push_node_boundaries(unsigned int nid,
 static void __meminit account_node_boundary(unsigned int nid,
                 unsigned long *start_pfn, unsigned long *end_pfn)
 {
-        printk(KERN_DEBUG "Entering account_node_boundary(%u, %lu, %lu)\n",
+        mminit_dprintk(MMINIT_TRACE, "zoneboundary",
+                        "Entering account_node_boundary(%u, %lu, %lu)\n",
                         nid, *start_pfn, *end_pfn);
 
         /* Return if boundary information has not been provided */
@@ -3368,8 +3370,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
                         PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT;
                 if (realsize >= memmap_pages) {
                         realsize -= memmap_pages;
-                        printk(KERN_DEBUG
-                                "  %s zone: %lu pages used for memmap\n",
+                        mminit_dprintk(MMINIT_TRACE, "memmap_init",
+                                "%s zone: %lu pages used for memmap\n",
                                 zone_names[j], memmap_pages);
                 } else
                         printk(KERN_WARNING
@@ -3379,7 +3381,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
                 /* Account for reserved pages */
                 if (j == 0 && realsize > dma_reserve) {
                         realsize -= dma_reserve;
-                        printk(KERN_DEBUG "  %s zone: %lu pages reserved\n",
+                        mminit_dprintk(MMINIT_TRACE, "memmap_init",
+                                        "%s zone: %lu pages reserved\n",
                                         zone_names[0], dma_reserve);
                 }
 
@@ -3520,10 +3523,11 @@ void __init add_active_range(unsigned int nid, unsigned long start_pfn,
 {
         int i;
 
-        printk(KERN_DEBUG "Entering add_active_range(%d, %#lx, %#lx) "
-                          "%d entries of %d used\n",
-                          nid, start_pfn, end_pfn,
-                          nr_nodemap_entries, MAX_ACTIVE_REGIONS);
+        mminit_dprintk(MMINIT_TRACE, "memory_register",
+                        "Entering add_active_range(%d, %#lx, %#lx) "
+                        "%d entries of %d used\n",
+                        nid, start_pfn, end_pfn,
+                        nr_nodemap_entries, MAX_ACTIVE_REGIONS);
 
         /* Merge with existing active regions if possible */
         for (i = 0; i < nr_nodemap_entries; i++) {