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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 47e7d87..5e20ccb 100644 (file)
--- 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 882c510..e1d4764 100644 (file)
--- 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 18c143b..4bbc8f0 100644 (file)
--- 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 0034e94..a7ee052 100644 (file)
--- 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 (file)
index 0000000..c01d8df
--- /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 79ac4af..0908352 100644 (file)
--- 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++) {