[PATCH 3/3] vmalloc: Add debugfs modfraginfo

[Rick Edgecombe]

Add debugfs file "modfraginfo" for providing info on module space
fragmentation.  This can be used for determining if loadable module
randomization is causing any problems for extreme module loading situations,
like huge numbers of modules or extremely large modules.

Sample output when RANDOMIZE_BASE and X86_64 is configured:
Largest free space:		847253504
External Memory Fragementation:	20%
Allocations in backup area:	0

Sample output when just X86_64:
Largest free space:		847253504
External Memory Fragementation:	20%

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
 mm/vmalloc.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b6f2449..85441f2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -18,6 +18,7 @@
 #include <linux/interrupt.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/debugfs.h>
 #include <linux/debugobjects.h>
 #include <linux/kallsyms.h>
 #include <linux/list.h>
@@ -33,6 +34,7 @@
 #include <linux/bitops.h>
 
 #include <linux/uaccess.h>
+#include <asm/setup.h>
 #include <asm/tlbflush.h>
 #include <asm/shmparam.h>
 
@@ -2922,7 +2924,104 @@ static int __init proc_vmalloc_init(void)
 		proc_create_seq("vmallocinfo", 0400, NULL, &vmalloc_op);
 	return 0;
 }
-module_init(proc_vmalloc_init);
+#else
+static int proc_vmalloc_init(void)
+{
+	return 0;
+}
+#endif
 
+#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_64)
+#if defined(CONFIG_RANDOMIZE_BASE)
+static void print_backup_area(struct seq_file *m, unsigned long backup_cnt)
+{
+	if (kaslr_enabled())
+		seq_printf(m, "Allocations in backup area:\t%lu\n", backup_cnt);
+}
+#else
+static void print_backup_area(struct seq_file *m, unsigned long backup_cnt)
+{
+}
 #endif
+static int modulefraginfo_debug_show(struct seq_file *m, void *v)
+{
+	struct list_head *i;
+	unsigned long last_end = MODULES_VADDR;
+	unsigned long total_free = 0;
+	unsigned long largest_free = 0;
+	unsigned long backup_cnt = 0;
+	unsigned long gap;
+
+	spin_lock(&vmap_area_lock);
+
+	list_for_each(i, &vmap_area_list) {
+		struct vmap_area *obj = list_entry(i, struct vmap_area, list);
+
+		if (!(obj->flags & VM_LAZY_FREE)
+			&& obj->va_start >= MODULES_VADDR
+			&& obj->va_end <= MODULES_END) {
+
+			if (obj->va_start >= MODULES_VADDR + MODULES_RAND_LEN)
+				backup_cnt++;
+
+			gap = (obj->va_start - last_end);
+			if (gap > largest_free)
+				largest_free = gap;
+			total_free += gap;
+
+			last_end = obj->va_end;
+		}
+	}
+
+	gap = (MODULES_END - last_end);
+	if (gap > largest_free)
+		largest_free = gap;
+	total_free += gap;
+
+	spin_unlock(&vmap_area_lock);
 
+	seq_printf(m, "Largest free space:\t\t%lu\n", largest_free);
+	if (total_free)
+		seq_printf(m, "External Memory Fragmentation:\t%lu%%\n",
+			100-(100*largest_free/total_free));
+	else
+		seq_puts(m, "External Memory Fragmentation:\t0%%\n");
+
+	print_backup_area(m, backup_cnt);
+
+	return 0;
+}
+
+static int proc_module_frag_debug_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, modulefraginfo_debug_show, NULL);
+}
+
+static const struct file_operations debug_module_frag_operations = {
+	.open       = proc_module_frag_debug_open,
+	.read       = seq_read,
+	.llseek     = seq_lseek,
+	.release    = single_release,
+};
+
+static void debug_modfrag_init(void)
+{
+	debugfs_create_file("modfraginfo", 0400, NULL, NULL,
+			&debug_module_frag_operations);
+}
+#else /* defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_64) */
+static void debug_modfrag_init(void)
+{
+}
+#endif
+
+#if defined(CONFIG_DEBUG_FS) || defined(CONFIG_PROC_FS)
+static int __init info_vmalloc_init(void)
+{
+	proc_vmalloc_init();
+	debug_modfrag_init();
+	return 0;
+}
+
+module_init(info_vmalloc_init);
+#endif
-- 
2.7.4