mm: cma: debugfs interface

I've noticed that there is no interfaces exposed by CMA which would let me
fuzz what's going on in there.

This small patchset exposes some information out to userspace, plus adds
the ability to trigger allocation and freeing from userspace.

This patch (of 3):

Implement a simple debugfs interface to expose information about CMA areas
in the system.

Useful for testing/sanity checks for CMA since it was impossible to
previously retrieve this information in userspace.

Signed-off-by: Sasha Levin <[email protected]>
Acked-by: Joonsoo Kim <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Laura Abbott <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/Kconfig

@@ -517,6 +517,12 @@ config CMA_DEBUG
 	  processing calls such as dma_alloc_from_contiguous().
 	  This option does not affect warning and error messages.
 
+config CMA_DEBUGFS
+	bool "CMA debugfs interface"
+	depends on CMA && DEBUG_FS
+	help
+	  Turns on the DebugFS interface for CMA.
+
 config CMA_AREAS
 	int "Maximum count of the CMA areas"
 	depends on CMA

mm/Makefile

@@ -76,3 +76,4 @@ obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
 obj-$(CONFIG_CMA)	+= cma.o
 obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
 obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
+obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o

mm/cma.c

@@ -35,16 +35,10 @@
 #include <linux/highmem.h>
 #include <linux/io.h>
 
-struct cma {
-	unsigned long	base_pfn;
-	unsigned long	count;
-	unsigned long	*bitmap;
-	unsigned int order_per_bit; /* Order of pages represented by one bit */
-	struct mutex	lock;
-};
-
-static struct cma cma_areas[MAX_CMA_AREAS];
-static unsigned cma_area_count;
+#include "cma.h"
+
+struct cma cma_areas[MAX_CMA_AREAS];
+unsigned cma_area_count;
 static DEFINE_MUTEX(cma_mutex);
 
 phys_addr_t cma_get_base(struct cma *cma)
@@ -77,11 +71,6 @@ static unsigned long cma_bitmap_aligned_offset(struct cma *cma, int align_order)
 		- cma->base_pfn) >> cma->order_per_bit;
 }
 
-static unsigned long cma_bitmap_maxno(struct cma *cma)
-{
-	return cma->count >> cma->order_per_bit;
-}
-
 static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
 						unsigned long pages)
 {

mm/cma.h

@@ -0,0 +1,20 @@
+#ifndef __MM_CMA_H__
+#define __MM_CMA_H__
+
+struct cma {
+	unsigned long   base_pfn;
+	unsigned long   count;
+	unsigned long   *bitmap;
+	unsigned int order_per_bit; /* Order of pages represented by one bit */
+	struct mutex    lock;
+};
+
+extern struct cma cma_areas[MAX_CMA_AREAS];
+extern unsigned cma_area_count;
+
+static unsigned long cma_bitmap_maxno(struct cma *cma)
+{
+	return cma->count >> cma->order_per_bit;
+}
+
+#endif

mm/cma_debug.c

@@ -0,0 +1,60 @@
+/*
+ * CMA DebugFS Interface
+ *
+ * Copyright (c) 2015 Sasha Levin <[email protected]>
+ */
+
+
+#include <linux/debugfs.h>
+#include <linux/cma.h>
+
+#include "cma.h"
+
+static struct dentry *cma_debugfs_root;
+
+static int cma_debugfs_get(void *data, u64 *val)
+{
+	unsigned long *p = data;
+
+	*val = *p;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(cma_debugfs_fops, cma_debugfs_get, NULL, "%llu\n");
+
+static void cma_debugfs_add_one(struct cma *cma, int idx)
+{
+	struct dentry *tmp;
+	char name[16];
+	int u32s;
+
+	sprintf(name, "cma-%d", idx);
+
+	tmp = debugfs_create_dir(name, cma_debugfs_root);
+
+	debugfs_create_file("base_pfn", S_IRUGO, tmp,
+				&cma->base_pfn, &cma_debugfs_fops);
+	debugfs_create_file("count", S_IRUGO, tmp,
+				&cma->count, &cma_debugfs_fops);
+	debugfs_create_file("order_per_bit", S_IRUGO, tmp,
+			&cma->order_per_bit, &cma_debugfs_fops);
+
+	u32s = DIV_ROUND_UP(cma_bitmap_maxno(cma), BITS_PER_BYTE * sizeof(u32));
+	debugfs_create_u32_array("bitmap", S_IRUGO, tmp, (u32*)cma->bitmap, u32s);
+}
+
+static int __init cma_debugfs_init(void)
+{
+	int i;
+
+	cma_debugfs_root = debugfs_create_dir("cma", NULL);
+	if (!cma_debugfs_root)
+		return -ENOMEM;
+
+	for (i = 0; i < cma_area_count; i++)
+		cma_debugfs_add_one(&cma_areas[i], i);
+
+	return 0;
+}
+late_initcall(cma_debugfs_init);