Subject: [PATCH] powerpc/msi: Remove VLA usage

From: Kees Cook <[email-masked]>
Date: Fri, 29 Jun 2018 11:52:54 -0700

In the quest to remove all stack VLA usage from the kernel[1], this
switches from an unchanging variable to a constant expression to eliminate
the VLA generation.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=[email-masked]

Cc: Benjamin Herrenschmidt <[email-masked]>
Cc: Paul Mackerras <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Cc: Andrew Morton <[email-masked]>
Cc: Randy Dunlap <[email-masked]>
Cc: Tyrel Datwyler <[email-masked]>
Cc: Rob Herring <[email-masked]>
Cc: Ingo Molnar <[email-masked]>
Cc: [email-masked]
Signed-off-by: Kees Cook <[email-masked]>
---
 arch/powerpc/sysdev/msi_bitmap.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c
index 6243a7e537d0..e64a411d1a00 100644
--- a/arch/powerpc/sysdev/msi_bitmap.c
+++ b/arch/powerpc/sysdev/msi_bitmap.c
@@ -225,22 +225,23 @@ static void __init test_of_node(void)
 	struct device_node of_node;
 	struct property prop;
 	struct msi_bitmap bmp;
-	int size = 256;
-	DECLARE_BITMAP(expected, size);
+#define SIZE_EXPECTED 256
+	DECLARE_BITMAP(expected, SIZE_EXPECTED);
 
 	/* There should really be a struct device_node allocator */
 	memset(&of_node, 0, sizeof(of_node));
 	of_node_init(&of_node);
 	of_node.full_name = node_name;
 
-	WARN_ON(msi_bitmap_alloc(&bmp, size, &of_node));
+	WARN_ON(msi_bitmap_alloc(&bmp, SIZE_EXPECTED, &of_node));
 
 	/* No msi-available-ranges, so expect > 0 */
 	WARN_ON(msi_bitmap_reserve_dt_hwirqs(&bmp) <= 0);
 
 	/* Should all still be free */
-	WARN_ON(bitmap_find_free_region(bmp.bitmap, size, get_count_order(size)));
-	bitmap_release_region(bmp.bitmap, 0, get_count_order(size));
+	WARN_ON(bitmap_find_free_region(bmp.bitmap, SIZE_EXPECTED,
+					get_count_order(SIZE_EXPECTED)));
+	bitmap_release_region(bmp.bitmap, 0, get_count_order(SIZE_EXPECTED));
 
 	/* Now create a fake msi-available-ranges property */
 
@@ -256,8 +257,8 @@ static void __init test_of_node(void)
 	WARN_ON(msi_bitmap_reserve_dt_hwirqs(&bmp));
 
 	/* Check we got the expected result */
-	WARN_ON(bitmap_parselist(expected_str, expected, size));
-	WARN_ON(!bitmap_equal(expected, bmp.bitmap, size));
+	WARN_ON(bitmap_parselist(expected_str, expected, SIZE_EXPECTED));
+	WARN_ON(!bitmap_equal(expected, bmp.bitmap, SIZE_EXPECTED));
 
 	msi_bitmap_free(&bmp);
 	kfree(bmp.bitmap);
-- 
2.17.1

-- 
Kees Cook
Pixel Security