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Date:   Mon, 27 Aug 2018 11:23:01 -0700
In-Reply-To: <20180827182315.126345-1-rkir@google.com>
Message-Id: <20180827182315.126345-6-rkir@google.com>
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References: <20180827182315.126345-1-rkir@google.com>
Subject: [PATCH 06/20] platform: goldfish: pipe: Fail compilation if structs
 are too large
From:   rkir@google.com
To:     gregkh@linuxfoundation.org
Cc:     linux-kernel@vger.kernel.org, tkjos@google.com,
        Roman Kiryanov <rkir@google.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Roman Kiryanov <rkir@google.com>

Since the driver provides no workaround prevent in cases if structs do
no fit into a memory page, it is better to fail complation to find about
the issue earlt instead of returning errors at runtime.

Signed-off-by: Roman Kiryanov <rkir@google.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index 0c55e657da5a..24e40deb98cc 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -64,6 +64,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/mm.h>
 #include <linux/acpi.h>
+#include <linux/bug.h>
 #include "goldfish_pipe_qemu.h"
 
 /*
@@ -689,6 +690,7 @@ static int goldfish_pipe_open(struct inode *inode, struct file *file)
 	 * Command buffer needs to be allocated on its own page to make sure
 	 * it is physically contiguous in host's address space.
 	 */
+	BUILD_BUG_ON(sizeof(struct goldfish_pipe_command) > PAGE_SIZE);
 	pipe->command_buffer =
 		(struct goldfish_pipe_command *)__get_free_page(GFP_KERNEL);
 	if (!pipe->command_buffer) {
@@ -798,9 +800,7 @@ static int goldfish_pipe_device_init(struct platform_device *pdev)
 	 * needs to be contained in a single physical page. The easiest choice
 	 * is to just allocate a page and place the buffers in it.
 	 */
-	if (WARN_ON(sizeof(*dev->buffers) > PAGE_SIZE))
-		return -ENOMEM;
-
+	BUILD_BUG_ON(sizeof(struct goldfish_pipe_dev_buffers) > PAGE_SIZE);
 	page = (char *)__get_free_page(GFP_KERNEL);
 	if (!page) {
 		kfree(dev->pipes);
@@ -843,9 +843,6 @@ static int goldfish_pipe_probe(struct platform_device *pdev)
 	struct resource *r;
 	struct goldfish_pipe_dev *dev = pipe_dev;
 
-	if (WARN_ON(sizeof(struct goldfish_pipe_command) > PAGE_SIZE))
-		return -ENOMEM;
-
 	/* not thread safe, but this should not happen */
 	WARN_ON(dev->base != NULL);
 
-- 
2.19.0.rc0.228.g281dcd1b4d0-goog