From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Fri, 14 Feb 2020 11:16:57 -0600
Subject: dmaengine: tegra210-adma: Replace zero-length array with
flexible-array member
Git-commit: 1ee44529cc79e1ae95dd613e03b0c2434da8d052
Patch-mainline: v5.7-rc1
References: jsc#SLE-15847
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200214171657.GA25663@embeddedor
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
drivers/dma/tegra210-adma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
index 6e1268552f74..c4ce5dfb149b 100644
--- a/drivers/dma/tegra210-adma.c
+++ b/drivers/dma/tegra210-adma.c
@@ -164,7 +164,7 @@ struct tegra_adma {
const struct tegra_adma_chip_data *cdata;
/* Last member of the structure */
- struct tegra_adma_chan channels[0];
+ struct tegra_adma_chan channels[];
};
static inline void tdma_write(struct tegra_adma *tdma, u32 reg, u32 val)
--
2.26.2