From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934147Ab3E3P7z (ORCPT ); Thu, 30 May 2013 11:59:55 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:44520 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933469Ab3E3P7s (ORCPT ); Thu, 30 May 2013 11:59:48 -0400 From: Stephen Warren To: Mark Brown , Grant Likely Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org, Stephen Warren Subject: [PATCH 1/3] spi: fix undefined behaviour in SPI_BPW_RANGE_MASK Date: Thu, 30 May 2013 09:59:39 -0600 Message-Id: <1369929581-30258-1-git-send-email-swarren@wwwdotorg.org> X-Mailer: git-send-email 1.7.10.4 X-NVConfidentiality: public Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stephen Warren The parameters to SPI_BPW_RANGE_MASK() are in the range 1..32. If 32 is used as a parameter, part of the expression is "1 << 32". Since 32 is >= the size of the type in use, such a shift is undefined behaviour. Add macro SPI_BIT_MASK to Implement a special case and thus avoid undefined behaviour. Use this new macro rather than BIT() when implementing SPI_BPW_RANGE_MASK(). This fixes build warnings such as: drivers/spi/spi-gpio.c:446:2: warning: left shift count >= width of type [enabled by default] SPI_BPW_MASK() already avoids this, since its parameter is also in range 1..32, yet it only shifts by up to one less than the input parameter. Reported-by: Fengguang Wu Signed-off-by: Stephen Warren --- include/linux/spi/spi.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 1737256..3e94791 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -309,7 +309,8 @@ struct spi_master { /* bitmask of supported bits_per_word for transfers */ u32 bits_per_word_mask; #define SPI_BPW_MASK(bits) BIT((bits) - 1) -#define SPI_BPW_RANGE_MASK(min, max) ((BIT(max) - 1) - (BIT(min) - 1)) +#define SPI_BIT_MASK(bits) (((bits) == 32) ? ~0UL : (BIT(bits) - 1)) +#define SPI_BPW_RANGE_MASK(min, max) (SPI_BIT_MASK(max) - SPI_BIT_MASK(min)) /* other constraints relevant to this driver */ u16 flags; -- 1.7.10.4