From patchwork Thu May 7 18:50:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 11534679 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DCF6F14B4 for ; Thu, 7 May 2020 18:45:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C68002145D for ; Thu, 7 May 2020 18:45:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877152; bh=dRXO8NWeYM9voX1lUqLjnyFnyymDA1FiAU3W8d8sdW4=; h=Date:From:To:Cc:Subject:List-ID:From; b=WvuYssNmwUVdWm7vMvirhufe3g5JsJwB/5Vj8ZFq1swOw/vyZL2hWtuEHP1588ZgK loZm7S45SN0GAR7NtunNWE+2t0Ng7Bs9l9WXx627CNzC3pNTZYHEiT6Nv15/w32kdv +FYJ75rhGGRPwNEKHhFygyH4kNsv9h0YbNqNu01o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726367AbgEGSpw (ORCPT ); Thu, 7 May 2020 14:45:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:46646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728309AbgEGSpv (ORCPT ); Thu, 7 May 2020 14:45:51 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3666920870; Thu, 7 May 2020 18:45:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877150; bh=dRXO8NWeYM9voX1lUqLjnyFnyymDA1FiAU3W8d8sdW4=; h=Date:From:To:Cc:Subject:From; b=lHeymKeiC/FcQsbXvpMS9igvZ7qvccUuVdEOaIBdd44VEwKRzFm5vVAv7ehaU5dWQ 3EP21nPSolm2gTd4IyfvCKKx8NJvlQkrCJxoQ7aLXA97yIc8tUwfV/j+q1z9hGM+gs g7bWGfCOS+scn4NNMoTpIV24Zn0KpPlSyy0fstzg= Date: Thu, 7 May 2020 13:50:16 -0500 From: "Gustavo A. R. Silva" To: Andy Gross , Bjorn Andersson Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] dmaengine: qcom: bam_dma: Replace zero-length array with flexible-array Message-ID: <20200507185016.GA13883@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 Reviewed-by: Jeffrey Hugo --- drivers/dma/qcom/bam_dma.c | 2 +- drivers/firmware/qcom_scm-legacy.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c index ef73f65224b1..5a08dd0d3388 100644 --- a/drivers/dma/qcom/bam_dma.c +++ b/drivers/dma/qcom/bam_dma.c @@ -74,7 +74,7 @@ struct bam_async_desc { struct list_head desc_node; enum dma_transfer_direction dir; size_t length; - struct bam_desc_hw desc[0]; + struct bam_desc_hw desc[]; }; enum bam_reg { diff --git a/drivers/firmware/qcom_scm-legacy.c b/drivers/firmware/qcom_scm-legacy.c index 8532e7c78ef7..eba6b60bfb61 100644 --- a/drivers/firmware/qcom_scm-legacy.c +++ b/drivers/firmware/qcom_scm-legacy.c @@ -56,7 +56,7 @@ struct scm_legacy_command { __le32 buf_offset; __le32 resp_hdr_offset; __le32 id; - __le32 buf[0]; + __le32 buf[]; }; /**