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GET /api/1.1/patches/2858/?format=api
{ "id": 2858, "url": "https://patchwork.libcamera.org/api/1.1/patches/2858/?format=api", "web_url": "https://patchwork.libcamera.org/patch/2858/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/1.1/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20200218141839.5574-1-kieran.bingham@ideasonboard.com>", "date": "2020-02-18T14:18:39", "name": "[libcamera-devel,v2] libcamera: media_device: prevent sign extension on casts", "commit_ref": "90240a79506a3c400f3af4cb0b08746ae87c79e2", "pull_url": null, "state": "accepted", "archived": false, "hash": "bc5628b7a1496bd7dbefdb1627c17101e8e191cd", "submitter": { "id": 4, "url": "https://patchwork.libcamera.org/api/1.1/people/4/?format=api", "name": "Kieran Bingham", "email": "kieran.bingham@ideasonboard.com" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/2858/mbox/", "series": [ { "id": 687, "url": "https://patchwork.libcamera.org/api/1.1/series/687/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=687", "date": "2020-02-18T14:18:39", "name": "[libcamera-devel,v2] libcamera: media_device: prevent sign extension on casts", "version": 2, "mbox": "https://patchwork.libcamera.org/series/687/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/2858/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/2858/checks/", "tags": {}, "headers": { "Return-Path": "<kieran.bingham@ideasonboard.com>", "Received": [ "from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id E34FD60837\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tTue, 18 Feb 2020 15:18:42 +0100 (CET)", "from localhost.localdomain\n\t(cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 4F55F2F9;\n\tTue, 18 Feb 2020 15:18:42 +0100 (CET)" ], "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1582035522;\n\tbh=bvGf19VUVpTEvuBqmphl5eQG+Xaks9QZTL6fF2OvU6k=;\n\th=From:To:Cc:Subject:Date:From;\n\tb=ZJwjENIWA/ydUZUxfNMp+dPiCvRZGLrjYM1sQCWZ7oq4fylsRyXGdMR4ijwQbXAHD\n\tawP3xJgmjhbRvjt318JrDDMhJBy/MLUefykVPwYdFEgnRzIrZOgS2g+3RWDF2GvSbk\n\tzvu6b3+ygLkJGB29VKvpgBx981sRVBxwy+4/V6bQ=", "From": "Kieran Bingham <kieran.bingham@ideasonboard.com>", "To": "libcamera devel <libcamera-devel@lists.libcamera.org>", "Date": "Tue, 18 Feb 2020 14:18:39 +0000", "Message-Id": "<20200218141839.5574-1-kieran.bingham@ideasonboard.com>", "X-Mailer": "git-send-email 2.20.1", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=UTF-8", "Content-Transfer-Encoding": "8bit", "Subject": "[libcamera-devel] [PATCH v2] libcamera: media_device: prevent sign\n\textension on casts", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "X-List-Received-Date": "Tue, 18 Feb 2020 14:18:43 -0000" }, "content": "The conversion of pointers to integers is implementation defined and\ndiffers between g++ and clang++ when utilising a uint64_t type.\n\n #include <iostream>\n\n int main(int argc, char **argv)\n {\n void *ptr = reinterpret_cast<void *>(0xf1234567);\n uint64_t u64 = reinterpret_cast<uint64_t>(ptr);\n\tuint64_t uint64 = reinterpret_cast<uintptr_t>(ptr);\n\n std::cout << \"ptr \" << ptr\n\t\t << \" u64 0x\" << std::hex << u64\n\t\t << \" uint64 0x\" << std::hex << uint64\n\t\t << std::endl;\n\n\treturn 0;\n }\n\nWhen compiled with g++ produces the following unexpected output:\n\n ptr 0xf1234567 u64 0xfffffffff1234567 uint64 0xf1234567\n\nThe standards states:\n\n\"A pointer can be explicitly converted to any integral type large enough\nto hold all values of its type. The mapping function is\nimplementation-defined. [Note: It is intended to be unsurprising to\nthose who know the addressing structure of the underlying machine. — end\nnote]\"\n\nAnd as such the g++ implementation appears to be little more surprising\nthan expected in this situation.\n\nThe MediaDevice passes pointers to the kernel via the struct\nmedia_v2_topology in which pointers are cast using a uint64 type (__u64),\nwhich is affected by the sign extension described above when BIT(32) is\nset and causes an invalid address to be given to the kernel.\n\nEnsure that we cast using uintptr_t which is not affected by the sign\nextension issue.\n\nSigned-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n---\nv2:\n - Expand commit message to explain the underlying issue.\n - include stdint.h\n - use uintptr_t instead of std::uintptr_t\n\n src/libcamera/media_device.cpp | 9 +++++----\n 1 file changed, 5 insertions(+), 4 deletions(-)", "diff": "diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp\nindex fad475b9ac76..0d6b5efd9e7a 100644\n--- a/src/libcamera/media_device.cpp\n+++ b/src/libcamera/media_device.cpp\n@@ -9,6 +9,7 @@\n \n #include <errno.h>\n #include <fcntl.h>\n+#include <stdint.h>\n #include <string>\n #include <string.h>\n #include <sys/ioctl.h>\n@@ -236,10 +237,10 @@ int MediaDevice::populate()\n \t */\n \twhile (true) {\n \t\ttopology.topology_version = 0;\n-\t\ttopology.ptr_entities = reinterpret_cast<__u64>(ents);\n-\t\ttopology.ptr_interfaces = reinterpret_cast<__u64>(interfaces);\n-\t\ttopology.ptr_links = reinterpret_cast<__u64>(links);\n-\t\ttopology.ptr_pads = reinterpret_cast<__u64>(pads);\n+\t\ttopology.ptr_entities = reinterpret_cast<uintptr_t>(ents);\n+\t\ttopology.ptr_interfaces = reinterpret_cast<uintptr_t>(interfaces);\n+\t\ttopology.ptr_links = reinterpret_cast<uintptr_t>(links);\n+\t\ttopology.ptr_pads = reinterpret_cast<uintptr_t>(pads);\n \n \t\tret = ioctl(fd_, MEDIA_IOC_G_TOPOLOGY, &topology);\n \t\tif (ret < 0) {\n", "prefixes": [ "libcamera-devel", "v2" ] }