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Fri, 29 May 2020 20:51:47 +0000 (GMT) Received: from b03ledav003.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3B8D76A04F; Fri, 29 May 2020 20:51:46 +0000 (GMT) Received: from Buonos-Thinkpad-X1.ibm.com (unknown [9.65.226.57]) by b03ledav003.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 29 May 2020 20:51:46 +0000 (GMT) From: Daniele Buono To: qemu-devel@nongnu.org Subject: [PATCH v2 2/4] coroutine: add check for SafeStack in sigaltstack Date: Fri, 29 May 2020 16:51:20 -0400 Message-Id: <20200529205122.714-3-dbuono@linux.vnet.ibm.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200529205122.714-1-dbuono@linux.vnet.ibm.com> References: <20200529205122.714-1-dbuono@linux.vnet.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-05-29_10:2020-05-28, 2020-05-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=1 clxscore=1015 impostorscore=0 adultscore=0 bulkscore=0 spamscore=0 mlxscore=0 phishscore=0 lowpriorityscore=0 cotscore=-2147483648 mlxlogscore=999 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005290150 Received-SPF: none client-ip=148.163.158.5; envelope-from=dbuono@linux.vnet.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/29 15:28:52 X-ACL-Warn: Detected OS = Linux 3.x [generic] X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, KHOP_DYNAMIC=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , Stefan Hajnoczi , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , dbuono@linux.vnet.ibm.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" Current implementation of LLVM's SafeStack is not compatible with code that uses an alternate stack created with sigaltstack(). Since coroutine-sigaltstack relies on sigaltstack(), it is not compatible with SafeStack. The resulting binary is incorrect, with different coroutines sharing the same unsafe stack and producing undefined behavior at runtime. In the future LLVM may provide a SafeStack implementation compatible with sigaltstack(). In the meantime, if SafeStack is desired, the coroutine implementation from coroutine-ucontext should be used. As a safety check, add a control in coroutine-sigaltstack to throw a preprocessor #error if SafeStack is enabled and we are trying to use coroutine-sigaltstack to implement coroutines. Signed-off-by: Daniele Buono --- util/coroutine-sigaltstack.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c index f6fc49a0e5..aade82afb8 100644 --- a/util/coroutine-sigaltstack.c +++ b/util/coroutine-sigaltstack.c @@ -30,6 +30,10 @@ #include "qemu-common.h" #include "qemu/coroutine_int.h" +#ifdef CONFIG_SAFESTACK +#error "SafeStack is not compatible with code run in alternate signal stacks" +#endif + typedef struct { Coroutine base; void *stack;