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[148.163.158.5]) by mx.google.com with ESMTPS id p123-20020a252981000000b00dbd4661c3casi3187491ybp.115.2024.01.29.01.34.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jan 2024 01:34:22 -0800 (PST) Received-SPF: pass (google.com: domain of iii@linux.ibm.com designates 148.163.158.5 as permitted sender) client-ip=148.163.158.5; Authentication-Results: mx.google.com; dkim=pass header.i=@ibm.com header.s=pp1 header.b=iKiG6O06; spf=pass (google.com: domain of iii@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=iii@linux.ibm.com; dmarc=pass (p=REJECT sp=NONE dis=NONE) header.from=ibm.com Received: from pps.filterd (m0353723.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 40T85RFo023735; Mon, 29 Jan 2024 09:34:21 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pp1; bh=EMJdS9hKoA7kur7DqvESiD5ICfk5HChs5chrzcRw4VA=; b=iKiG6O065kT97uCxVSERS2RUqwr84bZ5G8ph6PkYQMh4W525rQfTDuTSn8NhhVTxzV6G fmRoaX7wKpsWuJfYMsresSzCtNSCEwpK2rG5LKsK4S2XSBKglXNM9FTNx1HEy53qB7jx Vd+ToIuBIVppy2//ilGKBIl+AKjc+Nv7MTYDuM+sMS8qcRRsfGepwZRVT5FH0FKq4lek wAFGM5oXFKZ66jjxyABF0qHS8z9tNIRFWRiyiQ/TukPCySwWXD4AOWvX/+jGbC18+grv fx4LhyEN7naOX12OThZz+TO7K9uDRVW2YSzNPC2qY/WQ3XFvQ+61gvuRn8HoKF8yDYZJ ew== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3vx86vsvua-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 29 Jan 2024 09:34:21 +0000 Received: from m0353723.ppops.net (m0353723.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 40T8tqGD027692; Mon, 29 Jan 2024 09:34:20 GMT Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3vx86vsvu2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 29 Jan 2024 09:34:20 +0000 Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 40T6jKaV007188; Mon, 29 Jan 2024 09:34:20 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 3vwev1xvry-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 29 Jan 2024 09:34:20 +0000 Received: from smtpav04.fra02v.mail.ibm.com (smtpav04.fra02v.mail.ibm.com [10.20.54.103]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 40T9YIGH24314388 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 29 Jan 2024 09:34:18 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1870D20043; Mon, 29 Jan 2024 09:34:18 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7E2DF20040; Mon, 29 Jan 2024 09:34:17 +0000 (GMT) Received: from heavy.ibm.com (unknown [9.179.7.240]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 29 Jan 2024 09:34:17 +0000 (GMT) From: Ilya Leoshkevich To: Richard Henderson , Peter Maydell , =?UTF-8?q?Alex=20Benn=C3=A9e?= , David Hildenbrand Cc: Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, qemu-arm@nongnu.org, qemu-s390x@nongnu.org, Ilya Leoshkevich Subject: [PATCH v4 1/3] linux-user: Allow gdbstub to ignore page protection Date: Mon, 29 Jan 2024 10:32:14 +0100 Message-ID: <20240129093410.3151-2-iii@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240129093410.3151-1-iii@linux.ibm.com> References: <20240129093410.3151-1-iii@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: R7YmqST-Dcuiy1Fw9vbI2XzNZPN04mln X-Proofpoint-ORIG-GUID: wgwPKY-5wCbwjbq3D4rqeYil9sWISlbA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-01-29_05,2024-01-25_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 mlxlogscore=951 mlxscore=0 phishscore=0 bulkscore=0 suspectscore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2401290068 X-TUID: JhELGQYnzM98 gdbserver ignores page protection by virtue of using /proc/$pid/mem. Teach qemu gdbstub to do this too. This will not work if /proc is not mounted; accept this limitation. One alternative is to temporarily grant the missing PROT_* bit, but this is inherently racy. Another alternative is self-debugging with ptrace(POKE), which will break if QEMU itself is being debugged - a much more severe limitation. Reviewed-by: Richard Henderson Signed-off-by: Ilya Leoshkevich --- cpu-target.c | 78 ++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 63 insertions(+), 15 deletions(-) diff --git a/cpu-target.c b/cpu-target.c index f6e07c3deb1..958d63e8823 100644 --- a/cpu-target.c +++ b/cpu-target.c @@ -382,6 +382,9 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr, vaddr l, page; void * p; uint8_t *buf = ptr; + ssize_t written; + int ret = -1; + int fd = -1; while (len > 0) { page = addr & TARGET_PAGE_MASK; @@ -389,30 +392,75 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr, if (l > len) l = len; flags = page_get_flags(page); - if (!(flags & PAGE_VALID)) - return -1; + if (!(flags & PAGE_VALID)) { + goto out_close; + } if (is_write) { - if (!(flags & PAGE_WRITE)) - return -1; - /* XXX: this code should not depend on lock_user */ - if (!(p = lock_user(VERIFY_WRITE, addr, l, 0))) - return -1; - memcpy(p, buf, l); - unlock_user(p, addr, l); - } else { - if (!(flags & PAGE_READ)) - return -1; + if (flags & PAGE_WRITE) { + /* XXX: this code should not depend on lock_user */ + p = lock_user(VERIFY_WRITE, addr, l, 0); + if (!p) { + goto out_close; + } + memcpy(p, buf, l); + unlock_user(p, addr, l); + } else { + /* Bypass the host page protection using ptrace. */ + if (fd == -1) { + fd = open("/proc/self/mem", O_WRONLY); + if (fd == -1) { + goto out; + } + } + /* + * If there is a TranslationBlock and we weren't bypassing the + * host page protection, the memcpy() above would SEGV, + * ultimately leading to page_unprotect(). So invalidate the + * translations manually. Both invalidation and pwrite() must + * be under mmap_lock() in order to prevent the creation of + * another TranslationBlock in between. + */ + mmap_lock(); + tb_invalidate_phys_range(addr, addr + l - 1); + written = pwrite(fd, buf, l, + (off_t)(uintptr_t)g2h_untagged(addr)); + mmap_unlock(); + if (written != l) { + goto out_close; + } + } + } else if (flags & PAGE_READ) { /* XXX: this code should not depend on lock_user */ - if (!(p = lock_user(VERIFY_READ, addr, l, 1))) - return -1; + p = lock_user(VERIFY_READ, addr, l, 1); + if (!p) { + goto out_close; + } memcpy(buf, p, l); unlock_user(p, addr, 0); + } else { + /* Bypass the host page protection using ptrace. */ + if (fd == -1) { + fd = open("/proc/self/mem", O_RDONLY); + if (fd == -1) { + goto out; + } + } + if (pread(fd, buf, l, + (off_t)(uintptr_t)g2h_untagged(addr)) != l) { + goto out_close; + } } len -= l; buf += l; addr += l; } - return 0; + ret = 0; +out_close: + if (fd != -1) { + close(fd); + } +out: + return ret; } #endif -- 2.43.0