From patchwork Wed Mar 23 11:51:35 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Naveen N. Rao" X-Patchwork-Id: 1608562 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=j7qgUBBM; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KNmty4xnRz9sCD for ; Wed, 23 Mar 2022 22:52:41 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4KNmtt5tDxz30Cy for ; Wed, 23 Mar 2022 22:52:38 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=j7qgUBBM; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=naveen.n.rao@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=j7qgUBBM; dkim-atps=neutral Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4KNmtZ2zJdz2y8P for ; Wed, 23 Mar 2022 22:52:21 +1100 (AEDT) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 22N9aLAq010524; Wed, 23 Mar 2022 11:52:15 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=6mf/Yn93etqYMoIshl9s+PYEO6J4gI7JEbEjuC1AcTY=; b=j7qgUBBMUr0z9xep8/vxwxJAJ6R8CSSUbhnPDRXbabgtiwodeGz+WFuaIpXw2K0fBVhO oVz5oIWgOzS0dnXFH6ab4InLPgV5HQemu7T7uJunQYY4ThR7+4GSfA2xOWUERUvHPaPG vSCsRzYEShAE7W49WCHv4LIKjgra6Y1GM9kPdbbmWMKox5DMPqcBzFUVjwNtBDkzqd6P rAwt5t3RKeT/pwrtiRCKbL7FF7GjkU1T87CuQwVNczB4yoU/DbeFfNb/QycUcCcRqxJg YZHq+s2YhHYl4PcAjux937Co84oUY4bEpOOnTNorHR5bYC8vwjxDdpi8gNXJ9cWhrz8N 9A== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 3eywtc6eu2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:14 +0000 Received: from m0098414.ppops.net (m0098414.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 22NBMWYj028277; Wed, 23 Mar 2022 11:52:14 GMT Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 3eywtc6etd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:14 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 22NBhBFl002730; Wed, 23 Mar 2022 11:52:12 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma03ams.nl.ibm.com with ESMTP id 3ew6t90eun-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:12 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 22NBqAnk54526426 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 23 Mar 2022 11:52:10 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F282C4C040; Wed, 23 Mar 2022 11:52:09 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 762DF4C050; Wed, 23 Mar 2022 11:52:08 +0000 (GMT) Received: from li-NotSettable.ibm.com.com (unknown [9.43.106.108]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 23 Mar 2022 11:52:08 +0000 (GMT) From: "Naveen N. Rao" To: Michael Ellerman , Nicholas Piggin , Christophe Leroy Subject: [PATCH 1/2] powerpc: Reject probes on instructions that can't be single stepped Date: Wed, 23 Mar 2022 17:21:35 +0530 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: xCzmLhwOwdbTrKxAbiOpJ_tDkFixbr3l X-Proofpoint-GUID: OyRugh5Cw7XalZfaGwNnsoWvl4pO3PMn X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.850,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-23_06,2022-03-22_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 clxscore=1015 mlxlogscore=782 lowpriorityscore=0 mlxscore=0 impostorscore=0 bulkscore=0 adultscore=0 phishscore=0 suspectscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203230066 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Per the ISA, a Trace interrupt is not generated for: - [h|u]rfi[d] - rfscv - sc, scv, and Trap instructions that trap - Power-Saving Mode instructions - other instructions that cause interrupts (other than Trace interrupts) - the first instructions of any interrupt handler (applies to Branch and Single Step tracing; CIABR matches may still occur) - instructions that are emulated by software Add a helper to check for instructions belonging to the first four categories above and to reject kprobes, uprobes and xmon breakpoints on such instructions. We reject probing on instructions belonging to these categories across all ISA versions and across both BookS and BookE. For trap instructions, we can't know in advance if they can cause a trap, and there is no good reason to allow probing on those. Also, uprobes already refuses to probe trap instructions and kprobes does not allow probes on trap instructions used for kernel warnings and bugs. As such, stop allowing any type of probes/breakpoints on trap instruction across uprobes, kprobes and xmon. For some of the fp/altivec instructions that can generate an interrupt and which we emulate in the kernel (altivec assist, for example), we check and turn off single stepping in emulate_single_step(). Instructions generating a DSI are restarted and single stepping normally completes once the instruction is completed. In uprobes, if a single stepped instruction results in a non-fatal signal to be delivered to the task, such signals are "delayed" until after the instruction completes. For fatal signals, single stepping is cancelled and the instruction restarted in-place so that core dump captures proper addresses. In kprobes, we do not allow probes on instructions having an extable entry and we also do not allow probing interrupt vectors. Signed-off-by: Naveen N. Rao --- arch/powerpc/include/asm/probes.h | 55 +++++++++++++++++++++++++++++++ arch/powerpc/kernel/kprobes.c | 4 +-- arch/powerpc/kernel/uprobes.c | 5 +++ arch/powerpc/xmon/xmon.c | 11 +++---- 4 files changed, 67 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/include/asm/probes.h b/arch/powerpc/include/asm/probes.h index c5d984700d241a..21ab5b6256b590 100644 --- a/arch/powerpc/include/asm/probes.h +++ b/arch/powerpc/include/asm/probes.h @@ -31,6 +31,61 @@ typedef u32 ppc_opcode_t; #define MSR_SINGLESTEP (MSR_SE) #endif +static inline bool can_single_step(u32 inst) +{ + switch (inst >> 26) { + case 2: /* tdi */ + return false; + case 3: /* twi */ + return false; + case 17: /* sc and scv */ + return false; + case 19: + switch ((inst >> 1) & 0x3ff) { + case 18: /* rfid */ + return false; + case 38: /* rfmci */ + return false; + case 39: /* rfdi */ + return false; + case 50: /* rfi */ + return false; + case 51: /* rfci */ + return false; + case 82: /* rfscv */ + return false; + case 274: /* hrfid */ + return false; + case 306: /* urfid */ + return false; + case 370: /* stop */ + return false; + case 402: /* doze */ + return false; + case 434: /* nap */ + return false; + case 466: /* sleep */ + return false; + case 498: /* rvwinkle */ + return false; + } + break; + case 31: + switch ((inst >> 1) & 0x3ff) { + case 4: /* tw */ + return false; + case 68: /* td */ + return false; + case 146: /* mtmsr */ + return false; + case 178: /* mtmsrd */ + return false; + } + break; + } + return true; +} + /* Enable single stepping for the current task */ static inline void enable_single_step(struct pt_regs *regs) { diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 9a492fdec1dfbe..0936a6c8c256b9 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -129,8 +129,8 @@ int arch_prepare_kprobe(struct kprobe *p) if ((unsigned long)p->addr & 0x03) { printk("Attempt to register kprobe at an unaligned address\n"); ret = -EINVAL; - } else if (IS_MTMSRD(insn) || IS_RFID(insn)) { - printk("Cannot register a kprobe on mtmsr[d]/rfi[d]\n"); + } else if (!can_single_step(ppc_inst_val(insn))) { + printk("Cannot register a kprobe on instructions that can't be single stepped\n"); ret = -EINVAL; } else if ((unsigned long)p->addr & ~PAGE_MASK && ppc_inst_prefixed(ppc_inst_read(p->addr - 1))) { diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c index c6975467d9ffdc..95a41ae9dfa755 100644 --- a/arch/powerpc/kernel/uprobes.c +++ b/arch/powerpc/kernel/uprobes.c @@ -48,6 +48,11 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, return -EINVAL; } + if (!can_single_step(ppc_inst_val(ppc_inst_read(auprobe->insn)))) { + pr_info_ratelimited("Cannot register a uprobe on instructions that can't be single stepped\n"); + return -ENOTSUPP; + } + return 0; } diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index fd72753e8ad502..a92c5739d954e2 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -921,9 +921,9 @@ static void insert_bpts(void) bp->enabled = 0; continue; } - if (IS_MTMSRD(instr) || IS_RFID(instr)) { - printf("Breakpoint at %lx is on an mtmsrd or rfid " - "instruction, disabling it\n", bp->address); + if (!can_single_step(ppc_inst_val(instr))) { + printf("Breakpoint at %lx is on an instruction that can't be single stepped, disabling it\n", + bp->address); bp->enabled = 0; continue; } @@ -1470,9 +1470,8 @@ static long check_bp_loc(unsigned long addr) printf("Can't read instruction at address %lx\n", addr); return 0; } - if (IS_MTMSRD(instr) || IS_RFID(instr)) { - printf("Breakpoints may not be placed on mtmsrd or rfid " - "instructions\n"); + if (!can_single_step(ppc_inst_val(instr))) { + printf("Breakpoints may not be placed on instructions that can't be single stepped\n"); return 0; } return 1; From patchwork Wed Mar 23 11:51:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Naveen N. Rao" X-Patchwork-Id: 1608564 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=KnVxHmiv; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KNmwS5Bnmz9s0r for ; Wed, 23 Mar 2022 22:54:00 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4KNmwS3G96z3bYD for ; Wed, 23 Mar 2022 22:54:00 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=KnVxHmiv; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0b-001b2d01.pphosted.com; envelope-from=naveen.n.rao@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=KnVxHmiv; dkim-atps=neutral Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4KNmtb69Q4z2xCW for ; Wed, 23 Mar 2022 22:52:23 +1100 (AEDT) Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 22NAtNFj021712; Wed, 23 Mar 2022 11:52:16 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=ndWFjO7DF4CTxD0rXybl3lTSlt7zTbQTko/4ibiI4Bo=; b=KnVxHmivWXBKHn9eH+/IT02GoorMwst9rFHvAEBhl0dsEt84nD2SnAsCPOh9u+/cL1Dq GeXUSF0fXjPB5MwFg6NV5W7H7uhon/J85JNPFHIYQYJRhD81fzXhhR2g81Idbrk0bcnx K/Q3v8zp6Wk9/SQ3vcwMq9SdgXyM5RW6k1n2kwJpOAUMOrQXNBXsDpA18yi5zR8HEbmi ygaJY4vaSMdp38FmIwHgIoOBe/VjXpoFsVCM9xCmMfu1MMusuTh4VOe9xtZ1AVtMYrCl UQGkdnZ8+Z0Fb9nmXkc21VAeXMBOCZUa24COuQ8XZIbw52QuduTxtEBwwO8wKS04ssBW Mg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3f027nh3vf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:16 +0000 Received: from m0127361.ppops.net (m0127361.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 22NBfO7Z013061; Wed, 23 Mar 2022 11:52:16 GMT Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0a-001b2d01.pphosted.com with ESMTP id 3f027nh3ut-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:16 +0000 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 22NBi6MI004315; Wed, 23 Mar 2022 11:52:14 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma06fra.de.ibm.com with ESMTP id 3ew6ehy9j1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 23 Mar 2022 11:52:14 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 22NBqCnb39387490 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 23 Mar 2022 11:52:12 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E0ECB4C044; Wed, 23 Mar 2022 11:52:11 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 64D044C040; Wed, 23 Mar 2022 11:52:10 +0000 (GMT) Received: from li-NotSettable.ibm.com.com (unknown [9.43.106.108]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 23 Mar 2022 11:52:10 +0000 (GMT) From: "Naveen N. Rao" To: Michael Ellerman , Nicholas Piggin , Christophe Leroy Subject: [PATCH 2/2] powerpc/64: remove system call instruction emulation Date: Wed, 23 Mar 2022 17:21:36 +0530 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: a2dlMkPL4K-O1s1hjmeo4nxYmggGWH1V X-Proofpoint-ORIG-GUID: WW-OJqSF0s6Y4SrrkqTnm6lfkCh6SQ0U X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.850,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-23_06,2022-03-22_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 clxscore=1015 bulkscore=0 adultscore=0 mlxlogscore=999 phishscore=0 mlxscore=0 malwarescore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203230066 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Nicholas Piggin emulate_step instruction emulation including sc instruction emulation initially appeared in xmon. It then emulation code was then moved into sstep.c where kprobes could use it too, and later hw_breakpoint and uprobes started to use it. Until uprobes, the only instruction emulation users were for kernel mode instructions. - xmon only steps / breaks on kernel addresses. - kprobes is kernel only. - hw_breakpoint only emulates kernel instructions, single steps user. At one point there was support for the kernel to execute sc instructions, although that is long removed and it's not clear whether there was any in-tree code. So system call emulation is not required by the above users. uprobes uses emulate_step and it appears possible to emulate sc instruction in userspace. Userspace system call emulation is broken and it's not clear it ever worked well. The big complication is that userspace takes an interrupt to the kernel to emulate the instruction. The user->kernel interrupt sets up registers and interrupt stack frame expecting to return to userspace, then system call instruction emulation re-directs that stack frame to the kernel, early in the system call interrupt handler. This means the the interrupt return code takes the kernel->kernel restore path, which does not restore everything as the system call interrupt handler would expect coming from userspace. regs->iamr appears to get lost for example, because the kernel->kernel return does not restore the user iamr. Accounting such as irqflags tracing and CPU accounting does not get flipped back to user mode as the system call handler expects, so those appear to enter the kernel twice without returning to userspace. These things may be individually fixable with various complication, but it is a big complexity for unclear real benefit. This patch removes system call emulation and disables stepping system calls (because they don't work with trace interrupts, as commented). Signed-off-by: Nicholas Piggin [also get rid of '#ifdef CONFIG_PPC64'] Signed-off-by: Naveen N. Rao --- arch/powerpc/kernel/interrupt_64.S | 10 ------- arch/powerpc/lib/sstep.c | 46 +++++++----------------------- 2 files changed, 10 insertions(+), 46 deletions(-) diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index 7bab2d7de372e0..6471034c790973 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -219,16 +219,6 @@ system_call_vectored common 0x3000 */ system_call_vectored sigill 0x7ff0 - -/* - * Entered via kernel return set up by kernel/sstep.c, must match entry regs - */ - .globl system_call_vectored_emulate -system_call_vectored_emulate: -_ASM_NOKPROBE_SYMBOL(system_call_vectored_emulate) - li r10,IRQS_ALL_DISABLED - stb r10,PACAIRQSOFTMASK(r13) - b system_call_vectored_common #endif /* CONFIG_PPC_BOOK3S */ .balign IFETCH_ALIGN_BYTES diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index 3fda8d0a05b43f..01c8fd39f34981 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -15,9 +15,6 @@ #include #include -extern char system_call_common[]; -extern char system_call_vectored_emulate[]; - #ifdef CONFIG_PPC64 /* Bits in SRR1 that are copied from MSR */ #define MSR_MASK 0xffffffff87c0ffffUL @@ -1376,7 +1373,6 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, if (branch_taken(word, regs, op)) op->type |= BRTAKEN; return 1; -#ifdef CONFIG_PPC64 case 17: /* sc */ if ((word & 0xfe2) == 2) op->type = SYSCALL; @@ -1388,7 +1384,6 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, } else op->type = UNKNOWN; return 0; -#endif case 18: /* b */ op->type = BRANCH | BRTAKEN; imm = word & 0x03fffffc; @@ -3643,43 +3638,22 @@ int emulate_step(struct pt_regs *regs, ppc_inst_t instr) regs_set_return_msr(regs, (regs->msr & ~op.val) | (val & op.val)); goto instr_done; -#ifdef CONFIG_PPC64 case SYSCALL: /* sc */ /* - * N.B. this uses knowledge about how the syscall - * entry code works. If that is changed, this will - * need to be changed also. + * Per ISA v3.1, section 7.5.15 'Trace Interrupt', we can't + * single step a system call instruction: + * + * Successful completion for an instruction means that the + * instruction caused no other interrupt. Thus a Trace + * interrupt never occurs for a System Call or System Call + * Vectored instruction, or for a Trap instruction that + * traps. */ - if (IS_ENABLED(CONFIG_PPC_FAST_ENDIAN_SWITCH) && - cpu_has_feature(CPU_FTR_REAL_LE) && - regs->gpr[0] == 0x1ebe) { - regs_set_return_msr(regs, regs->msr ^ MSR_LE); - goto instr_done; - } - regs->gpr[9] = regs->gpr[13]; - regs->gpr[10] = MSR_KERNEL; - regs->gpr[11] = regs->nip + 4; - regs->gpr[12] = regs->msr & MSR_MASK; - regs->gpr[13] = (unsigned long) get_paca(); - regs_set_return_ip(regs, (unsigned long) &system_call_common); - regs_set_return_msr(regs, MSR_KERNEL); - return 1; - -#ifdef CONFIG_PPC_BOOK3S_64 + return -1; case SYSCALL_VECTORED_0: /* scv 0 */ - regs->gpr[9] = regs->gpr[13]; - regs->gpr[10] = MSR_KERNEL; - regs->gpr[11] = regs->nip + 4; - regs->gpr[12] = regs->msr & MSR_MASK; - regs->gpr[13] = (unsigned long) get_paca(); - regs_set_return_ip(regs, (unsigned long) &system_call_vectored_emulate); - regs_set_return_msr(regs, MSR_KERNEL); - return 1; -#endif - + return -1; case RFI: return -1; -#endif } return 0;