From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3001C433E0 for ; Sun, 21 Feb 2021 00:30:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83E5C64EE6 for ; Sun, 21 Feb 2021 00:30:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229925AbhBUA22 (ORCPT ); Sat, 20 Feb 2021 19:28:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229819AbhBUA1Y (ORCPT ); Sat, 20 Feb 2021 19:27:24 -0500 Received: from smtp.gentoo.org (woodpecker.gentoo.org [IPv6:2001:470:ea4a:1:5054:ff:fec7:86e4]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99F97C061786; Sat, 20 Feb 2021 16:26:44 -0800 (PST) Received: by sf.home (Postfix, from userid 1000) id A7DE75A2208B; Sun, 21 Feb 2021 00:25:58 +0000 (GMT) From: Sergei Trofimovich To: Andrew Morton , linux-kernel@vger.kernel.org Cc: Sergei Trofimovich , Oleg Nesterov , linux-ia64@vger.kernel.org, "Dmitry V . Levin" Subject: [PATCH] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls Date: Sun, 21 Feb 2021 00:25:53 +0000 Message-Id: <20210221002554.333076-1-slyfox@gentoo.org> X-Mailer: git-send-email 2.30.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In https://bugs.gentoo.org/769614 Dmitry noticed that `ptrace(PTRACE_GET_SYSCALL_INFO)` does not work for syscalls called via glibc's syscall() wrapper. ia64 has two ways to call syscalls from userspace: via `break` and via `eps` instructions. The difference is in stack layout: 1. `eps` creates simple stack frame: no locals, in{0..7} == out{0..8} 2. `break` uses userspace stack frame: may be locals (glibc provides one), in{0..7} == out{0..8}. Both work fine in syscall handling cde itself. But `ptrace(PTRACE_GET_SYSCALL_INFO)` uses unwind mechanism to re-extract syscall arguments but it does not account for locals. The change always skips locals registers. It should not change `eps` path as kernel's handler already enforces locals=0 and fixes `break`. Tested on v5.10 on rx3600 machine (ia64 9040 CPU). CC: Oleg Nesterov CC: linux-ia64@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: Andrew Morton Reported-by: Dmitry V. Levin Bug: https://bugs.gentoo.org/769614 Signed-off-by: Sergei Trofimovich --- arch/ia64/kernel/ptrace.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c index c3490ee2daa5..e14f5653393a 100644 --- a/arch/ia64/kernel/ptrace.c +++ b/arch/ia64/kernel/ptrace.c @@ -2013,27 +2013,39 @@ static void syscall_get_set_args_cb(struct unw_frame_info *info, void *data) { struct syscall_get_set_args *args = data; struct pt_regs *pt = args->regs; - unsigned long *krbs, cfm, ndirty; + unsigned long *krbs, cfm, ndirty, nlocals, nouts; int i, count; if (unw_unwind_to_user(info) < 0) return; + /* + * We get here via a few paths: + * - break instruction: cfm is shared with caller. + * syscall args are in out= regs, locals are non-empty. + * - epsinstruction: cfm is set by br.call + * locals don't exist. + * + * For both cases argguments are reachable in cfm.sof - cfm.sol. + * CFM: [ ... | sor: 17..14 | sol : 13..7 | sof : 6..0 ] + */ cfm = pt->cr_ifs; + nlocals = (cfm >> 7) & 0x7f; /* aka sol */ + nouts = (cfm & 0x7f) - nlocals; /* aka sof - sol */ krbs = (unsigned long *)info->task + IA64_RBS_OFFSET/8; ndirty = ia64_rse_num_regs(krbs, krbs + (pt->loadrs >> 19)); count = 0; if (in_syscall(pt)) - count = min_t(int, args->n, cfm & 0x7f); + count = min_t(int, args->n, nouts); + /* Iterate over outs. */ for (i = 0; i < count; i++) { + int j = ndirty + nlocals + i + args->i; if (args->rw) - *ia64_rse_skip_regs(krbs, ndirty + i + args->i) = - args->args[i]; + *ia64_rse_skip_regs(krbs, j) = args->args[i]; else - args->args[i] = *ia64_rse_skip_regs(krbs, - ndirty + i + args->i); + args->args[i] = *ia64_rse_skip_regs(krbs, j); } if (!args->rw) { -- 2.30.1