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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 46533C433E6 for ; Mon, 1 Feb 2021 19:42:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1997964DBA for ; Mon, 1 Feb 2021 19:42:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232357AbhBATmt (ORCPT ); Mon, 1 Feb 2021 14:42:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229879AbhBATml (ORCPT ); Mon, 1 Feb 2021 14:42:41 -0500 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 596A9C061573; Mon, 1 Feb 2021 11:42:00 -0800 (PST) Received: by mail-pj1-x102d.google.com with SMTP id s24so225082pjp.5; Mon, 01 Feb 2021 11:42:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=EQLuUgJy+o1hW9AunpfEc1qlY4Nc1HNzMaooRQ/maGI=; b=c+2FqPenYDUXmY2kNElCjc1zpbv1nfM3B2pKaKRri5HOpiZXABTyHA/PQlo65RJr+Z 14Pt8sXeP01DXpN2ebzEEbqt4n938aJ3hopdR7MCIZlmle6G3XvdFqZapeDec2yFUeUJ 0avNYAVfgR+txKKakSpI+lBCzfKr//gTUa7x9uJ2gwwFu8V7eldlnJMjKhTgEnsQzER7 d0L/5h4KFw/n8EMVErFTT/nrrzJtdlioCpEas5H7QzuuqaU1bqnMPpsf4yAQNMLU6zax /VMRyu313OLhK+I5lm57OtJpwofCPks0qjOWNX6mDMCAkxinGN7D9Mg5wEdg4IHQRdeX 6g8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=EQLuUgJy+o1hW9AunpfEc1qlY4Nc1HNzMaooRQ/maGI=; b=Me/jWZJqp3DRHh6WtxlJaqashfDB0RgB6RhW9fIR5z7xbmmJVRm1f5FUbTeY9XwOFA hZWqHiZy688Y/K9nBWoQCVpnCb4LWYMBDpcc+X8eyx5gxVyn9Sqj129H+im6iIO23E7X HycM2Bb/Hbihh/+7ovGT32Q5qOPp03zYrEc0oczc6855wkV6IbQSOEu8xf/udWyLnT77 A23uq5NhECABuVWTYwQsYOFXqIinIuzN/sF45Jw4VoBbmk5RsnA9ns7CfcG5nbwf2vWE /S5uPxn4j/zG3K2hqXT4UMo4Otq6r4Fom5cApzkJMzS4pQJUH+Xy+CIcMpjPsTv64jgx h58w== X-Gm-Message-State: AOAM5300LVvJShndznNrBDJ7T7IOtyEFI+5slzUSXX8YZOeyWGzTmcjP 3uwtXvstDl3z+liCU+6CJn0= X-Google-Smtp-Source: ABdhPJyUpFpB8WB7DGdGa42I0331TOpmj95xQ5DyrrcB4Il8FwZOLlGyylyvihXjujMle9NwJNLgTA== X-Received: by 2002:a17:902:7d96:b029:e0:151c:598b with SMTP id a22-20020a1709027d96b02900e0151c598bmr18881431plm.2.1612208519740; Mon, 01 Feb 2021 11:41:59 -0800 (PST) Received: from laptop.hsd1.wa.comcast.net ([2601:600:9b7f:872e:a655:30fb:7373:c762]) by smtp.gmail.com with ESMTPSA id i4sm18213155pfo.40.2021.02.01.11.41.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Feb 2021 11:41:59 -0800 (PST) From: Andrei Vagin To: Will Deacon , Catalin Marinas Cc: Oleg Nesterov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Anthony Steinhauser , Andrei Vagin , Dave Martin , Keno Fischer Subject: [PATCH 1/3] arm64/ptrace: don't clobber task registers on syscall entry/exit traps Date: Mon, 1 Feb 2021 11:40:10 -0800 Message-Id: <20210201194012.524831-2-avagin@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210201194012.524831-1-avagin@gmail.com> References: <20210201194012.524831-1-avagin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org ip/r12 for AArch32 and x7 for AArch64 is used to indicate whether or not the stop has been signalled from syscall entry or syscall exit. This means that: - Any writes by the tracer to this register during the stop are ignored/discarded. - The actual value of the register is not available during the stop, so the tracer cannot save it and restore it later. Right now, these registers are clobbered in tracehook_report_syscall. This change moves the logic to gpr_get and compat_gpr_get where registers are copied into a user-space buffer. This will allow to change these registers and to introduce a new ptrace option to get the full set of registers. Signed-off-by: Andrei Vagin --- arch/arm64/include/asm/ptrace.h | 5 ++ arch/arm64/kernel/ptrace.c | 104 ++++++++++++++++++++------------ 2 files changed, 69 insertions(+), 40 deletions(-) diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index e58bca832dff..0a9552b4f61e 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -170,6 +170,11 @@ static inline unsigned long pstate_to_compat_psr(const unsigned long pstate) return psr; } +enum ptrace_syscall_dir { + PTRACE_SYSCALL_ENTER = 0, + PTRACE_SYSCALL_EXIT, +}; + /* * This struct defines the way the registers are stored on the stack during an * exception. Note that sizeof(struct pt_regs) has to be a multiple of 16 (for diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 8ac487c84e37..39da03104528 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -40,6 +40,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -561,7 +562,31 @@ static int gpr_get(struct task_struct *target, struct membuf to) { struct user_pt_regs *uregs = &task_pt_regs(target)->user_regs; - return membuf_write(&to, uregs, sizeof(*uregs)); + unsigned long saved_reg; + int ret; + + /* + * We have some ABI weirdness here in the way that we handle syscall + * exit stops because we indicate whether or not the stop has been + * signalled from syscall entry or syscall exit by clobbering the general + * purpose register x7. + */ + saved_reg = uregs->regs[7]; + + switch (target->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + uregs->regs[7] = PTRACE_SYSCALL_ENTER; + break; + case PTRACE_EVENTMSG_SYSCALL_EXIT: + uregs->regs[7] = PTRACE_SYSCALL_EXIT; + break; + } + + ret = membuf_write(&to, uregs, sizeof(*uregs)); + + uregs->regs[7] = saved_reg; + + return ret; } static int gpr_set(struct task_struct *target, const struct user_regset *regset, @@ -575,6 +600,17 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset, if (ret) return ret; + /* + * Historically, x7 can't be changed if the stop has been signalled + * from syscall-enter of syscall-exit. + */ + switch (target->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + case PTRACE_EVENTMSG_SYSCALL_EXIT: + newregs.regs[7] = task_pt_regs(target)->regs[7]; + break; + } + if (!valid_user_regs(&newregs, target)) return -EINVAL; @@ -1206,6 +1242,20 @@ static inline compat_ulong_t compat_get_user_reg(struct task_struct *task, int i struct pt_regs *regs = task_pt_regs(task); switch (idx) { + case 12: + /* + * We have some ABI weirdness here in the way that we handle + * syscall exit stops because we indicate whether or not the + * stop has been signalled from syscall entry or syscall exit + * by clobbering the general purpose register r12. + */ + switch (task->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + return PTRACE_SYSCALL_ENTER; + case PTRACE_EVENTMSG_SYSCALL_EXIT: + return PTRACE_SYSCALL_EXIT; + } + return regs->regs[idx]; case 15: return regs->pc; case 16: @@ -1282,6 +1332,17 @@ static int compat_gpr_set(struct task_struct *target, } + /* + * Historically, x12 can't be changed if the stop has been signalled + * from syscall-enter of syscall-exit. + */ + switch (target->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + case PTRACE_EVENTMSG_SYSCALL_EXIT: + newregs.regs[12] = task_pt_regs(target)->regs[12]; + break; + } + if (valid_user_regs(&newregs.user_regs, target)) *task_pt_regs(target) = newregs; else @@ -1740,53 +1801,16 @@ long arch_ptrace(struct task_struct *child, long request, return ptrace_request(child, request, addr, data); } -enum ptrace_syscall_dir { - PTRACE_SYSCALL_ENTER = 0, - PTRACE_SYSCALL_EXIT, -}; - static void tracehook_report_syscall(struct pt_regs *regs, enum ptrace_syscall_dir dir) { - int regno; - unsigned long saved_reg; - - /* - * We have some ABI weirdness here in the way that we handle syscall - * exit stops because we indicate whether or not the stop has been - * signalled from syscall entry or syscall exit by clobbering a general - * purpose register (ip/r12 for AArch32, x7 for AArch64) in the tracee - * and restoring its old value after the stop. This means that: - * - * - Any writes by the tracer to this register during the stop are - * ignored/discarded. - * - * - The actual value of the register is not available during the stop, - * so the tracer cannot save it and restore it later. - * - * - Syscall stops behave differently to seccomp and pseudo-step traps - * (the latter do not nobble any registers). - */ - regno = (is_compat_task() ? 12 : 7); - saved_reg = regs->regs[regno]; - regs->regs[regno] = dir; - if (dir == PTRACE_SYSCALL_ENTER) { if (tracehook_report_syscall_entry(regs)) forget_syscall(regs); - regs->regs[regno] = saved_reg; - } else if (!test_thread_flag(TIF_SINGLESTEP)) { - tracehook_report_syscall_exit(regs, 0); - regs->regs[regno] = saved_reg; } else { - regs->regs[regno] = saved_reg; + int singlestep = test_thread_flag(TIF_SINGLESTEP); - /* - * Signal a pseudo-step exception since we are stepping but - * tracer modifications to the registers may have rewound the - * state machine. - */ - tracehook_report_syscall_exit(regs, 1); + tracehook_report_syscall_exit(regs, singlestep); } } -- 2.29.2