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=-15.8 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=unavailable 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 93B9AC433E0 for ; Tue, 19 Jan 2021 22:12:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F6BC230FE for ; Tue, 19 Jan 2021 22:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732018AbhASWLk (ORCPT ); Tue, 19 Jan 2021 17:11:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729778AbhASWIy (ORCPT ); Tue, 19 Jan 2021 17:08:54 -0500 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E95D3C0613C1 for ; Tue, 19 Jan 2021 14:08:13 -0800 (PST) Received: by mail-pl1-x62f.google.com with SMTP id s15so11337958plr.9 for ; Tue, 19 Jan 2021 14:08:13 -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=ZtvWiGPK2eweAPRjtJhZb7309sm3REWVBB+tfD69F30=; b=UUp1Z0eBKhUHBfdI83AvJ0436gY4K8mRwO4+iCyC1cdjEpBkDz0fEtQqNWLOo1RLyJ edyTCAwWw1jmaG8rElV8Jo6kHnmFMkjpiXb+Hy4vZDXwlm9AruyVqDrLFb0fP8m/5noE rnyw0qvkd9sRrRwzR3Xl6IMRkMfCqyK8PR+K8rnQ560jK0NU8P3pTkzqluJpu88YVx3d 7uIts3SNc/HOqQRQlIYYWnVAvdfgM7lrI+LLjj/k9CKE8kUMX6wvO/LTS1NSqaFGCI2B iDEZWwZmRPt541vMUH7DyH5z+MWOJwQBIxaiwrBHvzJf/9Tyie4AOlRKGYobM6PBZAXz 3+RA== 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=ZtvWiGPK2eweAPRjtJhZb7309sm3REWVBB+tfD69F30=; b=dFz2elcOpfTwzmnWp60AnbB28X9Y+yDt7zY2AfBg8iK32Nfa/2LFMKEo00sDHdYzl2 MAT5Vo3NIOsbuIFMqYr7Ag/gph+C/A0z0GvQBZS1SD9dimiYAMHgw8ZG2NzgHHAViDyQ Octl3F+SQPOW2uAby0VDxy0x98ZYXGC0iYIgJIWz3KO8mwNdDH6fw3dZCvlbmatS117O KBcZTSv5aYGzFowicbkQzQ+mdTleW0P9JMX5meVwHc4YLJsXITIE49rfE8y/S5m8zpFK M3dKfgCPV0ucDv49Sz2cO84JP+H23Il8JRK/KWMpMAHKK2ms5POvPJNsIN6LjFOt8vTV iCfA== X-Gm-Message-State: AOAM530xPcMm3es+JknyRZCJJwIzaASr70We8UEnQaF02aIvngqqH0vA wotH9jMW/22H6AynpXu/2PHgENE7HWOpKQ== X-Google-Smtp-Source: ABdhPJwVEJjtlAzTiLDNsWz7WVQ+ZoNp8rnM4n36DrBPJbku6zgklznseRI6dyryA7b5X3MK2hJnZg== X-Received: by 2002:a17:902:d48a:b029:de:ae4d:2c7b with SMTP id c10-20020a170902d48ab02900deae4d2c7bmr6838343plg.62.1611094093364; Tue, 19 Jan 2021 14:08:13 -0800 (PST) Received: from laptop.hsd1.wa.comcast.net ([2601:600:9b7f:872e:a655:30fb:7373:c762]) by smtp.gmail.com with ESMTPSA id 72sm95196pfw.170.2021.01.19.14.08.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 14:08:12 -0800 (PST) From: Andrei Vagin To: Will Deacon , Catalin Marinas Cc: Oleg Nesterov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Andrei Vagin Subject: [PATCH 1/3] arm64/ptrace: don't clobber task registers on syscall entry/exit traps Date: Tue, 19 Jan 2021 14:06:35 -0800 Message-Id: <20210119220637.494476-2-avagin@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210119220637.494476-1-avagin@gmail.com> References: <20210119220637.494476-1-avagin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 this 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 NT_ARM_PRSTATUS command 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, 67 insertions(+), 42 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..1863f080cb07 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 +562,33 @@ 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. + */ + switch (target->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + saved_reg = uregs->regs[7]; + uregs->regs[7] = PTRACE_SYSCALL_ENTER; + break; + case PTRACE_EVENTMSG_SYSCALL_EXIT: + saved_reg = uregs->regs[7]; + uregs->regs[7] = PTRACE_SYSCALL_EXIT; + break; + } + + ret = membuf_write(&to, uregs, sizeof(*uregs)); + + if (target->ptrace_message == PTRACE_EVENTMSG_SYSCALL_ENTRY || + target->ptrace_message == PTRACE_EVENTMSG_SYSCALL_EXIT) + uregs->regs[7] = saved_reg; + + return ret; } static int gpr_set(struct task_struct *target, const struct user_regset *regset, @@ -1221,10 +1248,40 @@ static int compat_gpr_get(struct task_struct *target, const struct user_regset *regset, struct membuf to) { + compat_ulong_t r12; + bool overwrite_r12; int i = 0; - while (to.left) - membuf_store(&to, compat_get_user_reg(target, i++)); + /* + * 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 (target->ptrace_message) { + case PTRACE_EVENTMSG_SYSCALL_ENTRY: + r12 = PTRACE_SYSCALL_ENTER; + overwrite_r12 = true; + break; + case PTRACE_EVENTMSG_SYSCALL_EXIT: + r12 = PTRACE_SYSCALL_EXIT; + overwrite_r12 = true; + break; + default: + overwrite_r12 = false; + break; + } + + while (to.left) { + compat_ulong_t val; + + if (!overwrite_r12 || i != 12) + val = compat_get_user_reg(target, i++); + else + val = r12; + membuf_store(&to, val); + } + return 0; } @@ -1740,53 +1797,16 @@ 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