From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-13.6 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE,T_DKIMWL_WL_MED, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 3AF317D2EF for ; Wed, 29 May 2019 14:23:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726897AbfE2OXm (ORCPT ); Wed, 29 May 2019 10:23:42 -0400 Received: from mail-yb1-f202.google.com ([209.85.219.202]:36434 "EHLO mail-yb1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726799AbfE2OXm (ORCPT ); Wed, 29 May 2019 10:23:42 -0400 Received: by mail-yb1-f202.google.com with SMTP id a62so2060230ybg.3 for ; Wed, 29 May 2019 07:23:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=hnwNAJD4/mUkL54igU9we9Ltgm5eIKoyhCAZZdgQs58=; b=YKxGQyRUZZMeXdD+5O/+YQ8S5R7eOVZ6kTD5No/AR7rwZ7z06vtDtTsA5SB6eDlc2f E2KpoyeE0R7XPJPqXP9mvFk+KK4l7E4JO+8U0EMM44C/XodSHzZK10dB8YhWF+0aCBRo 10xD9xjQcKooejbvTzCf+VuiKq6KV9TFG7DR+vypS+td8vr+/j4S66GYr81uQIaq6RvU 4jFJ0MzYenQJ5UIde94C2fBiEQl7uC08nCHiLZ+xDqNzLfLEQIa/L1hDx0g8CQJoXQlN VpVHu4wi4d0r79S5Q/w1CPEK4TKmjjKvLWvCmaql3MeHZS1MOYn/SrVopPlMbFMxYC34 kkKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=hnwNAJD4/mUkL54igU9we9Ltgm5eIKoyhCAZZdgQs58=; b=ApPm7aCfrqRPd1kTcm/Co9U/f7AMcNdUYpgXtkFG4u8ciBZjQQLkQZjlNPB2MWv23b lrJD8+NP/EKM1OrFYVXv8B+8P2kC5tXN6pTNxfKzuxhpYfbkTkCP2FUjHzXD5b2VIyPo FA6rWAkaJYo0Ku42CwtTOAhe71pmGO7pIbi4ffl3/zPAiVN1ZeXIwzDTR4x4hIh9kkZV poEyAhuyikZLhptnbbcHdPqA05ICcNru9Q4A3lj0NM2tqisR3asiXDXB4Do9izzpp9wS KODCr4IsrTUTIoSM1mbDpYAOKgogujzfRhZQ1L3hEWvsfHdPwxgG3+UjQovhlLu2KLvj IToQ== X-Gm-Message-State: APjAAAVcM+AVNUbsFIRNZq49BU8WzlX4mf21BwGtwcaXzHAviyLIgPBA BaxAuazJv2u3+DWgYzndu10ldRCk9A== X-Google-Smtp-Source: APXvYqxPWoe9RlRk/z6kL2jY6+AqJPi9cpOCsqgCyTYg8p3mqnqg2y3MWgDBA9joolHmfQ8GM4azzmSoWA== X-Received: by 2002:a81:a393:: with SMTP id a141mr11425823ywh.330.1559139821308; Wed, 29 May 2019 07:23:41 -0700 (PDT) Date: Wed, 29 May 2019 16:15:00 +0200 In-Reply-To: <20190529141500.193390-1-elver@google.com> Message-Id: <20190529141500.193390-3-elver@google.com> Mime-Version: 1.0 References: <20190529141500.193390-1-elver@google.com> X-Mailer: git-send-email 2.22.0.rc1.257.g3120a18244-goog Subject: [PATCH 2/3] x86: Move CPU feature test out of uaccess region From: Marco Elver To: peterz@infradead.org, aryabinin@virtuozzo.com, dvyukov@google.com, glider@google.com, andreyknvl@google.com, mark.rutland@arm.com Cc: corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, arnd@arndb.de, jpoimboe@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kasan-dev@googlegroups.com, Marco Elver Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org This patch is a pre-requisite for enabling KASAN bitops instrumentation: moves boot_cpu_has feature test out of the uaccess region, as boot_cpu_has uses test_bit. With instrumentation, the KASAN check would otherwise be flagged by objtool. This approach is preferred over adding the explicit kasan_check_* functions to the uaccess whitelist of objtool, as the case here appears to be the only one. Signed-off-by: Marco Elver --- v1: * This patch replaces patch: 'tools/objtool: add kasan_check_* to uaccess whitelist' --- arch/x86/ia32/ia32_signal.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c index 629d1ee05599..12264e3c9c43 100644 --- a/arch/x86/ia32/ia32_signal.c +++ b/arch/x86/ia32/ia32_signal.c @@ -333,6 +333,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig, void __user *restorer; int err = 0; void __user *fpstate = NULL; + bool has_xsave; /* __copy_to_user optimizes that into a single 8 byte store */ static const struct { @@ -352,13 +353,19 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig, if (!access_ok(frame, sizeof(*frame))) return -EFAULT; + /* + * Move non-uaccess accesses out of uaccess region if not strictly + * required; this also helps avoid objtool flagging these accesses with + * instrumentation enabled. + */ + has_xsave = boot_cpu_has(X86_FEATURE_XSAVE); put_user_try { put_user_ex(sig, &frame->sig); put_user_ex(ptr_to_compat(&frame->info), &frame->pinfo); put_user_ex(ptr_to_compat(&frame->uc), &frame->puc); /* Create the ucontext. */ - if (boot_cpu_has(X86_FEATURE_XSAVE)) + if (has_xsave) put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags); else put_user_ex(0, &frame->uc.uc_flags); -- 2.22.0.rc1.257.g3120a18244-goog