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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9165C4332F for ; Thu, 20 Jan 2022 16:09:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376874AbiATQJW (ORCPT ); Thu, 20 Jan 2022 11:09:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376873AbiATQJV (ORCPT ); Thu, 20 Jan 2022 11:09:21 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00CDAC061746; Thu, 20 Jan 2022 08:09:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=O4yxE5iBljUnz9jsYfJACEXe1y1JTPG27a4exjE3DTU=; b=N1I9L8vqLIoEjF6t+ZNSkBly0b sqgDFRzLWknIOXl6tCRnqlMxOkJ/xXXo53bEjoDT5ovaZrlI+PdcAdAcl+olnMfIc3AlP74Sm61zg 04j9SRoF5wGwCOUgF/VTuIXqL18OZ/fqq9ZDzKpoRgZqEHEi0gkRLa2DV20ZayIEI+Z42mPV4ytfY 6WnjWTTQ259UHUGnLykfNUS0KQl1hh9aPB/YrVlnALNschhfq1zdk3snBH+VtqtRYzHfV209c4M0w Vy3p04hlypEiQRgqnrnHJ3hdXXS2575F5iRfflIG0unT1/68dQwDJ9yDTnnXS6VtSFTuuZuGG4Qj2 aW9583Iw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nAZza-00EQ4G-4H; Thu, 20 Jan 2022 16:08:54 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BFE5830077D; Thu, 20 Jan 2022 17:08:51 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id A0A6A20279CE0; Thu, 20 Jan 2022 17:08:51 +0100 (CET) Message-ID: <20220120160822.852009966@infradead.org> User-Agent: quilt/0.66 Date: Thu, 20 Jan 2022 16:55:21 +0100 From: Peter Zijlstra To: mingo@redhat.com, tglx@linutronix.de, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, x86@kernel.org, peterz@infradead.org, pjt@google.com, posk@google.com, avagin@google.com, jannh@google.com, tdelisle@uwaterloo.ca, mark.rutland@arm.com, posk@posk.io, Sean Christopherson Subject: [RFC][PATCH v2 4/5] x86/uaccess: Implement unsafe_try_cmpxchg_user() References: <20220120155517.066795336@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Do try_cmpxchg() loops on userspace addresses. Cc: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/uaccess.h | 67 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -342,6 +342,24 @@ do { \ : [umem] "m" (__m(addr)) \ : : label) +#define __try_cmpxchg_user_asm(itype, ltype, _ptr, _pold, _new, label) ({ \ + bool success; \ + __typeof__(_ptr) _old = (__typeof__(_ptr))(_pold); \ + __typeof__(*(_ptr)) __old = *_old; \ + __typeof__(*(_ptr)) __new = (_new); \ + asm_volatile_goto("\n" \ + "1: " LOCK_PREFIX "cmpxchg"itype" %[new], %[ptr]\n"\ + _ASM_EXTABLE_UA(1b, %l[label]) \ + : CC_OUT(z) (success), \ + [ptr] "+m" (*_ptr), \ + [old] "+a" (__old) \ + : [new] ltype (__new) \ + : "memory", "cc" \ + : label); \ + if (unlikely(!success)) \ + *_old = __old; \ + likely(success); }) + #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT #ifdef CONFIG_X86_32 @@ -407,6 +425,30 @@ do { \ : [umem] "m" (__m(addr)), \ "0" (err)) +#define __try_cmpxchg_user_asm(itype, ltype, _ptr, _pold, _new, label) ({ \ + int __err = 0; \ + bool success; \ + __typeof__(_ptr) _old = (__typeof__(_ptr))(_pold); \ + __typeof__(*(_ptr)) __old = *_old; \ + __typeof__(*(_ptr)) __new = (_new); \ + asm volatile("\n" \ + "1: " LOCK_PREFIX "cmpxchg"itype" %[new], %[ptr]\n"\ + CC_SET(z) \ + "2:\n" \ + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, \ + %[errout]) \ + : CC_OUT(z) (success), \ + [errout] "+r" (__err), \ + [ptr] "+m" (*_ptr), \ + [old] "+a" (__old) \ + : [new] ltype (__new) \ + : "memory", "cc"); \ + if (unlikely(__err)) \ + goto label; \ + if (unlikely(!success)) \ + *_old = __old; \ + likely(success); }) + #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT /* FIXME: this hack is definitely wrong -AK */ @@ -501,6 +543,31 @@ do { \ } while (0) #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT +extern void __try_cmpxchg_user_wrong_size(void); + +#define unsafe_try_cmpxchg_user(_ptr, _oldp, _nval, _label) ({ \ + __typeof__(*(_ptr)) __ret; \ + switch (sizeof(__ret)) { \ + case 1: __ret = __try_cmpxchg_user_asm("b", "q", \ + (_ptr), (_oldp), \ + (_nval), _label); \ + break; \ + case 2: __ret = __try_cmpxchg_user_asm("w", "r", \ + (_ptr), (_oldp), \ + (_nval), _label); \ + break; \ + case 4: __ret = __try_cmpxchg_user_asm("l", "r", \ + (_ptr), (_oldp), \ + (_nval), _label); \ + break; \ + case 8: __ret = __try_cmpxchg_user_asm("q", "r", \ + (_ptr), (_oldp), \ + (_nval), _label); \ + break; \ + default: __try_cmpxchg_user_wrong_size(); \ + } \ + __ret; }) + /* * We want the unsafe accessors to always be inlined and use * the error labels - thus the macro games.