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 8EDC9C433EF for ; Thu, 13 Jan 2022 23:40:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238256AbiAMXkJ (ORCPT ); Thu, 13 Jan 2022 18:40:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238241AbiAMXkI (ORCPT ); Thu, 13 Jan 2022 18:40:08 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD147C061574 for ; Thu, 13 Jan 2022 15:40:07 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id g6-20020a25db06000000b00611ca09ecd0so4587567ybf.6 for ; Thu, 13 Jan 2022 15:40:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=wwJdGAN5osUC9HM7kKzj2Htmsov37Cc7r1NsvxZMlRg=; b=EqRlBPehovANSdBzY2evi/EKQYY+q7HLOecxR/MagzYR2LxVFJ2uK4VkjufpfGFEzx KIeCSUfIoiL1qoE5OPQTr4qRMnceLv7+32QM4Hl7gPahtlj2cTemKA31nN2Df8LfZhZa El2EqLCJCO1yQ/3YpQ/0XwnC8W2XEBXUm3dbCBExBLp/IGMMCLUgBq+B94A1I13rRSAN ukHIOytgnjWR7LSixoc/8BtU4PvqqLx30PpXNj3fgwOdLAk53TWQvhTQkjw3G0wKpYC8 PUt8wipSgOqEFQ+Y2EWyJvcrby1YZ8yF2OF7TvyETom5WyTQmwBDMAfStsNe41S0zUdC 0UTA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=wwJdGAN5osUC9HM7kKzj2Htmsov37Cc7r1NsvxZMlRg=; b=naL5EcjpEKT00Dyd9w5IbYjV0+DzxucynhT9hlWye7UqmWRm8ci9VXOjn/r+O/SYZd 0x53EzBfK1phnxxeZ+xTfo0g3OngJRNy8IPpKpEcuTkk3SuhGpnxiU3vRjd+oAPZGfGs kvjJWoVIX4x5EbaVBk/LW9OKw6ZxPAh96KgT4z37f/PTBomh5VckfXgVG/0qyiip8vCF T/yA6FWKPYp57t6gMDVBoqd35g27zE62m5IYb1sskIyyt/YDQCrHnnxwunGPRHEgxZ8P 1ecMVlhISJjDGw7t59HKF9HPlrp+O1enoFDSlihVwDqb9fjlGKQuV3FhmIVEqwG+K57c M5Dg== X-Gm-Message-State: AOAM5315b0osAhPfSMeFfirNL+aSrDjyNXWoBT6uqmclJt/+pQirgXGH yaSvgU5mra5rpWX1rw6a/857MtgG X-Google-Smtp-Source: ABdhPJzzGWHCGjZGF5k35EtO1RjDkQh8pxMnUpvwv8nSbHJHv8giYUEy9UlBMk+wUGWLFmwcfXW/lLPr X-Received: from posk.svl.corp.google.com ([2620:15c:2cd:202:c548:e79f:8954:121f]) (user=posk job=sendgmr) by 2002:a25:6d09:: with SMTP id i9mr4958623ybc.703.1642117206900; Thu, 13 Jan 2022 15:40:06 -0800 (PST) Date: Thu, 13 Jan 2022 15:39:37 -0800 In-Reply-To: <20220113233940.3608440-1-posk@google.com> Message-Id: <20220113233940.3608440-3-posk@google.com> Mime-Version: 1.0 References: <20220113233940.3608440-1-posk@google.com> X-Mailer: git-send-email 2.34.1.703.g22d0c6ccf7-goog Subject: [RFC PATCH v2 2/5] x86/uaccess: Implement unsafe_try_cmpxchg_user() From: Peter Oskolkov To: Peter Zijlstra , 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, pjt@google.com, posk@google.com, avagin@google.com, jannh@google.com, tdelisle@uwaterloo.ca, posk@posk.io Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Do try_cmpxchg() loops on userspace addresses. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/uaccess.h | 57 ++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index ac96f9b2d64b..8277ec05be02 100644 --- 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, _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] "r" (__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, _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] "r" (__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 +543,21 @@ 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 4: __ret = __try_cmpxchg_user_asm("l", (_ptr), (_oldp), \ + (_nval), _label); \ + break; \ + case 8: __ret = __try_cmpxchg_user_asm("q", (_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. -- 2.34.1.703.g22d0c6ccf7-goog