From patchwork Mon Mar 14 04:43:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Henderson X-Patchwork-Id: 551077 Delivered-To: patch@linaro.org Received: by 2002:a05:7000:6713:0:0:0:0 with SMTP id u19csp2250501mag; Sun, 13 Mar 2022 21:47:38 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw0cI//QiuntDVqz/MW//E/yQV6+ssz0vMMbPn+TKkz47lJDi4SK6pKmL8LZXvfSedPW/Pt X-Received: by 2002:a81:6bc6:0:b0:2db:fe24:d5ee with SMTP id g189-20020a816bc6000000b002dbfe24d5eemr16901872ywc.392.1647233258553; Sun, 13 Mar 2022 21:47:38 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1647233258; cv=none; d=google.com; s=arc-20160816; b=T8O1NT/0pAS03esl0VtzSjmOY6UlxKfQ91gJuES8+VWsNGpUrLLO98jZ8kV6pFlB8m 8LqxMfjWZFxI9qps8IQTdpuILahPcZ4FvT4tclNzl01szT6Eyp1YA2jEV1kK4T7g6v+s +/6bpUi2BdqXuwXKx0Wv4wv4uOwXruNl1CLX4BmTVx1wo2PfohUrTnmn3SGSpWR0tcz7 btRcC69WuQ9OyxwSRB+v4OFP4tAT7PQwI4iMM9+HhH8jZn46xuBzDWg281PEyR5Obyet a9/nFUR/URFOWAJILIfy6+Bb+wVTiScXPIEKMx708I+3J3EMgfeNIihv6DLLjWH6kHsk 07BA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:cc:list-subscribe:list-help:list-post:list-archive :list-unsubscribe:list-id:precedence:content-transfer-encoding :mime-version:references:in-reply-to:message-id:date:subject:to:from :dkim-signature; bh=lXfB6B+XqNR5xcS/TG/PElhQ8wbvELzxHwZ/ZITikII=; b=s/YX4NGQDyn25y1KkhRedXP5lt4SUWfyZODhTZR7xKQ8sB4//rW7keMwV01jJIocGd RjkLF9i/IQMqnMBuh9mn3e7FEpclKFA6vONjIOfVzNZWAFJgybr2K6SbNsvwd/ULchTN QYp9dt0Ej/VxglPHd+yFX0z5gx6xH9pupyQqAaR9+Q/6CnqMhyNLxuhBUMmlzm3Ge8Gi uPlwDnWDCfXOwK24IC9cLTlvlfYyf2nXh+Du469iujdrhVC/5u0uQIFcmR5sbECIpD12 yF0IoFcfpv3Mw/kbGfkChXz/bldy8wJszJxNZp2Adg5+9tunb9RAglKCW8k1TY3t2HP5 aFyA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=VweupA+x; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+patch=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from lists.gnu.org (lists.gnu.org. [209.51.188.17]) by mx.google.com with ESMTPS id t191-20020a8178c8000000b002d66b779de7si8097800ywc.176.2022.03.13.21.47.38 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sun, 13 Mar 2022 21:47:38 -0700 (PDT) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=VweupA+x; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+patch=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from localhost ([::1]:50290 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nTccM-0001FK-1X for patch@linaro.org; Mon, 14 Mar 2022 00:47:38 -0400 Received: from eggs.gnu.org ([209.51.188.92]:50062) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTcY4-0003DD-6f for qemu-devel@nongnu.org; Mon, 14 Mar 2022 00:43:13 -0400 Received: from [2607:f8b0:4864:20::434] (port=37483 helo=mail-pf1-x434.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nTcY2-0004Oo-Je for qemu-devel@nongnu.org; Mon, 14 Mar 2022 00:43:11 -0400 Received: by mail-pf1-x434.google.com with SMTP id t5so13230149pfg.4 for ; Sun, 13 Mar 2022 21:43:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=lXfB6B+XqNR5xcS/TG/PElhQ8wbvELzxHwZ/ZITikII=; b=VweupA+xP8WZZ+y5fvL1xPzWUC67e1jgCvXMDCoPxnp1WSvTk/hwLDTOTyCvTVWspE uVbj+CO1pjH5QxxpTHm2dZcUhKflHeu77kVBW68OBrpC4tNde5a8xjdyPRPOnQellKpQ OJnMhkw64CPe808MN6ehDYWxVF7naV4zhbiadCEjjgjEKHma3QWOdGK9C9bqaQi76ne2 qCGfNXP9aGtOgFjAoStPBKdZe1THCrIgtotk57Ok3wlvIdd7ys8flqfY6jf6oF536c7Z i1C1N5p/K2SU175mM5RI6/Jn6fptxX8Wjbr3eyZqOVr8O0y3DJQ784k6/FPLizTDKLeG nwtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=lXfB6B+XqNR5xcS/TG/PElhQ8wbvELzxHwZ/ZITikII=; b=wvqARGwOuOPT6sWY4u62nXbO5NAJpTQoRL5MeZgn0W9Ti+qdibpTEo6tbMjz2A193G 9xkyLDQ4y/yNRIPuQB/XxBUlH6zoy3x5CCzep42rfs8yTJoC4nMrwW9gM8lilpAnpZ3w OvwZ3MrOvTz59DnWpFyzIzO0n+uR71Syui6f8a12pSTT/Z65MbDiiZPr6mE5iJeY2fg2 5xce1P4QAbUWk6lRnYPGhg2hq9j1lrB6GfskW3u0nq1nQicQNeTDZneS+aE8R1kaImtM AShiviVtjf87+QpCEJKo8JC+ciQgjhGg/TFRKsEcki+AFywZxVXyPirsbrrf+OfPhZfz +9SA== X-Gm-Message-State: AOAM531RxmkAb6fWTgcT5PpD1ucCV9naaN9CzCH/7stGdAvrWrwNHBg6 5tr7TrYouJHy/VoouMgWbSHWHUL5X0HEfA== X-Received: by 2002:a63:2a0e:0:b0:380:aeb3:d46c with SMTP id q14-20020a632a0e000000b00380aeb3d46cmr18441023pgq.404.1647232988795; Sun, 13 Mar 2022 21:43:08 -0700 (PDT) Received: from localhost.localdomain (174-21-142-130.tukw.qwest.net. [174.21.142.130]) by smtp.gmail.com with ESMTPSA id l18-20020a056a00141200b004f75395b2cesm18258153pfu.150.2022.03.13.21.43.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Mar 2022 21:43:08 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH 2/3] linux-user/arm: Implement __kernel_cmpxchg with host atomics Date: Sun, 13 Mar 2022 21:43:04 -0700 Message-Id: <20220314044305.138794-3-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220314044305.138794-1-richard.henderson@linaro.org> References: <20220314044305.138794-1-richard.henderson@linaro.org> MIME-Version: 1.0 X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::434 (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::434; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x434.google.com X-Spam_score_int: -6 X-Spam_score: -0.7 X-Spam_bar: / X-Spam_report: (-0.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-arm@nongnu.org, laurent@vivier.eu Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" The existing implementation using start/end_exclusive does not provide atomicity across processes. Signed-off-by: Richard Henderson Reviewed-by: Peter Maydell --- linux-user/arm/cpu_loop.c | 85 +++++++++++++++++++++++++++------------ 1 file changed, 60 insertions(+), 25 deletions(-) diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c index a0e43b261c..0122bb34f7 100644 --- a/linux-user/arm/cpu_loop.c +++ b/linux-user/arm/cpu_loop.c @@ -75,7 +75,65 @@ put_user_u16(__x, (gaddr)); \ }) -/* Commpage handling -- there is no commpage for AArch64 */ +/* + * Similar to code in accel/tcg/user-exec.c, but outside the execution loop. + * Must be called with mmap_lock. + */ +static void *atomic_mmu_lookup(CPUArchState *env, uint32_t addr, int size) +{ + int need_flags = PAGE_READ | PAGE_WRITE_ORG | PAGE_VALID; + int page_flags; + + /* Enforce guest required alignment. */ + if (unlikely(addr & (size - 1))) { + force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, addr); + return NULL; + } + + page_flags = page_get_flags(addr); + if (unlikely((page_flags & need_flags) != need_flags)) { + force_sig_fault(TARGET_SIGSEGV, + page_flags & PAGE_VALID ? + TARGET_SEGV_ACCERR : TARGET_SEGV_MAPERR, addr); + return NULL; + } + + return g2h(env_cpu(env), addr); +} + +/* + * See the Linux kernel's Documentation/arm/kernel_user_helpers.rst + * Input: + * r0 = oldval + * r1 = newval + * r2 = pointer to target value + * + * Output: + * r0 = 0 if *ptr was changed, non-0 if no exchange happened + * C set if *ptr was changed, clear if no exchange happened + */ +static void arm_kernel_cmpxchg32_helper(CPUARMState *env) +{ + uint32_t oldval, newval, val, addr, cpsr, *host_addr; + + oldval = env->regs[0]; + newval = env->regs[1]; + addr = env->regs[2]; + + mmap_lock(); + host_addr = atomic_mmu_lookup(env, addr, 8); + if (!host_addr) { + mmap_unlock(); + return; + } + + val = qatomic_cmpxchg__nocheck(host_addr, oldval, newval); + mmap_unlock(); + + cpsr = (val == oldval) * CPSR_C; + cpsr_write(env, cpsr, CPSR_C, CPSRWriteByInstr); + env->regs[0] = cpsr ? 0 : -1; +} /* * See the Linux kernel's Documentation/arm/kernel_user_helpers.txt @@ -153,36 +211,13 @@ static int do_kernel_trap(CPUARMState *env) { uint32_t addr; - uint32_t cpsr; - uint32_t val; switch (env->regs[15]) { case 0xffff0fa0: /* __kernel_memory_barrier */ smp_mb(); break; case 0xffff0fc0: /* __kernel_cmpxchg */ - /* XXX: This only works between threads, not between processes. - It's probably possible to implement this with native host - operations. However things like ldrex/strex are much harder so - there's not much point trying. */ - start_exclusive(); - cpsr = cpsr_read(env); - addr = env->regs[2]; - /* FIXME: This should SEGV if the access fails. */ - if (get_user_u32(val, addr)) - val = ~env->regs[0]; - if (val == env->regs[0]) { - val = env->regs[1]; - /* FIXME: Check for segfaults. */ - put_user_u32(val, addr); - env->regs[0] = 0; - cpsr |= CPSR_C; - } else { - env->regs[0] = -1; - cpsr &= ~CPSR_C; - } - cpsr_write(env, cpsr, CPSR_C, CPSRWriteByInstr); - end_exclusive(); + arm_kernel_cmpxchg32_helper(env); break; case 0xffff0fe0: /* __kernel_get_tls */ env->regs[0] = cpu_get_tls(env);