From patchwork Tue Jul 20 23:26:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Alex_Benn=C3=A9e?= X-Patchwork-Id: 481697 Delivered-To: patch@linaro.org Received: by 2002:a17:907:d92:0:0:0:0 with SMTP id go18csp6019306ejc; Tue, 20 Jul 2021 16:52:11 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzDmY4KyXQoEHGDIMb+Yck3ZjZqI2oHjzDCYq+6mkV80NkZgHHTkYsFJhrNTI6ESWNRx0ek X-Received: by 2002:a25:e74f:: with SMTP id e76mr42015576ybh.386.1626825131647; Tue, 20 Jul 2021 16:52:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1626825131; cv=none; d=google.com; s=arc-20160816; b=QnJhirY7xyCl45RK0dfoo6PFVBJh/7Zmyna5SeqDSMstiZsi/nw2e0yvyHz9LpiC49 Y62mjufNrcbwSRlZ6O+zxasCDBwV1nQxGns+h6kBr4JxjQ30fJf8XNnYcIRVsj+Mvslp 0lgFiIFmOivgKPD0H3iOWqAmmxsT7NhewVhfiwn98R1JFfaqCqPn/xPbgBEIYXLCngqz pW9b7ouAUVEIrr4QyLJovAogIOfT/QzwCNs5AaFG1NyWEZUNrfKkMOZ7Tpi1n3SyuHdW LH+rqOarhOpjtVg+beke4OZtoP3lQjidYHXQB/SStTPeuBhapSpoTrl38Gw6sGh0Wh+I YAIQ== 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=N+lakEhYS4oxmf5efRPjQRugCOsER/QmZt+iu9N5l1M=; b=nfy2/swWV8GuJ6g6m1qeRXu2fBSfeS8WiYN5kD74fdjse1coBkBPE1hoNzw/+1G6Rz /IMUFzcnmCM7DEIk/R0ukLcTPIQ0vo1WlzwTwG4X7NmgcJblYcZt0tTUTwzOGf4RUqCf Ua135f4tHlpxEzKlJdTi9glNIea133MV0WWwMVo2TfZY9GHPmO0vre3tfFM8IcpycJrD KMJpkWHeoOwGO6Ar/vpf2HpCv+HrFZpISth3rPXdrlZReTDIoaLmSsyj40qBkg+S84Ah xs4yxdpWa8SkumPPJk9Xg1ANF0DE8BWTX4mT5BiAwXQFSv+Zt/aCYERxJYTXHLReJXfS 5uOQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=fail header.i=@linaro.org header.s=google header.b=T2OG26Co; 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=fail (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 r8si21406468ybp.312.2021.07.20.16.52.11 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 20 Jul 2021 16:52:11 -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=fail header.i=@linaro.org header.s=google header.b=T2OG26Co; 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=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from localhost ([::1]:43066 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m5zX1-0004HN-1K for patch@linaro.org; Tue, 20 Jul 2021 19:52:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43860) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m5zPT-0004tJ-US for qemu-devel@nongnu.org; Tue, 20 Jul 2021 19:44:26 -0400 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]:45814) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1m5zPR-00085z-I4 for qemu-devel@nongnu.org; Tue, 20 Jul 2021 19:44:23 -0400 Received: by mail-wm1-x32a.google.com with SMTP id u8-20020a7bcb080000b02901e44e9caa2aso480437wmj.4 for ; Tue, 20 Jul 2021 16:44:21 -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=N+lakEhYS4oxmf5efRPjQRugCOsER/QmZt+iu9N5l1M=; b=T2OG26Coe4kAlPQsnKm0EHNi/2k8BNvvdnPXWZPv5T5ANHjFUDTwttwF8T69wOQBx4 u8P6SDshStLch9uPuDHORM26el8/QQFHgufzweMOb3YIgzD+JSr02YONGTjEtDHz11fB mQjtWAz8MOGwCOk2ivwmpNeygxxTRVxLvH+TQVKPYotv9PEZbqNzyssngv51vIWmj6Px TZ3+DXrQPArjOTl7q3mZaqlImoj1+3FMTlPFKmFmuRXxGShNV7wJVwuvx1VBzSDIe/UV lIeijZi2tr3CNxFLxw0OeNHAGIRgn+7H9pcTpo3Lo25OT/iczj8eF7oHCOKgXHI0+HIk vVEg== 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=N+lakEhYS4oxmf5efRPjQRugCOsER/QmZt+iu9N5l1M=; b=TBC87kvMSXDwT6JezTWnKSFkTkMPXpuZXLWRRqJ2OaeLfUHQoNlLvneVkkca28/Ry9 TnArL+fsG5N7et+WJrRzq47Ul3kZ6QUexDpMzw47XrEP48spDq1viv72Qnnh8V5ZWuun yBIssKMEhfiik1ejueelNwxIdXj42a1oVjo5BLQcLRCuv45sV6rhmJf9f2C0+N+OJtxd REqIGg0lHZlDxW8Ch48+Rx+M2so6F5XexTlBRQihtpNUIgKziwxmT1r8opDw5QALIBiD EfC4hDOtnMGKEvZ2oXSWnJB9YXaU0+EmWrJ1pHYHGZl1ORwYw4fYBp0Ax9xAdmBKzdXf +eSg== X-Gm-Message-State: AOAM530FH8zuXcxvDeVleMIRmxpLGV5xCQxwXYY875yEQFcem81FOOQk nr5Qgyry9x0ahrvVxfBTYNbwWw== X-Received: by 2002:a1c:cc02:: with SMTP id h2mr33828976wmb.39.1626824659674; Tue, 20 Jul 2021 16:44:19 -0700 (PDT) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id e11sm30953346wrt.0.2021.07.20.16.44.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jul 2021 16:44:18 -0700 (PDT) Received: from zen.lan (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id B01A91FFA9; Wed, 21 Jul 2021 00:27:05 +0100 (BST) From: =?utf-8?q?Alex_Benn=C3=A9e?= To: qemu-devel@nongnu.org Subject: [PATCH v1 20/29] tcg/plugins: implement a qemu_plugin_user_exit helper Date: Wed, 21 Jul 2021 00:26:54 +0100 Message-Id: <20210720232703.10650-21-alex.bennee@linaro.org> X-Mailer: git-send-email 2.32.0.264.g75ae10bc75 In-Reply-To: <20210720232703.10650-1-alex.bennee@linaro.org> References: <20210720232703.10650-1-alex.bennee@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x32a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fam@euphon.net, berrange@redhat.com, Kyle Evans , f4bug@amsat.org, Laurent Vivier , Warner Losh , stefanha@redhat.com, crosa@redhat.com, pbonzini@redhat.com, Mahmoud Mandour , Alexandre Iooss , =?utf-8?q?Alex_Benn=C3=A9e?= , aurelien@aurel32.net Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" In user-mode emulation there is a small race between preexit_cleanup and exit_group() which means we may end up calling instrumented instructions before the kernel reaps child threads. To solve this we implement a new helper which ensures the callbacks are flushed along with any translations before we let the host do it's a thing. While we are at it make the documentation of qemu_plugin_register_atexit_cb clearer as to what the user can expect. Signed-off-by: Alex Bennée Reviewed-by: Mahmoud Mandour Acked-by: Warner Losh Message-Id: <20210719123732.24457-1-alex.bennee@linaro.org> --- v2 - included qemu_plugin_disable_mem_helpers --- include/qemu/plugin.h | 12 ++++++++++++ include/qemu/qemu-plugin.h | 13 +++++++++++++ bsd-user/syscall.c | 6 +++--- linux-user/exit.c | 2 +- plugins/core.c | 39 ++++++++++++++++++++++++++++++++++++++ 5 files changed, 68 insertions(+), 4 deletions(-) -- 2.32.0.264.g75ae10bc75 diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index 0fefbc6084..9a8438f683 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -190,6 +190,16 @@ void qemu_plugin_add_dyn_cb_arr(GArray *arr); void qemu_plugin_disable_mem_helpers(CPUState *cpu); +/** + * qemu_plugin_user_exit(): clean-up callbacks before calling exit callbacks + * + * This is a user-mode only helper that ensure we have fully cleared + * callbacks from all threads before calling the exit callbacks. This + * is so the plugins themselves don't have to jump through hoops to + * guard against race conditions. + */ +void qemu_plugin_user_exit(void); + #else /* !CONFIG_PLUGIN */ static inline void qemu_plugin_add_opts(void) @@ -250,6 +260,8 @@ void qemu_plugin_add_dyn_cb_arr(GArray *arr) static inline void qemu_plugin_disable_mem_helpers(CPUState *cpu) { } +static inline void qemu_plugin_user_exit(void) +{ } #endif /* !CONFIG_PLUGIN */ #endif /* QEMU_PLUGIN_H */ diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h index dc3496f36c..e6e815abc5 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -549,6 +549,19 @@ void qemu_plugin_vcpu_for_each(qemu_plugin_id_t id, void qemu_plugin_register_flush_cb(qemu_plugin_id_t id, qemu_plugin_simple_cb_t cb); +/** + * qemu_plugin_register_atexit_cb() - register exit callback + * @id: plugin ID + * @cb: callback + * @userdata: user data for callback + * + * The @cb function is called once execution has finished. Plugins + * should be able to free all their resources at this point much like + * after a reset/uninstall callback is called. + * + * In user-mode it is possible a few un-instrumented instructions from + * child threads may run before the host kernel reaps the threads. + */ void qemu_plugin_register_atexit_cb(qemu_plugin_id_t id, qemu_plugin_udata_cb_t cb, void *userdata); diff --git a/bsd-user/syscall.c b/bsd-user/syscall.c index 7d986e9700..3f44311396 100644 --- a/bsd-user/syscall.c +++ b/bsd-user/syscall.c @@ -335,7 +335,7 @@ abi_long do_freebsd_syscall(void *cpu_env, int num, abi_long arg1, _mcleanup(); #endif gdb_exit(arg1); - qemu_plugin_atexit_cb(); + qemu_plugin_user_exit(); /* XXX: should free thread stack and CPU env */ _exit(arg1); ret = 0; /* avoid warning */ @@ -437,7 +437,7 @@ abi_long do_netbsd_syscall(void *cpu_env, int num, abi_long arg1, _mcleanup(); #endif gdb_exit(arg1); - qemu_plugin_atexit_cb(); + qemu_plugin_user_exit(); /* XXX: should free thread stack and CPU env */ _exit(arg1); ret = 0; /* avoid warning */ @@ -516,7 +516,7 @@ abi_long do_openbsd_syscall(void *cpu_env, int num, abi_long arg1, _mcleanup(); #endif gdb_exit(arg1); - qemu_plugin_atexit_cb(); + qemu_plugin_user_exit(); /* XXX: should free thread stack and CPU env */ _exit(arg1); ret = 0; /* avoid warning */ diff --git a/linux-user/exit.c b/linux-user/exit.c index 70b344048c..527e29cbc1 100644 --- a/linux-user/exit.c +++ b/linux-user/exit.c @@ -35,5 +35,5 @@ void preexit_cleanup(CPUArchState *env, int code) __gcov_dump(); #endif gdb_exit(code); - qemu_plugin_atexit_cb(); + qemu_plugin_user_exit(); } diff --git a/plugins/core.c b/plugins/core.c index e1bcdb570d..7cf4f87e18 100644 --- a/plugins/core.c +++ b/plugins/core.c @@ -487,6 +487,45 @@ void qemu_plugin_register_atexit_cb(qemu_plugin_id_t id, plugin_register_cb_udata(id, QEMU_PLUGIN_EV_ATEXIT, cb, udata); } +/* + * Handle exit from linux-user. Unlike the normal atexit() mechanism + * we need to handle the clean-up manually as it's possible threads + * are still running. We need to remove all callbacks from code + * generation, flush the current translations and then we can safely + * trigger the exit callbacks. + */ + +void qemu_plugin_user_exit(void) +{ + enum qemu_plugin_event ev; + CPUState *cpu; + + QEMU_LOCK_GUARD(&plugin.lock); + + start_exclusive(); + + /* un-register all callbacks except the final AT_EXIT one */ + for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) { + if (ev != QEMU_PLUGIN_EV_ATEXIT) { + struct qemu_plugin_ctx *ctx; + QTAILQ_FOREACH(ctx, &plugin.ctxs, entry) { + plugin_unregister_cb__locked(ctx, ev); + } + } + } + + tb_flush(current_cpu); + + CPU_FOREACH(cpu) { + qemu_plugin_disable_mem_helpers(cpu); + } + + end_exclusive(); + + /* now it's safe to handle the exit case */ + qemu_plugin_atexit_cb(); +} + /* * Call this function after longjmp'ing to the main loop. It's possible that the * last instruction of a TB might have used helpers, and therefore the