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[209.51.188.17]) by mx.google.com with ESMTPS id m206si29513848ybc.141.2021.07.23.10.09.04 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 23 Jul 2021 10:09:04 -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=LKFLa8Wb; 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]:51916 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m6yfY-0003Gg-5H for patch@linaro.org; Fri, 23 Jul 2021 13:09:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58610) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m6ybr-0002Vm-3t for qemu-devel@nongnu.org; Fri, 23 Jul 2021 13:05:15 -0400 Received: from mail-wr1-x42e.google.com ([2a00:1450:4864:20::42e]:43695) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1m6ybp-0005uw-Ba for qemu-devel@nongnu.org; Fri, 23 Jul 2021 13:05:14 -0400 Received: by mail-wr1-x42e.google.com with SMTP id y8so3050719wrt.10 for ; Fri, 23 Jul 2021 10:05:12 -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=s69863l+rWiDp6mDSn3ApZU/tImeUHpGRfgaMe+i8/A=; b=LKFLa8WbOWQoaIfHMMrepR1LYHfYslOyuftmybS6WbDOmApNueF8zdAQkMjLiXoEsf pdwQ9+Zoh/dGBhtHhPDpUJvmLs7EDDf2K+J6uRnZ3PmFASsw9F190B6DOExi5S6XNJ5f bojt03GjMOfiFFB7fk6jlHMeF3zpCC7uBYMA6s4he7rCtUnhY6l0jLRKtCkI9vlDP79o YfoxlXN9RAhsqO1u9vZZymU7eHpoRgkz+XkkGYFDKa7nBl6IpTRjXxZ8phV5LDWS257K xJ7MOn75Ky9oBXw2oRHdNXEHVU6msgPwSXtZzfX9Av+i/yF+2vxczuKHgxuCbOayd0Xy yzsQ== 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=s69863l+rWiDp6mDSn3ApZU/tImeUHpGRfgaMe+i8/A=; b=VTIGd7CBEsXZectqJRqISTRuF10FRiqjxEzRrtYa6K04s6q0t9EknGPhmp9yvfDDBL 3sE0IQlOisTpRgTfTPudd52EYadzy2lSKzNd91pc4barU7/mOo8ySGkdmHT2jsJEdz2F HAwifCwmJf3E+u4EcfGP481nR6V6s14FRzHepXQXKfSoQEFOvgOo1DtluPfG09iTzOhO kW9JRFatpLTVDA29BcLMgVGTQthkTxieUOFlzDADGotXpxXvUihPiL++uaBYXTJPg0zx Rjg6d6rhuSuCUYsh4s4qYknrrhnMtFoMbhC3e9cULhtHwcIbGpqDK7ykwgvgEvC/RGV/ /VYw== X-Gm-Message-State: AOAM533vjw7psDmzi7Ra+ZeCkR3hJimb+RpZ4EkeaOCRaGPmyLukjMmr hLlhnUTe+3IEPoIs0cWE1t+87g== X-Received: by 2002:a5d:504d:: with SMTP id h13mr6383926wrt.46.1627059912167; Fri, 23 Jul 2021 10:05:12 -0700 (PDT) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id a8sm33471312wrt.61.2021.07.23.10.04.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Jul 2021 10:04:39 -0700 (PDT) Received: from zen.lan (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 13C231FFAA; Fri, 23 Jul 2021 18:03:56 +0100 (BST) From: =?utf-8?q?Alex_Benn=C3=A9e?= To: peter.maydell@linaro.org Subject: [PULL 20/28] tcg/plugins: implement a qemu_plugin_user_exit helper Date: Fri, 23 Jul 2021 18:03:46 +0100 Message-Id: <20210723170354.18975-21-alex.bennee@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210723170354.18975-1-alex.bennee@linaro.org> References: <20210723170354.18975-1-alex.bennee@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::42e; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x42e.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: Kyle Evans , qemu-devel@nongnu.org, Laurent Vivier , Alexandre Iooss , Mahmoud Mandour , =?utf-8?q?Alex_Benn=C3=A9e?= , Warner Losh 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: <20210720232703.10650-21-alex.bennee@linaro.org> -- 2.20.1 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 474db287cb..6b2490f973 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