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Mon, 14 Jun 2021 10:04:40 -0700 (PDT) Received: from [192.168.1.7] ([102.41.174.214]) by smtp.gmail.com with ESMTPSA id w13sm13324986wmi.48.2021.06.14.10.04.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jun 2021 10:04:40 -0700 (PDT) Subject: Re: [PATCH] contrib/plugins: add execlog to log instruction execution and memory access To: Alexandre Iooss , "open list:All patches CC here" References: <20210614090116.816833-1-erdnaxe@crans.org> From: Mahmoud Mandour Message-ID: Date: Mon, 14 Jun 2021 19:04:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210614090116.816833-1-erdnaxe@crans.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=2a00:1450:4864:20::42e; envelope-from=ma.mandourr@gmail.com; helo=mail-wr1-x42e.google.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 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, FREEMAIL_FROM=0.001, NICE_REPLY_A=-0.489, 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: =?UTF-8?Q?Alex_Benn=c3=a9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 14/06/2021 11:01, Alexandre Iooss wrote: > Log instruction execution and memory access to a file. > This plugin can be used for reverse engineering or for side-channel analysis > using QEMU. > > Signed-off-by: Alexandre Iooss > --- > MAINTAINERS | 1 + > contrib/plugins/Makefile | 1 + > contrib/plugins/execlog.c | 112 ++++++++++++++++++++++++++++++++++++++ > 3 files changed, 114 insertions(+) > create mode 100644 contrib/plugins/execlog.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 7d9cd29042..65942d5802 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2974,6 +2974,7 @@ F: include/tcg/ > > TCG Plugins > M: Alex Bennée > +R: Alexandre Iooss > S: Maintained > F: docs/devel/tcg-plugins.rst > F: plugins/ > diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile > index b9d7935e5e..51093acd17 100644 > --- a/contrib/plugins/Makefile > +++ b/contrib/plugins/Makefile > @@ -13,6 +13,7 @@ include $(BUILD_DIR)/config-host.mak > VPATH += $(SRC_PATH)/contrib/plugins > > NAMES := > +NAMES += execlog > NAMES += hotblocks > NAMES += hotpages > NAMES += howvec > diff --git a/contrib/plugins/execlog.c b/contrib/plugins/execlog.c > new file mode 100644 > index 0000000000..80716e8eed > --- /dev/null > +++ b/contrib/plugins/execlog.c > @@ -0,0 +1,112 @@ > +/* > + * Copyright (C) 2021, Alexandre Iooss > + * > + * Log instruction execution and memory access to a file. > + * You may pass the output filename as argument. > + * > + * License: GNU GPL, version 2 or later. > + * See the COPYING file in the top-level directory. > + */ > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include > + > +QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION; > + > +/* Execution trace buffer */ > +FILE *output; Is there a reason for using a regular FILE * instead of using `qemu_plugin_outs()`? I don't see a benefit and since there's an API for logging I guess it's better to use it instead > + > +/** > + * Log memory read or write > + */ > +static void vcpu_mem(unsigned int vcpu_index, qemu_plugin_meminfo_t info, > + uint64_t vaddr, void *udata) > +{ > + struct qemu_plugin_hwaddr *hwaddr = qemu_plugin_get_hwaddr(info, vaddr); > + if (!hwaddr) { > + return; > + } So you just reject all memory accesses in user mode? I think that it equally useful to log only the virtual address of a memory access in user-mode emulation? However, we better wait for Alex's opinion on all this since he had remarks about introducing a new ad-hoc tracing format... > + > + /* Add data to execution log */ > + const char *name = qemu_plugin_hwaddr_device_name(hwaddr); > + uint64_t addr = qemu_plugin_hwaddr_phys_addr(hwaddr); > + if (qemu_plugin_mem_is_store(info)) { > + fprintf(output, "mem: %s store at 0x%08lx\n", name, addr); > + } else { > + fprintf(output, "mem: %s load at 0x%08lx\n", name, addr); > + } > +} > + > +/** > + * Log instruction execution > + */ > +static void vcpu_insn_exec(unsigned int cpu_index, void *udata) > +{ > + char *insn_disas = (char *)udata; > + > + /* Add data to execution log */ > + fprintf(output, "insn: %s\n", insn_disas); > +} > + > +/** > + * On translation block new translation > + * > + * QEMU convert code by translation block (TB). By hooking here we can then hook > + * a callback on each instruction and memory access. > + */ > +static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb) > +{ > + size_t n = qemu_plugin_tb_n_insns(tb); > + for (size_t i = 0; i < n; i++) { > + /* insn is shared between translations in QEMU, copy needed data here */ > + struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i); > + char *insn_disas = qemu_plugin_insn_disas(insn); > + > + /* Register callback on memory read or write */ > + qemu_plugin_register_vcpu_mem_cb(insn, vcpu_mem, > + QEMU_PLUGIN_CB_NO_REGS, > + QEMU_PLUGIN_MEM_RW, NULL); > + > + /* Register callback on instruction */ > + qemu_plugin_register_vcpu_insn_exec_cb( > + insn, vcpu_insn_exec, QEMU_PLUGIN_CB_R_REGS, insn_disas); > + } > +} > + > +/** > + * On plugin exit, close output file > + */ > +static void plugin_exit(qemu_plugin_id_t id, void *p) > +{ > + fclose(output); > +} > + > +/** > + * Install the plugin > + */ > +QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id, > + const qemu_info_t *info, int argc, > + char **argv) > +{ > + /* Parse arguments to get output name and open for writing */ > + char *filename = "execution.log"; > + if (argc > 0) { > + filename = argv[0]; > + } > + output = fopen(filename, "w"); > + if (output == NULL) { > + qemu_plugin_outs("Cannot open output file for writing.\n"); Here, I think that it's more logical to output error messages to stderr since logging can be redirected to a file so QEMU will error but the error message would be written to the log file. > + return -1; > + } > + > + /* Register translation block and exit callbacks */ > + qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans); > + qemu_plugin_register_atexit_cb(id, plugin_exit, NULL); > + > + return 0; > +} Thanks, Mahmoud