From nobody Fri Nov 14 19:47:03 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1761116045286535.9139371724266; Tue, 21 Oct 2025 23:54:05 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vBSjL-00062d-GL; Wed, 22 Oct 2025 02:53:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vBSjI-0005sf-Es for qemu-devel@nongnu.org; Wed, 22 Oct 2025 02:53:52 -0400 Received: from smtp233.sjtu.edu.cn ([202.120.2.233]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vBSjF-0007RF-QH for qemu-devel@nongnu.org; Wed, 22 Oct 2025 02:53:52 -0400 Received: from mta91.sjtu.edu.cn (unknown [10.118.0.91]) by smtp233.sjtu.edu.cn (Postfix) with ESMTPS id 58F02101B694A; Wed, 22 Oct 2025 14:53:42 +0800 (CST) Received: from mstore136.sjtu.edu.cn (unknown [10.118.0.136]) by mta91.sjtu.edu.cn (Postfix) with ESMTP id 1DBBF37C8FB; Wed, 22 Oct 2025 14:53:42 +0800 (CST) Date: Wed, 22 Oct 2025 14:53:41 +0800 (CST) From: Ziyang Zhang To: qemu-devel Cc: Riku Voipio , Laurent Vivier , alex bennee , Alexandre Iooss , Mahmoud Mandour , Pierrick Bouvier , richard henderson , Zhengwei Qi , Yun Wang , Mingyuan Xia , Kailiang Xu Message-ID: <1236223604.5812631.1761116021855.JavaMail.zimbra@sjtu.edu.cn> In-Reply-To: <1341969682.5812455.1761115945695.JavaMail.zimbra@sjtu.edu.cn> References: <1341969682.5812455.1761115945695.JavaMail.zimbra@sjtu.edu.cn> Subject: [RFC PATCH V2 1/2] linux-user: add a plugin API to filter syscalls MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [119.237.255.163] X-Mailer: Zimbra 10.0.14_GA_4767 (ZimbraWebClient - GC141 (Win)/10.0.15_GA_4781) Thread-Topic: linux-user: add a plugin API to filter syscalls Thread-Index: O8UVQ/TJHmck9snQ4N2r1rVTqb8mpN2MhtjX Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=202.120.2.233; envelope-from=functioner@sjtu.edu.cn; helo=smtp233.sjtu.edu.cn X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1761116049521158500 Content-Type: text/plain; charset="utf-8" This commit adds a syscall filter API to the TCG plugin API set. Plugins can register a filter callback to QEMU to decide whether to intercept a syscall, process it and bypass the QEMU syscall handler. Signed-off-by: Ziyang Zhang --- include/qemu/plugin-event.h | 1 + include/qemu/plugin.h | 28 ++++++++++++++++++++-------- include/qemu/qemu-plugin.h | 24 ++++++++++++++++++++++++ include/user/syscall-trace.h | 16 ++++++++++++++++ linux-user/syscall.c | 7 +++++-- plugins/api.c | 7 +++++++ plugins/core.c | 34 ++++++++++++++++++++++++++++++++++ 7 files changed, 107 insertions(+), 10 deletions(-) diff --git a/include/qemu/plugin-event.h b/include/qemu/plugin-event.h index 7056d8427b..bbb1c2b91f 100644 --- a/include/qemu/plugin-event.h +++ b/include/qemu/plugin-event.h @@ -20,6 +20,7 @@ enum qemu_plugin_event { QEMU_PLUGIN_EV_VCPU_SYSCALL_RET, QEMU_PLUGIN_EV_FLUSH, QEMU_PLUGIN_EV_ATEXIT, + QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER, QEMU_PLUGIN_EV_MAX, /* total number of plugin events we support */ }; =20 diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index f355c7cb8a..adba2ac49c 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -55,14 +55,15 @@ void qemu_plugin_opt_parse(const char *optstr, QemuPlug= inList *head); int qemu_plugin_load_list(QemuPluginList *head, Error **errp); =20 union qemu_plugin_cb_sig { - qemu_plugin_simple_cb_t simple; - qemu_plugin_udata_cb_t udata; - qemu_plugin_vcpu_simple_cb_t vcpu_simple; - qemu_plugin_vcpu_udata_cb_t vcpu_udata; - qemu_plugin_vcpu_tb_trans_cb_t vcpu_tb_trans; - qemu_plugin_vcpu_mem_cb_t vcpu_mem; - qemu_plugin_vcpu_syscall_cb_t vcpu_syscall; - qemu_plugin_vcpu_syscall_ret_cb_t vcpu_syscall_ret; + qemu_plugin_simple_cb_t simple; + qemu_plugin_udata_cb_t udata; + qemu_plugin_vcpu_simple_cb_t vcpu_simple; + qemu_plugin_vcpu_udata_cb_t vcpu_udata; + qemu_plugin_vcpu_tb_trans_cb_t vcpu_tb_trans; + qemu_plugin_vcpu_mem_cb_t vcpu_mem; + qemu_plugin_vcpu_syscall_cb_t vcpu_syscall; + qemu_plugin_vcpu_syscall_ret_cb_t vcpu_syscall_ret; + qemu_plugin_vcpu_syscall_filter_cb_t vcpu_syscall_filter; void *generic; }; =20 @@ -165,6 +166,10 @@ qemu_plugin_vcpu_syscall(CPUState *cpu, int64_t num, u= int64_t a1, uint64_t a2, uint64_t a3, uint64_t a4, uint64_t a= 5, uint64_t a6, uint64_t a7, uint64_t a8); void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret); +bool +qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1, + uint64_t a2, uint64_t a3, uint64_t a4, uint64_t a= 5, + uint64_t a6, uint64_t a7, uint64_t a8, uint64_t *= ret); =20 void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr, uint64_t value_low, @@ -267,6 +272,13 @@ static inline void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret) { } =20 +static inline bool +qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1, + uint64_t a2, uint64_t a3, uint64_t a4, + uint64_t a5, uint64_t a6, uint64_t a7, + uint64_t a8, uint64_t *ret) +{ } + static inline void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr, uint64_t value_low, uint64_t value_high, diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h index c450106af1..719b070e32 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -738,6 +738,25 @@ typedef void uint64_t a3, uint64_t a4, uint64_t a5, uint64_t a6, uint64_t a7, uint64_t a8); =20 +/* + * typedef qemu_plugin_vcpu_syscall_filter_cb_t - vCPU syscall filter call= back + * function type + * @vcpu_index: the executing vCPU + * @num: the syscall number + * @a1-a8: the syscall arguments + * @ret: the address of the syscall return value, set this if filtered + * + * Returns: true if you want to filter this syscall (i.e. stop it being ha= ndled + * further), otherwise return false. + */ +typedef bool +(*qemu_plugin_vcpu_syscall_filter_cb_t)(qemu_plugin_id_t id, + unsigned int vcpu_index, + int64_t num, uint64_t a1, uint64_t a2, + uint64_t a3, uint64_t a4, uint64_t a5, + uint64_t a6, uint64_t a7, uint64_t a8, + uint64_t *ret); + QEMU_PLUGIN_API void qemu_plugin_register_vcpu_syscall_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_cb_t cb= ); @@ -751,6 +770,11 @@ void qemu_plugin_register_vcpu_syscall_ret_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_ret_cb_t= cb); =20 +QEMU_PLUGIN_API +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filter_cb_t c= b); + =20 /** * qemu_plugin_insn_disas() - return disassembly string for instruction diff --git a/include/user/syscall-trace.h b/include/user/syscall-trace.h index 9bd7ca19c8..34f7d6c7d4 100644 --- a/include/user/syscall-trace.h +++ b/include/user/syscall-trace.h @@ -39,5 +39,21 @@ static inline void record_syscall_return(CPUState *cpu, = int num, abi_long ret) gdb_syscall_return(cpu, num); } =20 +static inline bool send_through_syscall_filters(CPUState *cpu, int num, + abi_long arg1, abi_long arg2, + abi_long arg3, abi_long arg4, + abi_long arg5, abi_long arg6, + abi_long arg7, abi_long arg8, abi_long *= ret) +{ + uint64_t sysret64 =3D 0; + bool filtered =3D qemu_plugin_vcpu_syscall_filter(cpu, num, + arg1, arg2, arg3, arg4, + arg5, arg6, arg7, arg8, &sysret64); + if (filtered) { + *ret =3D sysret64; + } + return filtered; +} + =20 #endif /* SYSCALL_TRACE_H */ diff --git a/linux-user/syscall.c b/linux-user/syscall.c index d78b2029fa..b8225f838f 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -14084,8 +14084,11 @@ abi_long do_syscall(CPUArchState *cpu_env, int num= , abi_long arg1, print_syscall(cpu_env, num, arg1, arg2, arg3, arg4, arg5, arg6); } =20 - ret =3D do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, - arg5, arg6, arg7, arg8); + if (!send_through_syscall_filters(cpu, num, arg1, arg2, arg3, arg4, ar= g5, + arg6, arg7, arg8, &ret)) { + ret =3D do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, + arg5, arg6, arg7, arg8); + } =20 if (unlikely(qemu_loglevel_mask(LOG_STRACE))) { print_syscall_ret(cpu_env, num, ret, arg1, arg2, diff --git a/plugins/api.c b/plugins/api.c index eac04cc1f6..478d0c8889 100644 --- a/plugins/api.c +++ b/plugins/api.c @@ -208,6 +208,13 @@ qemu_plugin_register_vcpu_syscall_ret_cb(qemu_plugin_i= d_t id, plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_SYSCALL_RET, cb); } =20 +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filte= r_cb_t cb) +{ + plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER, cb); +} + /* * Plugin Queries * diff --git a/plugins/core.c b/plugins/core.c index ead09fd2f1..1b2f875fb1 100644 --- a/plugins/core.c +++ b/plugins/core.c @@ -538,6 +538,40 @@ void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64= _t num, int64_t ret) } } =20 +/* + * Disable CFI checks. + * The callback function has been loaded from an external library so we do= not + * have type information + */ +QEMU_DISABLE_CFI +bool +qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1, + uint64_t a2, uint64_t a3, uint64_t a4, uint64_t a= 5, + uint64_t a6, uint64_t a7, uint64_t a8, uint64_t *= ret) +{ + struct qemu_plugin_cb *cb, *next; + enum qemu_plugin_event ev =3D QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER; + + if (!test_bit(ev, cpu->plugin_state->event_mask)) { + return false; + } + + bool filtered =3D false; + QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) { + qemu_plugin_vcpu_syscall_filter_cb_t func =3D cb->f.vcpu_syscall_f= ilter; + + qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS); + if (func(cb->ctx->id, cpu->cpu_index, num, a1, a2, a3, a4, + a5, a6, a7, a8, ret)) { + filtered =3D true; + qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS); + break; + } + qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS); + } + return filtered; +} + void qemu_plugin_vcpu_idle_cb(CPUState *cpu) { /* idle and resume cb may be called before init, ignore in this case */ --=20 2.25.1