* [PATCH v3 0/2] linux-user: add plugin API to filter syscalls @ 2025-12-14 14:19 Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 1/2] " Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 2/2] tcg tests: add a test to verify the syscall filter plugin API Ziyang Zhang 0 siblings, 2 replies; 4+ messages in thread From: Ziyang Zhang @ 2025-12-14 14:19 UTC (permalink / raw) 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, Ziyang Zhang We choose a smaller magic syscall number to avoid the illegal instruction exception [1] on qemu-arm. PATCH v3: 1. Change to a smaller magic syscall number and add comments 2. Set register flags out of the for-loop PATCH v2: 1. Rebased on newest version of master PATCH v1: 1. Format the code RFC v2: 1. Simplify the syscall filter mechanism and remove fork-cpu 2. Add QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER enum RFC v1: 1. Add syscall filter registry 2. Add fork-cpu interface to re-enter cpu_loop when handling syscalls [1] https://lore.kernel.org/qemu-devel/20251212141541.1792111-1-functioner@sjtu.edu.cn/T/#m0e6809c5a894d64a8b7e67324a4b7cb414c644bf Ziyang Zhang (2): linux-user: add plugin API to filter syscalls tcg tests: add a test to verify the syscall filter plugin API include/qemu/plugin-event.h | 1 + include/qemu/plugin.h | 33 ++++++++++++----- include/qemu/qemu-plugin.h | 32 ++++++++++++++++ include/user/syscall-trace.h | 17 +++++++++ linux-user/syscall.c | 7 +++- plugins/api.c | 7 ++++ plugins/core.c | 37 +++++++++++++++++++ tests/tcg/multiarch/Makefile.target | 4 +- .../multiarch/test-plugin-syscall-filter.c | 35 ++++++++++++++++++ tests/tcg/plugins/syscall.c | 19 ++++++++++ 10 files changed, 180 insertions(+), 12 deletions(-) create mode 100644 tests/tcg/multiarch/test-plugin-syscall-filter.c -- 2.34.1 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v3 1/2] linux-user: add plugin API to filter syscalls 2025-12-14 14:19 [PATCH v3 0/2] linux-user: add plugin API to filter syscalls Ziyang Zhang @ 2025-12-14 14:19 ` Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 2/2] tcg tests: add a test to verify the syscall filter plugin API Ziyang Zhang 1 sibling, 0 replies; 4+ messages in thread From: Ziyang Zhang @ 2025-12-14 14:19 UTC (permalink / raw) 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, Ziyang Zhang 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 <functioner@sjtu.edu.cn> Co-authored-by: Mingyuan Xia <xiamy@ultrarisc.com> --- include/qemu/plugin-event.h | 1 + include/qemu/plugin.h | 33 +++++++++++++++++++++++--------- include/qemu/qemu-plugin.h | 32 +++++++++++++++++++++++++++++++ include/user/syscall-trace.h | 17 +++++++++++++++++ linux-user/syscall.c | 7 +++++-- plugins/api.c | 7 +++++++ plugins/core.c | 37 ++++++++++++++++++++++++++++++++++++ 7 files changed, 123 insertions(+), 11 deletions(-) diff --git a/include/qemu/plugin-event.h b/include/qemu/plugin-event.h index 1100dae212..7f3c5927f1 100644 --- a/include/qemu/plugin-event.h +++ b/include/qemu/plugin-event.h @@ -23,6 +23,7 @@ enum qemu_plugin_event { QEMU_PLUGIN_EV_VCPU_INTERRUPT, QEMU_PLUGIN_EV_VCPU_EXCEPTION, QEMU_PLUGIN_EV_VCPU_HOSTCALL, + QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER, QEMU_PLUGIN_EV_MAX, /* total number of plugin events we support */ }; diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index cea0a68858..91df1e78d2 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -55,15 +55,16 @@ void qemu_plugin_opt_parse(const char *optstr, QemuPluginList *head); int qemu_plugin_load_list(QemuPluginList *head, Error **errp); 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_discon_cb_t vcpu_discon; - 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_discon_cb_t vcpu_discon; + 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; }; @@ -169,6 +170,11 @@ qemu_plugin_vcpu_syscall(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); 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 a5, uint64_t a6, uint64_t a7, + uint64_t a8, uint64_t *ret); void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr, uint64_t value_low, @@ -280,6 +286,15 @@ static inline void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret) { } +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) +{ + return false; +} + 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 60de4fdd3f..f3bff82257 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -798,6 +798,33 @@ typedef void uint64_t a3, uint64_t a4, uint64_t a5, uint64_t a6, uint64_t a7, uint64_t a8); +/** + * typedef qemu_plugin_vcpu_syscall_filter_cb_t - vCPU syscall filter callback + * function type + * @id: plugin id + * @vcpu_index: the executing vCPU + * @num: the syscall number + * @a1: the 1st syscall argument + * @a2: the 2nd syscall argument + * @a3: the 3rd syscall argument + * @a4: the 4th syscall argument + * @a5: the 5th syscall argument + * @a6: the 6th syscall argument + * @a7: the 7th syscall argument + * @a8: the 8th syscall argument + * @sysret: the reference of the syscall return value, must set this if filtered + * + * Returns true if you want to filter this syscall (i.e. stop it being + * handled further), otherwise returns 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 *sysret); + QEMU_PLUGIN_API void qemu_plugin_register_vcpu_syscall_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_cb_t cb); @@ -811,6 +838,11 @@ void qemu_plugin_register_vcpu_syscall_ret_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_ret_cb_t cb); +QEMU_PLUGIN_API +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filter_cb_t cb); + /** * 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..4ee6c4e513 100644 --- a/include/user/syscall-trace.h +++ b/include/user/syscall-trace.h @@ -39,5 +39,22 @@ static inline void record_syscall_return(CPUState *cpu, int num, abi_long ret) gdb_syscall_return(cpu, num); } +static 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 *sysret) +{ + uint64_t sysret64 = 0; + bool filtered = qemu_plugin_vcpu_syscall_filter(cpu, num, arg1, arg2, + arg3, arg4, arg5, arg6, + arg7, arg8, &sysret64); + if (filtered) { + *sysret = sysret64; + } + return filtered; +} + #endif /* SYSCALL_TRACE_H */ diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 2060e561a2..9ae3c5bfbd 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -14201,8 +14201,11 @@ abi_long do_syscall(CPUArchState *cpu_env, int num, abi_long arg1, print_syscall(cpu_env, num, arg1, arg2, arg3, arg4, arg5, arg6); } - ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, - arg5, arg6, arg7, arg8); + if (!send_through_syscall_filters(cpu, num, arg1, arg2, arg3, arg4, arg5, + arg6, arg7, arg8, &ret)) { + ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, + arg5, arg6, arg7, arg8); + } 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_id_t id, plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_SYSCALL_RET, cb); } +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filter_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 b4b783008f..85fabf9ec8 100644 --- a/plugins/core.c +++ b/plugins/core.c @@ -564,6 +564,43 @@ void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret) } } +/* + * 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 a5, uint64_t a6, uint64_t a7, + uint64_t a8, uint64_t *sysret) +{ + struct qemu_plugin_cb *cb, *next; + enum qemu_plugin_event ev = QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER; + bool filtered = false; + + if (!test_bit(ev, cpu->plugin_state->event_mask)) { + return false; + } + + qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS); + + QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) { + qemu_plugin_vcpu_syscall_filter_cb_t func = cb->f.vcpu_syscall_filter; + + if (func(cb->ctx->id, cpu->cpu_index, num, a1, a2, a3, a4, + a5, a6, a7, a8, sysret)) { + filtered = true; + 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 */ -- 2.34.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v3 2/2] tcg tests: add a test to verify the syscall filter plugin API 2025-12-14 14:19 [PATCH v3 0/2] linux-user: add plugin API to filter syscalls Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 1/2] " Ziyang Zhang @ 2025-12-14 14:19 ` Ziyang Zhang 1 sibling, 0 replies; 4+ messages in thread From: Ziyang Zhang @ 2025-12-14 14:19 UTC (permalink / raw) 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, Ziyang Zhang Register a syscall filter callback in tests/tcg/plugins/sycall.c, returns a specific value for a magic system call number, and check it in tests/tcg/multiarch/test-plugin-syscall-filter.c. Signed-off-by: Ziyang Zhang <functioner@sjtu.edu.cn> Co-authored-by: Mingyuan Xia <xiamy@ultrarisc.com> --- tests/tcg/multiarch/Makefile.target | 4 ++- .../multiarch/test-plugin-syscall-filter.c | 35 +++++++++++++++++++ tests/tcg/plugins/syscall.c | 19 ++++++++++ 3 files changed, 57 insertions(+), 1 deletion(-) create mode 100644 tests/tcg/multiarch/test-plugin-syscall-filter.c diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target index f5b4d2b813..4005e3a8a9 100644 --- a/tests/tcg/multiarch/Makefile.target +++ b/tests/tcg/multiarch/Makefile.target @@ -202,8 +202,10 @@ run-plugin-test-plugin-mem-access-with-libmem.so: \ CHECK_PLUGIN_OUTPUT_COMMAND= \ $(SRC_PATH)/tests/tcg/multiarch/check-plugin-output.sh \ $(QEMU) $< +run-plugin-test-plugin-syscall-filter-with-libsyscall.so: -EXTRA_RUNS_WITH_PLUGIN += run-plugin-test-plugin-mem-access-with-libmem.so +EXTRA_RUNS_WITH_PLUGIN += run-plugin-test-plugin-mem-access-with-libmem.so \ + run-plugin-test-plugin-syscall-filter-with-libsyscall.so endif # Update TESTS diff --git a/tests/tcg/multiarch/test-plugin-syscall-filter.c b/tests/tcg/multiarch/test-plugin-syscall-filter.c new file mode 100644 index 0000000000..caa2063a46 --- /dev/null +++ b/tests/tcg/multiarch/test-plugin-syscall-filter.c @@ -0,0 +1,35 @@ +/* + * SPDX-License-Identifier: GPL-2.0-or-later + * + * This test attempts to execute a magic syscall. The syscall test plugin + * should intercept this and return an expected value. + */ + +#include <stdint.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> + +int main(int argc, char *argv[]) +{ + /* + * We cannot use a very large magic syscall number, because on some ISAs, + * QEMU will treat it as an illegal instruction and trigger a critical + * exception. For instance, on arm32, the syscall number cannot exceed + * ARM_NR_BASE (0xf0000), as can be seen in + * "linux-user/arm/cpu_loop.c:cpu_loop". + * + * Therefore, we pick 2048 because, as of now, no ISA in Linux uses this + * number. This is just a test case; replace this number as needed in the + * future. + * + * The corresponding syscall filter is implemented in + * "tests/tcg/plugins/syscall.c". + */ + long ret = syscall(2048, 0x66CCFF); + if (ret != 0xFFCC66) { + fprintf(stderr, "Error: unexpected syscall return value %ld\n", ret); + return EXIT_FAILURE; + } + return EXIT_SUCCESS; +} diff --git a/tests/tcg/plugins/syscall.c b/tests/tcg/plugins/syscall.c index 42801f5c86..e7d4e9b589 100644 --- a/tests/tcg/plugins/syscall.c +++ b/tests/tcg/plugins/syscall.c @@ -170,6 +170,24 @@ static void vcpu_syscall_ret(qemu_plugin_id_t id, unsigned int vcpu_idx, } } +static bool vcpu_syscall_filter(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 *sysret) +{ + /* Special syscall to test the filter functionality. */ + if (num == 2048 && a1 == 0x66CCFF) { + *sysret = 0xFFCC66; + + if (!statistics) { + qemu_plugin_outs("magic syscall filtered, set magic return\n"); + } + return true; + } + return false; +} + static void print_entry(gpointer val, gpointer user_data) { SyscallStats *entry = (SyscallStats *) val; @@ -255,6 +273,7 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id, qemu_plugin_register_vcpu_syscall_cb(id, vcpu_syscall); qemu_plugin_register_vcpu_syscall_ret_cb(id, vcpu_syscall_ret); + qemu_plugin_register_vcpu_syscall_filter_cb(id, vcpu_syscall_filter); qemu_plugin_register_atexit_cb(id, plugin_exit, NULL); return 0; } -- 2.34.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v3 0/2] linux-user: add plugin API to filter syscalls @ 2025-12-14 14:10 Ziyang Zhang 2025-12-14 14:10 ` [PATCH v3 1/2] " Ziyang Zhang 0 siblings, 1 reply; 4+ messages in thread From: Ziyang Zhang @ 2025-12-14 14:10 UTC (permalink / raw) 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, Ziyang Zhang We choose a smaller magic syscall number to avoid the illegal instruction exception [1] on qemu-arm. PATCH v3: 1. Change to a smaller magic syscall number and add comments 2. Set register flags out of the for-loop PATCH v2: 1. Rebased on newest version of master PATCH v1: 1. Format the code RFC v2: 1. Simplify the syscall filter mechanism and remove fork-cpu 2. Add QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER enum RFC v1: 1. Add syscall filter registry 2. Add fork-cpu interface to re-enter cpu_loop when handling syscalls [1] https://lore.kernel.org/qemu-devel/20251212141541.1792111-1-functioner@sjtu.edu.cn/T/#m0e6809c5a894d64a8b7e67324a4b7cb414c644bf Ziyang Zhang (2): linux-user: add plugin API to filter syscalls tcg tests: add a test to verify the syscall filter plugin API include/qemu/plugin-event.h | 1 + include/qemu/plugin.h | 33 ++++++++++++----- include/qemu/qemu-plugin.h | 32 ++++++++++++++++ include/user/syscall-trace.h | 17 +++++++++ linux-user/syscall.c | 7 +++- plugins/api.c | 7 ++++ plugins/core.c | 37 +++++++++++++++++++ tests/tcg/multiarch/Makefile.target | 4 +- .../multiarch/test-plugin-syscall-filter.c | 35 ++++++++++++++++++ tests/tcg/plugins/syscall.c | 19 ++++++++++ 10 files changed, 180 insertions(+), 12 deletions(-) create mode 100644 tests/tcg/multiarch/test-plugin-syscall-filter.c -- 2.34.1 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v3 1/2] linux-user: add plugin API to filter syscalls 2025-12-14 14:10 [PATCH v3 0/2] linux-user: add plugin API to filter syscalls Ziyang Zhang @ 2025-12-14 14:10 ` Ziyang Zhang 0 siblings, 0 replies; 4+ messages in thread From: Ziyang Zhang @ 2025-12-14 14:10 UTC (permalink / raw) 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, Ziyang Zhang 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 <functioner@sjtu.edu.cn> Co-authored-by: Mingyuan Xia <xiamy@ultrarisc.com> --- include/qemu/plugin-event.h | 1 + include/qemu/plugin.h | 33 +++++++++++++++++++++++--------- include/qemu/qemu-plugin.h | 32 +++++++++++++++++++++++++++++++ include/user/syscall-trace.h | 17 +++++++++++++++++ linux-user/syscall.c | 7 +++++-- plugins/api.c | 7 +++++++ plugins/core.c | 37 ++++++++++++++++++++++++++++++++++++ 7 files changed, 123 insertions(+), 11 deletions(-) diff --git a/include/qemu/plugin-event.h b/include/qemu/plugin-event.h index 1100dae212..7f3c5927f1 100644 --- a/include/qemu/plugin-event.h +++ b/include/qemu/plugin-event.h @@ -23,6 +23,7 @@ enum qemu_plugin_event { QEMU_PLUGIN_EV_VCPU_INTERRUPT, QEMU_PLUGIN_EV_VCPU_EXCEPTION, QEMU_PLUGIN_EV_VCPU_HOSTCALL, + QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER, QEMU_PLUGIN_EV_MAX, /* total number of plugin events we support */ }; diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index cea0a68858..91df1e78d2 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -55,15 +55,16 @@ void qemu_plugin_opt_parse(const char *optstr, QemuPluginList *head); int qemu_plugin_load_list(QemuPluginList *head, Error **errp); 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_discon_cb_t vcpu_discon; - 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_discon_cb_t vcpu_discon; + 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; }; @@ -169,6 +170,11 @@ qemu_plugin_vcpu_syscall(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); 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 a5, uint64_t a6, uint64_t a7, + uint64_t a8, uint64_t *ret); void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr, uint64_t value_low, @@ -280,6 +286,15 @@ static inline void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret) { } +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) +{ + return false; +} + 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 60de4fdd3f..f3bff82257 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -798,6 +798,33 @@ typedef void uint64_t a3, uint64_t a4, uint64_t a5, uint64_t a6, uint64_t a7, uint64_t a8); +/** + * typedef qemu_plugin_vcpu_syscall_filter_cb_t - vCPU syscall filter callback + * function type + * @id: plugin id + * @vcpu_index: the executing vCPU + * @num: the syscall number + * @a1: the 1st syscall argument + * @a2: the 2nd syscall argument + * @a3: the 3rd syscall argument + * @a4: the 4th syscall argument + * @a5: the 5th syscall argument + * @a6: the 6th syscall argument + * @a7: the 7th syscall argument + * @a8: the 8th syscall argument + * @sysret: the reference of the syscall return value, must set this if filtered + * + * Returns true if you want to filter this syscall (i.e. stop it being + * handled further), otherwise returns 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 *sysret); + QEMU_PLUGIN_API void qemu_plugin_register_vcpu_syscall_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_cb_t cb); @@ -811,6 +838,11 @@ void qemu_plugin_register_vcpu_syscall_ret_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_syscall_ret_cb_t cb); +QEMU_PLUGIN_API +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filter_cb_t cb); + /** * 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..4ee6c4e513 100644 --- a/include/user/syscall-trace.h +++ b/include/user/syscall-trace.h @@ -39,5 +39,22 @@ static inline void record_syscall_return(CPUState *cpu, int num, abi_long ret) gdb_syscall_return(cpu, num); } +static 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 *sysret) +{ + uint64_t sysret64 = 0; + bool filtered = qemu_plugin_vcpu_syscall_filter(cpu, num, arg1, arg2, + arg3, arg4, arg5, arg6, + arg7, arg8, &sysret64); + if (filtered) { + *sysret = sysret64; + } + return filtered; +} + #endif /* SYSCALL_TRACE_H */ diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 2060e561a2..9ae3c5bfbd 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -14201,8 +14201,11 @@ abi_long do_syscall(CPUArchState *cpu_env, int num, abi_long arg1, print_syscall(cpu_env, num, arg1, arg2, arg3, arg4, arg5, arg6); } - ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, - arg5, arg6, arg7, arg8); + if (!send_through_syscall_filters(cpu, num, arg1, arg2, arg3, arg4, arg5, + arg6, arg7, arg8, &ret)) { + ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4, + arg5, arg6, arg7, arg8); + } 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_id_t id, plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_SYSCALL_RET, cb); } +void +qemu_plugin_register_vcpu_syscall_filter_cb(qemu_plugin_id_t id, + qemu_plugin_vcpu_syscall_filter_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 b4b783008f..85fabf9ec8 100644 --- a/plugins/core.c +++ b/plugins/core.c @@ -564,6 +564,43 @@ void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret) } } +/* + * 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 a5, uint64_t a6, uint64_t a7, + uint64_t a8, uint64_t *sysret) +{ + struct qemu_plugin_cb *cb, *next; + enum qemu_plugin_event ev = QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER; + bool filtered = false; + + if (!test_bit(ev, cpu->plugin_state->event_mask)) { + return false; + } + + qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS); + + QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) { + qemu_plugin_vcpu_syscall_filter_cb_t func = cb->f.vcpu_syscall_filter; + + if (func(cb->ctx->id, cpu->cpu_index, num, a1, a2, a3, a4, + a5, a6, a7, a8, sysret)) { + filtered = true; + 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 */ -- 2.34.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-12-14 14:21 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2025-12-14 14:19 [PATCH v3 0/2] linux-user: add plugin API to filter syscalls Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 1/2] " Ziyang Zhang 2025-12-14 14:19 ` [PATCH v3 2/2] tcg tests: add a test to verify the syscall filter plugin API Ziyang Zhang -- strict thread matches above, loose matches on Subject: below -- 2025-12-14 14:10 [PATCH v3 0/2] linux-user: add plugin API to filter syscalls Ziyang Zhang 2025-12-14 14:10 ` [PATCH v3 1/2] " Ziyang Zhang
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