Re: [PATCH v2 2/2] tcg tests: add a test to verify the syscall filter plugin API

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 12/12/25 8:00 AM, Alex Bennée wrote:
> Ziyang Zhang <functioner@sjtu.edu.cn> writes:
> 
>> 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    | 20 +++++++++++++++++++
>>   tests/tcg/plugins/syscall.c                   | 15 ++++++++++++++
>>   3 files changed, 38 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..cc694e0a71
>> --- /dev/null
>> +++ b/tests/tcg/multiarch/test-plugin-syscall-filter.c
>> @@ -0,0 +1,20 @@
>> +/*
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + *
>> + * This test attempts to execute a magic syscall. The syscall test plugin
>> + * should intercept this and returns an expected value.
>> + */
>> +
>> +#include <stdint.h>
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <unistd.h>
>> +
>> +int main(int argc, char *argv[]) {
>> +    long ret = syscall(0x66CCFF);
>> +    if (ret != 0xFFCC66) {
>> +        perror("ERROR: syscall returned unexpected value!!!");
>> +        return EXIT_FAILURE;
>> +    }
>> +    return EXIT_SUCCESS;
>> +}
> 
>    This breaks some arches:
> 
>    (gdb) r
>    Starting program: /home/alex/lsrc/qemu.git/builds/sanitisers/qemu-arm -plugin tests/tcg/plugins/libsyscall.so -d plugin ./tests/tcg/arm-linux-user/test-plugin-syscall-filter
>    [New Thread 0x7ffff37ff6c0 (LWP 63692)]
>    qemu: uncaught target signal 4 (Illegal instruction) - core dumped
>    syscall no.  calls  errors
>    45           5      0
>    338          1      1
>    256          1      0
>    191          1      0
>    398          1      1
>    125          1      0
>    384          1      0
>    332          1      0
> 
>    Thread 1 "qemu-arm" received signal SIGILL, Illegal instruction.
>    Download failed: Invalid argument.  Continuing without source file ./nptl/../sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S.
>    __syscall_cancel_arch () at ../sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S:56
>    warning: 56     ../sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S: No such file or directory
>    (gdb) bt
>    #0  __syscall_cancel_arch () at ../sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S:56
>    #1  0x00007ffff6a51668 in __internal_syscall_cancel (a1=<optimized out>, a2=a2@entry=8, a3=a3@entry=0, a4=a4@entry=0, a5=a5@entry=0, a6=a6@entry=0, nr=130)
>        at ./nptl/cancellation.c:49
>    #2  0x00007ffff6a516ad in __syscall_cancel (a1=<optimized out>, a2=a2@entry=8, a3=a3@entry=0, a4=a4@entry=0, a5=a5@entry=0, a6=a6@entry=0, nr=130)
>        at ./nptl/cancellation.c:75
>    #3  0x00007ffff6a0207d in __GI___sigsuspend (set=<optimized out>) at ../sysdeps/unix/sysv/linux/sigsuspend.c:26
>    #4  0x0000555555a49b80 in die_with_signal (host_sig=4) at ../../linux-user/signal.c:807
>    #5  0x0000555555a49ed0 in dump_core_and_abort (env=0x532000004300, target_sig=4) at ../../linux-user/signal.c:847
>    #6  0x0000555555a4c969 in handle_pending_signal (cpu_env=0x532000004300, sig=4, k=0x5250000029d0) at ../../linux-user/signal.c:1306
>    #7  0x0000555555a4d0e5 in process_pending_signals (cpu_env=0x532000004300) at ../../linux-user/signal.c:1386
>    #8  0x0000555555873930 in cpu_loop (env=0x532000004300) at ../../linux-user/arm/cpu_loop.c:479
>    #9  0x0000555555a3eca7 in main (argc=6, argv=0x7fffffffe588, envp=0x7fffffffe5c0) at ../../linux-user/main.c:1035
>    (gdb)
> 
>> \ No newline at end of file
>> diff --git a/tests/tcg/plugins/syscall.c b/tests/tcg/plugins/syscall.c
>> index 42801f5c86..1323e18bc0 100644
>> --- a/tests/tcg/plugins/syscall.c
>> +++ b/tests/tcg/plugins/syscall.c
>> @@ -170,6 +170,20 @@ 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 *ret)
>> +{
>> +    if (num == 0x66CCFF) {
>> +        *ret = 0xFFCC66;
>> +        qemu_plugin_outs("syscall 0x66CCFF filtered, ret=0xFFCC66\n");
>> +        return true;
>> +    }
>> +    return false;
>> +}
>> +
>>   static void print_entry(gpointer val, gpointer user_data)
>>   {
>>       SyscallStats *entry = (SyscallStats *) val;
>> @@ -255,6 +269,7 @@ 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;
>>   }
> 

Looks like a simple issue with 32 bits target.