Re: [Valgrind-users] Difference between "truss" and "valgrind --trace-syscalls=yes" on FreeBSD

[Yue C. <yc...@gm...>]

Any approach that can distinguish which syscalls are from the application,
and which syscalls are from Valgrind itself?

On Tue, Sep 8, 2015 at 2:04 AM, Ivo Raisr <ivo...@gm...> wrote:

>
>
> 2015-09-08 1:35 GMT+02:00 Yue Chen <yc...@gm...>:
>
>> I tried to use Valgrind syscall tracing utility on FreeBSD 10.1. I found
>> that that the results of ``truss'' and ``valgrind --trace-syscalls=yes''
>> are a little different. For example, the result of Valgrind has extra
>> syscalls like sys_sysctl, sys_fstatfs6 and [async].
>> Is it because Valgrind result contains the syscalls issued from the
>> instrumentation code, or something else?
>> Thanks.
>>
>
> Think of Valgrind as a virtual machine.
> Truss observes behaviour of the host (Valgrind itself) while
> --trace-syscalls traces behavior of the guest (your application).
> Valgrind syscall machinery intercepts all syscalls from the application
> and in general they are not mapped 1:1 to native ones.
> Some of these might be changed or intercepted completely.
> Valgrind will also issue syscalls on its own.
> I.
>