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

[John R. <jr...@bi...>]

> For a simple example, just compare the results of ``strace date'' and ``valgrind --trace-syscalls=yes date'' on Linux.
>
> E.g., it records syscalls only related to Valgrind, like
> sys_open ( 0x40244a0(/usr/local/lib/valgrind/vgpreload_core-amd64-linux.so)
> sys_open ( 0x40249d8(/usr/local/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
>
> It also has other different operations like memory/signal/file operations, sysctl, etc.
>
> How to tell which are extra ones caused by Valgrind, which are not?

A filename which contains "valgrind/vgpreload_<tool-name>-<arch-name>-<os-name>.so"
gives a hint that syscalls (or calls to wrappers for syscalls)
from such a file should be re-directed to the non-traced versions.
Depending on the details of how the current non-interception operates,
such re-direction could be done when processing pre-loaded libraries,
or might require a dynamic check of the program counter
for every syscall that is simulated.