Re: [Valgrind-users] Using System Call in a Valgrind Tool

[Philippe W. <phi...@sk...>]

On Thu, 2012-08-02 at 18:21 -0400, Wonjoon Song wrote:
...
> 
> valgrind: the 'impossible' happened:
>    Killed by fatal signal
> ==24479==    at 0x38059A25: vgPlain_do_syscall (m_syscall.c:72)
> ==24479==    by 0x3808E5E1: handle_syscall (scheduler.c:1057)
...
> 
> I tried to search for examples using system call in tools but it seems
> they(memcheck, massif, lackey) don't use it.
Difficult to see what is going wrong without looking at (some of) the
code.

For sure, tools are e.g. calling VG_(getpid) without crashing :).

For what concerns mmap, you should not use mmap syscall
directly.
Instead, you should use the interface of the Valgrind address space
manager (i.e. pub_tool_aspacemgr.h).

> 
> 
> My question is, is it allowed to use system call in a valgrind tool?
> Is it recommended not to use system call? If it is allowed to use
> system call in a  tool, what should I do to make this thing work?
You can use syscalls, but you must have the "interface" defined
for it.
See e.g. m_libcproc.c and similar to see how the "VG(xxxxxx)"
are providing the equivalent of the xxxxxx syscall.

Philippe