To further investigate, some more info might be useful, and some
actions below might help.
General info:
Which version of valgrind are you using ? On which platform ?
The function setup_client_env in initimg-linux.c is responsible
to modify LD_PRELOAD (as valgrind needs to add some values there).
To check this is working properly, you can do the below:
* change Bool debug = False; to True
and/or
* do:
LD_PRELOAD=xxxxx valgrind <any shell that works under valgrind>
echo $LD_PRELOAD # this should show the modified by valgrind LD_PRELOAD
(bash fails under valgrind, I tried with dash)
Please run with -v -v -v -d -d -d your program and examine the trace.
At least at the end of execution, you should find a trace
of the address space manager showing which files are mapped,
and that should contain your preloaded library.
If LD_PRELOAD is correct, but the lib is not mapped, then
you might trace ld.so using LD_DEBUG
(see man ld.so)
If the lib is loaded, but no signals seems to arrive,
you might try:
valgrind --trace-signals=yes sleep 100000
and in another shell, send the signal to the valgrind pid
and observe the trace (which should show the signal arriving)
Then do the same but when valgrind runs your program.
Philippe
On Mon, 2018-03-05 at 11:12 +0000, Hari via Valgrind-users wrote:
> Hi John,
>
> Thanks for your inputs. I tried both --trace-signals=yes and strace options
> indicated but i could not see any traces of signal sent reaching my_process.
>
> I suspect if LD_PRELOAD itself did not happen with the following command to
> my_process
>
> LD_PRELOAD=./libfake.so valgrind ./my_process
>
> Is there a different way to make sure that LD_PRELOAD done above is indeed
> successful? I checked few online portals and i see /proc/<pid>/maps (pid of
> my_process) and i see references to the libfake.so. Does this confirm that
> LD_PRELOAD is indeed successful? Is there any other way to trace where the
> signal is reaching?
>
> Thanks
> Hari
>
>
> On Wednesday, February 28, 2018, 9:43:29 AM GMT+5:30, John Reiser
> <jrei...@bitwagon.com> wrote:
>
>
> > LD_PRELOAD=./libfake.so ./my_process --> runs fine and prints memory stats
> >
> > But,
> >
> > LD_PRELOAD=./libfake.so valgrind ./my_process --> doesnt print the memory
> > stats
> >
> > From few online blogs, i understand that valgrind does forward any signals
> >to the child process that it is running on but it doesnt seem to work here.
>
> There is no parent-child relationship between valgrind and ./my_process.
> Both valgrind and ./my_process run in the same address space as just one
> process.
> The inter-process communication would be extremely expensive if valgrind
> and ./my_process did not share the same address space, and memcheck tracking
> of each memory access would be difficult if there were 2 threads of control.
>
> The command-line parameter "--trace-signals=yes" causes valgrind to report on
> signals.
> The Linux utility /usr/bin/strace also reports on signals. (Probably use
> something like "strace -e trace=file" to reduce the syscalls that strace
> reports;
> in particular 'read' and 'write' are usually heavily used and ignorable.)
>
>
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