Re: [Valgrind-users] valgind with LD_PRELOAD

[Hari <har...@ya...>]

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?
ThanksHari 

    On Wednesday, February 28, 2018, 9:43:29 AM GMT+5:30, John Reiser <jr...@bi...> 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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