CODEWITHSUNDEEP
debugginggdbintel-pin
fakub
fakub

Reputation: 327

GDB does not break on a read access to an address caught by PIN

I've captured a read memory trace (i.e. addresses of all read accesses) of a program-run by Intel PIN, ASLR was off. I can capture it several times and the trace is still exactly the same.

Then I take an address from the trace (a specific address I am interested in), set a watchpoint in GDB by rwatch *0x7fffe309e643 but GDB does not notice the access. I'm doing this in the same terminal where the trace has been taken so it should access the same addresses; when I capture it then again, the trace is still very the same.

Do you have any ideas or hints why GDB does not catch it?

I have to note that the access very likely happens within a (C++) structure loaded from a Boost serialization and that the code has been compiled with -g3 -O1 flags (-O1 is really crucial for other reasons but a minimal example showed me that GDB breaks correctly even with -O1).

UPDATE:

As suggested, I tried PIN debugger (which actually utilizes GDB) but there is some problem with watchpoints. To present this problem, I made a minimal example.

int main()
{
  unsigned char i = 4;
  i++;
  i = 3;
  return 0;
}

I acquired a read memory trace with PIN and chose 0x7fffffffd89f (or similar) as the address of interest. Then I started PIN debugger and GDB in parallel terminals and connected GDB to PIN ((gdb) target remote :57946, as suggested by PIN). In GDB I set watchpoint (gdb) rwatch *0x7fffffffd89f and started execution but I get

Continuing.
Warning:
Could not insert hardware watchpoint 1.
Could not insert hardware breakpoints:
You may have requested too many hardware breakpoints/watchpoints.

even though I only inserted a single watchpoint. I also tried to explicitly disable hardware breakpoints by set can-use-hw-watchpoints 0 but then it ran for an hour with no result and no processor load so I killed it.

Is there any other way how to set a functional watchpoint at a specific address when GDB is connected to PIN debugger? Note that there is no such problem with standalone GDB.

I use GDB 7.7.1, PIN 2.14-71313 and GCC 4.4.7, running Ubuntu 14.04.

The original problem would be likely solved then.

Upvotes: 0

Views: 288

Answers (1)

Employed Russian
Employed Russian

Reputation: 213829

From pin user guide:

The "pin" Executable (Launcher)

The kit's root directory contains a "pin" executable. This is a 32-bit
launcher, used for launching Pin in 32 and 64 bit modes. The launcher
sets up the environment to find the libraries supplied with the kit.

It is likely that the environment is different when running pinbin, and therefore stack addresses will also be different (0x7fffe309e643 looks like a possible stack address) even without ASLR.

Your best bet is probably to use Pin application debugging interface.

Upvotes: 1

Related Questions