Re: [Valgrind-developers] 2013-04-18 02:31:36 BST nightly build (bristol, x86_64, Fedora 19 (Schrödinger’s Cat))

[Tom H. <to...@co...>]

On 18/04/13 03:02, Tom Hughes wrote:

> ! gdbserver_tests/mcbreak                  (stdout)
> ! gdbserver_tests/mcbreak                  (stdoutB)
> ! gdbserver_tests/mcbreak                  (stderrB)
> ! gdbserver_tests/mcinfcallRU              (stderr)
> ! gdbserver_tests/mcinfcallWSRU            (stderr)
> ! gdbserver_tests/mcinfcallWSRU            (stderrB)
> ! gdbserver_tests/mcmain_pic               (stdout)
> ! gdbserver_tests/mcmain_pic               (stderr)
> ! gdbserver_tests/mcmain_pic               (stdoutB)
> ! gdbserver_tests/mcmain_pic               (stderrB)

These failiures are caused by the change I committed yesterday to 
respect the PT_GNU_STACK information and make stacks non-executable
when possible.

It seems that when GDB wants to call a function in the target it is 
poking an INT3 instruction onto the targets stack, then poking the 
address of that instruction on to the stack as the return address and 
resuming at the address of the function it wants to call.

So when the target returns from that function it tries to execute on the 
stack and fails...

Presumably when gdb is running the target directly it turns on execute 
permission for the stack?

Tom

-- 
Tom Hughes (to...@co...)
http://compton.nu/