On Wed, Apr 28, 2010 at 12:07 AM, Venkatram Tummala <venkatram867@xxxxxxxxx> wrote:
Apparently the trick didn't work for me because the vm in vmware workstation is supposed to get freezed when a breakpoint is encountered. So, the kernel freezes & we only have the gdb console to play with. Once we hit continue, the vm & hence the kernel comes back alive but again by that time, the initialization function finishes executing.
So, i cannot look at a /sys entry to find the module section addresses while gdb is sitting on a breakpoint. We only have the gdb console to look the section address & nothing else while at a breakpoint. "p modules" will help but it is too much of a work every time one tries to debug.
In Summary, the only way is to force the kernel to place the module at exactly the same address everytime. Anybody has any ideas as to how we can achieve this?
Thanks.
Venkatram
On Tue, Apr 27, 2010 at 11:58 PM, Joel Fernandes <agnel.joel@xxxxxxxxx> wrote:
Hey Venkatram,On Wed, Apr 28, 2010 at 11:33 AM, Venkatram Tummala <venkatram867@xxxxxxxxx> wrote:to find these addresses by "p modules", the module has to be already loaded.....right? So, the initialization function of the module must have been already executed....right? So, the question is how can we step through the initialization function of the module..? "p modules" won't help us..probably looking at /sys is a faster way to find module segment addresses, or am I missing something here in "p modules"??Why don't you try setting breakpoints in kernel (kernel/module.c) after the module has been loaded but before your modules' init function is called?From kernel/module.c , in SYSCALL_DEFINE3(init_module..):the line load_module(...) loads your module into the kernel, and the line do_one_initcall(mod->init); calls the init functions.So I think if you set a break point in between these lines, you should be able to get the address of text section etc just in time before the init functions is called, using p modules or something.
Apparently the trick didn't work for me because the vm in vmware workstation is supposed to get freezed when a breakpoint is encountered. So, the kernel freezes & we only have the gdb console to play with. Once we hit continue, the vm & hence the kernel comes back alive but again by that time, the initialization function finishes executing.
So, i cannot look at a /sys entry to find the module section addresses while gdb is sitting on a breakpoint. We only have the gdb console to look the section address & nothing else while at a breakpoint. "p modules" will help but it is too much of a work every time one tries to debug.
In Summary, the only way is to force the kernel to place the module at exactly the same address everytime. Anybody has any ideas as to how we can achieve this?
Thanks.
Venkatram
Hey Joel,
Yup, that is exactly the trick mentioned by Mulyadi in the previous post. Will try that & there is no reason why this won't work. This will definitely solve the problem.
Thanks Everybody,
Venkatram-Joel
