How gdb's 'attach' command work ?

Hi everyone,
I wanna know why the gdb's 'attach' command can work?
In the virtual memory enviornment,Does it say that a program can't
direct 'invade' another's processs's space? Please tell me the
reason why gdb can do so...


thnx

On 2007-11-20, xi4oyu <Evil.xi4oyu@gmail.com> wrote:
> I wanna know why the gdb's 'attach' command can work?
> In the virtual memory enviornment,Does it say that a program can't
> direct 'invade' another's processs's space? Please tell me the
> reason why gdb can do so...

I think you just misunderstand the statement about virtual memory.
Virtual memory is separate for each process, so the process may think
that it's the only process in memory. But since the virtual memory is
actually stored in RAM (or swap), then of course kernel has access to
that memory and may provide such access to programs that need it. So no
process can directly access the memory of another process, but some
process may request from kernel indirect access to the memory of another
process.


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