> On Mon, 26 Feb 2007 15:51:54 -0800 Stephane Eranian <eranian@xxxxxxxxxx> wrote: > Hello, > > I have come across an issue with a monitoring using the > hardware debug registers on ia64/i386/x86-64. > > It seems that the way debug registers are inherited across fork > differs between ia-64 and i386/x86-64. On ia-64, the debug registers > are NEVER inherited in the child. The copy_thread() routine clears > the necessary thread flags to avoid reloading the debug registers in > the child. > > Now, on x86-64, it appears that the TIF_DEBUG flag is inherited via > setup_thread_stack(). By virtue of dup_task_struct() the debug registers > get copied into the child task on fork. So the child has active breakpoints, > unless I am mistaken somewhere. > > Given the way the ptrace() interface works, I would tend to > think that the ia-64 way is the correct one. Any comment? > > Furthermore, on i386/x86-64, when switching out from a task with TIF_DEBUG > enabled to another which does not, it seems we do not clear the debug > registers (at least dr7) so they become inactive. > Let's cc Roland - he's totally rewritten ptrace and probably knows this stuff. - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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