Messages in this thread |  | | | Date | 27 Oct 2007 21:00:31 +0200 | | Date | Sat, 27 Oct 2007 21:00:31 +0200 | | From | Andi Kleen <> | | Subject | Re: Adding TIF_TRACE_KERNEL to x86_64 |
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On Fri, Oct 26, 2007 at 03:37:38PM -0400, Mathieu Desnoyers wrote: > > 1 - process A enters in a syscall, TIF_KERNEL_TRACE is cleared > 2 - we activate TIF_KERNEL_TRACE > 3 - process A returns from syscall (with wrong top of stack ?) -> segfault. > > Am I on the right track ?
Yes. The code was not designed to allow that. The syscall path has been optimized to go as fast as possible.
> > Can this be a concern with TIF_SYSCALL_TRACE also ? (potential race in > ptrace ?)
ptrace only changes state in stopped processes; and those are not hanging in syscalls. So no there is no race in a standard kernel.
If you wanted to change it the right way would be probably to test for SYSCALL_TRACE too in the work flags and handle it there
-Andi
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