> The base of the bounds directory is set into mm_struct during
> PR_MPX_REGISTER command execution. This member can be used to
> check whether one application is mpx enabled.
Not really because by the time you ask the question another thread might
have decided to unregister it.
> +int mpx_register(struct task_struct *tsk)
> +{
> + struct mm_struct *mm = tsk->mm;
> +
> + if (!cpu_has_mpx)
> + return -EINVAL;
> +
> + /*
> + * runtime in the userspace will be responsible for allocation of
> + * the bounds directory. Then, it will save the base of the bounds
> + * directory into XSAVE/XRSTOR Save Area and enable MPX through
> + * XRSTOR instruction.
> + *
> + * fpu_xsave() is expected to be very expensive. In order to do
> + * performance optimization, here we get the base of the bounds
> + * directory and then save it into mm_struct to be used in future.
> + */
> + mm->bd_addr = task_get_bounds_dir(tsk);
> + if (!mm->bd_addr)
> + return -EINVAL;
What stops two threads calling this in parallel ?
> +
> + return 0;
> +}
> +
> +int mpx_unregister(struct task_struct *tsk)
> +{
> + struct mm_struct *mm = current->mm;
> +
> + if (!cpu_has_mpx)
> + return -EINVAL;
> +
> + mm->bd_addr = NULL;
or indeed calling this in parallel
What are the semantics across execve() ?
Alan
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