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SubjectRe: [Patch 01/11] Introducing generic hardware breakpoint handler interfaces

* Alan Stern <stern@rowland.harvard.edu> wrote:

> > + * Kernel breakpoints grow downwards, starting from HB_NUM
> > + * 'hbkpt_kernel_pos' denotes lowest numbered breakpoint register occupied for
> > + * kernel-space request
> > + */
> > +unsigned int hbkpt_kernel_pos;
>
> This doesn't make much sense. All you need to know is which
> registers are in use; all others are available.
>
> For example, suppose the kernel allocated breakpoints 3, 2, and 1,
> and then deallocated 2. Then bp 2 would be available for use,
> even though 2 > 1.

it's a high/low watermark mechanism. Yes, it's not an allocator that
can allocate into a debug registrs 'hole', but it is a simple one
that matches current hardware breakpoint usages and enables the
kernel to utilize them as well - and keeps all the code simple.

Ingo


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