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From: parag on 31 Jan 2010 07:14
hi All,

is it possible to write some API that will attach a callback as a
harware breakpoint on a address at runtime


int* a = malloc(20);

now

API(a, <func>);

will call func everytime a is changed or accessed ( access mdoes could
also be added during attaching the callback )

I asked in the C forum, the moderator said, that this is an OS
specific question and rejected the question in the C forum

comp.lang.c.moderated

please help
-Parag
From: Daniel Molina Wegener on 31 Jan 2010 09:15
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On Dom 31 Ene 2010 09:14,
parag wrote:

> hi All,
>
> is it possible to write some API that will attach a callback as a
> harware breakpoint on a address at runtime
>
>
> int* a = malloc(20);
>
> now
>
> API(a, <func>);
>
> will call func everytime a is changed or accessed ( access mdoes could
> also be added during attaching the callback )

I don't know any /standard/ way to that task. You can try
operating system specific system calls, for example in Linux
you can use ptrace(2) to create that kind of wrapper.

>
> I asked in the C forum, the moderator said, that this is an OS
> specific question and rejected the question in the C forum
>
> comp.lang.c.moderated
>
> please help
> -Parag

Best regards,
- --
| Daniel Molina <dmw [at] coder [dot] cl> |
| IT Consulting & Software Development |
| Phone: +56 2 9790277 | http://coder.cl/ |
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From: David Schwartz on 31 Jan 2010 09:33
On Jan 31, 4:14 am, parag <parag.p...(a)gmail.com> wrote:

> is it possible to write some API that will attach a callback as a
> harware breakpoint on a address at runtime
>
> int* a = malloc(20);
>
> now
>
> API(a, <func>);
>
> will call func everytime a is changed or accessed ( access mdoes could
> also be added during attaching the callback )

It's much easier if you can combine them into one function. It's very
hard to protect just 20 bytes with most hardware. However, if you can
have a special allocation function, it can 'mmap' its own pages and
protect them with 'mprotect'. Then attempts to access the pages will
result in SIGSEGV/SIGFAULT, which you can catch.

DS
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