assert macro to check null

assert macro to check null

[Saket Sinha]

I have developed a driver which has become unstable. Now when I debug,I
find that it is crashing at
http://lxr.free-electrons.com/source/kernel/cred.c?v=3.8#L431
get_cred(new); where null is struct cred *new.

I think this new might be NULL.

Now I plan to add an assert in our macro that deals with creds, like for
asserting passed object isn't NULL.

Any suggestions as to how I can do that?

Regards,
Saket Sinha
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assert macro to check null

[Valdis.Kletnieks at vt.edu]

On Sat, 10 Aug 2013 09:58:10 +0530, Saket Sinha said:

> get_cred(new); where null is struct cred *new.
>
> I think this new might be NULL.
>
> Now I plan to add an assert in our macro that deals with creds, like for
> asserting passed object isn't NULL.
>
> Any suggestions as to how I can do that?

	WARN_ON(!new);

is probably your best bet.
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assert macro to check null

[Saket Sinha]

Actually  WARN_ON macro has been defined slightly differently for each
Acrhitecture in kernel.

Can you specifically point out the definition of macro you have suggested
 and where it is defined in kernel.

Regards,
Saket Sinha


On Sat, Aug 10, 2013 at 11:05 AM, <Valdis.Kletnieks@vt.edu> wrote:

> On Sat, 10 Aug 2013 09:58:10 +0530, Saket Sinha said:
>
> > get_cred(new); where null is struct cred *new.
> >
> > I think this new might be NULL.
> >
> > Now I plan to add an assert in our macro that deals with creds, like for
> > asserting passed object isn't NULL.
> >
> > Any suggestions as to how I can do that?
>
>         WARN_ON(!new);
>
> is probably your best bet.
>
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assert macro to check null

[Valdis.Kletnieks at vt.edu]

On Sat, 10 Aug 2013 11:16:07 +0530, Saket Sinha said:

> Actually  WARN_ON macro has been defined slightly differently for each
> Acrhitecture in kernel.

And that matters for the *caller*, why, exactly?  (Hint - the vast majority
of calls to WARN_ON() are in non-arch code, so it pretty much has to have
the same semantics on all architectures, even if the actual macro is
different)

> Can you specifically point out the definition of macro you have suggested
>  and where it is defined in kernel.

cd /usr/src/linux &&  find include arch -type f -name '*.h' | xargs egrep 'define.*WARN_ON'

If you're on parisc, avr32, s390, powerpc, sh, or blackfin, you'll
get the appropriate version in arch/.  If you're on anything else, you'll
get the version from include/asm-generic/bug.h

Not that it matters - you end up using it exactly the same no matter what arch.
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assert macro to check null

[apazmd at gmail.com]

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