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Date: Mon, 23 Apr 2001 20:58:54 +0100 (BST)
From: Matt <madmatt@bits.bris.ac.uk>
To: linux-kernel@vger.kernel.org
Subject: Re: ioctl arg passing
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Matt aka Doofus festures mentioned the following:

| struct instruction_t local;
| __s16 *temp;
| 
| copy_from_user( &local, ( struct instruction_t * ) arg, sizeof( struct instruction_t ) );
| temp = kmalloc( sizeof( __s16 ) * local.rxlen, GFP_KERNEL );
| copy_from_user( temp, arg, sizeof( __s16 ) * local.rxlen );

I meant that last line to be:

copy_from_user( temp, local.rxbuf, sizeof( __s16 ) * local.rxlen );
                      ^^^^^^^^^^^

Which'd clear up any confusion as to why I'd want two copies of the same
argument.

That's the main crux of my query, can I retrieve the value of a pointer
in some struct passed via ioctl? In this case, the struct/chunk of memory
referenced by local.rxbuf, (which is rxlen x 2 bytes big).

Apologies, I'm a muppet.

Matt

PS. Thanks for the help so far, I'd meant to add error checking and what
not, I just kept it out to keep the e-mail smaller.

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