Re: [PATCH v4 2/9] liblockdep: Wrap kernel/lockdep.c to allow usagefrom userspace

From: Peter Zijlstra
Date: Wed May 22 2013 - 05:14:58 EST

On Wed, May 15, 2013 at 11:15:34PM -0400, Sasha Levin wrote:
> kernel/lockdep.c deals with validating locking scenarios for
> various architectures supported by the kernel. There isn't
> anything kernel specific going on in lockdep, and when we
> compare userspace to other architectures that don't have to deal
> with irqs such as s390, they become all too similar.
> We wrap kernel/lockdep.c and include/linux/lockdep.h with
> several headers which allow us to build and use lockdep from
> userspace. We don't touch the kernel code itself which means
> that any work done on lockdep in the kernel will automatically
> benefit userspace lockdep as well!
> +
> +#ifndef CALLER_ADDR0
> +#define _THIS_IP_ CALLER_ADDR0
> +#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
> +#endif

Why are you making _THIS_IP_ equal to _RET_IP_ ?
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