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From: "H. Peter Anvin" <hpa@zytor.com>
To: David Howells <dhowells@redhat.com>,
	Stephen Hemminger <shemminger@vyatta.com>,
	Alexander van Heukelum <heukelum@mailshack.com>,
	Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: x86: fls64() exported to user space but not fls()?
Date: Thu, 15 Dec 2011 14:42:41 -0800	[thread overview]
Message-ID: <4EEA77E1.6050009@zytor.com> (raw)

I'm trying to grok why fls64() seems to be exported to user space in
<asm/bitops.h> on x86 by unconditional inclusion of
<asm-generic/bitops/fls64.h>:

...
#endif /* __KERNEL__ */

#include <asm-generic/bitops/fls64.h>

#ifdef __KERNEL__
...


 whereas fls() isn't (although __fls() is!)

This is even more bizarre since <asm-generic/bitops/fls64.h> contains:

...
#if BITS_PER_LONG == 32
static __always_inline int fls64(__u64 x)
{
        __u32 h = x >> 32;
        if (h)
                return fls(h) + 32;
        return fls(x);
}
#elif BITS_PER_LONG == 64
static __always_inline int fls64(__u64 x)
{
        if (x == 0)
                return 0;
        return __fls(x) + 1;
}
#else
#error BITS_PER_LONG not 32 or 64
#endif
...

Both BITS_PER_LONG and fls() are non-user-visible symbols, so this code
should fail on user space.  Finally, <asm-generic/bitops/*> are
non-exported headers; they are not installed by make headers_install.

Is the #endif..#ifdef in <asm/bitops.h> a bug, plain and simple?

	-hpa

             reply	other threads:[~2011-12-15 22:43 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-15 22:42 H. Peter Anvin [this message]
2011-12-15 23:25 ` [tip:x86/asm] x86, bitops: Move fls64.h inside __KERNEL__ tip-bot for H. Peter Anvin

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