linux-kernel - link error in today's x86.git

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Date:	Thu, 17 Jan 2008 10:29:37 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: link error in today's x86.git

I'm seeing this with the current x86.git:

arch/x86/mm/built-in.o: In function `fix_to_virt': /home/jeremy/hg/xen/paravirt/linux-i386/include2/asm/fixmap_32.h:157: undefined reference to `__this_fixmap_does_not_exist'

It appears to be coming from ioremap_32.c.

I can't see any particular change which would have caused this, but this 
loop in early_ioremap_reset:

	for (idx = FIX_BTMAP_BEGIN; idx <= FIX_BTMAP_END; idx--) {
		addr = fix_to_virt(idx);
		pte = early_ioremap_pte(addr);
		if (!*pte & _PAGE_PRESENT) {
			phys = *pte & PAGE_MASK;
			set_fixmap(idx, phys);
		}
	}

seems incompatible with the test in fix_to_virt:

	/*
	 * this branch gets completely eliminated after inlining,
	 * except when someone tries to use fixaddr indices in an
	 * illegal way. (such as mixing up address types or using
	 * out-of-range indices).
	 *
	 * If it doesn't get removed, the linker will complain
	 * loudly with a reasonably clear error message..
	 */
	if (idx >= __end_of_fixed_addresses)
		__this_fixmap_does_not_exist();

While the compiler could prove that idx is within range here, it seems a 
bit much to require it to.

    J
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