Messages in this thread | | | Date | Sun, 04 May 2008 11:35:20 -0600 | From | Robert Hancock <> | Subject | Re: undefined reference to __udivdi3 (gcc-4.3) |
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Christian Kujau wrote: > Hi, > > while trying to compile current -git or 2.6.25.1 with gcc (Debian > 4.3.0-4) 4.3.1 20080501 (prerelease), the following error occurs during > linking: > > arch/x86/xen/built-in.o: In function `xen_timer_interrupt': > time.c:(.text+0x2992): undefined reference to `__udivdi3' > time.c:(.text+0x2a13): undefined reference to `__udivdi3' > make: *** [.tmp_vmlinux1] Error 1 > > > Searching the archives brought up old issues with gcc-3.4 [0] and not so > old posting from 01/2008 [1], but I could not find a solution (or a > consense about (not to) include libgcc.a). > > Full make.log and .config: http://nerdbynature.de/bits/2.6.25.1/xen/ > > Hints welcome :) > > Thanks, > Christian. > > [0] http://gcc.gnu.org/ml/gcc/2004-01/msg01975.html > [1] http://www.nabble.com/gcc-4.3:-Kernel-build-fails-td15135607.html
I assume it's one or both of these loops in arch/x86/xen/time.c do_stolen_accounting() that are being optimized into a divide which generates a libgcc call:
while (stolen >= NS_PER_TICK) { ticks++; stolen -= NS_PER_TICK; }
or
while (blocked >= NS_PER_TICK) { ticks++; blocked -= NS_PER_TICK; }
I seem to recall in one previous case we added some dummy assembly code to stop gcc from doing this. Not sure if that is a sustainable fix, though..
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