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    SubjectRe: unresolved symbols __udivdi3 and __umoddi3
    First of all I would like to thank all the people that responded to my 
    mail. Unfortunately the numbers I am using are not restricted to
    powers of two so I could not simply shift the data. I have decided to
    use the div64.h solution and it seems to work well.

    I have looked at this header file and I do not understand the asm
    syntax.

    In particular the only x86 div instruction I know only returns a 32 bit
    div result. Because I don't understand the div64 header I cannot
    see how a 64 bit result is calculated.

    I also tried this header in a regular application. This failed to return
    the modulus although it works in a module.

    Is this asm syntax documented anywhere ?

    Thanks Again

    Simon.


    On 25 Jan 2002, at 22:42, Tim Schmielau wrote:

    > On Fri, 25 Jan 2002, Richard B. Johnson wrote:
    >
    > > On Fri, 25 Jan 2002, wrote:
    > >
    > > > I am writing a module and would like to perform arithmetic on long
    > > > long variables. When I try to do this the module does not load due
    > > > to the unresolved symbols __udivdi3 and __umoddi3. I notice these
    > > > are normally defined in libc. Is there any way I can do this in a
    > > > kernel module.
    > > >
    > > > Many Thanks
    > > >
    > > > Simon.
    > >
    > > Normally, in modules, the granularity is such that divisions can
    > > be made by powers-of-two. In a 32-bit world, the modulus that you
    > > obtain with umoddi3 (the remainder from a long-long, division) should
    > > normally fit within a 32-bit variable. If you insist upon doing 64-bit
    > > math in a 32-bit world, then you can either make your own procedures
    > > and link them, of you can "appropriate" them from the 'C' runtime
    > > library code, include them with your source, assemble, and link them
    > > in.
    >
    > If 64-bit arithmetics cannot be avoided, the do_div64() macro defined in
    > include/asm/div64.h comes in handy.
    > mod = do_div((unsigned long) x, (long) y)
    > will set x to the quotient x/y and mod to the remainder x%y .
    >
    > Tim
    >
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