There can be two return values from a syscall.  Most only use one.  As
an example, though, fork() always returns the pid of the `other' process
in %eax, and %edx specifies whether it's returned to the parent or the
child.  (This is used by libc to force %eax to be 0 in the child.)

Generally, you should be able to look for occurences of `retval[1]' in
the kernel to find other uses of %edx.


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