Re: Intel floating-point initialization

David S. Miller (
Tue, 19 May 1998 04:11:07 -0700

From: (H. Peter Anvin)
Date: 19 May 1998 10:36:11 GMT

If the FPU registers are otherwise preserved across a system call,
they should be copied by fork(). Otherwise it will not work
properly if you use floating point in the same routine that does a
fork() (remember, to the C compiler, fork() is just another

Most ABI's I've seen say FPU regs are clobbered across a function
call, or some subset of them are. And the same holds for system
calls. The one case to be careful about, as Xavier has mentioned, is
the FPU control register.

David S. Miller

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