Re: [PATCH 1/2] alpha: Remove "strange" OSF/1 fork semantics

From: Richard Henderson
Date: Wed Jul 30 2014 - 19:07:18 EST

On 07/30/2014 12:04 PM, Måns Rullgård wrote:
> Richard Henderson <rth@xxxxxxxxxxx> writes:
>> The assignment to regs->r20 kills the original tls_val input
>> to the clone syscall, which means that clone can no longer be
>> restarted with the original inputs.
>> We could, perhaps, retain this result for true fork, but OSF/1
>> compatibility is no longer important. Note that glibc has never
>> used the r20 result value, instead always testing r0 vs 0 to
>> determine the child/parent status.
> What effect does this have on OSF/1 compat?

I don't know, as I've never had access to osf/1 myself. It depends on how that
$20 value is used -- potentially, fork(3) no longer works.

I can imagine that we could retain these assignments under the condition of
clone_flags == 0, which both implies a basic fork as well as the fact that the
tls_val argument is unused.

But I do have to ask first if anyone actually cares. Surely the amount of
osf-on-linux emulation is a vanishingly small proportion of the already small
alpha-linux population.

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