CVS log for src/sys/arch/i386/i386/cpufunc.S

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Default branch: MAIN
Current tag: pgoyette-compat-1226

Revision 1.26 / (download) - annotate - [select for diffs], Sat Dec 22 21:27:22 2018 UTC (5 years, 3 months ago) by cherry
Branch: MAIN
CVS Tags: pgoyette-compat-1226
Changes since 1.25: +18 -6 lines
Diff to previous 1.25 (colored)

Introduce a weak alias method of exporting different implementations
of the same API.

For eg: the amd64 native implementation of invlpg() now becomes
amd64_invlpg() with a weak symbol export of invlpg(), while the XEN
implementation becomes xen_invlpg(), also weakly exported as invlpg()

Note that linking in both together without having an override function
named invlpg() would be a mistake, as we have limited control over
which of the two options would emerge as the finally exported invlpg()
resulting in a potential situation where the wrong function is finally
exported. This change avoids this situation.

We should however include an override function invlpg() in that case,
such that it is able to then pass on the call to the appropriate
backing function (amd64_invlpg() in the case of native, and
xen_invlpg() in the case of under XEN virtualisation) at runtime.

This change does not introduce such a function and therefore does not
alter builds to include native as well as XEN implementations in the
same binary. This will be done later, with the introduction of XEN
PVHVM mode, where precisely such a runtime switch is required.

There are no operational changes introduced by this change.

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