---
- branch: MAIN
  date: Sat Dec 22 21:27:22 UTC 2018
  files:
  - new: '1.34'
    old: '1.33'
    path: src/sys/arch/amd64/amd64/cpufunc.S
    pathrev: src/sys/arch/amd64/amd64/cpufunc.S@1.34
    type: modified
  - new: '1.26'
    old: '1.25'
    path: src/sys/arch/i386/i386/cpufunc.S
    pathrev: src/sys/arch/i386/i386/cpufunc.S@1.26
    type: modified
  - new: '1.19'
    old: '1.18'
    path: src/sys/arch/i386/i386/i386func.S
    pathrev: src/sys/arch/i386/i386/i386func.S@1.19
    type: modified
  - new: '1.23'
    old: '1.22'
    path: src/sys/arch/xen/x86/xenfunc.c
    pathrev: src/sys/arch/xen/x86/xenfunc.c@1.23
    type: modified
  id: 20181222T212722Z.1b0ff27a57bdc1a6cad0aadf91ad2a96ec0884a0
  log: |
    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.
  module: src
  subject: 'CVS commit: src/sys/arch'
  unixtime: '1545514042'
  user: cherry