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author | Jamie Liu <jamieliu@google.com> | 2021-10-08 18:00:36 -0700 |
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committer | gVisor bot <gvisor-bot@google.com> | 2021-10-08 18:03:23 -0700 |
commit | 3f1642e4bc86c6e7febc6b2dd2b83ad48c5ee201 (patch) | |
tree | d7b6428e36cda75eb7a8702d22923cc13c22f0cc /website | |
parent | 34e68b6b4ff04de5c7b5e2dc46e5bd44c6845e63 (diff) |
Remove ring0 floating point save/load functions on amd64.
ring0.Save/LoadFloatingPoint() are only usable if the caller can ensure that Go
will not clobber floating point registers before/after calling them
respectively. Due to regabig in Go 1.17, this is no longer the case; regabig
(among other things) maintains a zeroed XMM15 during ABIInternal execution,
including by zeroing it after ABI0-to-ABIInternal transitions. In
ring0.sysenter/exception, this happens in
ring0.kernelSyscall/kernelException.abi0 respectively; in
ring0.CPU.SwitchToUser, this happens after returning from
ring0.sysret/iret.abi0. Delete these functions and do floating point save/load
in assembly.
While arm64 doesn't appear to be immediately affected (so this CL permits us to
resume usage of Go 1.17), its use of Save/LoadFloatingPoint() still seems to be
incorrect for the same fundamental reason (Go code can't sanely assume what
registers the Go compiler will or won't use) and should be fixed eventually.
PiperOrigin-RevId: 401895658
Diffstat (limited to 'website')
0 files changed, 0 insertions, 0 deletions