From 3f1642e4bc86c6e7febc6b2dd2b83ad48c5ee201 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Fri, 8 Oct 2021 18:00:36 -0700 Subject: 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 --- pkg/ring0/kernel.go | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'pkg/ring0/kernel.go') diff --git a/pkg/ring0/kernel.go b/pkg/ring0/kernel.go index 292f9d0cc..e7dd84929 100644 --- a/pkg/ring0/kernel.go +++ b/pkg/ring0/kernel.go @@ -14,6 +14,10 @@ package ring0 +import ( + "gvisor.dev/gvisor/pkg/sentry/arch/fpu" +) + // Init initializes a new kernel. // //go:nosplit @@ -80,6 +84,7 @@ func (c *CPU) Init(k *Kernel, cpuID int, hooks Hooks) { c.self = c // Set self reference. c.kernel = k // Set kernel reference. c.init(cpuID) // Perform architectural init. + c.floatingPointState = fpu.NewState() // Require hooks. if hooks != nil { -- cgit v1.2.3