Go 1.17 support for the KVM platform

Go 1.17 adds a new register-based calling convention. While transparent for
most applications, the KVM platform needs special work in a few cases.

First of all, we need the actual address of some assembly functions, rather
than the address of a wrapper. See http://gvisor.dev/pr/5832 for complete
discussion of this.

More relevant to this CL is that ABI0-to-ABIInternal wrappers (i.e., calls from
assembly to Go) access the G via FS_BASE. The KVM quite fast-and-loose about
the Go environment, often calling into (nosplit) Go functions with
uninitialized FS_BASE.

That will no longer work in Go 1.17, so this CL changes the platform to
consistently restore FS_BASE before calling into Go code.

This CL does not affect arm64 code. Go 1.17 does not support the register-based
calling convention for arm64 (it will come in 1.18), but arm64 also does not
use a non-standard register like FS_BASE for TLS, so it may not require any
changes.

PiperOrigin-RevId: 384234305

1 files changed, 72 insertions, 25 deletions

diff --git a/pkg/ring0/entry_amd64.go b/pkg/ring0/entry_amd64.go
index d87b1fd00..397ccac7b 100644
--- a/pkg/ring0/entry_amd64.go
+++ b/pkg/ring0/entry_amd64.go
@@ -31,6 +31,13 @@ import (
 // executed from kernel mode or not and the appropriate stub is called.
 func sysenter()
 
+// addrOfSysenter returns the start address of sysenter.
+//
+// In Go 1.17+, Go references to assembly functions resolve to an ABIInternal
+// wrapper function rather than the function itself. We must reference from
+// assembly to get the ABI0 (i.e., primary) address.
+func addrOfSysenter() uintptr
+
 // swapgs swaps the current GS value.
 //
 // This must be called prior to sysret/iret.
@@ -39,6 +46,9 @@ func swapgs()
 // jumpToKernel jumps to the kernel version of the current RIP.
 func jumpToKernel()
 
+// jumpToUser jumps to the user version of the current RIP.
+func jumpToUser()
+
 // sysret returns to userspace from a system call.
 //
 // The return code is the vector that interrupted execution.
@@ -65,7 +75,12 @@ func exception()
 // This is used when processing kernel exceptions and syscalls.
 func resume()
 
-// Start is the CPU entrypoint.
+// start is the CPU entrypoint.
+//
+// See requirements below.
+func start()
+
+// AddrOfStart return the address of the CPU entrypoint.
 //
 // The following start conditions must be satisfied:
 //
@@ -78,7 +93,11 @@ func resume()
 //  * c.EFER() should be the current EFER value.
 //
 // The CPU state will be set to c.Registers().
-func Start()
+//
+// In Go 1.17+, Go references to assembly functions resolve to an ABIInternal
+// wrapper function rather than the function itself. We must reference from
+// assembly to get the ABI0 (i.e., primary) address.
+func AddrOfStart() uintptr
 
 // Exception stubs.
 func divideByZero()
@@ -104,28 +123,56 @@ func virtualizationException()
 func securityException()
 func syscallInt80()
 
+// These returns the start address of the functions above.
+//
+// In Go 1.17+, Go references to assembly functions resolve to an ABIInternal
+// wrapper function rather than the function itself. We must reference from
+// assembly to get the ABI0 (i.e., primary) address.
+func addrOfDivideByZero() uintptr
+func addrOfDebug() uintptr
+func addrOfNMI() uintptr
+func addrOfBreakpoint() uintptr
+func addrOfOverflow() uintptr
+func addrOfBoundRangeExceeded() uintptr
+func addrOfInvalidOpcode() uintptr
+func addrOfDeviceNotAvailable() uintptr
+func addrOfDoubleFault() uintptr
+func addrOfCoprocessorSegmentOverrun() uintptr
+func addrOfInvalidTSS() uintptr
+func addrOfSegmentNotPresent() uintptr
+func addrOfStackSegmentFault() uintptr
+func addrOfGeneralProtectionFault() uintptr
+func addrOfPageFault() uintptr
+func addrOfX87FloatingPointException() uintptr
+func addrOfAlignmentCheck() uintptr
+func addrOfMachineCheck() uintptr
+func addrOfSimdFloatingPointException() uintptr
+func addrOfVirtualizationException() uintptr
+func addrOfSecurityException() uintptr
+func addrOfSyscallInt80() uintptr
+
 // Exception handler index.
-var handlers = map[Vector]func(){
-	DivideByZero:               divideByZero,
-	Debug:                      debug,
-	NMI:                        nmi,
-	Breakpoint:                 breakpoint,
-	Overflow:                   overflow,
-	BoundRangeExceeded:         boundRangeExceeded,
-	InvalidOpcode:              invalidOpcode,
-	DeviceNotAvailable:         deviceNotAvailable,
-	DoubleFault:                doubleFault,
-	CoprocessorSegmentOverrun:  coprocessorSegmentOverrun,
-	InvalidTSS:                 invalidTSS,
-	SegmentNotPresent:          segmentNotPresent,
-	StackSegmentFault:          stackSegmentFault,
-	GeneralProtectionFault:     generalProtectionFault,
-	PageFault:                  pageFault,
-	X87FloatingPointException:  x87FloatingPointException,
-	AlignmentCheck:             alignmentCheck,
-	MachineCheck:               machineCheck,
-	SIMDFloatingPointException: simdFloatingPointException,
-	VirtualizationException:    virtualizationException,
-	SecurityException:          securityException,
-	SyscallInt80:               syscallInt80,
+var handlers = map[Vector]uintptr{
+	DivideByZero:               addrOfDivideByZero(),
+	Debug:                      addrOfDebug(),
+	NMI:                        addrOfNMI(),
+	Breakpoint:                 addrOfBreakpoint(),
+	Overflow:                   addrOfOverflow(),
+	BoundRangeExceeded:         addrOfBoundRangeExceeded(),
+	InvalidOpcode:              addrOfInvalidOpcode(),
+	DeviceNotAvailable:         addrOfDeviceNotAvailable(),
+	DoubleFault:                addrOfDoubleFault(),
+	CoprocessorSegmentOverrun:  addrOfCoprocessorSegmentOverrun(),
+	InvalidTSS:                 addrOfInvalidTSS(),
+	SegmentNotPresent:          addrOfSegmentNotPresent(),
+	StackSegmentFault:          addrOfStackSegmentFault(),
+	GeneralProtectionFault:     addrOfGeneralProtectionFault(),
+	PageFault:                  addrOfPageFault(),
+	X87FloatingPointException:  addrOfX87FloatingPointException(),
+	AlignmentCheck:             addrOfAlignmentCheck(),
+	MachineCheck:               addrOfMachineCheck(),
+	SIMDFloatingPointException: addrOfSimdFloatingPointException(),
+	VirtualizationException:    addrOfVirtualizationException(),
+	SecurityException:          addrOfSecurityException(),
+	SyscallInt80:               addrOfSyscallInt80(),
 }