Extract kvm variants of Syscall helpers to their own pkg.

These are already used in platform/kvm and pkg/sigframe. Maybe there will be
more in the future that are outside KVM, we don't want to keep redefining
these.

PiperOrigin-RevId: 680737814

pkg/hostsyscall/BUILD

@@ -0,0 +1,17 @@
+load("//tools:defs.bzl", "go_library")
+
+package(
+    default_applicable_licenses = ["//:license"],
+    licenses = ["notice"],
+)
+
+go_library(
+    name = "hostsyscall",
+    srcs = [
+        "hostsyscall.go",
+        "hostsyscall_amd64.s",
+        "hostsyscall_arm64.s",
+    ],
+    visibility = ["//:sandbox"],
+    deps = ["@org_golang_x_sys//unix:go_default_library"],
+)

pkg/hostsyscall/hostsyscall.go

@@ -0,0 +1,45 @@
+// Copyright 2024 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build linux
+// +build linux
+
+// Package hostsyscall provides functions like unix.RawSyscall, but without the
+// overhead of multiple stack frame allocations.
+//
+// This is mostly relevant for platform/kvm which needs to execute some function
+// call chains in a go:nosplit environment. Debug builds specifically make using
+// unix.RawSyscall variants infeasible.
+package hostsyscall
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// RawSyscall6 is a copy of runtime.Syscall6.
+func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, errno unix.Errno)
+
+// RawSyscall is a copy of runtime.Syscall6, but only uses the first three arguments.
+func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, errno unix.Errno)
+
+// Variants of runtime.Syscall6 that use slightly less stack space by only
+// returning errno.
+
+// RawSyscallErrno6 is like RawSyscall6, but only returns errno,
+// and 0 if successful.
+func RawSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) unix.Errno
+
+// RawSyscallErrno is like RawSyscall, but only returns errno,
+// and 0 if successful.
+func RawSyscallErrno(trap, a1, a2, a3 uintptr) unix.Errno

pkg/hostsyscall/hostsyscall_amd64.s

@@ -0,0 +1,100 @@
+// Copyright 2024 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "textflag.h"
+
+// func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno)
+TEXT ·RawSyscall6(SB),NOSPLIT,$0-80
+	MOVQ a1+8(FP), DI
+	MOVQ a2+16(FP), SI
+	MOVQ a3+24(FP), DX
+	MOVQ a4+32(FP), R10
+	MOVQ a5+40(FP), R8
+	MOVQ a6+48(FP), R9
+	MOVQ trap+0(FP), AX  // syscall entry
+	SYSCALL
+	CMPQ AX, $0xfffffffffffff001
+	JLS ok
+	MOVQ $-1, r1+56(FP)
+	MOVQ $0, r2+64(FP)
+	NEGQ AX
+	MOVQ AX, errno+72(FP)
+	RET
+ok:
+	MOVQ AX, r1+56(FP)
+	MOVQ DX, r2+64(FP)
+	MOVQ $0, errno+72(FP)
+	RET
+
+// func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, errno)
+TEXT ·RawSyscall(SB),NOSPLIT,$0-56
+	MOVQ a1+8(FP), DI
+	MOVQ a2+16(FP), SI
+	MOVQ a3+24(FP), DX
+	MOVQ $0, R10
+	MOVQ $0, R8
+	MOVQ $0, R9
+	MOVQ trap+0(FP), AX  // syscall entry
+	SYSCALL
+	CMPQ AX, $0xfffffffffffff001
+	JLS ok
+	MOVQ $-1, r1+32(FP)
+	MOVQ $0, r2+40(FP)
+	NEGQ AX
+	MOVQ AX, errno+48(FP)
+	RET
+ok:
+	MOVQ AX, r1+32(FP)
+	MOVQ DX, r2+40(FP)
+	MOVQ $0, errno+48(FP)
+	RET
+
+
+// func RawSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) (ret unix.Errno)
+TEXT ·RawSyscallErrno6(SB),NOSPLIT,$0-64
+	MOVQ a1+8(FP), DI
+	MOVQ a2+16(FP), SI
+	MOVQ a3+24(FP), DX
+	MOVQ a4+32(FP), R10
+	MOVQ a5+40(FP), R8
+	MOVQ a6+48(FP), R9
+	MOVQ trap+0(FP), AX  // syscall entry
+	SYSCALL
+	CMPQ AX, $0xfffffffffffff001
+	JLS ok
+	NEGQ AX
+	MOVQ AX, ret+56(FP)
+	RET
+ok:
+	MOVQ $0, ret+56(FP)
+	RET
+
+// func RawSyscallErrno(trap, a1, a2, a3 uintptr) (ret unix.Errno)
+TEXT ·RawSyscallErrno(SB),NOSPLIT,$0-40
+	MOVQ a1+8(FP), DI
+	MOVQ a2+16(FP), SI
+	MOVQ a3+24(FP), DX
+	MOVQ $0, R10
+	MOVQ $0, R8
+	MOVQ $0, R9
+	MOVQ trap+0(FP), AX  // syscall entry
+	SYSCALL
+	CMPQ AX, $0xfffffffffffff001
+	JLS ok
+	NEGQ AX
+	MOVQ AX, ret+32(FP)
+	RET
+ok:
+	MOVQ $0, ret+32(FP)
+	RET

pkg/hostsyscall/hostsyscall_arm64.s

@@ -0,0 +1,101 @@
+// Copyright 2024 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "textflag.h"
+
+// func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr)
+TEXT ·RawSyscall6(SB),NOSPLIT,$0-80
+	MOVD trap+0(FP), R8   // syscall entry
+	MOVD a1+8(FP), R0
+	MOVD a2+16(FP), R1
+	MOVD a3+24(FP), R2
+	MOVD a4+32(FP), R3
+	MOVD a5+40(FP), R4
+	MOVD a6+48(FP), R5
+	SVC
+	CMN $4095, R0
+	BCC ok
+	MOVD $-1, R4
+	MOVD R4, r1+56(FP)
+	MOVD ZR, r2+64(FP)
+	NEG R0, R0
+	MOVD R0, errno+72(FP)
+	RET
+ok:
+	MOVD R0, r1+56(FP)
+	MOVD R1, r2+64(FP)
+	MOVD ZR, errno+72(FP)
+	RET
+
+// func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, errno uintptr)
+TEXT ·RawSyscall(SB),NOSPLIT,$0-56
+	MOVD trap+0(FP), R8   // syscall entry
+	MOVD a1+8(FP), R0
+	MOVD a2+16(FP), R1
+	MOVD a3+24(FP), R2
+	MOVD ZR, R3
+	MOVD ZR, R4
+	MOVD ZR, R5
+	SVC
+	CMN $4095, R0
+	BCC ok
+	MOVD $-1, R4
+	MOVD R4, r1+32(FP)
+	MOVD ZR, r2+40(FP)
+	NEG R0, R0
+	MOVD R0, errno+48(FP)
+	RET
+ok:
+	MOVD R0, r1+32(FP)
+	MOVD R1, r2+40(FP)
+	MOVD ZR, errno+48(FP)
+	RET
+
+// func RawSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) (errno unix.Errno)
+TEXT ·RawSyscallErrno6(SB),NOSPLIT,$0-64
+	MOVD trap+0(FP), R8   // syscall entry
+	MOVD a1+8(FP), R0
+	MOVD a2+16(FP), R1
+	MOVD a3+24(FP), R2
+	MOVD a4+32(FP), R3
+	MOVD a5+40(FP), R4
+	MOVD a6+48(FP), R5
+	SVC
+	CMN $4095, R0
+	BCC ok
+	NEG R0, R0
+	MOVD R0, ret+56(FP) // errno
+	RET
+ok:
+	MOVD ZR, ret+56(FP) // errno
+	RET
+
+// func RawSyscallErrno(trap, a1, a2, a3 uintptr) (errno unix.Errno)
+TEXT ·RawSyscallErrno(SB),NOSPLIT,$0-40
+	MOVD trap+0(FP), R8   // syscall entry
+	MOVD a1+8(FP), R0
+	MOVD a2+16(FP), R1
+	MOVD a3+24(FP), R2
+	MOVD ZR, R3
+	MOVD ZR, R4
+	MOVD ZR, R5
+	SVC
+	CMN $4095, R0
+	BCC ok
+	NEG R0, R0
+	MOVD R0, ret+32(FP) // errno
+	RET
+ok:
+	MOVD ZR, ret+32(FP) // errno
+	RET

pkg/sentry/platform/kvm/BUILD

@@ -93,6 +93,7 @@ go_library(
         "//pkg/fd",
         "//pkg/hostarch",
         "//pkg/hostos",
+        "//pkg/hostsyscall",
         "//pkg/hosttid",
         "//pkg/log",
         "//pkg/metric",

pkg/sentry/platform/kvm/bluepill.go

@@ -16,6 +16,7 @@ package kvm
 
 import (
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/ring0"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
@@ -70,7 +71,7 @@ const _SYS_KVM_RETURN_TO_HOST = ^uintptr(0)
 //
 //go:nosplit
 func redpill() {
-	kvmSyscallErrno(_SYS_KVM_RETURN_TO_HOST, 0, 0, 0)
+	hostsyscall.RawSyscallErrno(_SYS_KVM_RETURN_TO_HOST, 0, 0, 0)
 }
 
 // dieHandler is called by dieTrampoline.

pkg/sentry/platform/kvm/bluepill_amd64.s

@@ -91,38 +91,3 @@ TEXT ·currentCPU(SB), $0-8
 	MOVQ ENTRY_CPU_SELF(GS), AX
 	MOVQ AX, ret+0(FP)
 	RET
-
-// func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) (ret unix.Errno)
-TEXT ·kvmSyscallErrno6(SB),NOSPLIT,$0-64
-	MOVQ a1+8(FP), DI
-	MOVQ a2+16(FP), SI
-	MOVQ a3+24(FP), DX
-	MOVQ a4+32(FP), R10
-	MOVQ a5+40(FP), R8
-	MOVQ a6+48(FP), R9
-	MOVQ trap+0(FP), AX  // syscall entry
-	SYSCALL
-	CMPQ AX, $0xfffffffffffff001
-	JLS ok
-	NEGQ AX
-	MOVQ AX, ret+56(FP)  // ret
-	RET
-ok:
-	MOVQ $0, ret+56(FP)  // ret
-	RET
-
-// func kvmSyscallErrno(trap, a1, a2, a3 uintptr) (ret unix.Errno)
-TEXT ·kvmSyscallErrno(SB),NOSPLIT,$0-40
-	MOVQ a1+8(FP), DI
-	MOVQ a2+16(FP), SI
-	MOVQ a3+24(FP), DX
-	MOVQ trap+0(FP), AX  // syscall entry
-	SYSCALL
-	CMPQ AX, $0xfffffffffffff001
-	JLS ok
-	NEGQ AX
-	MOVQ AX, ret+32(FP)  // ret
-	RET
-ok:
-	MOVQ $0, ret+32(FP)  // ret
-	RET

pkg/sentry/platform/kvm/bluepill_amd64_unsafe.go

@@ -25,6 +25,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/cpuid"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/ring0"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sigframe"
@@ -74,7 +75,7 @@ func getHypercallID(addr uintptr) int {
 func bluepillStopGuest(c *vCPU) {
 	// Interrupt: we must have requested an interrupt
 	// window; set the interrupt line.
-	if errno := kvmSyscallErrno(
+	if errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_INTERRUPT,
@@ -89,7 +90,7 @@ func bluepillStopGuest(c *vCPU) {
 //
 //go:nosplit
 func bluepillSigBus(c *vCPU) {
-	if errno := kvmSyscallErrno(
+	if errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_NMI, 0); errno != 0 {

pkg/sentry/platform/kvm/bluepill_arm64.s

@@ -145,38 +145,3 @@ TEXT ·addrOfDieTrampoline(SB), $0-8
 	MOVD	$·dieTrampoline(SB), R0
 	MOVD	R0, ret+0(FP)
 	RET
-
-// func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) (errno unix.Errno)
-TEXT	·kvmSyscallErrno6(SB),NOSPLIT,$0-64
-	MOVD trap+0(FP), R8   // syscall entry
-	MOVD a1+8(FP), R0
-	MOVD a2+16(FP), R1
-	MOVD a3+24(FP), R2
-	MOVD a4+32(FP), R3
-	MOVD a5+40(FP), R4
-	MOVD a6+48(FP), R5
-	SVC
-	CMN $4095, R0
-	BCC ok
-	NEG R0, R0
-	MOVD R0, ret+56(FP)
-	RET
-ok:
-	MOVD $0, ret+56(FP)
-	RET
-
-// func kvmSyscallErrno(trap, a1, a2, a3 uintptr) (errno unix.Errno)
-TEXT ·kvmSyscallErrno(SB),NOSPLIT,$0-40
-	MOVD trap+0(FP), R8   // syscall entry
-	MOVD a1+8(FP), R0
-	MOVD a2+16(FP), R1
-	MOVD a3+24(FP), R2
-	SVC
-	CMN $4095, R0
-	BCC ok
-	NEG R0, R0
-	MOVD R0, ret+32(FP)
-	RET
-ok:
-	MOVD ZR, ret+32(FP)
-	RET

pkg/sentry/platform/kvm/bluepill_arm64_unsafe.go

@@ -21,6 +21,7 @@ import (
 	"unsafe"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/ring0"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
@@ -88,7 +89,7 @@ func bluepillStopGuest(c *vCPU) {
 		},
 	}
 
-	if errno := kvmSyscallErrno( // escapes: no.
+	if errno := hostsyscall.RawSyscallErrno( // escapes: no.
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_SET_VCPU_EVENTS,
@@ -111,7 +112,7 @@ func bluepillSigBus(c *vCPU) {
 	}
 
 	// Host must support ARM64_HAS_RAS_EXTN.
-	if errno := kvmSyscallErrno( // escapes: no.
+	if errno := hostsyscall.RawSyscallErrno( // escapes: no.
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_SET_VCPU_EVENTS,
@@ -134,7 +135,7 @@ func bluepillExtDabt(c *vCPU) {
 		},
 	}
 
-	if errno := kvmSyscallErrno( // escapes: no.
+	if errno := hostsyscall.RawSyscallErrno( // escapes: no.
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_SET_VCPU_EVENTS,

pkg/sentry/platform/kvm/bluepill_fault.go

@@ -19,6 +19,7 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 )
 
 var (
@@ -40,7 +41,7 @@ var (
 //
 //go:nosplit
 func yield() {
-	kvmSyscallErrno(unix.SYS_SCHED_YIELD, 0, 0, 0)
+	hostsyscall.RawSyscallErrno(unix.SYS_SCHED_YIELD, 0, 0, 0)
 }
 
 // calculateBluepillFault calculates the fault address range.

pkg/sentry/platform/kvm/bluepill_unsafe.go

@@ -25,17 +25,10 @@ import (
 	"unsafe"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
 
-// Local variants of unix.RawSyscall that use slightly less stack space.
-
-// kvmSyscallErrno6 only returns errno, and 0 if successful.
-func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) unix.Errno
-
-// kvmSyscallErrno only returns errno, and 0 if successful.
-func kvmSyscallErrno(trap, a1, a2, a3 uintptr) unix.Errno
-
 //go:linkname throw runtime.throw
 func throw(s string)
 
@@ -99,8 +92,8 @@ func printHex(title []byte, val uint64) {
 	}
 	str[0] = ' '
 	str[17] = '\n'
-	kvmSyscallErrno(unix.SYS_WRITE, uintptr(unix.Stderr), uintptr(unsafe.Pointer(&title[0])), uintptr(len(title)))
-	kvmSyscallErrno(unix.SYS_WRITE, uintptr(unix.Stderr), uintptr(unsafe.Pointer(&str)), 18)
+	hostsyscall.RawSyscallErrno(unix.SYS_WRITE, uintptr(unix.Stderr), uintptr(unsafe.Pointer(&title[0])), uintptr(len(title)))
+	hostsyscall.RawSyscallErrno(unix.SYS_WRITE, uintptr(unix.Stderr), uintptr(unsafe.Pointer(&str)), 18)
 }
 
 // bluepillHandler is called from the signal stub.

pkg/sentry/platform/kvm/machine_amd64_unsafe.go

@@ -23,6 +23,7 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 )
 
 // loadSegments copies the current segments.
@@ -132,7 +133,7 @@ func (c *vCPU) setTSC(value uint64) error {
 //
 //go:nosplit
 func (c *vCPU) setUserRegisters(uregs *userRegs) unix.Errno {
-	if errno := kvmSyscallErrno(
+	if errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_SET_REGS,
@@ -148,7 +149,7 @@ func (c *vCPU) setUserRegisters(uregs *userRegs) unix.Errno {
 //
 //go:nosplit
 func (c *vCPU) getUserRegisters(uregs *userRegs) unix.Errno {
-	if errno := kvmSyscallErrno( // escapes: no.
+	if errno := hostsyscall.RawSyscallErrno( // escapes: no.
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_GET_REGS,
@@ -160,7 +161,7 @@ func (c *vCPU) getUserRegisters(uregs *userRegs) unix.Errno {
 
 // setSystemRegisters sets system registers.
 func (c *vCPU) setSystemRegisters(sregs *systemRegs) error {
-	if errno := kvmSyscallErrno(
+	if errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_SET_SREGS,
@@ -174,7 +175,7 @@ func (c *vCPU) setSystemRegisters(sregs *systemRegs) error {
 //
 //go:nosplit
 func (c *vCPU) getSystemRegisters(sregs *systemRegs) unix.Errno {
-	if errno := kvmSyscallErrno(
+	if errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(c.fd),
 		KVM_GET_SREGS,
@@ -189,9 +190,9 @@ func seccompMmapSyscall(context unsafe.Pointer) (uintptr, uintptr, unix.Errno) {
 	ctx := bluepillArchContext(context)
 
 	// MAP_DENYWRITE is deprecated and ignored by kernel. We use it only for seccomp filters.
-	addr, _, e := unix.RawSyscall6(uintptr(ctx.Rax), uintptr(ctx.Rdi), uintptr(ctx.Rsi),
+	addr, _, e := hostsyscall.RawSyscall6(uintptr(ctx.Rax), uintptr(ctx.Rdi), uintptr(ctx.Rsi),
 		uintptr(ctx.Rdx), uintptr(ctx.R10)|unix.MAP_DENYWRITE, uintptr(ctx.R8), uintptr(ctx.R9))
 	ctx.Rax = uint64(addr)
 
-	return addr, uintptr(ctx.Rsi), e
+	return addr, uintptr(ctx.Rsi), unix.Errno(e)
 }

pkg/sentry/platform/kvm/machine_arm64_unsafe.go

@@ -25,6 +25,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/ring0"
 	"gvisor.dev/gvisor/pkg/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
@@ -354,9 +355,9 @@ func seccompMmapSyscall(context unsafe.Pointer) (uintptr, uintptr, unix.Errno) {
 	ctx := bluepillArchContext(context)
 
 	// MAP_DENYWRITE is deprecated and ignored by kernel. We use it only for seccomp filters.
-	addr, _, e := unix.RawSyscall6(uintptr(ctx.Regs[8]), uintptr(ctx.Regs[0]), uintptr(ctx.Regs[1]),
+	addr, _, e := hostsyscall.RawSyscall6(uintptr(ctx.Regs[8]), uintptr(ctx.Regs[0]), uintptr(ctx.Regs[1]),
 		uintptr(ctx.Regs[2]), uintptr(ctx.Regs[3])|unix.MAP_DENYWRITE, uintptr(ctx.Regs[4]), uintptr(ctx.Regs[5]))
 	ctx.Regs[0] = uint64(addr)
 
-	return addr, uintptr(ctx.Regs[1]), e
+	return addr, uintptr(ctx.Regs[1]), unix.Errno(e)
 }

pkg/sentry/platform/kvm/machine_unsafe.go

@@ -31,6 +31,7 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/atomicbitops"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 )
 
 //go:linkname entersyscall runtime.entersyscall
@@ -55,7 +56,7 @@ func (m *machine) setMemoryRegion(slot int, physical, length, virtual uintptr, f
 	}
 
 	// Set the region.
-	errno := kvmSyscallErrno(
+	errno := hostsyscall.RawSyscallErrno(
 		unix.SYS_IOCTL,
 		uintptr(m.fd),
 		KVM_SET_USER_MEMORY_REGION,
@@ -119,7 +120,7 @@ func (a *atomicAddressSpace) get() *addressSpace {
 //
 //go:nosplit
 func (c *vCPU) notify() {
-	errno := kvmSyscallErrno6( // escapes: no.
+	errno := hostsyscall.RawSyscallErrno6( // escapes: no.
 		unix.SYS_FUTEX,
 		uintptr(unsafe.Pointer(&c.state)),
 		linux.FUTEX_WAKE|linux.FUTEX_PRIVATE_FLAG,
@@ -178,7 +179,7 @@ func (c *vCPU) setSignalMask() error {
 // instances.
 var seccompMmapHandlerCnt atomicbitops.Int64
 
-// seccompMmapSync waits for all currently runnuing seccompMmapHandler
+// seccompMmapSync waits for all currently running seccompMmapHandler
 // instances.
 //
 // The standard locking primitives can't be used in this case since

pkg/sigframe/BUILD

@@ -14,6 +14,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/abi/linux",
+        "//pkg/hostsyscall",
         "//pkg/sentry/arch",
         "@org_golang_x_sys//unix:go_default_library",
     ],

pkg/sigframe/sigframe_amd64.s

@@ -88,22 +88,3 @@ TEXT ·retjmp(SB),NOSPLIT,$0-0
 	MOVQ 8(SP), BP
 	ADDQ    $0x10,SP
 	RET
-
-// func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) (ret unix.Errno)
-TEXT ·kvmSyscallErrno6(SB),NOSPLIT,$0-64
-	MOVQ a1+8(FP), DI
-	MOVQ a2+16(FP), SI
-	MOVQ a3+24(FP), DX
-	MOVQ a4+32(FP), R10
-	MOVQ a5+40(FP), R8
-	MOVQ a6+48(FP), R9
-	MOVQ trap+0(FP), AX  // syscall entry
-	SYSCALL
-	CMPQ AX, $0xfffffffffffff001
-	JLS ok
-	NEGQ AX
-	MOVQ AX, ret+56(FP)  // ret
-	RET
-ok:
-	MOVQ $0, ret+56(FP)  // ret
-	RET

pkg/sigframe/sigframe_amd64_unsafe.go

@@ -22,6 +22,7 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/hostsyscall"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
 
@@ -30,9 +31,6 @@ func callWithSignalFrame(stack uintptr, handler uintptr, sigframe *arch.UContext
 //go:linkname throw runtime.throw
 func throw(s string)
 
-// kvmSyscallErrno6 only returns errno, and 0 if successful.
-func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) unix.Errno
-
 // CallWithSignalFrame sets up a signal frame on the stack and executes a
 // user-defined callback function within that context.
 //
@@ -41,7 +39,7 @@ func kvmSyscallErrno6(trap, a1, a2, a3, a4, a5, a6 uintptr) unix.Errno
 //
 //go:nosplit
 func CallWithSignalFrame(stack uintptr, handlerAddr uintptr, sigframe *arch.UContext64, fpstate uintptr, sigmask *linux.SignalSet) error {
-	errno := kvmSyscallErrno6(
+	errno := hostsyscall.RawSyscallErrno6(
 		unix.SYS_RT_SIGPROCMASK, linux.SIG_BLOCK,
 		uintptr(unsafe.Pointer(sigmask)),
 		uintptr(unsafe.Pointer(&sigframe.Sigset)),