nintendoswitch: Add experimental Nintendo Switch support without CRT

Bare minimal nintendo switch support using LLD

src/runtime/runtime_nintendoswitch.go

@@ -0,0 +1,73 @@
+// +build nintendoswitch
+
+package runtime
+
+type timeUnit int64
+
+const asyncScheduler = false
+
+func postinit() {}
+
+// Entry point for Go. Initialize all packages and call main.main().
+//export main
+func main() int {
+	preinit()
+	run()
+
+	// Call exit to correctly finish the program
+	// Without this, the application crashes at start, not sure why
+	return exit(0)
+}
+
+// sleepTicks sleeps for the specified system ticks
+func sleepTicks(d timeUnit) {
+	sleepThread(uint64(ticksToNanoseconds(d)))
+}
+
+// armTicksToNs converts cpu ticks to nanoseconds
+// Nintendo Switch CPU ticks has a fixed rate at 19200000
+// It is basically 52 ns per tick
+// The formula 625 / 12 is equivalent to 1e9 / 19200000
+func ticksToNanoseconds(tick timeUnit) int64 {
+	return int64(tick * 625 / 12)
+}
+
+func nanosecondsToTicks(ns int64) timeUnit {
+	return timeUnit(12 * ns / 625)
+}
+
+func ticks() timeUnit {
+	return timeUnit(ticksToNanoseconds(timeUnit(getArmSystemTick())))
+}
+
+var stdoutBuffer = make([]byte, 0, 120)
+
+func putchar(c byte) {
+	if c == '\n' || len(stdoutBuffer)+1 >= 120 {
+		NxOutputString(string(stdoutBuffer))
+		stdoutBuffer = stdoutBuffer[:0]
+		return
+	}
+
+	stdoutBuffer = append(stdoutBuffer, c)
+}
+
+func usleep(usec uint) int {
+	sleepThread(uint64(usec) * 1000)
+	return 0
+}
+
+func abort() {
+	for {
+		exit(1)
+	}
+}
+
+//export sleepThread
+func sleepThread(nanos uint64)
+
+//export exit
+func exit(code int) int
+
+//export armGetSystemTick
+func getArmSystemTick() int64

src/runtime/runtime_nintendoswitch.s

@@ -0,0 +1,45 @@
+.section .text.armGetSystemTick, "ax", %progbits
+.global  armGetSystemTick
+.type    armGetSystemTick, %function
+.align 2
+armGetSystemTick:
+    mrs x0, cntpct_el0
+    ret
+
+.section .text.nxOutputString, "ax", %progbits
+.global nxOutputString
+.type nxOutputString, %function
+.align 2
+.cfi_startproc
+nxOutputString:
+	svc 0x27
+	ret
+.cfi_endproc
+
+.section .text.exit, "ax", %progbits
+.global exit
+.type exit, %function
+.align 2
+exit:
+	svc 0x7
+	ret
+
+.section .text.setHeapSize, "ax", %progbits
+.global setHeapSize
+.type setHeapSize, %function
+.align 2
+setHeapSize:
+	str x0, [sp, #-16]!
+	svc 0x1
+	ldr x2, [sp], #16
+	str x1, [x2]
+	ret
+
+
+.section .text.sleepThread, "ax", %progbits
+.global sleepThread
+.type sleepThread, %function
+.align 2
+sleepThread:
+	svc 0xB
+	ret

src/runtime/runtime_nintendoswitch_heap.go

@@ -0,0 +1,31 @@
+// +build nintendoswitch
+
+// +build gc.conservative gc.leaking
+
+package runtime
+
+import "unsafe"
+
+const heapSize = 0x2000000 * 16 // Default by libnx
+
+//go:extern _stack_top
+var stackTopSymbol [0]byte
+
+var (
+	heapStart = uintptr(0)
+	heapEnd   = uintptr(0)
+	stackTop  = uintptr(unsafe.Pointer(&stackTopSymbol))
+)
+
+//export setHeapSize
+func setHeapSize(addr *uintptr, length uint64) uint64
+
+func preinit() {
+	setHeapSize(&heapStart, heapSize)
+
+	if heapStart == 0 {
+		panic("failed to allocate heap")
+	}
+
+	heapEnd = heapStart + heapSize
+}

src/runtime/runtime_nintendoswitch_noheap.go

@@ -0,0 +1,7 @@
+// +build nintendoswitch
+
+// +build gc.none gc.extalloc
+
+package runtime
+
+func preinit() {}

src/runtime/runtime_nintendoswitch_svc.go

@@ -0,0 +1,22 @@
+// +build nintendoswitch
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+// Result nxOutputString(const char *str, u64 size)
+//export nxOutputString
+func nxOutputString(str *uint8, size uint64) uint64
+
+func NxOutputString(str string) uint64 {
+	strData := (*_string)(unsafe.Pointer(&str))
+	return nxOutputString((*uint8)(unsafe.Pointer(strData.ptr)), uint64(strData.length))
+}
+
+//export malloc
+func extalloc(size uintptr) unsafe.Pointer
+
+//export free
+func extfree(ptr unsafe.Pointer)

src/runtime/runtime_unix.go

@@ -1,4 +1,5 @@
 // +build darwin linux,!baremetal freebsd,!baremetal
+// +build !nintendoswitch
 
 package runtime
 

src/runtime/runtime_unix_heap.go

@@ -1,4 +1,5 @@
 // +build darwin linux,!baremetal freebsd,!baremetal
+// +build !nintendoswitch
 
 // +build gc.conservative gc.leaking
 

src/runtime/runtime_unix_noheap.go

@@ -1,5 +1,7 @@
 // +build darwin linux,!baremetal freebsd,!baremetal
 
+// +build !nintendoswitch
+
 // +build gc.none gc.extalloc
 
 package runtime

src/syscall/syscall_libc.go

@@ -1,4 +1,4 @@
-// +build darwin
+// +build darwin nintendoswitch
 
 package syscall
 

src/syscall/syscall_nintendoswitch.go

@@ -0,0 +1,48 @@
+// +build nintendoswitch
+
+package syscall
+
+import "errors"
+
+// A Signal is a number describing a process signal.
+// It implements the os.Signal interface.
+type Signal int
+
+const (
+	_ Signal = iota
+	SIGCHLD
+	SIGINT
+	SIGKILL
+	SIGTRAP
+	SIGQUIT
+	SIGTERM
+)
+
+// File system
+
+const (
+	Stdin  = 0
+	Stdout = 1
+	Stderr = 2
+)
+
+const (
+	O_RDONLY = 0
+	O_WRONLY = 1
+	O_RDWR   = 2
+
+	O_CREAT  = 0100
+	O_CREATE = O_CREAT
+	O_TRUNC  = 01000
+	O_APPEND = 02000
+	O_EXCL   = 0200
+	O_SYNC   = 010000
+
+	O_CLOEXEC = 0
+)
+
+var dummyError = errors.New("unknown syscall error")
+
+func getErrno() error {
+	return dummyError
+}

src/syscall/tables_baremetal.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build baremetal
+// +build baremetal nintendoswitch
 
 package syscall