Files
tinygo/src/runtime/runtime_mgba.go
T
zoey 7cbbfd6fc5 gba: add support for mGBA debugging
Implements `putchar` when `mgbadebug` build tag is set which outputs
text through the mGBA debugging output interface.

mGBA allows the games running in the emulator to output debug text the
process to do so is:
1. set 0x4FFF780 to value of 0xC0DE
2. write text in memory 0x4FFF600 to 0x4FFF700
3. set 0x4FFF700 to the desired log level value from 0x100 (fatal) to
0x104 (debug)

Once this is done mGBA will output the text in its logs view as well as
through stdout. (Setting the log level to fatal also produces a dialog
box with the text)

The text output in the CLI is prefixed with `[DEBUG] GBA Debug: ` so I
modified the regex used for address matching in panic messages to be
able to read the address when the output line doesn't start with
`panic`.
2026-06-05 17:55:03 +02:00

122 lines
2.2 KiB
Go

//go:build gameboyadvance && mgbadebug
package runtime
import (
_ "runtime/interrupt" // make sure the interrupt handler is defined
"runtime/volatile"
"unsafe"
)
var (
// Setting this memory address to 0xC0DE enables mGBA's debug printing
debugEnable = (*volatile.Register16)(unsafe.Pointer(uintptr(0x4FFF780)))
// mGBA supports log levels from 0x100(fatal) to 0x104(debug)
logLevel uint16 = 0x104 // use the debug log level
// Once we are ready to output we set the debug flags register to logLevel
// mGBA will output the text and then clear the text buffer when set
debugFlags = (*volatile.Register16)(unsafe.Pointer(uintptr(0x4FFF700)))
textBuffer = (*[255]byte)(unsafe.Pointer(uintptr(0x4FFF600)))
index = 0
)
func putchar(c byte) {
if c == '\n' || index >= len(textBuffer) {
debugFlags.Set(logLevel)
index = 0
// mGBA automatically prints a new line so we can ignore it
if c == '\n' {
return
}
}
textBuffer[index] = c
index++
}
func getchar() byte {
// dummy, TODO
return 0
}
func buffered() int {
// dummy, TODO
return 0
}
//go:extern _sbss
var _sbss [0]byte
//go:extern _ebss
var _ebss [0]byte
//go:extern _sdata
var _sdata [0]byte
//go:extern _sidata
var _sidata [0]byte
//go:extern _edata
var _edata [0]byte
// Entry point for Go. Initialize all packages and call main.main().
//
//export main
func main() {
// Initialize .data and .bss sections.
preinit()
// Enable mGBA debugging.
debugEnable.Set(0xC0DE)
// Run program.
run()
}
func preinit() {
// Initialize .bss: zero-initialized global variables.
ptr := unsafe.Pointer(&_sbss)
for ptr != unsafe.Pointer(&_ebss) {
*(*uint32)(ptr) = 0
ptr = unsafe.Add(ptr, 4)
}
// Initialize .data: global variables initialized from flash.
src := unsafe.Pointer(&_sidata)
dst := unsafe.Pointer(&_sdata)
for dst != unsafe.Pointer(&_edata) {
*(*uint32)(dst) = *(*uint32)(src)
dst = unsafe.Add(dst, 4)
src = unsafe.Add(src, 4)
}
}
func ticksToNanoseconds(ticks timeUnit) int64 {
return int64(ticks)
}
func nanosecondsToTicks(ns int64) timeUnit {
return timeUnit(ns)
}
func ticks() timeUnit {
// TODO
return 0
}
func sleepTicks(d timeUnit) {
// TODO
}
func exit(code int) {
abort()
}
func abort() {
// TODO
for {
}
}