all: add emulation support for Cortex-M3 with QEMU

src/device/arm/semihosting.go

@@ -0,0 +1,63 @@
+package arm
+
+// Semihosting commands.
+// http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471c/Bgbjhiea.html
+const (
+	// Regular semihosting calls
+	SemihostingClock      = 0x10
+	SemihostingClose      = 0x02
+	SemihostingElapsed    = 0x30
+	SemihostingErrno      = 0x13
+	SemihostingFileLen    = 0x0C
+	SemihostingGetCmdline = 0x15
+	SemihostingHeapInfo   = 0x16
+	SemihostingIsError    = 0x08
+	SemihostingIsTTY      = 0x09
+	SemihostingOpen       = 0x01
+	SemihostingRead       = 0x06
+	SemihostingReadByte   = 0x07
+	SemihostingRemove     = 0x0E
+	SemihostingRename     = 0x0F
+	SemihostingSeek       = 0x0A
+	SemihostingSystem     = 0x12
+	SemihostingTickFreq   = 0x31
+	SemihostingTime       = 0x11
+	SemihostingTmpName    = 0x0D
+	SemihostingWrite      = 0x05
+	SemihostingWrite0     = 0x04
+	SemihostingWriteByte  = 0x03
+
+	// Angel semihosting calls
+	SemihostingEnterSVC        = 0x17
+	SemihostingReportException = 0x18
+)
+
+// Special codes for the Angel Semihosting interface.
+const (
+	// Hardware vector reason codes
+	SemihostingBranchThroughZero = 20000
+	SemihostingUndefinedInstr    = 20001
+	SemihostingSoftwareInterrupt = 20002
+	SemihostingPrefetchAbort     = 20003
+	SemihostingDataAbort         = 20004
+	SemihostingAddressException  = 20005
+	SemihostingIRQ               = 20006
+	SemihostingFIQ               = 20007
+
+	// Software reason codes
+	SemihostingBreakPoint          = 20020
+	SemihostingWatchPoint          = 20021
+	SemihostingStepComplete        = 20022
+	SemihostingRunTimeErrorUnknown = 20023
+	SemihostingInternalError       = 20024
+	SemihostingUserInterruption    = 20025
+	SemihostingApplicationExit     = 20026
+	SemihostingStackOverflow       = 20027
+	SemihostingDivisionByZero      = 20028
+	SemihostingOSSpecific          = 20029
+)
+
+// Call a semihosting function.
+// TODO: implement it here using inline assembly.
+//go:linkname SemihostingCall SemihostingCall
+func SemihostingCall(num int, arg uintptr) int

src/runtime/runtime_qemu.go

@@ -0,0 +1,45 @@
+// +build qemu
+
+package runtime
+
+// This file implements the Stellaris LM3S6965 Cortex-M3 chip as implemented by
+// QEMU.
+
+import (
+	"device/arm"
+	"unsafe"
+)
+
+type timeUnit int64
+
+const tickMicros = 1
+
+var timestamp timeUnit
+
+//go:export Reset_Handler
+func main() {
+	preinit()
+	initAll()
+	mainWrapper()
+	arm.SemihostingCall(arm.SemihostingReportException, arm.SemihostingApplicationExit)
+	abort()
+}
+
+func sleepTicks(d timeUnit) {
+	// TODO: actually sleep here for the given time.
+	timestamp += d
+}
+
+func ticks() timeUnit {
+	return timestamp
+}
+
+//go:volatile
+type regValue uint32
+
+// UART0 output register.
+var stdoutWrite *regValue = (*regValue)(unsafe.Pointer(uintptr(0x4000c000)))
+
+func putchar(c byte) {
+	*stdoutWrite = regValue(c)
+}