runtime: improve hardfault handler and stack reporting on Cortex-M

[digitalentity]

Add reference to the current goroutine stack (PSP) when showing the hardfault info on Cortex-M. The stack where the hardfault happens is usually the scheduler's stack (MSP), which provides no information about the goroutine that actually caused the fault.

This was required to debug random crashes (#5375). The reason was stack overflow, which trigered the udf instruction. The MSP only pointed to the HardFault handler and the PC initially suggested stack corruption and nil dereference, while in reality the stack canary was overwritten which triggered a panic.

[digitalentity]

The TestBuild test is flaky - I've seen it failing randomly even locally.

[aykevl]

Yes this looks useful to me, though see some concerns below.

One possible improvement could be to recognize this line in the monitor, so that the source line is automatically printed in a panic:

tinygo/monitor.go

Lines 281 to 293 in de83d67

	var addressMatch = regexp.MustCompile(`^panic: runtime error at 0x([0-9a-f]+): `)
	// Extract the address from the "panic: runtime error at" message.
	func extractPanicAddress(line []byte) uint64 {
	matches := addressMatch.FindSubmatch(line)
	if matches != nil {
	address, err := strconv.ParseUint(string(matches[1]), 16, 64)
	if err == nil {
	return address
	}
	}
	return 0
	}

[aykevl]

Assuming 256kB of RAM seems kind of arbitrary?
I would suggest either using the range according to the Cortex-M memory map (0x2000_0000..0x3fff_ffff) or using the actual chip RAM (currently exposed as _heap_end).

[digitalentity]

Good point. Updated.

[aykevl]

I suspect you'll also need a declaration of this for -scheduler=cores (try tinygo build -scheduler=cores -target=pico examples/blinky1).

[digitalentity]

No, the file has a build constraint of //go:build (scheduler.tasks || scheduler.cores) && cortexm - already including the scheduler.cores.

[deadprogram]

@digitalentity could you please rebase this PR against the latest dev branch to resolve merge conflicts? Thank you.

[digitalentity]

@deadprogram done

[deadprogram]

Thanks for the improvements here @digitalentity now merging.