dwt/loader: COFF loader places GSPLNK images and runs them via create_process

dwt/loader/marker.asm

@@ -0,0 +1,66 @@
+; marker.asm -- loader acceptance app.
+;
+; Built by dwt/loader/build.sh with three separate section origins:
+;   .text 018C0000h   (byte 0x318000)
+;   .data 018D0000h   (byte 0x31A000)
+;   .bss  018D8000h   (byte 0x31B000)
+;
+; It is the *COFF image* that the loader must place; it is never poked as a
+; raw blob.  The loader parses the COFF, copies .text and .data, zeroes .bss,
+; and calls create_process() with the image's entry point.
+;
+; Evidence cells (32-bit, bit addresses; outside every app section):
+;   018E0000  _start address at run time (must be 018C0000)
+;   018E0020  d_magic read from .data  (must be DEADBEEF)
+;   018E0040  d_two   read from .data  (must be 12345678)
+;   018E0060  b_zero  read from .bss   (must be 0; the harness pre-fills A5)
+;   018E0080  b_counter, incremented forever (proves the child is scheduled)
+;
+; The harness pre-fills the whole .bss range with A5A5A5A5 before the load, so
+; a zero at 018E0060 is the loader's zero-fill, not a fresh-RAM accident.
+
+	.def	_start
+	.text
+_start:
+	setf	16, 0, 0
+	setf	32, 0, 1
+
+	; Run-time address of this code: position dependence, made visible.
+	movi	_start, a2, L
+	move	a2, @018E0000h, 1
+
+	; Initialised .data must have been copied by the loader.
+	move	@d_magic, a0, 1
+	move	a0, @018E0020h, 1
+
+	move	@d_two, a1, 1
+	move	a1, @018E0040h, 1
+
+	; .bss must have been zeroed by the loader (harness pre-fills A5).
+	move	@b_zero, a3, 1
+	move	a3, @018E0060h, 1
+
+	; A live counter: a created process, not a one-shot jump.
+	sub	a4, a4
+loop:
+	addi	1, a4
+	move	a4, @b_counter, 1
+	move	a4, @018E0080h, 1
+	movi	2000h, a5, L
+delay:
+	dsjs	a5, delay
+	jruc	loop
+
+	; Kept to leave a call in the image (and a relocation in the .obj).
+	.global	sub
+sub:
+	rets
+
+	.data
+d_magic: .long	0DEADBEEFh
+d_two:	 .long	012345678h
+
+	.bss	b_zero, 32, 1
+	.bss	b_counter, 32, 1
+
+	.end