// rt/alloc.s — raw page primitive via the mmap syscall.
//
// rt_segmalloc(n: u64) returns a *void aligned at a page boundary, sized
// to the next page multiple. It is the primitive under rt/malloc.ww's
// bump allocator (renamed from rt_malloc, task #8) — callers use the
// bump rt_malloc, not this directly.
//
// We pin to PROT_READ|PROT_WRITE and MAP_PRIVATE|MAP_ANONYMOUS so
// callers never have to plumb file descriptors through.
//
// On mmap failure the raw syscall returns -errno (negative); we map
// that to 0 so the bump allocator's null-check (and the alloc builtin's
// `!`/`?` lowering, task #30) sees a clean nil.

TEXT rt_segmalloc,$0
	MOVQ	DI, SI		// arg 1: length = caller's n
	MOVQ	$0, DI		// arg 0: addr = NULL (kernel chooses)
	MOVQ	$3, DX		// arg 2: prot = R|W
	MOVQ	$34, R10	// arg 3: flags = MAP_PRIVATE|MAP_ANON
	MOVQ	$-1, R8		// arg 4: fd = -1
	MOVQ	$0, R9		// arg 5: offset = 0
	MOVQ	$9, AX		// syscall: mmap
	SYSCALL
	CMPQ	$0, AX
	JGE	rt_segmalloc_ok
	XORQ	AX, AX
rt_segmalloc_ok:
	RET

// rt_free is a no-op: ww is a no-free runtime. rt/malloc.ww bumps over
// shared 2MiB chunks, so a mid-chunk pointer cannot be unmapped without
// corrupting its neighbours; all memory is reclaimed at process exit.
// Kept as a symbol because os.free re-exports it (lib/os/os.ww) for the
// public API — callers' frees become harmless leaks. (task #8)
TEXT rt_free,$0
	RET