// selfhost/cmd/6l/pass.ww — port of cmd/6l/pass.c.
//
// Resolution + relocation. l_resolve flags every undefined symbol
// referenced by a relocation. l_relocate walks the rel list and
// patches the .text bytes in place once the final virtual base is
// known. Supported relocation kinds: PC32 (=2), PLT32 (=4); both
// are 32-bit PC-relative displacements (PLT32 == PC32 for static).

use os;
use sym;

def R_X86_64_PC32:  i32 = 2;
def R_X86_64_PLT32: i32 = 4;

export fn l_resolve(l: *lnk) i32 = {
	let r: *lrel = l.rels;
	for (r != nil) {
		if (r.sym != nil) {
			if (r.sym.defined == 0) {
				os.write(2, "6l: undefined reference to '".ptr, 28u64);
				let nm: str = r.sym.name;
				os.write(2, nm.ptr, nm.len: u64);
				os.write(2, "'\n".ptr, 2u64);
				l.errs += 1;
			};
		};
		r = r.rnext;
	};
	return l.errs;
};

fn patch_u32(p: *u8, v: u32) void = {
	p[0] = (v & 255u32): u8;
	p[1] = ((v >> 8u32) & 255u32): u8;
	p[2] = ((v >> 16u32) & 255u32): u8;
	p[3] = ((v >> 24u32) & 255u32): u8;
};

export fn l_relocate(l: *lnk, base: u64) i32 = {
	let r: *lrel = l.rels;
	for (r != nil) {
		if (r.sym != nil) {
			if (r.sym.defined != 0) {
				let k: i32 = r.kind;
				if (k == R_X86_64_PC32) {
					let site: u64 = base + r.off;
					let target: i64 = (base + r.sym.val): i64;
					let rel: i64 = (target - site: i64) + r.addend;
					patch_u32(l.text + r.off, rel: u32);
				} else { if (k == R_X86_64_PLT32) {
					let site: u64 = base + r.off;
					let target: i64 = (base + r.sym.val): i64;
					let rel: i64 = (target - site: i64) + r.addend;
					patch_u32(l.text + r.off, rel: u32);
				} else {
					os.write(2, "6l: unsupported reloc kind\n".ptr, 27u64);
					l.errs += 1;
				};};
			};
		};
		r = r.rnext;
	};
	return l.errs;
};