fix(elf): relocation records, DWARF tables and per-architecture frame data

Assisted-by: GLM 5.3

asm/elfarm64_test.go

@@ -6,6 +6,7 @@ package asm
 import (
 	"bytes"
 	"debug/elf"
+	"encoding/binary"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
@@ -28,6 +29,7 @@ TEXT ·add(SB), NOSPLIT, $0-24
 
 TEXT ·getanswer(SB), NOSPLIT, $0-8
 	MOVD answer<>(SB), R4
+	MOVD $answer<>(SB), R5
 	MOVD R4, ret+0(FP)
 	RET
 
@@ -102,8 +104,63 @@ DATA answer<>+0(SB)/8, $42
 	// Check that .rela.text exists (getanswer has SB reference).
 	relaText := ef.Section(".rela.text")
 	if relaText == nil {
-		t.Error("missing .rela.text section")
+		t.Fatal("missing .rela.text section")
 	}
+
+	// The SB references of getanswer form two ADRP pairs: the load
+	// (MOVD answer<>(SB), R4) is ADRP+LDR carrying HI21 at the ADRP and
+	// LDST64_ABS_LO12_NC at the LDR word, and the address-of
+	// (MOVD $answer<>(SB), R5) is ADRP+ADD carrying HI21 and
+	// ADD_ABS_LO12_NC.  cmd/link's own conversion emits exactly this
+	// sectoff / sectoff+4 pairing; a second HI21 at the ADD or LDR word
+	// corrupts the pair.
+	raw, err := relaText.Data()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(raw)%24 != 0 || len(raw)/24 != 4 {
+		t.Fatalf(".rela.text has %d bytes, want four 24-byte entries", len(raw))
+	}
+	wantRela := []struct {
+		typ elf.R_AARCH64
+		off uint64 // relative to the getanswer function start
+	}{
+		{elf.R_AARCH64_ADR_PREL_PG_HI21, 0},
+		{elf.R_AARCH64_LDST64_ABS_LO12_NC, 4},
+		{elf.R_AARCH64_ADR_PREL_PG_HI21, 8},
+		{elf.R_AARCH64_ADD_ABS_LO12_NC, 12},
+	}
+	getanswer := byNameElf(t, ef, "getanswer")
+	for i, w := range wantRela {
+		e := raw[i*24 : (i+1)*24]
+		off := binary.LittleEndian.Uint64(e[0:])
+		info := binary.LittleEndian.Uint64(e[8:])
+		typ := elf.R_AARCH64(info & 0xffffffff)
+		sym := int(info >> 32)
+		if typ != w.typ || off != getanswer.Value+w.off {
+			t.Errorf("reloc %d: type %v off %d, want %v at %d", i, typ, off, w.typ, getanswer.Value+w.off)
+		}
+		if sym != 3 { // NULL, .text, .data, then the first local: answer
+			t.Errorf("reloc %d: symbol index %d, want 3 (answer)", i, sym)
+		}
+	}
+}
+
+// byNameElf returns the symbol table entry for name from the raw .symtab,
+// which carries every entry including the null and section symbols in order.
+func byNameElf(t *testing.T, ef *elf.File, name string) elf.Symbol {
+	t.Helper()
+	syms, err := ef.Symbols()
+	if err != nil {
+		t.Fatalf("symbols: %v", err)
+	}
+	for _, s := range syms {
+		if s.Name == name {
+			return s
+		}
+	}
+	t.Fatalf("symbol %q not found", name)
+	return elf.Symbol{}
 }
 
 // TestELFAARCH64ObjectNoRelocations checks the ELF output when there are no