feat(asm): resolve external GOOBJ symbols from archive data

asm/goobjriscv.go

@@ -113,16 +113,47 @@ func (img *Image) GOObjectRISCV(pkgPath, srcPath string) ([]byte, error) {
 		})
 	}
 
+	// Resolve external symbol references (cross-package).
+	var extPkgTable []string
+	var extPkgIdx map[string]int
+	var extSymIdx map[string]int
+	if len(img.Externals) > 0 {
+		var err error
+		extPkgTable, extPkgIdx, extSymIdx, err = resolveExternalSymbols(img.Externals)
+		if err != nil {
+			return nil, fmt.Errorf("GOOBJ emission: resolving external symbols: %w", err)
+		}
+	}
+
 	// Relocations, per defined symbol in definition order (package defs,
-	// then non-package defs).  Only file-local GLOBL references resolve;
-	// external symbols need the import machinery of a later increment.
+	// then non-package defs).
 	nsyms := len(defs) + len(nps)
 	symRelocs := make([][]byte, nsyms) // flat 23-byte records
 	for i, fn := range img.Funcs {
 		si := len(defs) + fnNpIdx[i]
 		for _, r := range fn.Relocs {
 			if r.External {
-				return nil, fmt.Errorf("GOOBJ emission: external symbol %q is not supported yet", r.Name)
+				pkg, name := splitQualified(r.Name)
+				if pkg == "" {
+					return nil, fmt.Errorf("GOOBJ emission: external symbol %q has no package prefix", r.Name)
+				}
+				pIdx, ok := extPkgIdx[pkg]
+				if !ok {
+					return nil, fmt.Errorf("GOOBJ emission: package %q not resolved", pkg)
+				}
+				sIdx, ok := extSymIdx[pkg+"·"+name]
+				if !ok {
+					return nil, fmt.Errorf("GOOBJ emission: symbol %s·%s not resolved", pkg, name)
+				}
+				var rec [23]byte
+				binary.LittleEndian.PutUint32(rec[0:], uint32(int32(r.Off)))
+				rec[4] = 4 // field width
+				binary.LittleEndian.PutUint16(rec[5:], relocRISCVPcrelHi20)
+				binary.LittleEndian.PutUint64(rec[7:], uint64(r.Addend))
+				binary.LittleEndian.PutUint32(rec[15:], uint32(pIdx))
+				binary.LittleEndian.PutUint32(rec[19:], uint32(sIdx))
+				symRelocs[si] = append(symRelocs[si], rec[:]...)
+				continue
 			}
 			di, ok := defIdx[r.Name]
 			if !ok {
@@ -179,6 +210,20 @@ func (img *Image) GOObjectRISCV(pkgPath, srcPath string) ([]byte, error) {
 	for _, s := range nps {
 		addStr(s.sym.name)
 	}
+	for _, pkg := range extPkgTable {
+		addStr(pkg)
+	}
+
+	// Package index block: index 0 is the dummy invalid package, followed by
+	// external packages.
+	var pkgIdxBlk bytes.Buffer
+	pkgIdxBlk.Write(binary.LittleEndian.AppendUint32(nil, 0)) // len("")
+	pkgIdxBlk.Write(binary.LittleEndian.AppendUint32(nil, 0)) // offset of ""
+	for _, pkg := range extPkgTable {
+		off := strOff[pkg]
+		pkgIdxBlk.Write(binary.LittleEndian.AppendUint32(nil, uint32(len(pkg))))
+		pkgIdxBlk.Write(binary.LittleEndian.AppendUint32(nil, off))
+	}
 
 	// Symbol definition records (21 bytes each).
 	var symdef, nonpkgdef []byte
@@ -258,24 +303,24 @@ func (img *Image) GOObjectRISCV(pkgPath, srcPath string) ([]byte, error) {
 	// Blocks in order: autolib, pkgidx, file, symdef, hashed64def, hasheddef,
 	// nonpkgdef, nonpkgref, refflags, hash64, hash, relocidx, auxidx, dataidx,
 	// reloc, aux, data, refname.
-	writeBlock(nil)       // autolib
-	writeBlock(nil)       // pkgidx
-	writeBlock(fileBlk)   // file
-	writeBlock(symdef)    // symdef
-	writeBlock(nil)       // hashed64def
-	writeBlock(nil)       // hasheddef
-	writeBlock(nonpkgdef) // nonpkgdef
-	writeBlock(nil)       // nonpkgref
-	writeBlock(nil)       // refflags
-	writeBlock(nil)       // hash64
-	writeBlock(nil)       // hash
-	writeBlock(relocIdx)  // relocidx
-	writeBlock(auxIdx)    // auxidx
-	writeBlock(dataIdx)   // dataidx
-	writeBlock(relocBlk)  // reloc
-	writeBlock(auxBlk)    // aux
-	writeBlock(dataBlk)   // data
-	writeBlock(nil)       // refname
+	writeBlock(nil)               // autolib
+	writeBlock(pkgIdxBlk.Bytes()) // pkgidx
+	writeBlock(fileBlk)           // file
+	writeBlock(symdef)            // symdef
+	writeBlock(nil)               // hashed64def
+	writeBlock(nil)               // hasheddef
+	writeBlock(nonpkgdef)         // nonpkgdef
+	writeBlock(nil)               // nonpkgref
+	writeBlock(nil)               // refflags
+	writeBlock(nil)               // hash64
+	writeBlock(nil)               // hash
+	writeBlock(relocIdx)          // relocidx
+	writeBlock(auxIdx)            // auxidx
+	writeBlock(dataIdx)           // dataidx
+	writeBlock(relocBlk)          // reloc
+	writeBlock(auxBlk)            // aux
+	writeBlock(dataBlk)           // data
+	writeBlock(nil)               // refname
 
 	// Fill in the block offsets.
 	le := binary.LittleEndian