cmd/link, runtime: add external linking support for linux/mips64x

Fixes #12560

Change-Id: Ic2004fc7b09f2dbbf83c41f8c6307757c0e1676d
Reviewed-on: https://go-review.googlesource.com/19803
Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/link/internal/ld/elf.go

@@ -489,6 +489,55 @@ const (
 	R_386_IRELATIVE     = 42
 	R_386_GOT32X        = 43
 
+	R_MIPS_NONE            = 0
+	R_MIPS_16              = 1
+	R_MIPS_32              = 2
+	R_MIPS_REL32           = 3
+	R_MIPS_26              = 4
+	R_MIPS_HI16            = 5
+	R_MIPS_LO16            = 6
+	R_MIPS_GPREL16         = 7
+	R_MIPS_LITERAL         = 8
+	R_MIPS_GOT16           = 9
+	R_MIPS_PC16            = 10
+	R_MIPS_CALL16          = 11
+	R_MIPS_GPREL32         = 12
+	R_MIPS_SHIFT5          = 16
+	R_MIPS_SHIFT6          = 17
+	R_MIPS_64              = 18
+	R_MIPS_GOT_DISP        = 19
+	R_MIPS_GOT_PAGE        = 20
+	R_MIPS_GOT_OFST        = 21
+	R_MIPS_GOT_HI16        = 22
+	R_MIPS_GOT_LO16        = 23
+	R_MIPS_SUB             = 24
+	R_MIPS_INSERT_A        = 25
+	R_MIPS_INSERT_B        = 26
+	R_MIPS_DELETE          = 27
+	R_MIPS_HIGHER          = 28
+	R_MIPS_HIGHEST         = 29
+	R_MIPS_CALL_HI16       = 30
+	R_MIPS_CALL_LO16       = 31
+	R_MIPS_SCN_DISP        = 32
+	R_MIPS_REL16           = 33
+	R_MIPS_ADD_IMMEDIATE   = 34
+	R_MIPS_PJUMP           = 35
+	R_MIPS_RELGOT          = 36
+	R_MIPS_JALR            = 37
+	R_MIPS_TLS_DTPMOD32    = 38
+	R_MIPS_TLS_DTPREL32    = 39
+	R_MIPS_TLS_DTPMOD64    = 40
+	R_MIPS_TLS_DTPREL64    = 41
+	R_MIPS_TLS_GD          = 42
+	R_MIPS_TLS_LDM         = 43
+	R_MIPS_TLS_DTPREL_HI16 = 44
+	R_MIPS_TLS_DTPREL_LO16 = 45
+	R_MIPS_TLS_GOTTPREL    = 46
+	R_MIPS_TLS_TPREL32     = 47
+	R_MIPS_TLS_TPREL64     = 48
+	R_MIPS_TLS_TPREL_HI16  = 49
+	R_MIPS_TLS_TPREL_LO16  = 50
+
 	R_PPC_NONE            = 0
 	R_PPC_ADDR32          = 1
 	R_PPC_ADDR24          = 2

src/cmd/link/internal/ld/lib.go

@@ -1298,6 +1298,8 @@ func hostlinkArchArgs() []string {
 		return []string{"-marm"}
 	case sys.ARM64:
 		// nothing needed
+	case '0':
+		return []string{"-mabi=64"}
 	}
 	return nil
 }

src/cmd/link/internal/mips64/asm.go

@@ -45,7 +45,49 @@ func adddynrel(s *ld.LSym, r *ld.Reloc) {
 }
 
 func elfreloc1(r *ld.Reloc, sectoff int64) int {
-	return -1
+	// mips64 ELF relocation (endian neutral)
+	//		offset	uint64
+	//		sym		uint32
+	//		ssym	uint8
+	//		type3	uint8
+	//		type2	uint8
+	//		type	uint8
+	//		addend	int64
+
+	ld.Thearch.Vput(uint64(sectoff))
+
+	elfsym := r.Xsym.ElfsymForReloc()
+	ld.Thearch.Lput(uint32(elfsym))
+	ld.Cput(0)
+	ld.Cput(0)
+	ld.Cput(0)
+	switch r.Type {
+	default:
+		return -1
+
+	case obj.R_ADDR:
+		switch r.Siz {
+		case 4:
+			ld.Cput(ld.R_MIPS_32)
+		case 8:
+			ld.Cput(ld.R_MIPS_64)
+		default:
+			return -1
+		}
+
+	case obj.R_ADDRMIPS:
+		ld.Cput(ld.R_MIPS_LO16)
+
+	case obj.R_ADDRMIPSU:
+		ld.Cput(ld.R_MIPS_HI16)
+
+	case obj.R_CALLMIPS,
+		obj.R_JMPMIPS:
+		ld.Cput(ld.R_MIPS_26)
+	}
+	ld.Thearch.Vput(uint64(r.Xadd))
+
+	return 0
 }
 
 func elfsetupplt() {
@@ -58,7 +100,36 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 
 func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 	if ld.Linkmode == ld.LinkExternal {
-		return -1
+		switch r.Type {
+		default:
+			return -1
+
+		case obj.R_ADDRMIPS,
+			obj.R_ADDRMIPSU:
+			r.Done = 0
+
+			// set up addend for eventual relocation via outer symbol.
+			rs := r.Sym
+			r.Xadd = r.Add
+			for rs.Outer != nil {
+				r.Xadd += ld.Symaddr(rs) - ld.Symaddr(rs.Outer)
+				rs = rs.Outer
+			}
+
+			if rs.Type != obj.SHOSTOBJ && rs.Type != obj.SDYNIMPORT && rs.Sect == nil {
+				ld.Diag("missing section for %s", rs.Name)
+			}
+			r.Xsym = rs
+
+			return 0
+
+		case obj.R_CALLMIPS,
+			obj.R_JMPMIPS:
+			r.Done = 0
+			r.Xsym = r.Sym
+			r.Xadd = r.Add
+			return 0
+		}
 	}
 
 	switch r.Type {

src/cmd/link/internal/mips64/obj.go

@@ -107,6 +107,9 @@ func archinit() {
 		if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
 			log.Fatalf("cannot use -linkmode=external with -H %s", ld.Headstr(int(ld.HEADTYPE)))
 		}
+
+	case obj.Hlinux:
+		break
 	}
 
 	switch ld.HEADTYPE {

src/runtime/asm_mips64x.s

@@ -12,14 +12,14 @@
 #define	REGCTXT	R22
 
 TEXT runtime·rt0_go(SB),NOSPLIT,$0
-	// R29 = stack; R1 = argc; R2 = argv
+	// R29 = stack; R4 = argc; R5 = argv
 
 	// initialize essential registers
 	JAL	runtime·reginit(SB)
 
 	ADDV	$-24, R29
-	MOVW	R1, 8(R29) // argc
-	MOVV	R2, 16(R29) // argv
+	MOVW	R4, 8(R29) // argc
+	MOVV	R5, 16(R29) // argv
 
 	// create istack out of the given (operating system) stack.
 	// _cgo_init may update stackguard.

src/runtime/rt0_linux_mips64x.s

@@ -19,18 +19,21 @@ TEXT _main<>(SB),NOSPLIT,$-8
 	// sequence of string pointers followed by a NULL, and auxv.
 	// There is no TLS base pointer.
 #ifdef GOARCH_mips64
-	MOVW 4(R29), R1 // argc, big-endian ABI places int32 at offset 4
+	MOVW	4(R29), R4 // argc, big-endian ABI places int32 at offset 4
 #else
-	MOVW 0(R29), R1 // argc
+	MOVW	0(R29), R4 // argc
 #endif
-	ADDV $8, R29, R2 // argv
-	JMP main(SB)
+	ADDV	$8, R29, R5 // argv
+	JMP	main(SB)
 
 TEXT main(SB),NOSPLIT,$-8
+	// in external linking, glibc jumps to main with argc in R4
+	// and argv in R5
+
 	// initalize REGSB = PC&0xffffffff00000000
 	BGEZAL	R0, 1(PC)
 	SRLV	$32, R31, RSB
 	SLLV	$32, RSB
 
-	MOVV	$runtime·rt0_go(SB), R4
-	JMP	(R4)
+	MOVV	$runtime·rt0_go(SB), R1
+	JMP	(R1)