all: switch linux-ppc64 target to ELFv2 ABI

Go is only capable of producing internally linked, static binaries
on linux-ppc64. As such, binaries should run in either ELFv1 or
ELFv2 ppc64 userspaces today.

This opens the door to enabling cgo and external linking which
will require ELFv2 support and userspace, eventually.

Fixes #76244

Change-Id: I5ca15037cbe546f352e8693dcf14da51a308b8ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/734540
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

5 files changed, 24 insertions, 61 deletions

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 12218feb31..8cd9e9f1b4 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -178,14 +178,7 @@ func Elfinit(ctxt *Link) {
 
 	switch ctxt.Arch.Family {
 	// 64-bit architectures
-	case sys.PPC64, sys.S390X:
-		if ctxt.Arch.ByteOrder == binary.BigEndian && ctxt.HeadType != objabi.Hopenbsd {
-			ehdr.Flags = 1 // Version 1 ABI
-		} else {
-			ehdr.Flags = 2 // Version 2 ABI
-		}
-		fallthrough
-	case sys.AMD64, sys.ARM64, sys.Loong64, sys.MIPS64, sys.RISCV64:
+	case sys.AMD64, sys.ARM64, sys.Loong64, sys.MIPS64, sys.PPC64, sys.RISCV64, sys.S390X:
 		if ctxt.Arch.Family == sys.MIPS64 {
 			ehdr.Flags = 0x20000004 // MIPS 3 CPIC
 		}
@@ -195,6 +188,12 @@ func Elfinit(ctxt *Link) {
 		if ctxt.Arch.Family == sys.RISCV64 {
 			ehdr.Flags = 0x4 // RISCV Float ABI Double
 		}
+		if ctxt.Arch.Family == sys.S390X {
+			ehdr.Flags = 1 // Version 1 ABI
+		}
+		if ctxt.Arch.Family == sys.PPC64 {
+			ehdr.Flags = 2 // Version 2 ABI
+		}
 		elf64 = true
 
 		ehdr.Phoff = ELF64HDRSIZE      // Must be ELF64HDRSIZE: first PHdr must follow ELF header
diff --git a/src/runtime/asm_ppc64x.h b/src/runtime/asm_ppc64x.h
index 65870fe020..8b8149f97b 100644
--- a/src/runtime/asm_ppc64x.h
+++ b/src/runtime/asm_ppc64x.h
@@ -37,19 +37,3 @@
 	GLOBL	funcname(SB), NOPTR, $24
 #endif
 #endif
-
-// linux/ppc64 uses ELFv1 which uses function descriptors.
-// These must also look like ABI0 functions on linux/ppc64
-// to work with abi.FuncPCABI0(sigtramp) in os_linux.go.
-// Only static codegen is supported on linux/ppc64, so TOC
-// is not needed.
-#ifdef GOOS_linux
-#ifdef GOARCH_ppc64
-#define GO_PPC64X_HAS_FUNCDESC
-#define DEFINE_PPC64X_FUNCDESC(funcname, localfuncname)	\
-	TEXT	funcname(SB),NOSPLIT|NOFRAME,$0		\
-		DWORD	$localfuncname(SB)		\
-		DWORD	$0				\
-		DWORD	$0
-#endif
-#endif
diff --git a/src/runtime/rt0_linux_ppc64.s b/src/runtime/rt0_linux_ppc64.s
deleted file mode 100644
index f527170ed2..0000000000
--- a/src/runtime/rt0_linux_ppc64.s
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-#include "textflag.h"
-#include "asm_ppc64x.h"
-
-DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_linux, _main<>)
-DEFINE_PPC64X_FUNCDESC(main, _main<>)
-
-TEXT _main<>(SB),NOSPLIT,$-8
-	// In a statically linked binary, the stack contains argc,
-	// argv as argc string pointers followed by a NULL, envv as a
-	// sequence of string pointers followed by a NULL, and auxv.
-	// There is no TLS base pointer.
-	//
-	// TODO(austin): Support ABI v1 dynamic linking entry point
-	XOR	R0, R0 // Note, newer kernels may not always set R0 to 0.
-	MOVD	$runtime·rt0_go(SB), R12
-	MOVD	R12, CTR
-	MOVBZ	runtime·iscgo(SB), R5
-	CMP	R5, $0
-	BEQ	nocgo
-	BR	(CTR)
-nocgo:
-	MOVD	0(R1), R3 // argc
-	ADD	$8, R1, R4 // argv
-	BR	(CTR)
diff --git a/src/runtime/rt0_linux_ppc64le.s b/src/runtime/rt0_linux_ppc64x.s
index 3a6e8863b2..b1d174dbcd 100644
--- a/src/runtime/rt0_linux_ppc64le.s
+++ b/src/runtime/rt0_linux_ppc64x.s
@@ -2,15 +2,25 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build (ppc64 || ppc64le) && linux
+
 #include "go_asm.h"
 #include "textflag.h"
 #include "asm_ppc64x.h"
 
-TEXT _rt0_ppc64le_linux(SB),NOSPLIT,$0
+#ifdef GOARCH_ppc64
+#define ENTRYPOINT	_rt0_ppc64_linux
+#define ENTRYPOINT_LIB	_rt0_ppc64_linux_lib
+#else
+#define ENTRYPOINT	_rt0_ppc64le_linux
+#define ENTRYPOINT_LIB	_rt0_ppc64le_linux_lib
+#endif
+
+TEXT ENTRYPOINT(SB),NOSPLIT,$0
 	XOR R0, R0	  // Make sure R0 is zero before _main
 	BR _main<>(SB)
 
-TEXT _rt0_ppc64le_linux_lib(SB),NOSPLIT|NOFRAME,$0
+TEXT ENTRYPOINT_LIB(SB),NOSPLIT|NOFRAME,$0
 	JMP _rt0_ppc64x_lib(SB)
 
 TEXT _main<>(SB),NOSPLIT,$-8
diff --git a/src/runtime/sys_linux_ppc64x.s b/src/runtime/sys_linux_ppc64x.s
index 8735b932ed..5ecfb0ec62 100644
--- a/src/runtime/sys_linux_ppc64x.s
+++ b/src/runtime/sys_linux_ppc64x.s
@@ -447,13 +447,12 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	MOVD	24(R1), R2
 	RET
 
-#ifdef GO_PPC64X_HAS_FUNCDESC
-DEFINE_PPC64X_FUNCDESC(runtime·sigtramp, sigtramp<>)
+#ifdef GOARCH_ppc64
 // cgo isn't supported on ppc64, but we need to supply a cgoSigTramp function.
-DEFINE_PPC64X_FUNCDESC(runtime·cgoSigtramp, sigtramp<>)
-TEXT sigtramp<>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
-#else
-// ppc64le doesn't need function descriptors
+TEXT runtime·cgoSigtramp(SB),NOSPLIT|NOFRAME,$0
+	BR	runtime·sigtramp(SB)
+#endif
+
 // Save callee-save registers in the case of signal forwarding.
 // Same as on ARM64 https://golang.org/issue/31827 .
 //
@@ -461,7 +460,6 @@ TEXT sigtramp<>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
 // a function pointer) as R2 may not be preserved when calling this
 // function. In those cases, the caller preserves their R2.
 TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
-#endif
 	// This is called with ELF calling conventions. Convert to Go.
 	// Allocate space for argument storage to call runtime.sigtrampgo.
 	STACK_AND_SAVE_HOST_TO_GO_ABI(32)