reserve at least 48 bytes in stack frame when calling C functions for ppc64

Author: zte-majiang

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

@@ -247,9 +247,6 @@ func determineLinkMode(ctxt *Link) {
 			}
 			ctxt.LinkMode = LinkInternal
 		case "1":
-			if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" {
-				Exitf("external linking requested via GO_EXTLINK_ENABLED but not supported for %s/ppc64", objabi.GOOS)
-			}
 			ctxt.LinkMode = LinkExternal
 		default:
 			if needed, _ := mustLinkExternal(ctxt); needed {
@@ -261,17 +258,10 @@ func determineLinkMode(ctxt *Link) {
 			} else {
 				ctxt.LinkMode = LinkInternal
 			}
-			if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" && ctxt.LinkMode == LinkExternal {
-				Exitf("external linking is not supported for %s/ppc64", objabi.GOOS)
-			}
 		}
 	case LinkInternal:
 		if needed, reason := mustLinkExternal(ctxt); needed {
 			Exitf("internal linking requested but external linking required: %s", reason)
 		}
-	case LinkExternal:
-		if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" {
-			Exitf("external linking not supported for %s/ppc64", objabi.GOOS)
-		}
 	}
 }

src/runtime/asm_ppc64x.s

@@ -10,7 +10,7 @@
 #include "textflag.h"
 #include "asm_ppc64x.h"
 
-#ifdef GOOS_aix
+#ifdef GOARCH_ppc64
 #define cgoCalleeStackSize 48
 #else
 #define cgoCalleeStackSize 32
@@ -562,7 +562,7 @@ TEXT gosave<>(SB),NOSPLIT|NOFRAME,$0
 	BL	runtime·badctxt(SB)
 	RET
 
-#ifdef GOOS_aix
+#ifdef GOARCH_ppc64
 #define asmcgocallSaveOffset cgoCalleeStackSize + 8
 #else
 #define asmcgocallSaveOffset cgoCalleeStackSize

src/runtime/rt0_linux_ppc64.s

@@ -18,6 +18,7 @@ TEXT _main<>(SB),NOSPLIT,$-8
 	// There is no TLS base pointer.
 	//
 	// TODO(austin): Support ABI v1 dynamic linking entry point
+	XOR	R0, R0 // following functions assume R0 is zero
 	MOVD	$runtime·rt0_go(SB), R12
 	MOVD	R12, CTR
 	MOVBZ	runtime·iscgo(SB), R5