runtime: consolidate function descriptor definitions on PPC64

This is a cleanup to allow a consistent definitions of a function
descriptor on code shared between AIX and Linux. They need to be
declared in slightly different ways, but we can hide that in one
macro.

And, update all usage.

Change-Id: I10f3580473db555b4fb4d2597b856f3a67d01a53
Reviewed-on: https://go-review.googlesource.com/c/go/+/478917
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Paul Murphy <murp@ibm.com>

src/runtime/asm_ppc64x.h

@@ -24,16 +24,32 @@
 
 #define FIXED_FRAME 32
 
-// aix/ppc64 uses XCOFF which has function descriptors.
+// aix/ppc64 uses XCOFF which uses function descriptors.
+// AIX cannot perform the TOC relocation in a text section.
+// Therefore, these descriptors must live in a data section.
 #ifdef GOOS_aix
 #ifdef GOARCH_ppc64
 #define GO_PPC64X_HAS_FUNCDESC
+#define DEFINE_PPC64X_FUNCDESC(funcname, localfuncname)	\
+	DATA	funcname+0(SB)/8, $localfuncname(SB) 	\
+	DATA	funcname+8(SB)/8, $TOC(SB)		\
+	DATA	funcname+16(SB)/8, $0			\
+	GLOBL	funcname(SB), NOPTR, $24
 #endif
 #endif
 
-// linux/ppc64 uses ELFv1 which has function descriptors.
+// 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

src/runtime/asm_ppc64x.s

@@ -771,26 +771,11 @@ TEXT runtime·setg(SB), NOSPLIT, $0-8
 	BL	runtime·save_g(SB)
 	RET
 
-#ifdef GOARCH_ppc64
+#ifdef GO_PPC64X_HAS_FUNCDESC
-#ifdef GOOS_aix
+DEFINE_PPC64X_FUNCDESC(setg_gcc<>, _setg_gcc<>)
-DATA    setg_gcc<>+0(SB)/8, $_setg_gcc<>(SB)
-DATA    setg_gcc<>+8(SB)/8, $TOC(SB)
-DATA    setg_gcc<>+16(SB)/8, $0
-GLOBL   setg_gcc<>(SB), NOPTR, $24
-#else
-TEXT setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
-	DWORD	$_setg_gcc<>(SB)
-	DWORD	$0
-	DWORD	$0
-#endif
-#endif
-
-// void setg_gcc(G*); set g in C TLS.
-// Must obey the gcc calling convention.
-#ifdef GOARCH_ppc64le
-TEXT setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
-#else
 TEXT _setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
+#else
+TEXT setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
 #endif
 	// The standard prologue clobbers R31, which is callee-save in
 	// the C ABI, so we have to use $-8-0 and save LR ourselves.

src/runtime/cgo/asm_ppc64x.s

@@ -7,26 +7,25 @@
 #include "textflag.h"
 #include "asm_ppc64x.h"
 
+#ifdef GO_PPC64X_HAS_FUNCDESC
+// crosscall2 is marked with go:cgo_export_static. On AIX, this creates and exports
+// the symbol name and descriptor as the AIX linker expects, but does not work if
+// referenced from within Go. Create and use an aliased descriptor of crosscall2
+// to workaround this.
+DEFINE_PPC64X_FUNCDESC(_crosscall2<>, crosscall2)
+#define CROSSCALL2_FPTR $_crosscall2<>(SB)
+#else
+#define CROSSCALL2_FPTR $crosscall2(SB)
+#endif
+
 // Set the x_crosscall2_ptr C function pointer variable point to crosscall2.
 // It's such a pointer chain: _crosscall2_ptr -> x_crosscall2_ptr -> crosscall2
 TEXT ·set_crosscall2(SB),NOSPLIT,$0-0
 	MOVD	_crosscall2_ptr(SB), R5
-#ifdef GOARCH_ppc64
+	MOVD	CROSSCALL2_FPTR, R6
-	MOVD	$_crosscall2<>(SB), R6
-#else
-	MOVD	$crosscall2(SB), R6
-#endif
 	MOVD	R6, (R5)
 	RET
 
-#ifdef GO_PPC64X_HAS_FUNCDESC
-// _crosscall2<> is a function descriptor to the real crosscall2.
-DATA    _crosscall2<>+0(SB)/8, $crosscall2(SB)
-DATA    _crosscall2<>+8(SB)/8, $TOC(SB)
-DATA    _crosscall2<>+16(SB)/8, $0
-GLOBL   _crosscall2<>(SB), NOPTR, $24
-#endif
-
 // Called by C code generated by cmd/cgo.
 // func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
 // Saves C callee-saved registers and calls cgocallback with three arguments.

src/runtime/rt0_aix_ppc64.s

@@ -3,13 +3,11 @@
 // license that can be found in the LICENSE file.
 
 #include "textflag.h"
+#include "asm_ppc64x.h"
 
 // _rt0_ppc64_aix is a function descriptor of the entrypoint function
 // __start. This name is needed by cmd/link.
-DATA	_rt0_ppc64_aix+0(SB)/8, $__start<>(SB)
+DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_aix, __start<>)
-DATA	_rt0_ppc64_aix+8(SB)/8, $TOC(SB)
-GLOBL	_rt0_ppc64_aix(SB), NOPTR, $16
-
 
 // The starting function must return in the loader to
 // initialise some libraries, especially libthread which
@@ -37,11 +35,7 @@ TEXT __start<>(SB),NOSPLIT,$-8
 	BL _main(SB)
 
 
-DATA	main+0(SB)/8, $_main(SB)
+DEFINE_PPC64X_FUNCDESC(main, _main)
-DATA	main+8(SB)/8, $TOC(SB)
-DATA	main+16(SB)/8, $0
-GLOBL	main(SB), NOPTR, $24
-
 TEXT _main(SB),NOSPLIT,$-8
 	MOVD $runtime·rt0_go(SB), R12
 	MOVD R12, CTR
@@ -181,10 +175,7 @@ done:
 	MOVD	R0, LR
 	RET
 
-DATA	_rt0_ppc64_aix_lib_go+0(SB)/8, $__rt0_ppc64_aix_lib_go(SB)
+DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_aix_lib_go, __rt0_ppc64_aix_lib_go)
-DATA	_rt0_ppc64_aix_lib_go+8(SB)/8, $TOC(SB)
-DATA	_rt0_ppc64_aix_lib_go+16(SB)/8, $0
-GLOBL	_rt0_ppc64_aix_lib_go(SB), NOPTR, $24
 
 TEXT __rt0_ppc64_aix_lib_go(SB),NOSPLIT,$0
 	MOVD	_rt0_ppc64_aix_lib_argc<>(SB), R3

src/runtime/rt0_linux_ppc64.s

@@ -3,17 +3,10 @@
 // license that can be found in the LICENSE file.
 
 #include "textflag.h"
+#include "asm_ppc64x.h"
 
-// actually a function descriptor for _main<>(SB)
+DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_linux, _main<>)
-TEXT _rt0_ppc64_linux(SB),NOSPLIT,$0
+DEFINE_PPC64X_FUNCDESC(main, _main<>)
-	DWORD $_main<>(SB)
-	DWORD $0
-	DWORD $0
-
-TEXT main(SB),NOSPLIT,$0
-	DWORD $_main<>(SB)
-	DWORD $0
-	DWORD $0
 
 TEXT _main<>(SB),NOSPLIT,$-8
 	// In a statically linked binary, the stack contains argc,

src/runtime/sys_linux_ppc64x.s

@@ -447,18 +447,16 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	MOVD	24(R1), R2
 	RET
 
-#ifdef GOARCH_ppc64le
+#ifdef GO_PPC64X_HAS_FUNCDESC
+DEFINE_PPC64X_FUNCDESC(runtime·sigtramp, sigtramp<>)
+// 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
 // Save callee-save registers in the case of signal forwarding.
 // Same as on ARM64 https://golang.org/issue/31827 .
 TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
-#else
-// function descriptor for the real sigtramp
-TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0
-	DWORD	$sigtramp<>(SB)
-	DWORD	$0
-	DWORD	$0
-TEXT sigtramp<>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
 #endif
 	// Start with standard C stack frame layout and linkage.
 	MOVD    LR, R0
@@ -627,7 +625,6 @@ TEXT sigtramp<>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
 	RET
 
 #ifdef GOARCH_ppc64le
-// ppc64le doesn't need function descriptors
 TEXT runtime·cgoSigtramp(SB),NOSPLIT|NOFRAME,$0
 	// The stack unwinder, presumably written in C, may not be able to
 	// handle Go frame correctly. So, this function is NOFRAME, and we
@@ -722,14 +719,6 @@ sigtrampnog:
 	MOVD	R12, CTR
 	MOVD	R10, LR // restore LR
 	JMP	(CTR)
-#else
-// function descriptor for the real sigtramp
-TEXT runtime·cgoSigtramp(SB),NOSPLIT|NOFRAME,$0
-	DWORD	$cgoSigtramp<>(SB)
-	DWORD	$0
-	DWORD	$0
-TEXT cgoSigtramp<>(SB),NOSPLIT,$0
-	JMP	sigtramp<>(SB)
 #endif
 
 // Used by cgoSigtramp to inspect without clobbering R30/R31 via runtime.load_g.