Revert "Revert "Revert "runtime: consolidate function descriptor definitions on PPC64"""

This reverts CL 481075 (a re-apply of previously reverted CL 478917).

Reason for revert: CL 481061 causes C TSAN failures and must be
reverted. See CL 485275. This CL depends on CL 481061.

For #59678.

Change-Id: I4bf7f43d9df1ae28e04cd4065552bcbee82ef13f
Reviewed-on: https://go-review.googlesource.com/c/go/+/485316
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

src/runtime/asm_ppc64x.h

@@ -24,32 +24,16 @@
 
 #define FIXED_FRAME 32
 
-// aix/ppc64 uses XCOFF which uses function descriptors.
+// aix/ppc64 uses XCOFF which has 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 uses function descriptors.
+// linux/ppc64 uses ELFv1 which has 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

@@ -771,11 +771,26 @@ TEXT runtime·setg(SB), NOSPLIT, $0-8
 	BL	runtime·save_g(SB)
 	RET
 
-#ifdef GO_PPC64X_HAS_FUNCDESC
+#ifdef GOARCH_ppc64
-DEFINE_PPC64X_FUNCDESC(setg_gcc<>, _setg_gcc<>)
+#ifdef GOOS_aix
-TEXT _setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
+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
 #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

@@ -7,25 +7,26 @@
 #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
-	MOVD	CROSSCALL2_FPTR, R6
+#ifdef GOARCH_ppc64
+	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

@@ -3,11 +3,13 @@
 // 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.
-DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_aix, __start<>)
+DATA	_rt0_ppc64_aix+0(SB)/8, $__start<>(SB)
+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
@@ -35,7 +37,11 @@ TEXT __start<>(SB),NOSPLIT,$-8
 	BL _main(SB)
 
 
-DEFINE_PPC64X_FUNCDESC(main, _main)
+DATA	main+0(SB)/8, $_main(SB)
+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
@@ -175,7 +181,10 @@ done:
 	MOVD	R0, LR
 	RET
 
-DEFINE_PPC64X_FUNCDESC(_rt0_ppc64_aix_lib_go, __rt0_ppc64_aix_lib_go)
+DATA	_rt0_ppc64_aix_lib_go+0(SB)/8, $__rt0_ppc64_aix_lib_go(SB)
+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

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

@@ -447,12 +447,7 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	MOVD	24(R1), R2
 	RET
 
-#ifdef GO_PPC64X_HAS_FUNCDESC
+#ifdef GOARCH_ppc64le
-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 .
@@ -461,6 +456,13 @@ 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
+#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
 	// This is called with ELF calling conventions. Convert to Go.
 	// Allocate space for argument storage to call runtime.sigtrampgo.
@@ -489,6 +491,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$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
@@ -583,6 +586,14 @@ 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.