reflect: add register ABI support for makeFuncStub and methodValueCall

This change finishes off functionality register ABI for the reflect
package.

Specifically, it implements a call on a MakeFunc'd value by performing
the reverse process that reflect.Value.Call does, using the same ABI
steps. It implements a call on a method value created by reflect by
translating between the method value's ABI to the method's ABI.

Tests are added for both cases.

For #40724.

Change-Id: I302820b61fc0a8f94c5525a002bc02776aef41af
Reviewed-on: https://go-review.googlesource.com/c/go/+/298670
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

4 files changed, 45 insertions, 18 deletions

diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 193d8f00bb..dbe7f7f381 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -473,7 +473,7 @@ TEXT runtime·morestack_noctxt(SB),NOSPLIT,$0
 
 #ifdef GOEXPERIMENT_REGABI_REFLECT
 // spillArgs stores return values from registers to a *internal/abi.RegArgs in R12.
-TEXT spillArgs<>(SB),NOSPLIT,$0-0
+TEXT ·spillArgs<ABIInternal>(SB),NOSPLIT,$0-0
 	MOVQ AX, 0(R12)
 	MOVQ BX, 8(R12)
 	MOVQ CX, 16(R12)
@@ -501,7 +501,7 @@ TEXT spillArgs<>(SB),NOSPLIT,$0-0
 	RET
 
 // unspillArgs loads args into registers from a *internal/abi.RegArgs in R12.
-TEXT unspillArgs<>(SB),NOSPLIT,$0-0
+TEXT ·unspillArgs<ABIInternal>(SB),NOSPLIT,$0-0
 	MOVQ 0(R12), AX
 	MOVQ 8(R12), BX
 	MOVQ 16(R12), CX
@@ -529,11 +529,11 @@ TEXT unspillArgs<>(SB),NOSPLIT,$0-0
 	RET
 #else
 // spillArgs stores return values from registers to a pointer in R12.
-TEXT spillArgs<>(SB),NOSPLIT,$0-0
+TEXT ·spillArgs<ABIInternal>(SB),NOSPLIT,$0-0
 	RET
 
 // unspillArgs loads args into registers from a pointer in R12.
-TEXT unspillArgs<>(SB),NOSPLIT,$0-0
+TEXT ·unspillArgs<ABIInternal>(SB),NOSPLIT,$0-0
 	RET
 #endif
 
@@ -592,7 +592,7 @@ TEXT NAME(SB), WRAPPER, $MAXSIZE-48;		\
 	REP;MOVSB;				\
 	/* set up argument registers */		\
 	MOVQ    regArgs+40(FP), R12;		\
-	CALL    unspillArgs<>(SB);		\
+	CALL    ·unspillArgs<ABIInternal>(SB);		\
 	/* call function */			\
 	MOVQ	f+8(FP), DX;			\
 	PCDATA  $PCDATA_StackMapIndex, $0;	\
@@ -600,7 +600,7 @@ TEXT NAME(SB), WRAPPER, $MAXSIZE-48;		\
 	CALL	R12;				\
 	/* copy register return values back */		\
 	MOVQ    regArgs+40(FP), R12;		\
-	CALL    spillArgs<>(SB);		\
+	CALL    ·spillArgs<ABIInternal>(SB);		\
 	MOVLQZX	stackArgsSize+24(FP), CX;		\
 	MOVLQZX	stackRetOffset+28(FP), BX;		\
 	MOVQ	stackArgs+16(FP), DI;		\
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 5c7fadc2d2..cdccdcc2c5 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -5,6 +5,7 @@
 package runtime
 
 import (
+	"internal/abi"
 	"internal/cpu"
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
@@ -1312,23 +1313,42 @@ func getStackMap(frame *stkframe, cache *pcvalueCache, debug bool) (locals, args
 	}
 
 	// stack objects.
-	p := funcdata(f, _FUNCDATA_StackObjects)
-	if p != nil {
-		n := *(*uintptr)(p)
-		p = add(p, sys.PtrSize)
-		*(*slice)(unsafe.Pointer(&objs)) = slice{array: noescape(p), len: int(n), cap: int(n)}
-		// Note: the noescape above is needed to keep
-		// getStackMap from "leaking param content:
-		// frame".  That leak propagates up to getgcmask, then
-		// GCMask, then verifyGCInfo, which converts the stack
-		// gcinfo tests into heap gcinfo tests :(
+	if GOARCH == "amd64" && unsafe.Sizeof(abi.RegArgs{}) > 0 && frame.argmap != nil {
+		// argmap is set when the function is reflect.makeFuncStub or reflect.methodValueCall.
+		// We don't actually use argmap in this case, but we need to fake the stack object
+		// record for these frames which contain an internal/abi.RegArgs at a hard-coded offset
+		// on amd64.
+		objs = methodValueCallFrameObjs
+	} else {
+		p := funcdata(f, _FUNCDATA_StackObjects)
+		if p != nil {
+			n := *(*uintptr)(p)
+			p = add(p, sys.PtrSize)
+			*(*slice)(unsafe.Pointer(&objs)) = slice{array: noescape(p), len: int(n), cap: int(n)}
+			// Note: the noescape above is needed to keep
+			// getStackMap from "leaking param content:
+			// frame".  That leak propagates up to getgcmask, then
+			// GCMask, then verifyGCInfo, which converts the stack
+			// gcinfo tests into heap gcinfo tests :(
+		}
 	}
 
 	return
 }
 
+var (
+	abiRegArgsEface          interface{} = abi.RegArgs{}
+	abiRegArgsType           *_type      = efaceOf(&abiRegArgsEface)._type
+	methodValueCallFrameObjs             = []stackObjectRecord{
+		{
+			off: -int(alignUp(abiRegArgsType.size, 8)), // It's always the highest address local.
+			typ: abiRegArgsType,
+		},
+	}
+)
+
 // A stackObjectRecord is generated by the compiler for each stack object in a stack frame.
-// This record must match the generator code in cmd/compile/internal/gc/ssa.go:emitStackObjects.
+// This record must match the generator code in cmd/compile/internal/liveness/plive.go:emitStackObjects.
 type stackObjectRecord struct {
 	// offset in frame
 	// if negative, offset from varp
diff --git a/src/runtime/stubs_amd64.go b/src/runtime/stubs_amd64.go
index bf98493e9d..687a506cdd 100644
--- a/src/runtime/stubs_amd64.go
+++ b/src/runtime/stubs_amd64.go
@@ -40,3 +40,10 @@ func retpolineR15()
 
 //go:noescape
 func asmcgocall_no_g(fn, arg unsafe.Pointer)
+
+// Used by reflectcall and the reflect package.
+//
+// Spills/loads arguments in registers to/from an internal/abi.RegArgs
+// respectively. Does not follow the Go ABI.
+func spillArgs()
+func unspillArgs()
diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go
index f8cda83098..0969af1a21 100644
--- a/src/runtime/traceback.go
+++ b/src/runtime/traceback.go
@@ -630,7 +630,7 @@ func getArgInfo(frame *stkframe, f funcInfo, needArgMap bool, ctxt *funcval) (ar
 				// Figure out whether the return values are valid.
 				// Reflect will update this value after it copies
 				// in the return values.
-				retValid = *(*bool)(unsafe.Pointer(arg0 + 3*sys.PtrSize))
+				retValid = *(*bool)(unsafe.Pointer(arg0 + 4*sys.PtrSize))
 			}
 			if mv.fn != f.entry {
 				print("runtime: confused by ", funcname(f), "\n")