runtime: disable pprof test with cgo on aix/ppc64

This commit disables new cgo pprof tests and adds an handler in sigtramp
to refuse SIGPROF signal.

Updates #28555

Change-Id: I152a871f8636e93328d411329104c6f023bd1691
Reviewed-on: https://go-review.googlesource.com/c/go/+/164013
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/crash_cgo_test.go

@@ -229,6 +229,9 @@ func TestCgoPanicDeadlock(t *testing.T) {
 }
 
 func TestCgoCCodeSIGPROF(t *testing.T) {
+	if runtime.GOOS == "aix" {
+		t.Skip("pprof not yet available on AIX (see golang.org/issue/28555)")
+	}
 	t.Parallel()
 	got := runTestProg(t, "testprogcgo", "CgoCCodeSIGPROF")
 	want := "OK\n"

src/runtime/pprof/proto_test.go

@@ -312,6 +312,10 @@ func TestMapping(t *testing.T) {
 	testenv.MustHaveGoRun(t)
 	testenv.MustHaveCGO(t)
 
+	if runtime.GOOS == "aix" {
+		t.Skip("pprof not yet available on AIX (see golang.org/issue/28555)")
+	}
+
 	prog := "./testdata/mappingtest/main.go"
 
 	// GoOnly includes only Go symbols that runtime will symbolize.

src/runtime/sys_aix_ppc64.s

@@ -109,6 +109,9 @@ TEXT runtime·_sigtramp(SB),NOSPLIT|NOFRAME,$0
 
 	BL	runtime·load_g(SB)
 
+	CMP	$0, g
+	BEQ	sigtrampnog // g == nil
+
 	// Save m->libcall. We need to do this because we
 	// might get interrupted by a signal in runtime·asmcgocall.
 
@@ -155,6 +158,7 @@ TEXT runtime·_sigtramp(SB),NOSPLIT|NOFRAME,$0
 	MOVD	120(R1), R8
 	MOVD	R8, 0(R7)
 
+exit:
 	// restore registers
 	MOVD	56(R1),R31
 	MOVD	64(R1),g
@@ -166,6 +170,19 @@ TEXT runtime·_sigtramp(SB),NOSPLIT|NOFRAME,$0
 	MOVD	R0, LR
 	BR (LR)
 
+sigtrampnog:
+	// Signal arrived on a non-Go thread.
+	// SIGPROF handler is not yet available so simply call badsignal,
+	// after having created *sigctxt.
+	MOVD	R4, 80(R1)
+	MOVD	R5, 88(R1)
+	MOVD	R1, R4
+	ADD		$80, R4
+	MOVD	R4, FIXED_FRAME+8(R1)
+	MOVD	R3, FIXED_FRAME+0(R1)
+	BL runtime·badsignal(SB)
+	JMP	exit
+
 // runtime.tstart is a function descriptor to the real tstart.
 DATA	runtime·tstart+0(SB)/8, $runtime·_tstart(SB)
 DATA	runtime·tstart+8(SB)/8, $TOC(SB)