runtime: fix errno sign for epollctl on mips, mips64 and ppc64

The caller of epollctl expects it to return a negative errno value,
but it returns a positive errno value on mips, mips64 and ppc64.
The change fixes this.

Updates #23446

Change-Id: Ie6372eca6c23de21964caaaa433c9a45ef93531e
Reviewed-on: https://go-review.googlesource.com/89235
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/runtime/runtime_linux_test.go b/src/runtime/runtime_linux_test.go
index 612397293f..17d6fbde46 100644
--- a/src/runtime/runtime_linux_test.go
+++ b/src/runtime/runtime_linux_test.go
@@ -52,3 +52,12 @@ func TestMincoreErrorSign(t *testing.T) {
 		t.Errorf("mincore = %v, want %v", v, -EINVAL)
 	}
 }
+
+func TestEpollctlErrorSign(t *testing.T) {
+	v := Epollctl(-1, 1, -1, unsafe.Pointer(&struct{}{}))
+
+	const EBADF = 0x09
+	if v != -EBADF {
+		t.Errorf("epollctl = %v, want %v", v, -EBADF)
+	}
+}