[release-branch.go1.16] runtime: keep //go:cgo_unsafe_args arguments alive to prevent GC

When syscall's DLL.FindProc calls into syscall_getprocaddress with a
byte slice pointer, we need to keep those bytes alive. Otherwise the GC
will collect the allocation, and we wind up calling `GetProcAddress` on
garbage, which showed up as various flakes in the builders. It turns out
that this problem extends to many uses of //go:cgo_unsafe_args
throughout, on all platforms. So this patch fixes the issue by keeping
non-integer pointer arguments alive through their invocation in
//go:cgo_unsafe_args functions.

Fixes #49867.
Updates #49731.

Change-Id: I93e4fbc2e8e210cb3fc53149708758bb33f2f9c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/368356
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/runtime/syscall_solaris.go b/src/runtime/syscall_solaris.go
index 094516927f..ed5b7d19f9 100644
--- a/src/runtime/syscall_solaris.go
+++ b/src/runtime/syscall_solaris.go
@@ -303,6 +303,8 @@ func syscall_wait4(pid uintptr, wstatus *uint32, options uintptr, rusage unsafe.
 	entersyscallblock()
 	asmcgocall(unsafe.Pointer(&asmsysvicall6x), unsafe.Pointer(&call))
 	exitsyscall()
+	KeepAlive(wstatus)
+	KeepAlive(rusage)
 	return int(call.r1), call.err
 }