Revert "runtime: allow update of system stack bounds on callback from C thread"

This reverts CL 525455. The test fails to build on darwin, alpine, and
android.

For #62440.

Change-Id: I39c6b1e16499bd61e0f166de6c6efe7a07961e62
Reviewed-on: https://go-review.googlesource.com/c/go/+/527317
Auto-Submit: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

2 files changed, 0 insertions, 124 deletions

diff --git a/src/runtime/testdata/testprogcgo/stackswitch.c b/src/runtime/testdata/testprogcgo/stackswitch.c
deleted file mode 100644
index 9c0c583bf4..0000000000
--- a/src/runtime/testdata/testprogcgo/stackswitch.c
+++ /dev/null
@@ -1,81 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build unix && !openbsd
-
-#include <assert.h>
-#include <pthread.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <ucontext.h>
-
-// Use a stack size larger than the 32kb estimate in
-// runtime.callbackUpdateSystemStack. This ensures that a second stack
-// allocation won't accidentally count as in bounds of the first stack
-#define STACK_SIZE	(64ull << 10)
-
-static ucontext_t uctx_save, uctx_switch;
-
-extern void stackSwitchCallback(void);
-
-static void *stackSwitchThread(void *arg) {
-	// Simple test: callback works from the normal system stack.
-	stackSwitchCallback();
-
-	// Next, verify that switching stacks doesn't break callbacks.
-
-	char *stack1 = malloc(STACK_SIZE);
-	if (stack1 == NULL) {
-		perror("malloc");
-		exit(1);
-	}
-
-	// Allocate the second stack before freeing the first to ensure we don't get
-	// the same address from malloc.
-	char *stack2 = malloc(STACK_SIZE);
-	if (stack1 == NULL) {
-		perror("malloc");
-		exit(1);
-	}
-
-	if (getcontext(&uctx_switch) == -1) {
-		perror("getcontext");
-		exit(1);
-	}
-	uctx_switch.uc_stack.ss_sp = stack1;
-	uctx_switch.uc_stack.ss_size = STACK_SIZE;
-	uctx_switch.uc_link = &uctx_save;
-	makecontext(&uctx_switch, stackSwitchCallback, 0);
-
-	if (swapcontext(&uctx_save, &uctx_switch) == -1) {
-		perror("swapcontext");
-		exit(1);
-	}
-
-	if (getcontext(&uctx_switch) == -1) {
-		perror("getcontext");
-		exit(1);
-	}
-	uctx_switch.uc_stack.ss_sp = stack2;
-	uctx_switch.uc_stack.ss_size = STACK_SIZE;
-	uctx_switch.uc_link = &uctx_save;
-	makecontext(&uctx_switch, stackSwitchCallback, 0);
-
-	if (swapcontext(&uctx_save, &uctx_switch) == -1) {
-		perror("swapcontext");
-		exit(1);
-	}
-
-	free(stack1);
-	free(stack2);
-
-	return NULL;
-}
-
-void callStackSwitchCallbackFromThread(void) {
-	pthread_t thread;
-	assert(pthread_create(&thread, NULL, stackSwitchThread, NULL) == 0);
-	assert(pthread_join(thread, NULL) == 0);
-}
diff --git a/src/runtime/testdata/testprogcgo/stackswitch.go b/src/runtime/testdata/testprogcgo/stackswitch.go
deleted file mode 100644
index b4bb5f5fd9..0000000000
--- a/src/runtime/testdata/testprogcgo/stackswitch.go
+++ /dev/null
@@ -1,43 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build unix && !openbsd
-
-package main
-
-/*
-void callStackSwitchCallbackFromThread(void);
-*/
-import "C"
-
-import (
-	"fmt"
-	"runtime/debug"
-)
-
-func init() {
-	register("StackSwitchCallback", StackSwitchCallback)
-}
-
-//export stackSwitchCallback
-func stackSwitchCallback() {
-	// We want to trigger a bounds check on the g0 stack. To do this, we
-	// need to call a splittable function through systemstack().
-	// SetGCPercent contains such a systemstack call.
-	gogc := debug.SetGCPercent(100)
-	debug.SetGCPercent(gogc)
-}
-
-
-// Regression test for https://go.dev/issue/62440. It should be possible for C
-// threads to call into Go from different stacks without crashing due to g0
-// stack bounds checks.
-//
-// N.B. This is only OK for threads created in C. Threads with Go frames up the
-// stack must not change the stack out from under us.
-func StackSwitchCallback() {
-	C.callStackSwitchCallbackFromThread();
-
-	fmt.Printf("OK\n")
-}