runtime: move exit hooks into internal/runtime/exithook

This removes a //go:linkname usage in the coverage implementation.

For #67401.

Change-Id: I0602172c7e372a84465160dbf46d9fa371582fff
Reviewed-on: https://go-review.googlesource.com/c/go/+/586259
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

4 files changed, 23 insertions, 89 deletions

diff --git a/src/runtime/exithook.go b/src/runtime/exithook.go
deleted file mode 100644
index 37d68bd767..0000000000
--- a/src/runtime/exithook.go
+++ /dev/null
@@ -1,68 +0,0 @@
-// Copyright 2022 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.
-
-package runtime
-
-// addExitHook registers the specified function 'f' to be run at
-// program termination (e.g. when someone invokes os.Exit(), or when
-// main.main returns). Hooks are run in reverse order of registration:
-// first hook added is the last one run.
-//
-// CAREFUL: the expectation is that addExitHook should only be called
-// from a safe context (e.g. not an error/panic path or signal
-// handler, preemption enabled, allocation allowed, write barriers
-// allowed, etc), and that the exit function 'f' will be invoked under
-// similar circumstances. That is the say, we are expecting that 'f'
-// uses normal / high-level Go code as opposed to one of the more
-// restricted dialects used for the trickier parts of the runtime.
-func addExitHook(f func(), runOnNonZeroExit bool) {
-	exitHooks.hooks = append(exitHooks.hooks, exitHook{f: f, runOnNonZeroExit: runOnNonZeroExit})
-}
-
-// exitHook stores a function to be run on program exit, registered
-// by the utility runtime.addExitHook.
-type exitHook struct {
-	f                func() // func to run
-	runOnNonZeroExit bool   // whether to run on non-zero exit code
-}
-
-// exitHooks stores state related to hook functions registered to
-// run when program execution terminates.
-var exitHooks struct {
-	hooks            []exitHook
-	runningExitHooks bool
-}
-
-// runExitHooks runs any registered exit hook functions (funcs
-// previously registered using runtime.addExitHook). Here 'exitCode'
-// is the status code being passed to os.Exit, or zero if the program
-// is terminating normally without calling os.Exit.
-func runExitHooks(exitCode int) {
-	if exitHooks.runningExitHooks {
-		throw("internal error: exit hook invoked exit")
-	}
-	exitHooks.runningExitHooks = true
-
-	runExitHook := func(f func()) (caughtPanic bool) {
-		defer func() {
-			if x := recover(); x != nil {
-				caughtPanic = true
-			}
-		}()
-		f()
-		return
-	}
-
-	for i := range exitHooks.hooks {
-		h := exitHooks.hooks[len(exitHooks.hooks)-i-1]
-		if exitCode != 0 && !h.runOnNonZeroExit {
-			continue
-		}
-		if caughtPanic := runExitHook(h.f); caughtPanic {
-			throw("internal error: exit hook invoked panic")
-		}
-	}
-	exitHooks.hooks = nil
-	exitHooks.runningExitHooks = false
-}
diff --git a/src/runtime/linkname.go b/src/runtime/linkname.go
index 42d8d245a6..19318cd9a9 100644
--- a/src/runtime/linkname.go
+++ b/src/runtime/linkname.go
@@ -29,9 +29,6 @@ import _ "unsafe"
 //go:linkname overflowError
 //go:linkname divideError
 
-// used in runtime/coverage and in tests
-//go:linkname addExitHook
-
 // used in tests
 //go:linkname extraMInUse
 //go:linkname getm
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 68296bd1e4..c5bf537a75 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -10,6 +10,7 @@ import (
 	"internal/goarch"
 	"internal/goos"
 	"internal/runtime/atomic"
+	"internal/runtime/exithook"
 	"internal/stringslite"
 	"runtime/internal/sys"
 	"unsafe"
@@ -309,6 +310,12 @@ func os_beforeExit(exitCode int) {
 	}
 }
 
+func runExitHooks(code int) {
+	if err := exithook.Run(code); err != nil {
+		throw(err.Error())
+	}
+}
+
 // start forcegc helper goroutine
 func init() {
 	go forcegchelper()
diff --git a/src/runtime/testdata/testexithooks/testexithooks.go b/src/runtime/testdata/testexithooks/testexithooks.go
index ceb3326c4f..151b5dc62b 100644
--- a/src/runtime/testdata/testexithooks/testexithooks.go
+++ b/src/runtime/testdata/testexithooks/testexithooks.go
@@ -7,6 +7,7 @@ package main
 import (
 	"flag"
 	"os"
+	"internal/runtime/exithook"
 	_ "unsafe"
 )
 
@@ -30,22 +31,19 @@ func main() {
 	}
 }
 
-//go:linkname runtime_addExitHook runtime.addExitHook
-func runtime_addExitHook(f func(), runOnNonZeroExit bool)
-
 func testSimple() {
 	f1 := func() { println("foo") }
 	f2 := func() { println("bar") }
-	runtime_addExitHook(f1, false)
-	runtime_addExitHook(f2, false)
+	exithook.Add(exithook.Hook{F: f1})
+	exithook.Add(exithook.Hook{F: f2})
 	// no explicit call to os.Exit
 }
 
 func testGoodExit() {
 	f1 := func() { println("apple") }
 	f2 := func() { println("orange") }
-	runtime_addExitHook(f1, false)
-	runtime_addExitHook(f2, false)
+	exithook.Add(exithook.Hook{F: f1})
+	exithook.Add(exithook.Hook{F: f2})
 	// explicit call to os.Exit
 	os.Exit(0)
 }
@@ -56,11 +54,11 @@ func testBadExit() {
 	f3 := func() { println("blek") }
 	f4 := func() { println("blub") }
 	f5 := func() { println("blat") }
-	runtime_addExitHook(f1, false)
-	runtime_addExitHook(f2, true)
-	runtime_addExitHook(f3, false)
-	runtime_addExitHook(f4, true)
-	runtime_addExitHook(f5, false)
+	exithook.Add(exithook.Hook{F: f1})
+	exithook.Add(exithook.Hook{F: f2, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f3})
+	exithook.Add(exithook.Hook{F: f4, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f5})
 	os.Exit(1)
 }
 
@@ -68,9 +66,9 @@ func testPanics() {
 	f1 := func() { println("ok") }
 	f2 := func() { panic("BADBADBAD") }
 	f3 := func() { println("good") }
-	runtime_addExitHook(f1, true)
-	runtime_addExitHook(f2, true)
-	runtime_addExitHook(f3, true)
+	exithook.Add(exithook.Hook{F: f1, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f2, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f3, RunOnFailure: true})
 	os.Exit(0)
 }
 
@@ -78,8 +76,8 @@ func testHookCallsExit() {
 	f1 := func() { println("ok") }
 	f2 := func() { os.Exit(1) }
 	f3 := func() { println("good") }
-	runtime_addExitHook(f1, true)
-	runtime_addExitHook(f2, true)
-	runtime_addExitHook(f3, true)
+	exithook.Add(exithook.Hook{F: f1, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f2, RunOnFailure: true})
+	exithook.Add(exithook.Hook{F: f3, RunOnFailure: true})
 	os.Exit(1)
 }