cmd/link: establish dependable package initialization order

(This is a retry of CL 462035 which was reverted at 474976.
The only change from that CL is the aix fix SRODATA->SNOPTRDATA
at inittask.go:141)

As described here:

https://github.com/golang/go/issues/31636#issuecomment-493271830

"Find the lexically earliest package that is not initialized yet,
but has had all its dependencies initialized, initialize that package,
 and repeat."

Simplify the runtime a bit, by just computing the ordering required
in the linker and giving a list to the runtime.

Update #31636
Fixes #57411

RELNOTE=yes

Change-Id: I28c09451d6aa677d7394c179d23c2c02c503fc56
Reviewed-on: https://go-review.googlesource.com/c/go/+/478916
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

3 files changed, 40 insertions, 34 deletions

diff --git a/src/runtime/plugin.go b/src/runtime/plugin.go
index a61dcc3b5d..312802de00 100644
--- a/src/runtime/plugin.go
+++ b/src/runtime/plugin.go
@@ -7,7 +7,7 @@ package runtime
 import "unsafe"
 
 //go:linkname plugin_lastmoduleinit plugin.lastmoduleinit
-func plugin_lastmoduleinit() (path string, syms map[string]any, errstr string) {
+func plugin_lastmoduleinit() (path string, syms map[string]any, initTasks []*initTask, errstr string) {
 	var md *moduledata
 	for pmd := firstmoduledata.next; pmd != nil; pmd = pmd.next {
 		if pmd.bad {
@@ -23,13 +23,13 @@ func plugin_lastmoduleinit() (path string, syms map[string]any, errstr string) {
 		throw("runtime: plugin has empty pluginpath")
 	}
 	if md.typemap != nil {
-		return "", nil, "plugin already loaded"
+		return "", nil, nil, "plugin already loaded"
 	}
 
 	for _, pmd := range activeModules() {
 		if pmd.pluginpath == md.pluginpath {
 			md.bad = true
-			return "", nil, "plugin already loaded"
+			return "", nil, nil, "plugin already loaded"
 		}
 
 		if inRange(pmd.text, pmd.etext, md.text, md.etext) ||
@@ -51,7 +51,7 @@ func plugin_lastmoduleinit() (path string, syms map[string]any, errstr string) {
 	for _, pkghash := range md.pkghashes {
 		if pkghash.linktimehash != *pkghash.runtimehash {
 			md.bad = true
-			return "", nil, "plugin was built with a different version of package " + pkghash.modulename
+			return "", nil, nil, "plugin was built with a different version of package " + pkghash.modulename
 		}
 	}
 
@@ -90,7 +90,7 @@ func plugin_lastmoduleinit() (path string, syms map[string]any, errstr string) {
 		}
 		syms[name] = val
 	}
-	return md.pluginpath, syms, ""
+	return md.pluginpath, syms, md.inittasks, ""
 }
 
 func pluginftabverify(md *moduledata) {
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 4152aa4852..90b6d81bf8 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -117,11 +117,9 @@ var (
 	raceprocctx0 uintptr
 )
 
-//go:linkname runtime_inittask runtime..inittask
-var runtime_inittask initTask
-
-//go:linkname main_inittask main..inittask
-var main_inittask initTask
+// This slice records the initializing tasks that need to be
+// done to start up the runtime. It is built by the linker.
+var runtime_inittasks []*initTask
 
 // main_init_done is a signal used by cgocallbackg that initialization
 // has been completed. It is made before _cgo_notify_runtime_init_done,
@@ -196,7 +194,7 @@ func main() {
 		inittrace.active = true
 	}
 
-	doInit(&runtime_inittask) // Must be before defer.
+	doInit(runtime_inittasks) // Must be before defer.
 
 	// Defer unlock so that runtime.Goexit during init does the unlock too.
 	needUnlock := true
@@ -241,7 +239,14 @@ func main() {
 		cgocall(_cgo_notify_runtime_init_done, nil)
 	}
 
-	doInit(&main_inittask)
+	// Run the initializing tasks. Depending on build mode this
+	// list can arrive a few different ways, but it will always
+	// contain the init tasks computed by the linker for all the
+	// packages in the program (excluding those added at runtime
+	// by package plugin).
+	for _, m := range activeModules() {
+		doInit(m.inittasks)
+	}
 
 	// Disable init tracing after main init done to avoid overhead
 	// of collecting statistics in malloc and newproc
@@ -6520,14 +6525,11 @@ func gcd(a, b uint32) uint32 {
 }
 
 // An initTask represents the set of initializations that need to be done for a package.
-// Keep in sync with ../../test/initempty.go:initTask
+// Keep in sync with ../../test/noinit.go:initTask
 type initTask struct {
-	// TODO: pack the first 3 fields more tightly?
-	state uintptr // 0 = uninitialized, 1 = in progress, 2 = done
-	ndeps uintptr
-	nfns  uintptr
-	// followed by ndeps instances of an *initTask, one per package depended on
-	// followed by nfns pcs, one per init function to run
+	state uint32 // 0 = uninitialized, 1 = in progress, 2 = done
+	nfns  uint32
+	// followed by nfns pcs, uintptr sized, one per init function to run
 }
 
 // inittrace stores statistics for init functions which are
@@ -6541,7 +6543,13 @@ type tracestat struct {
 	bytes  uint64 // heap allocated bytes
 }
 
-func doInit(t *initTask) {
+func doInit(ts []*initTask) {
+	for _, t := range ts {
+		doInit1(t)
+	}
+}
+
+func doInit1(t *initTask) {
 	switch t.state {
 	case 2: // fully initialized
 		return
@@ -6550,17 +6558,6 @@ func doInit(t *initTask) {
 	default: // not initialized yet
 		t.state = 1 // initialization in progress
 
-		for i := uintptr(0); i < t.ndeps; i++ {
-			p := add(unsafe.Pointer(t), (3+i)*goarch.PtrSize)
-			t2 := *(**initTask)(p)
-			doInit(t2)
-		}
-
-		if t.nfns == 0 {
-			t.state = 2 // initialization done
-			return
-		}
-
 		var (
 			start  int64
 			before tracestat
@@ -6572,9 +6569,14 @@ func doInit(t *initTask) {
 			before = inittrace
 		}
 
-		firstFunc := add(unsafe.Pointer(t), (3+t.ndeps)*goarch.PtrSize)
-		for i := uintptr(0); i < t.nfns; i++ {
-			p := add(firstFunc, i*goarch.PtrSize)
+		if t.nfns == 0 {
+			// We should have pruned all of these in the linker.
+			throw("inittask with no functions")
+		}
+
+		firstFunc := add(unsafe.Pointer(t), 8)
+		for i := uint32(0); i < t.nfns; i++ {
+			p := add(firstFunc, uintptr(i)*goarch.PtrSize)
 			f := *(*func())(unsafe.Pointer(&p))
 			f()
 		}
diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index e2533ae250..7bf96c31fc 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -446,6 +446,10 @@ type moduledata struct {
 	pluginpath string
 	pkghashes  []modulehash
 
+	// This slice records the initializing tasks that need to be
+	// done to start up the program. It is built by the linker.
+	inittasks []*initTask
+
 	modulename   string
 	modulehashes []modulehash