cmd/link, runtime: initialize packages in shared build mode

Currently, for the shared build mode, we don't generate the module
inittasks. Instead, we rely on the main executable to do the
initialization, for both the executable and the shared library.
But, with the model as of CL 478916, the main executable only
has relocations to packages that are directly imported. It won't
see the dependency edges between packages within a shared library.
Therefore indirect dependencies are not included, and thus not
initialized. E.g. main imports a, which imports b, but main
doesn't directly import b. a and b are in a shared object. When
linking main, it sees main depends on a, so it generates main's
inittasks to run a's init before main's, but it doesn't know b,
so b's init doesn't run.

This CL makes it initialize all packages in a shared library when
the library is loaded, as any of them could potentially be
imported, directly or indirectly.

Also, in the runtime, when running the init functions, make sure
to go through the DSOs in dependency order. Otherwise packages
can be initialized in the wrong order.

Fixes #61973.

Change-Id: I2a090336fe9fa0d6c7e43912f3ab233c9c47e247
Reviewed-on: https://go-review.googlesource.com/c/go/+/520375
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 263945dd6c..fa76d3250c 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -244,8 +244,10 @@ func main() {
 	// 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() {
+	// by package plugin). Run through the modules in dependency
+	// order (the order they are initialized by the dynamic
+	// loader, i.e. they are added to the moduledata linked list).
+	for m := &firstmoduledata; m != nil; m = m.next {
 		doInit(m.inittasks)
 	}