cmd/link: detect trampoline of deferreturn call

The runtime needs to find the PC of the deferreturn call in a few
places. So for functions that have defer, we record the PC of
deferreturn call in its funcdata.

For very large binaries, the deferreturn call could be made
through a trampoline. The current code of finding deferreturn PC
fails in this case. This CL handles the trampoline as well.

Fixes #39049.

Change-Id: I929be54d6ae436f5294013793217dc2a35f080d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/234105
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 2627218ced..8e6451d270 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -236,7 +236,8 @@ type Loader struct {
 	outdata   [][]byte     // symbol's data in the output buffer
 	extRelocs [][]ExtReloc // symbol's external relocations
 
-	itablink map[Sym]struct{} // itablink[j] defined if j is go.itablink.*
+	itablink         map[Sym]struct{} // itablink[j] defined if j is go.itablink.*
+	deferReturnTramp map[Sym]bool     // whether the symbol is a trampoline of a deferreturn call
 
 	objByPkg map[string]*oReader // map package path to its Go object reader
 
@@ -362,6 +363,7 @@ func NewLoader(flags uint32, elfsetstring elfsetstringFunc, reporter *ErrorRepor
 		attrCgoExportDynamic: make(map[Sym]struct{}),
 		attrCgoExportStatic:  make(map[Sym]struct{}),
 		itablink:             make(map[Sym]struct{}),
+		deferReturnTramp:     make(map[Sym]bool),
 		extStaticSyms:        make(map[nameVer]Sym),
 		builtinSyms:          make([]Sym, nbuiltin),
 		flags:                flags,
@@ -1062,6 +1064,16 @@ func (l *Loader) IsItabLink(i Sym) bool {
 	return false
 }
 
+// Return whether this is a trampoline of a deferreturn call.
+func (l *Loader) IsDeferReturnTramp(i Sym) bool {
+	return l.deferReturnTramp[i]
+}
+
+// Set that i is a trampoline of a deferreturn call.
+func (l *Loader) SetIsDeferReturnTramp(i Sym, v bool) {
+	l.deferReturnTramp[i] = v
+}
+
 // growValues grows the slice used to store symbol values.
 func (l *Loader) growValues(reqLen int) {
 	curLen := len(l.values)