From: Cherry Mui <cherryyz@google.com>
Date: Mon, 15 Dec 2025 18:45:28 +0000 (-0500)
Subject: cmd/link: don't create __x86.get_pc_thunk symbol if it already exists
X-Git-Tag: go1.26rc1~1^2~1
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=9ba0948172cbb05308fb2a9db823a720f8ffb9ad;p=gostls13.git

cmd/link: don't create __x86.get_pc_thunk symbol if it already exists

On 386, in some build modes we need to create the __x86.get_pc_thunk
symbols, to support PC-relative addressing. In some situation
the thunk symbols may already exist, e.g. loaded from a C object
in internal linking mode. In this case, we should use the exiting
symbol instead of making a new one. The current code updates the
symbol content in place but also adds a duplicated entry to Textp,
which breaks the address sorting order.

Fixes #76815.

Change-Id: Iab11106ce592dc5219b7a0e07cfafcd270661a2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/730161
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/cmd/link/internal/x86/asm.go b/src/cmd/link/internal/x86/asm.go
index 036514819a..2c38473702 100644
--- a/src/cmd/link/internal/x86/asm.go
+++ b/src/cmd/link/internal/x86/asm.go
@@ -72,6 +72,9 @@ func gentext(ctxt *ld.Link, ldr *loader.Loader) {
 		{"di", 7},
 	} {
 		thunkfunc := ldr.CreateSymForUpdate("__x86.get_pc_thunk."+r.name, 0)
+		if t := thunkfunc.Type(); t != 0 && t != sym.SXREF && t != sym.SDYNIMPORT && t != sym.SUNDEFEXT {
+			continue // symbol already exists, probably loaded from a C object
+		}
 		thunkfunc.SetType(sym.STEXT)
 		ldr.SetAttrLocal(thunkfunc.Sym(), true)
 		o := func(op ...uint8) {