From: Cherry Zhang <cherryyz@google.com>
Date: Wed, 9 Dec 2020 17:14:00 +0000 (-0500)
Subject: cmd/link: reject too-large relocation addend on darwin/arm64
X-Git-Tag: go1.16beta1~54
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b110733327a66870da9c5f482d8fd3275dae55f3;p=gostls13.git

cmd/link: reject too-large relocation addend on darwin/arm64

Mach-O relocation addend is signed 24-bit. If the addend
overflows, it is better to fail the build than emitting an
incorrect binary. (I'm still working on a fix.)

Updates #42738.

Change-Id: I647f0cd4f6b84d9ac75ef3bf36673bea01dfc211
Reviewed-on: https://go-review.googlesource.com/c/go/+/276694
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
---

diff --git a/src/cmd/link/internal/arm64/asm.go b/src/cmd/link/internal/arm64/asm.go
index a7af855646..30819db4c6 100644
--- a/src/cmd/link/internal/arm64/asm.go
+++ b/src/cmd/link/internal/arm64/asm.go
@@ -463,6 +463,9 @@ func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 	return true
 }
 
+// sign-extends from 24-bit.
+func signext24(x int64) int64 { return x << 40 >> 40 }
+
 func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, sectoff int64) bool {
 	var v uint32
 
@@ -486,6 +489,10 @@ func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sy
 		}
 	}
 
+	if r.Xadd != signext24(r.Xadd) {
+		ldr.Errorf(s, "relocation addend overflow: %s+0x%x", ldr.SymName(rs), r.Xadd)
+	}
+
 	switch rt {
 	default:
 		return false