cmd/link: always use symbol-targeted relocations on Mach-O

In Mach-O object files, there are two kinds of relocations:
"external" relocation, which targets a symbol, and "non-external"
relocation, which targets a section. For targeting symbols not in
the current object, we must use symbol-targeted relocations. For
targeting symbols defined in the current object, for some
relocation types, both kinds can be used. We currently use
section-targeted relocations for R_ADDR targeting locally defined
symbols.

Modern Apple toolchain seems to prefer symbol-targeted relocations.
Also, Apple's new linker, ld-prime, seems to not handle section-
targeted relocations well in some cases. So this CL switches to
always generate symbol-targeted relocations. This also simplifies
the code.

One exception is that DWARF tools seem to handle only section-
targeted relocations. So generate those in DWARF sections.

This CL supersedes CL 502616.

Fixes #60694.
For #61229.

Change-Id: I3b74df64f21114635061bcd89114392b3a2d588b
Reviewed-on: https://go-review.googlesource.com/c/go/+/503935
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index 21b2e9a9d4..95fc8b5a42 100644
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -368,9 +368,11 @@ func (st *relocSymState) relocsym(s loader.Sym, P []byte) {
 						o = 0
 					}
 				} else if target.IsDarwin() {
-					if ldr.SymType(rs) != sym.SHOSTOBJ && ldr.SymType(s) != sym.SINITARR {
-						// ld-prime drops the offset in data for SINITARR. We need to use
-						// symbol-targeted relocation. See also machoreloc1.
+					if ldr.SymType(s).IsDWARF() {
+						// We generally use symbol-targeted relocations.
+						// DWARF tools seem to only handle section-targeted relocations,
+						// so generate section-targeted relocations in DWARF sections.
+						// See also machoreloc1.
 						o += ldr.SymValue(rs)
 					}
 				} else if target.IsWindows() {