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, 4 insertions, 0 deletions

diff --git a/src/cmd/link/internal/sym/symkind.go b/src/cmd/link/internal/sym/symkind.go
index 77dbf75a51..08cafb206b 100644
--- a/src/cmd/link/internal/sym/symkind.go
+++ b/src/cmd/link/internal/sym/symkind.go
@@ -184,3 +184,7 @@ var RelROMap = map[SymKind]SymKind{
 func (t SymKind) IsData() bool {
 	return t == SDATA || t == SNOPTRDATA || t == SBSS || t == SNOPTRBSS
 }
+
+func (t SymKind) IsDWARF() bool {
+	return t >= SDWARFSECT && t <= SDWARFLINES
+}