[AArch64] Allow COPY relocation elimination

  As discussed at the PR, this patch tries to avoid COPY relocation generation
and propagate the original relocation into runtime if it was relocating on
writable section.  The ELIMINATE_COPY_RELOCS has been set to true and it's
underlying infrastructure has been improved so that the COPY reloc elimination
at least working on absoluate relocations (ABS64) on AArch64.

  BFD linker copy relocation elimination framwork requires the backend to always
allocate dynrelocs for all those relocation types that are possible to introduce
copy relocations.  This is for adjust_dynamic_symbol hook to be able to get all
symbol reference information.  Should one symbol is referenced by more than one
relocations, if there is any of them needs copy relocation then linker should
generate it.

bfd/
	PR ld/21532
	* elfnn-aarch64.c (ELIMINATE_COPY_RELOCS): Set to 1.
	(elfNN_aarch64_final_link_relocate): Also propagate relocations to
	runtime for if there needs copy relocation elimination.
	(need_copy_relocation_p): New function.  Return true for symbol with
	pc-relative references and if it's against read-only sections.
	(elfNN_aarch64_adjust_dynamic_symbol): Use need_copy_relocation_p.
	(elfNN_aarch64_check_relocs): Allocate dynrelocs for relocation types
	that are related with accessing external objects.
	(elfNN_aarch64_gc_sweep_hook): Sync the relocation types with the change
	in elfNN_aarch64_check_relocs.

ld/
	* testsuite/ld-aarch64/copy-reloc-exe-2.s: New test source file.
	* testsuite/ld-aarch64/copy-reloc-2.d: New test.
	* testsuite/ld-aarch64/copy-reloc-exe-eliminate.s: New test source file.
	* testsuite/ld-aarch64/copy-reloc-eliminate.d: New test.
	* testsuite/ld-aarch64/copy-reloc-so.s: Define new global objects.
	* testsuite/ld-aarch64/aarch64-elf.exp: Run new tests.

6 files changed, 73 insertions, 0 deletions

diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index ca21e171a11..f171f6fe348 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -335,6 +335,10 @@ set aarch64elflinktests {
     {} "copy-reloc-so.so"}
   {"ld-aarch64/exe with copy relocation" "-e0 tmpdir/copy-reloc-so.so" "" ""
     {copy-reloc-exe.s} {{objdump -R copy-reloc.d}} "copy-reloc"}
+  {"ld-aarch64/exe with copy relocation 2" "-e0 tmpdir/copy-reloc-so.so" "" ""
+    {copy-reloc-exe-2.s} {{objdump -R copy-reloc-2.d}} "copy-reloc-2"}
+  {"ld-aarch64/exe with copy relocation elimination" "-e0 tmpdir/copy-reloc-so.so" "" ""
+    {copy-reloc-exe-eliminate.s} {{objdump -R copy-reloc-eliminate.d}} "copy-reloc-elimination"}
   {"ld-aarch64/so with global func" "-shared" "" "" {func-in-so.s}
     {} "func-in-so.so"}
   {"ld-aarch64/func sym hash opt for exe"
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-2.d b/ld/testsuite/ld-aarch64/copy-reloc-2.d
new file mode 100644
index 00000000000..87ddccd7486
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-2.d
@@ -0,0 +1,7 @@
+.*
+DYNAMIC RELOCATION RECORDS
+OFFSET.*TYPE.*VALUE.*
+.*R_AARCH64_COPY.*global_[abcd]
+.*R_AARCH64_COPY.*global_[abcd]
+.*R_AARCH64_COPY.*global_[abcd]
+.*R_AARCH64_COPY.*global_[abcd]
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-eliminate.d b/ld/testsuite/ld-aarch64/copy-reloc-eliminate.d
new file mode 100644
index 00000000000..9657d651132
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-eliminate.d
@@ -0,0 +1,4 @@
+.*
+DYNAMIC RELOCATION RECORDS
+OFFSET.*TYPE.*VALUE.*
+.*R_AARCH64_ABS64.*global_a
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-exe-2.s b/ld/testsuite/ld-aarch64/copy-reloc-exe-2.s
new file mode 100644
index 00000000000..d83658c4fa8
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-exe-2.s
@@ -0,0 +1,32 @@
+	# expect copy relocation for all these scenarios.
+	.global	p
+	.global	q
+	.global	r
+	.section	.data.rel.ro,"aw",%progbits
+	.align	3
+	.type	p, %object
+	.size	p, 8
+p:
+	.xword	global_a
+
+	.type	q, %object
+	.size	q, 8
+q:
+	.xword	global_b
+
+	.type	r, %object
+	.size	r, 8
+r:
+	# Any pc-rel relocation as no dynamic linker support on AArch64.
+	.xword	global_c - .
+
+	.text
+	.global main
+main:
+	# Symbols are referenced by any other relocation against read-only
+	# section.
+	movz x0, :abs_g0_nc:global_a
+	adrp x1, global_b
+	# pc-rel.
+	adrp x2, global_d
+	add x2, x2, #:lo12:global_c
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-exe-eliminate.s b/ld/testsuite/ld-aarch64/copy-reloc-exe-eliminate.s
new file mode 100644
index 00000000000..33227aad3ee
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-exe-eliminate.s
@@ -0,0 +1,7 @@
+	.global	p
+	.section	.data.rel.ro,"aw",%progbits
+	.align	3
+	.type	p, %object
+	.size	p, 8
+p:
+	.xword	global_a
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-so.s b/ld/testsuite/ld-aarch64/copy-reloc-so.s
index 07ec44a2c7d..af40f69a0a0 100644
--- a/ld/testsuite/ld-aarch64/copy-reloc-so.s
+++ b/ld/testsuite/ld-aarch64/copy-reloc-so.s
@@ -1,6 +1,25 @@
 	.global global_a
 	.type	global_a, %object
 	.size	global_a, 4
+
+	.global global_b
+	.type	global_b, %object
+	.size	global_b, 4
+
+	.global global_c
+	.type	global_c, %object
+	.size	global_c, 4
+
+	.global global_d
+	.type	global_d, %object
+	.size	global_d, 4
+
 	.data
 global_a:
 	.word 0xcafedead
+global_b:
+	.word 0xcafecafe
+global_c:
+	.word 0xdeadcafe
+global_d:
+	.word 0xdeaddead