Re: [AArch64] Also puts value in place for R_AARCH64_RELATIVE

[Jiong Wang <jiong dot wang at foss dot arm dot com>]

On 28/04/16 14:15, Nick Clifton wrote:
> Hi Jiong,
>
> > static linking stage for scenario described above.  Meanwhile I noticed
> > old AArch64 android loader has a bug (PR19163) which relies on current
> > linker behavior as a workaround, so the same option --no-apply-dynamic-relocs
> > added.
> The patch looks OK to me, but it is lacking one detail: since you are adding a
> new feature to the linker you need to add some documentation to ld/ld.texinfo
> and mentions it in ld/NEWS.

Thanks for the review, documentation and NEWS updated.

OK for master?

Thanks.

bfd/
  * bfd-in.h (bfd_elf64_aarch64_set_options): Update prototype.
  * bfd-in2.h (bfd_elf64_aarch64_set_options): Likewise.
  * elfnn-aarch64.c (bfd_elfNN_aarch64_set_options): Initialize
  no_apply_dynamic_relocs.
  (elfNN_aarch64_final_link_relocate): Apply absolute relocations even though
  dynamic relocations generated.

ld/
  * emultempl/aarch64elf.em (--no-apply-dynamic-relocs): New option.
  * NEWS: Mention --no-apply-dynamic-relocs.
  * ld.texinfo (ld and the ARM family): Document --no-apply-dynamic-relocs.
  * testsuite/ld-aarch64/rela-abs-relative.s: New test source.
  * testsuite/ld-aarch64/rela-abs-relative.d: New expected result.
  * testsuite/ld-aarch64/rela-abs-relative-be.d: Likewise for big-endian.
  * estsuite/ld-aarch64/rela-abs-relative-opt.d: Likewise, but enable new
  option.

diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
index 5df2bab..4641405 100644
--- a/bfd/bfd-in.h
+++ b/bfd/bfd-in.h
@@ -961,10 +961,10 @@ extern void bfd_elf32_aarch64_init_maps
   (bfd *);
 
 extern void bfd_elf64_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int);
+  (bfd *, struct bfd_link_info *, int, int, int, int, int, int);
 
 extern void bfd_elf32_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int);
+  (bfd *, struct bfd_link_info *, int, int, int, int, int, int);
 
 /* ELF AArch64 mapping symbol support.  */
 #define BFD_AARCH64_SPECIAL_SYM_TYPE_MAP	(1 << 0)
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 6532f6e..9b6a4e2 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -968,10 +968,10 @@ extern void bfd_elf32_aarch64_init_maps
   (bfd *);
 
 extern void bfd_elf64_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int);
+  (bfd *, struct bfd_link_info *, int, int, int, int, int, int);
 
 extern void bfd_elf32_aarch64_set_options
-  (bfd *, struct bfd_link_info *, int, int, int, int, int);
+  (bfd *, struct bfd_link_info *, int, int, int, int, int, int);
 
 /* ELF AArch64 mapping symbol support.  */
 #define BFD_AARCH64_SPECIAL_SYM_TYPE_MAP	(1 << 0)
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 5b9878e..b24bc5d 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -2289,6 +2289,9 @@ struct elf_aarch64_link_hash_table
   /* Enable ADRP->ADR rewrite for erratum 843419 workaround.  */
   int fix_erratum_843419_adr;
 
+  /* Don't apply link-time values for dynamic relocations.  */
+  int no_apply_dynamic_relocs;
+
   /* The number of bytes in the initial entry in the PLT.  */
   bfd_size_type plt_header_size;
 
@@ -4334,7 +4337,8 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
 			       int no_enum_warn,
 			       int no_wchar_warn, int pic_veneer,
 			       int fix_erratum_835769,
-			       int fix_erratum_843419)
+			       int fix_erratum_843419,
+			       int no_apply_dynamic_relocs)
 {
   struct elf_aarch64_link_hash_table *globals;
 
@@ -4343,6 +4347,7 @@ bfd_elfNN_aarch64_set_options (struct bfd *output_bfd,
   globals->fix_erratum_835769 = fix_erratum_835769;
   globals->fix_erratum_843419 = fix_erratum_843419;
   globals->fix_erratum_843419_adr = TRUE;
+  globals->no_apply_dynamic_relocs = no_apply_dynamic_relocs;
 
   BFD_ASSERT (is_aarch64_elf (output_bfd));
   elf_aarch64_tdata (output_bfd)->no_enum_size_warning = no_enum_warn;
@@ -5208,6 +5213,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
 		 relocate the text and data segments independently,
 		 so the symbol does not matter.  */
 	      symbol = 0;
+	      relocate = globals->no_apply_dynamic_relocs ? FALSE : TRUE;
 	      outrel.r_info = ELFNN_R_INFO (symbol, AARCH64_R (RELATIVE));
 	      outrel.r_addend += value;
 	    }
diff --git a/ld/NEWS b/ld/NEWS
index b4abd0b..228fddf 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -11,6 +11,9 @@
 
 * The NOCROSSREFSTO command was added to the linker script language.
 
+* Add --no-apply-dynamic-relocs to the AArch64 linker to do not apply link-time
+  values for dynamic relocations.
+
 Changes in 2.26:
 
 * Add --fix-stm32l4xx-629360 to the ARM linker to enable a link-time
diff --git a/ld/emultempl/aarch64elf.em b/ld/emultempl/aarch64elf.em
index 9923be3..a17553a 100644
--- a/ld/emultempl/aarch64elf.em
+++ b/ld/emultempl/aarch64elf.em
@@ -32,6 +32,7 @@ static int no_wchar_size_warning = 0;
 static int pic_veneer = 0;
 static int fix_erratum_835769 = 0;
 static int fix_erratum_843419 = 0;
+static int no_apply_dynamic_relocs = 0;
 
 static void
 gld${EMULATION_NAME}_before_parse (void)
@@ -305,7 +306,8 @@ aarch64_elf_create_output_section_statements (void)
 				 no_enum_size_warning,
 				 no_wchar_size_warning,
 				 pic_veneer,
-				 fix_erratum_835769, fix_erratum_843419);
+				 fix_erratum_835769, fix_erratum_843419,
+				 no_apply_dynamic_relocs);
 
   stub_file = lang_add_input_file ("linker stubs",
 				   lang_input_file_is_fake_enum,
@@ -356,6 +358,7 @@ PARSE_AND_LIST_PROLOGUE='
 #define OPTION_NO_WCHAR_SIZE_WARNING	312
 #define OPTION_FIX_ERRATUM_835769	313
 #define OPTION_FIX_ERRATUM_843419	314
+#define OPTION_NO_APPLY_DYNAMIC_RELOCS	315
 '
 
 PARSE_AND_LIST_SHORTOPTS=p
@@ -368,6 +371,7 @@ PARSE_AND_LIST_LONGOPTS='
   { "no-wchar-size-warning", no_argument, NULL, OPTION_NO_WCHAR_SIZE_WARNING},
   { "fix-cortex-a53-835769", no_argument, NULL, OPTION_FIX_ERRATUM_835769},
   { "fix-cortex-a53-843419", no_argument, NULL, OPTION_FIX_ERRATUM_843419},
+  { "no-apply-dynamic-relocs", no_argument, NULL, OPTION_NO_APPLY_DYNAMIC_RELOCS},
 '
 
 PARSE_AND_LIST_OPTIONS='
@@ -387,6 +391,7 @@ PARSE_AND_LIST_OPTIONS='
 		   ));
   fprintf (file, _("  --fix-cortex-a53-835769      Fix erratum 835769\n"));
   fprintf (file, _("  --fix-cortex-a53-843419      Fix erratum 843419\n"));
+  fprintf (file, _("  --no-apply-dynamic-relocs	   Do not apply link-time values for dynamic relocations\n"));
 '
 
 PARSE_AND_LIST_ARGS_CASES='
@@ -414,6 +419,10 @@ PARSE_AND_LIST_ARGS_CASES='
       fix_erratum_843419 = 1;
       break;
 
+    case OPTION_NO_APPLY_DYNAMIC_RELOCS:
+      no_apply_dynamic_relocs = 1;
+      break;
+
     case OPTION_STUBGROUP_SIZE:
       {
 	const char *end;
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 7a2ed3a..bc16764 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -6848,6 +6848,11 @@ The @samp{--long-plt} option enables the use of 16 byte PLT entries
 which support up to 4Gb of code.  The default is to use 12 byte PLT
 entries which only support 512Mb of code.
 
+@kindex --no-apply-dynamic-relocs
+@cindex AArch64 rela addend
+The @samp{--no-apply-dynamic-relocs} option makes AArch64 linker do not apply
+link-time values for dynamic relocations.
+
 @ifclear GENERIC
 @lowersections
 @end ifclear
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index b9c4133..b27da52 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -285,6 +285,10 @@ run_dump_test "dt_textrel"
 
 run_dump_test "plt_mapping_symbol"
 
+run_dump_test "rela-abs-relative"
+run_dump_test "rela-abs-relative-be"
+run_dump_test "rela-abs-relative-opt"
+
 set aarch64elflinktests {
   {"ld-aarch64/so with global symbol" "-shared" "" "" {copy-reloc-so.s}
     {} "copy-reloc-so.so"}
diff --git a/ld/testsuite/ld-aarch64/rela-abs-relative-be.d b/ld/testsuite/ld-aarch64/rela-abs-relative-be.d
new file mode 100644
index 0000000..88ba58d
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/rela-abs-relative-be.d
@@ -0,0 +1,13 @@
+#name: rela-abs-relative (big endian)
+#source: rela-abs-relative.s
+#ld: -shared -Ttext-segment=0x100000 -Tdata=0x200000 -Trelocs.ld
+#target: aarch64_be-*-*
+#objdump: -dR -j .data
+#...
+
+Disassembly of section .data:
+
+.* <a>:
+  200000:	00 00 00 00 ca fe ca fe 00 00 00 00 00 01 00 ca.*
+			200008: R_AARCH64_RELATIVE	\*ABS\*\+0x100ca
+  200010:	00 00 00 00 de ad de ad.*
diff --git a/ld/testsuite/ld-aarch64/rela-abs-relative-opt.d b/ld/testsuite/ld-aarch64/rela-abs-relative-opt.d
new file mode 100644
index 0000000..a1e5ca0
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/rela-abs-relative-opt.d
@@ -0,0 +1,13 @@
+#name: rela-abs-relative --no-apply-dynamic-relocs
+#source: rela-abs-relative.s
+#ld: -shared -Ttext-segment=0x100000 -Tdata=0x200000 -Trelocs.ld --no-apply-dynamic-relocs
+#notarget: aarch64_be-*-*
+#objdump: -dR -j .data
+#...
+
+Disassembly of section .data:
+
+.* <a>:
+  200000:	fe ca fe ca 00 00 00 00 00 00 00 00 00 00 00 00.*
+			200008: R_AARCH64_RELATIVE	\*ABS\*\+0x100ca
+  200010:	ad de ad de 00 00 00 00.*
diff --git a/ld/testsuite/ld-aarch64/rela-abs-relative.d b/ld/testsuite/ld-aarch64/rela-abs-relative.d
new file mode 100644
index 0000000..aba876b
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/rela-abs-relative.d
@@ -0,0 +1,13 @@
+#name: rela-abs-relative
+#source: rela-abs-relative.s
+#ld: -shared -Ttext-segment=0x100000 -Tdata=0x200000 -Trelocs.ld
+#notarget: aarch64_be-*-*
+#objdump: -dR -j .data
+#...
+
+Disassembly of section .data:
+
+.* <a>:
+  200000:	fe ca fe ca 00 00 00 00 ca 00 01 00 00 00 00 00.*
+			200008: R_AARCH64_RELATIVE	\*ABS\*\+0x100ca
+  200010:	ad de ad de 00 00 00 00.*
diff --git a/ld/testsuite/ld-aarch64/rela-abs-relative.s b/ld/testsuite/ld-aarch64/rela-abs-relative.s
new file mode 100644
index 0000000..d4c4663
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/rela-abs-relative.s
@@ -0,0 +1,16 @@
+	.section	.rodata
+	.align	3
+	.type	string1, %object
+	.size	string1, 8
+local_foo:
+	.string	"local_foo"
+
+	.section	.data,"aw",%progbits
+	.align	3
+	.global	a
+	.type	a, %object
+	.size	a, 24
+a:
+	.xword	0xcafecafe
+	.xword	local_foo + 0xca
+	.xword	0xdeaddead