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[AArch64] Also puts value in place for R_AARCH64_RELATIVE 

When handling absolute relocations for global symbols bind within the
shared object, AArch64 will generate one dynamic RELATIVE relocation,
but won't apply the value for this absolution relocations at static
linking stage. This is different from AArch64 gold linker and x86-64.

This is not a bug as AArch64 is RELA, there is only guarantee that
relocation addend is placed in the relocation entry.  But some
system softwares originally writen for x86-64 might assume AArch64
bfd linker gets the same behavior as x86-64, then they could take
advantage of this buy skipping those RELATIVE dynamic relocations
if the load address is the same as the static linking address.

This patch makes AArch64 BFD linker applies absolution relocations at
static linking stage for scenario described above.  Meanwhile 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.
This commit is contained in:
Jiong Wang 2016-05-03 11:59:37 +01:00
parent 20f55f3866
commit 1f56df9d0d
13 changed files with 109 additions and 6 deletions
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9
bfd/ChangeLog
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@ -1,3 +1,12 @@
2016-05-03 Jiong Wang <jiong.wang@arm.com>
* 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.
2016-04-29 H.J. Lu <hongjiu.lu@intel.com>
* elf32-i386.c (elf_i386_size_dynamic_sections): Move interp

4
bfd/bfd-in.h
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@ -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)

4
bfd/bfd-in2.h
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@ -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)

8
bfd/elfnn-aarch64.c
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@ -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;
}

12
ld/ChangeLog
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@ -1,3 +1,15 @@
2016-05-03 Jiong Wang <jiong.wang@arm.com>
* 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.
2016-05-03 Senthil Kumar Selvaraj <senthil_kumar.selvaraj@atmel.com>
* testsuite/ld-elfcomm/elfcomm.exp: Check for shared lib support

3
ld/NEWS
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@ -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

11
ld/emultempl/aarch64elf.em
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@ -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;

5
ld/ld.texinfo
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@ -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

4
ld/testsuite/ld-aarch64/aarch64-elf.exp
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@ -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"}

13
ld/testsuite/ld-aarch64/rela-abs-relative-be.d Normal file
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@ -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.*

13
ld/testsuite/ld-aarch64/rela-abs-relative-opt.d Normal file
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@ -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.*

13
ld/testsuite/ld-aarch64/rela-abs-relative.d Normal file
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@ -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.*

16
ld/testsuite/ld-aarch64/rela-abs-relative.s Normal file
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@ -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