* [PATCH][AArch64] Improve copy relocation support on four absolute relocation types
@ 2014-08-13 14:32 Jiong Wang
2014-08-26 14:17 ` Nicholas Clifton
0 siblings, 1 reply; 2+ messages in thread
From: Jiong Wang @ 2014-08-13 14:32 UTC (permalink / raw)
To: binutils
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aarch64 static linker fail linking unreasonably when trying to link executable from .o
written by handle assembly which contain access of global symbol and generated without -fPIC.
/usr/bin/ld: x.o(.text+0x8): unresolvable R_AARCH64_MOVW_UABS_G0_NC relocation against...
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status
I found the problem is caused by our incomplete support for calculating address of
global symbol by absolute relocation.
currently, if we calculating address by 32/64 bit absolute relocation, it's OK.
for example:
x.s
.8byte global_a
for .o, a ABS64 relocation created.
Relocation section '*.rela.text*' at offset 0x360 contains 1 entries:
R_AARCH64_ABS64 0000000000000000 global_a + 0
then if we:
link into executable
============================
copy relocation generated, and the original address in text section
will point to .dynbss which this copy relocation will happen.
*readelf -r x.exe*
Relocation section '*.rela.dyn*' at offset 0x460 contains 9 entries:
R_AARCH64_COPY 0000000000410830 stdout + 0
link into shared library
========================
R_AARCH64_ABS64 will be propagated to dynamic relocation section to let the
runtime linker relocate on the text section directly.
*readelf -r x.so*
Relocation section '*.rela.dyn*' at offset 0x460 contains 9 entries:
R_AARCH64_ABS64 0000000000000000 stdout + 0
while there is another way to form 64 bit address for global symbol by using
movz x0,:abs_g0_nc:global_a (BFD_RELOC_AARCH64_MOVW_G0_NC)
movk x0,:abs_g1_nc:global_a (BFD_RELOC_AARCH64_MOVW_G1_NC)
movk x0,:abs_g2_nc:global_a (BFD_RELOC_AARCH64_MOVW_G2_NC)
movk x0,:abs_g3:global_a (BFD_RELOC_AARCH64_MOVW_G3)
to form the address from pieces instead of one single R_AARCH64_ABS64.
so for the above four relocation types, we need to support all those logic
AARCH64_ABS64 supported except when linking shared library to prevent
copy on write penalty.
* for executable linking, generate copy relocation.
* reject them when linking shared library.
this is also the approach arm32 adopted.
ok for trunk?
thanks.
-- Jiong
bfd/
* elfnn-aarch64.c (elfNN_aarch64_check_relocs): Initialize non_got_ref
properly for MOVW_G0/1/2_NC and MOVW_G3. Reject them when linking
shared library.
(elfNN_aarch64_gc_sweep_hook): Add check on these relocs.
ld/testsuite/
* ld-aarch64/copy-relocs-so.s: New test file.
* ld-aarch64/copy-relocs-exe.s: Likewise.
* ld-aarch64/copy-relocs.d: New expectation file.
* ld-aarch64/emit-relocs-264-bad.d: New test file.
* ld-aarch64/emit-relocs-266-bad.d: Likewise.
* ld-aarch64/emit-relocs-268-bad.d: Likewise.
* ld-aarch64/emit-relocs-269-bad.d: Likewise.
* ld-aarch64/aarch64-elf.exp: Run new added test.
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commit 755d9ef68978198eb3e022d6fad86e4a54f97f2b
Author: Jiong Wang <jiong.wang@arm.com>
Date: Mon Aug 11 14:52:24 2014 +0100
Fix
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 4dfb604..d7b3037 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -4766,16 +4766,6 @@ elfNN_aarch64_gc_sweep_hook (bfd *abfd,
}
break;
- case BFD_RELOC_AARCH64_ADR_HI21_NC_PCREL:
- case BFD_RELOC_AARCH64_ADR_HI21_PCREL:
- case BFD_RELOC_AARCH64_ADR_LO21_PCREL:
- if (h != NULL && info->executable)
- {
- if (h->plt.refcount > 0)
- h->plt.refcount -= 1;
- }
- break;
-
case BFD_RELOC_AARCH64_CALL26:
case BFD_RELOC_AARCH64_JUMP26:
/* If this is a local symbol then we resolve it
@@ -4787,6 +4777,13 @@ elfNN_aarch64_gc_sweep_hook (bfd *abfd,
h->plt.refcount -= 1;
break;
+ case BFD_RELOC_AARCH64_MOVW_G0_NC:
+ case BFD_RELOC_AARCH64_MOVW_G1_NC:
+ case BFD_RELOC_AARCH64_MOVW_G2_NC:
+ case BFD_RELOC_AARCH64_MOVW_G3:
+ case BFD_RELOC_AARCH64_ADR_HI21_NC_PCREL:
+ case BFD_RELOC_AARCH64_ADR_HI21_PCREL:
+ case BFD_RELOC_AARCH64_ADR_LO21_PCREL:
case BFD_RELOC_AARCH64_NN:
if (h != NULL && info->executable)
{
@@ -5283,6 +5280,22 @@ elfNN_aarch64_check_relocs (bfd *abfd, struct bfd_link_info *info,
break;
}
+ case BFD_RELOC_AARCH64_MOVW_G0_NC:
+ case BFD_RELOC_AARCH64_MOVW_G1_NC:
+ case BFD_RELOC_AARCH64_MOVW_G2_NC:
+ case BFD_RELOC_AARCH64_MOVW_G3:
+ if (info->shared)
+ {
+ int howto_index = bfd_r_type - BFD_RELOC_AARCH64_RELOC_START;
+ (*_bfd_error_handler)
+ (_("%B: relocation %s against `%s' can not be used when making "
+ "a shared object; recompile with -fPIC"),
+ abfd, elfNN_aarch64_howto_table[howto_index].name,
+ (h) ? h->root.root.string : "a local symbol");
+ bfd_set_error (bfd_error_bad_value);
+ return FALSE;
+ }
+
case BFD_RELOC_AARCH64_ADR_HI21_NC_PCREL:
case BFD_RELOC_AARCH64_ADR_HI21_PCREL:
case BFD_RELOC_AARCH64_ADR_LO21_PCREL:
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 36babf3..b3f6eb5 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -51,11 +51,15 @@ run_dump_test "emit-relocs-260-be"
run_dump_test "emit-relocs-262"
run_dump_test "emit-relocs-263"
run_dump_test "emit-relocs-264"
+run_dump_test "emit-relocs-264-bad"
run_dump_test "emit-relocs-265"
run_dump_test "emit-relocs-266"
+run_dump_test "emit-relocs-266-bad"
run_dump_test "emit-relocs-267"
run_dump_test "emit-relocs-268"
+run_dump_test "emit-relocs-268-bad"
run_dump_test "emit-relocs-269"
+run_dump_test "emit-relocs-269-bad"
run_dump_test "emit-relocs-270"
run_dump_test "emit-relocs-270-bad"
run_dump_test "emit-relocs-271"
@@ -163,3 +167,12 @@ run_dump_test "ifunc-21"
run_dump_test "ifunc-22"
run_dump_test "relasz"
+
+set aarch64elflinktests {
+ {"ld-aarch64/so with global symbol" "-shared" "" "" {copy-reloc-so.s}
+ {} "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"}
+}
+
+run_ld_link_tests $aarch64elflinktests
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-exe.s b/ld/testsuite/ld-aarch64/copy-reloc-exe.s
new file mode 100644
index 0000000..cafc700
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-exe.s
@@ -0,0 +1,7 @@
+ .text
+ .global main
+main:
+ movz x0,:abs_g0_nc:global_a
+ movk x0,:abs_g1_nc:global_a
+ movk x0,:abs_g2_nc:global_a
+ movk x0,:abs_g3:global_a
diff --git a/ld/testsuite/ld-aarch64/copy-reloc-so.s b/ld/testsuite/ld-aarch64/copy-reloc-so.s
new file mode 100644
index 0000000..07ec44a
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc-so.s
@@ -0,0 +1,6 @@
+ .global global_a
+ .type global_a, %object
+ .size global_a, 4
+ .data
+global_a:
+ .word 0xcafedead
diff --git a/ld/testsuite/ld-aarch64/copy-reloc.d b/ld/testsuite/ld-aarch64/copy-reloc.d
new file mode 100644
index 0000000..c4eed84
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/copy-reloc.d
@@ -0,0 +1,4 @@
+.*
+DYNAMIC RELOCATION RECORDS
+OFFSET.*TYPE.*VALUE.*
+.*R_AARCH64_COPY.*global_a
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-264-bad.d b/ld/testsuite/ld-aarch64/emit-relocs-264-bad.d
new file mode 100644
index 0000000..22718ca
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-264-bad.d
@@ -0,0 +1,3 @@
+#source: emit-relocs-264.s
+#ld: -T relocs.ld --defsym tempy=0x11000 --defsym tempy2=0x45000 --defsym tempy3=0x1234 -e0 -shared
+#error: .*relocation R_AARCH64_MOVW_UABS_G0_NC.*can not.*shared object.*fPIC
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-266-bad.d b/ld/testsuite/ld-aarch64/emit-relocs-266-bad.d
new file mode 100644
index 0000000..886494d
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-266-bad.d
@@ -0,0 +1,3 @@
+#source: emit-relocs-266.s
+#ld: -T relocs.ld --defsym tempy=0x11000 --defsym tempy2=0x45000 --defsym tempy3=0x1234 -e0 -shared
+#error: .*relocation R_AARCH64_MOVW_UABS_G1_NC.*can not.*shared object.*fPIC
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-268-bad.d b/ld/testsuite/ld-aarch64/emit-relocs-268-bad.d
new file mode 100644
index 0000000..ea97541
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-268-bad.d
@@ -0,0 +1,3 @@
+#source: emit-relocs-268.s
+#ld: -T relocs.ld --defsym tempy=0x11000 --defsym tempy2=0x45000 --defsym tempy3=0x1234 -e0 -shared
+#error: .*relocation R_AARCH64_MOVW_UABS_G2_NC.*can not.*shared object.*fPIC
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-269-bad.d b/ld/testsuite/ld-aarch64/emit-relocs-269-bad.d
new file mode 100644
index 0000000..9292855
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-269-bad.d
@@ -0,0 +1,3 @@
+#source: emit-relocs-269.s
+#ld: -T relocs.ld --defsym tempy=0x11000 --defsym tempy2=0x45000 --defsym tempy3=0x1234 -e0 -shared
+#error: .*relocation R_AARCH64_MOVW_UABS_G3.*can not.*shared object.*fPIC
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH][AArch64] Improve copy relocation support on four absolute relocation types
2014-08-13 14:32 [PATCH][AArch64] Improve copy relocation support on four absolute relocation types Jiong Wang
@ 2014-08-26 14:17 ` Nicholas Clifton
0 siblings, 0 replies; 2+ messages in thread
From: Nicholas Clifton @ 2014-08-26 14:17 UTC (permalink / raw)
To: Jiong Wang, binutils
Hi Jiong,
> bfd/
> * elfnn-aarch64.c (elfNN_aarch64_check_relocs): Initialize non_got_ref
> properly for MOVW_G0/1/2_NC and MOVW_G3. Reject them when linking
> shared library.
> (elfNN_aarch64_gc_sweep_hook): Add check on these relocs.
>
> ld/testsuite/
> * ld-aarch64/copy-relocs-so.s: New test file.
> * ld-aarch64/copy-relocs-exe.s: Likewise.
> * ld-aarch64/copy-relocs.d: New expectation file.
> * ld-aarch64/emit-relocs-264-bad.d: New test file.
> * ld-aarch64/emit-relocs-266-bad.d: Likewise.
> * ld-aarch64/emit-relocs-268-bad.d: Likewise.
> * ld-aarch64/emit-relocs-269-bad.d: Likewise.
> * ld-aarch64/aarch64-elf.exp: Run new added test.
Approved - please apply.
Cheers
Nick
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