From 7e05773767820b441b23a16628b55c98cb1aef46 Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddesh.poyarekar@arm.com>
Date: Tue, 19 May 2020 11:07:52 +0100
Subject: [PATCH] [PATCH v3] aarch64: Emit jump slot for conditional branch to
undefined symbols
The linker silently writes out a conditional branch to 0 if the
target symbol in R_AARCH64_CONDBR19 or R_AARCH64_TSTBR14 relocations is
undefined. Emit a PLT instead so that behaviour is the same for these
relocations as the llvm linker.
The special behaviour for undefined weak symbols, where conditional
branches to such symbols result in a branch unto themselves, has been
retained. This is because the weak-undefined.s test explicitly checks
for that, leading me to conclude that it's expected behaviour.
bfd * elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Club
BFD_RELOC_AARCH64_BRANCH19 and BFD_RELOC_AARCH64_TSTBR14
cases with BFD_RELOC_AARCH64_JUMP26.
(elfNN_aarch64_check_relocs): Likewise.
ld * testsuite/ld-aarch64/aarch64-elf.exp: New test
emit-relocs-560.
* testsuite/ld-aarch64/emit-relocs-560.d: New file.
* testsuite/ld-aarch64/emit-relocs-560.s: New file.
---
bfd/ChangeLog | 7 +++++++
bfd/elfnn-aarch64.c | 22 ++++++++++++++++++----
ld/ChangeLog | 7 +++++++
ld/testsuite/ld-aarch64/aarch64-elf.exp | 1 +
ld/testsuite/ld-aarch64/emit-relocs-560.d | 8 ++++++++
ld/testsuite/ld-aarch64/emit-relocs-560.s | 3 +++
6 files changed, 44 insertions(+), 4 deletions(-)
create mode 100644 ld/testsuite/ld-aarch64/emit-relocs-560.d
create mode 100644 ld/testsuite/ld-aarch64/emit-relocs-560.s
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index d9892235721..c10c1e93c9a 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2020-05-19 Siddhesh Poyarekar <siddesh.poyarekar@arm.com>
+
+ * elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Club
+ BFD_RELOC_AARCH64_BRANCH19 and BFD_RELOC_AARCH64_TSTBR14
+ cases with BFD_RELOC_AARCH64_JUMP26.
+ (elfNN_aarch64_check_relocs): Likewise.
+
2020-05-19 Alan Modra <amodra@gmail.com>
* aix5ppc-core.c (xcoff64_core_file_matches_executable_p): Use
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 4bb5707d2f4..02df893fcdd 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -5494,6 +5494,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
bfd_vma orig_value = value;
bfd_boolean resolved_to_zero;
bfd_boolean abs_symbol_p;
+ bfd_boolean via_plt_p;
globals = elf_aarch64_hash_table (info);
@@ -5515,6 +5516,8 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
: bfd_is_und_section (sym_sec));
abs_symbol_p = h != NULL && bfd_is_abs_symbol (&h->root);
+ via_plt_p = (globals->root.splt != NULL && h != NULL
+ && h->plt.offset != (bfd_vma) - 1);
/* Since STT_GNU_IFUNC symbol must go through PLT, we handle
it here if it is defined in a non-shared object. */
@@ -5850,12 +5853,23 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
value += signed_addend;
break;
+ case BFD_RELOC_AARCH64_BRANCH19:
+ case BFD_RELOC_AARCH64_TSTBR14:
+ /* A conditional branch to an undefined weak symbol is converted to a
+ branch to itself. */
+ if (weak_undef_p && !via_plt_p)
+ {
+ value = _bfd_aarch64_elf_resolve_relocation (input_bfd, bfd_r_type,
+ place, value,
+ signed_addend,
+ weak_undef_p);
+ break;
+ }
+ /* Fall through. */
case BFD_RELOC_AARCH64_CALL26:
case BFD_RELOC_AARCH64_JUMP26:
{
asection *splt = globals->root.splt;
- bfd_boolean via_plt_p =
- splt != NULL && h != NULL && h->plt.offset != (bfd_vma) - 1;
/* A call to an undefined weak symbol is converted to a jump to
the next instruction unless a PLT entry will be created.
@@ -5943,7 +5957,6 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
case BFD_RELOC_AARCH64_32:
#endif
case BFD_RELOC_AARCH64_ADD_LO12:
- case BFD_RELOC_AARCH64_BRANCH19:
case BFD_RELOC_AARCH64_LDST128_LO12:
case BFD_RELOC_AARCH64_LDST16_LO12:
case BFD_RELOC_AARCH64_LDST32_LO12:
@@ -5959,7 +5972,6 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
case BFD_RELOC_AARCH64_MOVW_G2_NC:
case BFD_RELOC_AARCH64_MOVW_G2_S:
case BFD_RELOC_AARCH64_MOVW_G3:
- case BFD_RELOC_AARCH64_TSTBR14:
value = _bfd_aarch64_elf_resolve_relocation (input_bfd, bfd_r_type,
place, value,
signed_addend, weak_undef_p);
@@ -8022,6 +8034,8 @@ elfNN_aarch64_check_relocs (bfd *abfd, struct bfd_link_info *info,
break;
}
+ case BFD_RELOC_AARCH64_BRANCH19:
+ case BFD_RELOC_AARCH64_TSTBR14:
case BFD_RELOC_AARCH64_CALL26:
case BFD_RELOC_AARCH64_JUMP26:
/* If this is a local symbol then we resolve it
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 730517124e9..cf566b32559 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2020-05-19 Siddhesh Poyarekar <siddesh.poyarekar@arm.com>
+
+ * testsuite/ld-aarch64/aarch64-elf.exp: New test
+ emit-relocs-560.
+ * testsuite/ld-aarch64/emit-relocs-560.d: New file.
+ * testsuite/ld-aarch64/emit-relocs-560.s: New file.
+
2020-05-19 Alan Modra <amodra@gmail.com>
* emultempl/beos.em (sort_by_file_name): Use bfd_get_filename
diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
index 297a3e96db9..4c44fa1642b 100644
--- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
+++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
@@ -236,6 +236,7 @@ run_dump_test_lp64 "emit-relocs-557"
run_dump_test_lp64 "emit-relocs-558"
run_dump_test_lp64 "emit-relocs-558-overflow"
run_dump_test_lp64 "emit-relocs-559"
+run_dump_test_lp64 "emit-relocs-560"
run_dump_test "reloc-overflow-bad"
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-560.d b/ld/testsuite/ld-aarch64/emit-relocs-560.d
new file mode 100644
index 00000000000..153532457b4
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-560.d
@@ -0,0 +1,8 @@
+#source: emit-relocs-560.s
+#ld: -shared
+#readelf: -r
+
+Relocation section '.rela.plt' at offset 0x[0-9a-f]+ contains 2 entries:
+ Offset Info Type Sym. Value Sym. Name \+ Addend
+[0-9a-f]+ 000100000402 R_AARCH64_JUMP_SL 0000000000000000 baz \+ 0
+[0-9a-f]+ 000200000402 R_AARCH64_JUMP_SL 0000000000000000 bar \+ 0
diff --git a/ld/testsuite/ld-aarch64/emit-relocs-560.s b/ld/testsuite/ld-aarch64/emit-relocs-560.s
new file mode 100644
index 00000000000..9529e8fd5e2
--- /dev/null
+++ b/ld/testsuite/ld-aarch64/emit-relocs-560.s
@@ -0,0 +1,3 @@
+foo:
+ tbz x0, 1, bar
+ cbnz x1, baz
--
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