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aarch64: Allow PC-relative relocations against protected STT_FUNC for -shared

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__attribute__((visibility("protected"))) void *foo() {
      return (void *)foo;
    }

gcc -fpic -shared -fuse-ld=bfd fails with the confusing diagnostic:

    relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `foo' which may bind externally can not be used when making a shared object; recompile with -fPIC

Call _bfd_elf_symbol_refs_local_p with local_protected==true to suppress
the error.  The new behavior matches gold and ld.lld.

Note: if some code tries to use direct access relocations to take the
address of foo (likely due to -fno-pic), the pointer equality will
break, but the error should be reported on the executable link, not on
the innocent shared object link.  glibc 2.36 will give a warning at
relocation resolving time.
This commit is contained in:
Fangrui Song
2022-06-23 01:10:44 -07:00
committed by Fangrui Song
parent 4fb55bf6a9
commit 83c325007c
4 changed files with 20 additions and 1 deletions
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2
bfd/elfnn-aarch64.c
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@ -5888,7 +5888,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
if (bfd_link_pic (info)
&& (input_section->flags & SEC_ALLOC) != 0
&& (input_section->flags & SEC_READONLY) != 0
&& !SYMBOL_REFERENCES_LOCAL (info, h))
&& !_bfd_elf_symbol_refs_local_p (h, info, 1))
{
int howto_index = bfd_r_type - BFD_RELOC_AARCH64_RELOC_START;

1
ld/testsuite/ld-aarch64/aarch64-elf.exp
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@ -248,6 +248,7 @@ run_dump_test_lp64 "local-addend-r"
# test error handling on pcrel relocation for shared libraries.
run_dump_test_lp64 "pcrel_pic_undefined"
run_dump_test_lp64 "pcrel_pic_defined"
run_dump_test_lp64 "pcrel_pic_protected"
run_dump_test "limit-b"
run_dump_test "limit-bl"

11
ld/testsuite/ld-aarch64/pcrel-protected.s Normal file
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@ -0,0 +1,11 @@
.protected protected_a, protected_b, protected_c
.type protected_b, %object
.type protected_c, %function
.text
adrp x0, protected_a
add x0, x0, :lo12:protected_a
adrp x0, protected_b
add x0, x0, :lo12:protected_b
adrp x0, protected_c
add x0, x0, :lo12:protected_c

7
ld/testsuite/ld-aarch64/pcrel_pic_protected.d Normal file
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@ -0,0 +1,7 @@
#name: PC-Rel relocation against protected
#source: pcrel-protected.s
#target: [check_shared_lib_support]
#ld: -shared -e0 --defsym protected_a=0x1000 --defsym protected_b=0x1010 --defsym protected_c=0x1020
#readelf: -r -W
#...
There are no relocations in this file.