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PR22374, PowerPC unnecessary PLT entries 

We don't need a PLT entry when function pointer initialization in a
read/write section is the only reference to a given function symbol.
This patch prevents the unnecessary PLT entry, and ensures no dynamic
relocs are emitted when UNDEFWEAK_NO_DYNAMIC_RELOC says so.

bfd/
	PR 22374
	* elf32-ppc.c (ppc_elf_adjust_dynamic_symbol): Don't create a plt
	entry when just a dynamic reloc can serve.  Ensure no dynamic
	relocations when UNDEFWEAK_NO_DYNAMIC_RELOC by setting non_got_ref.
	Expand and move the non_got_ref comment.
	* elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol): Likewise.
ld/
	* testsuite/ld-powerpc/ambiguousv2.d: Remove FIXME.
This commit is contained in:
Alan Modra 2017-10-31 22:13:21 +10:30
parent e48f0c8f1b
commit 3988aed54a
5 changed files with 58 additions and 13 deletions
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9
bfd/ChangeLog
View File

@ -1,3 +1,12 @@
2017-11-01 Alan Modra <amodra@gmail.com>
PR 22374
* elf32-ppc.c (ppc_elf_adjust_dynamic_symbol): Don't create a plt
entry when just a dynamic reloc can serve. Ensure no dynamic
relocations when UNDEFWEAK_NO_DYNAMIC_RELOC by setting non_got_ref.
Expand and move the non_got_ref comment.
* elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol): Likewise.
2017-10-31 Nick Clifton <nickc@redhat.com>
PR 22373

23
bfd/elf32-ppc.c
View File

@ -5507,6 +5507,16 @@ ppc_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
h->plt.plist = NULL;
h->needs_plt = 0;
h->pointer_equality_needed = 0;
/* After adjust_dynamic_symbol, non_got_ref set in the
non-pic case means that dyn_relocs for this symbol should
be discarded. We either want the symbol to remain
undefined, or we have a local definition of some sort.
The "local definition" for non-function symbols may be
due to creating a local definition in .dynbss, and for
function symbols, defining the symbol on the PLT call
stub code. Set non_got_ref here to ensure undef weaks
stay undefined. */
h->non_got_ref = 1;
}
else
{
@ -5520,19 +5530,24 @@ ppc_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
resolution of the symbol to be set at load time rather
than link time. */
if ((h->pointer_equality_needed
|| (!h->ref_regular_nonweak && h->non_got_ref))
|| (h->non_got_ref
&& !h->ref_regular_nonweak
&& !UNDEFWEAK_NO_DYNAMIC_RELOC (info, h)))
&& !htab->is_vxworks
&& !ppc_elf_hash_entry (h)->has_sda_refs
&& !readonly_dynrelocs (h, NULL))
{
h->pointer_equality_needed = 0;
/* After adjust_dynamic_symbol, non_got_ref set in the
non-pic case means that dyn_relocs for this symbol
should be discarded. */
/* Say that we do want dynamic relocs. */
h->non_got_ref = 0;
/* If we haven't seen a branch reloc then we don't need
a plt entry. */
if (!h->needs_plt)
h->plt.plist = NULL;
}
}
h->protected_def = 0;
/* Function symbols can't have copy relocs. */
return TRUE;
}
else

30
bfd/elf64-ppc.c
View File

@ -7193,6 +7193,16 @@ ppc64_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
h->plt.plist = NULL;
h->needs_plt = 0;
h->pointer_equality_needed = 0;
/* After adjust_dynamic_symbol, non_got_ref set in the
non-pic case means that dyn_relocs for this symbol should
be discarded. We either want the symbol to remain
undefined, or we have a local definition of some sort.
The "local definition" for non-function symbols may be
due to creating a local definition in .dynbss, and for
ELFv2 function symbols, defining the symbol on the PLT
call stub code. Set non_got_ref here to ensure undef
weaks stay undefined. */
h->non_got_ref = 1;
}
else if (abiversion (info->output_bfd) >= 2)
{
@ -7207,13 +7217,25 @@ ppc64_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
&& !alias_readonly_dynrelocs (h))
{
h->pointer_equality_needed = 0;
/* After adjust_dynamic_symbol, non_got_ref set in
the non-pic case means that dyn_relocs for this
symbol should be discarded. */
/* Say that we do want dynamic relocs. */
h->non_got_ref = 0;
/* If we haven't seen a branch reloc then we don't need
a plt entry. */
if (!h->needs_plt)
h->plt.plist = NULL;
}
/* If making a plt entry, then we don't need copy relocs. */
/* ELFv2 function symbols can't have copy relocs. */
return TRUE;
}
else if (!h->needs_plt
&& !alias_readonly_dynrelocs (h))
{
/* If we haven't seen a branch reloc then we don't need a
plt entry. */
h->plt.plist = NULL;
h->pointer_equality_needed = 0;
h->non_got_ref = 0;
return TRUE;
}
}

4
ld/ChangeLog
View File

@ -1,3 +1,7 @@
2017-11-01 Alan Modra <amodra@gmail.com>
* testsuite/ld-powerpc/ambiguousv2.d: Remove FIXME.
2017-11-01 Alan Modra <amodra@gmail.com>
PR 22374

5
ld/testsuite/ld-powerpc/ambiguousv2.d
View File

@ -8,16 +8,11 @@
# anything to mark it as ELFv1 or ELFv2. We should get a dynamic
# reloc on the function address, not have a global entry stub, and
# my_func should be undefined dynamic with value zero.
# FIXME someday: No need for a plt entry.
Relocation section .* contains 1 entries:
.*
.* R_PPC64_ADDR64 .* my_func \+ 0
Relocation section .* contains 1 entries:
.*
.* R_PPC64_JMP_SLOT .* my_func \+ 0
Symbol table '\.dynsym' contains 5 entries:
.*
0: .*