This patch adds --enable-separate-code to ld configure to turn on
-z separate-code by default and enables it by default for Linux/x86.
This avoids mixing code pages with data to improve cache performance
as well as security.
To reduce x86-64 executable and shared object sizes, the maximum page
size is reduced from 2MB to 4KB when -z separate-code is turned on by
default. Note: -z max-page-size= can be used to set the maximum page
size.
We compared SPEC CPU 2017 performance before and after this change on
Skylake server. There are no any significant performance changes.
Everything is mostly below +/-1%.
bfd/
* config.in: Regenerated.
* configure: Likewise.
* configure.ac: Add --enable-separate-code.
(DEFAULT_LD_Z_SEPARATE_CODE): New AC_DEFINE_UNQUOTED. Default
to 1 for Linux/x86 targets,
* elf64-x86-64.c (ELF_MAXPAGESIZE): Set to 0x1000 if
DEFAULT_LD_Z_SEPARATE_CODE is 1.
ld/
* NEWS: Mention --enable-separate-code.
* configure.ac: Add --enable-separate-code.
(DEFAULT_LD_Z_SEPARATE_CODE): New AC_DEFINE_UNQUOTED.
* configure.tgt: Default ac_default_ld_z_separate_code to 1 for
Linux/x86 targets.
* config.in: Regenerated.
* configure: Likewise.
* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse): Set
link_info.separate_code DEFAULT_LD_Z_SEPARATE_CODE.
This reverts most of commit 1be5d8d3bb.
Left in place are addition of --no-plt-align to some ppc32 ld tests
and the ld.texinfo --no-plt-thread-safe fix.
Since all ELF linkers call check_relocs after opening all inputs, we
can fold after_allocation into before_allocation so that local dynamic
symbols will be placed before global dynamic symbols in .dynsym section.
This fixed:
FAIL: Common symbol override test (auxiliary shared object build)
FAIL: ld-elf/pr19617a
FAIL: ld-elf/pr19698
for i386-solaris2.12 and x86_64-solaris2.12 targets.
PR ld/22728
* emultempl/solaris2.em (elf_solaris2_after_allocation): Fold
into ...
(elf_solaris2_before_allocation): This.
(LDEMUL_AFTER_ALLOCATION): Removed.
Asking for ppc32 plt call stubs to be aligned at 32 byte boundaries
didn't quite work. For ld.bfd they were spaced 32 bytes apart, but
only started on a 16 byte boundary. ld.gold also didn't get it right.
Finding that bug made me check over the ppc64 plt stub alignment,
where I found that negative values for alignment (meaning align to
minimize boundary crossing) were not accepted. Since no one has
complained about that, I guess I could have removed the feature from
ld.bfd documentation, but I've opted instead to correct the code.
I've also added an optional alignment paramenter for ppc32
--plt-align, for some consistency with gold and ppc64 ld.bfd.
bfd/
* elf32-ppc.c (ppc_elf_create_glink): Correct alignment of .glink.
* elf64-ppc.c (ppc64_elf_size_stubs): Handle negative plt_stub_align.
(ppc64_elf_build_stubs): Likewise.
gold/
* powerpc.cc (param_plt_align): New function supplying default
--plt-align values. Use it..
(Stub_table::plt_call_align): ..here, and..
(Output_data_glink::global_entry_align): ..here.
(Stub_table::stub_align): Correct 32-bit minimum alignment.
ld/
* emultempl/ppc32elf.em: Support optional --plt-align arg.
* emultempl/ppc64elf.em: Support negative --plt-align arg.
This is in preparation for the next patch adding Spectre variant 2
mitigation for PowerPC and PowerPC64. Besides tidying code involved
in stub output (to reduce the number of places where bctr is output),
the patch adds some user visible features:
1) PowerPC64 ELFv2 global entry stubs now are aligned under the
control of --plt-align, with a default alignment of 32 bytes.
2) PowerPC64 __glink_PLTresolve is no longer padded out with nops.
3) PowerPC32 PLT stubs are aligned under the control of --plt-align,
with the default alignment being 16 bytes as before.
4) The PowerPC32 branch/nop table emitted before __glink_PLTresolve
is now smaller in many cases. It was sized incorrectly when the
__tls_get_addr_opt stub was used, and unnecessarily included space
for local ifuncs.
bfd/
* elf32-ppc.c (GLINK_ENTRY_SIZE): Add parameters, handle
__tls_get_addr_opt, and alignment sizing.
(TLS_GET_ADDR_GLINK_SIZE): Delete.
(is_nonpic_glink_stub): Don't use GLINK_ENTRY_SIZE.
(ppc_elf_get_synthetic_symtab): Recognize stubs spaced at 4, 6,
or 8 insns.
(ppc_elf_link_hash_table_create): Init new ppc_elf_params field.
(allocate_dynrelocs): Use new GLINK_ENTRY_SIZE.
(ppc_elf_size_dynamic_sections): Likewise. Size branch table
by PLT reloc count.
(write_glink_stub): Handle __tls_get_addr_opt stub.
Pad out to size given by GLINK_ENTRY_SIZE.
(ppc_elf_relocate_section): Adjust write_glink_stub call.
(ppc_elf_finish_dynamic_symbol): Likewise.
(ppc_elf_finish_dynamic_sections): Write PLTresolve without using
insn array since so many need rewriting.
* elf32-ppc.h (struct ppc_elf_params): Add plt_stub_align.
* elf64-ppc.c (GLINK_PLTRESOLVE_SIZE): Rename from
GLINK_CALL_STUB_SIZE. Add htab param and evaluate to size without
nops. Adjust all uses.
(ppc64_elf_get_synthetic_symtab): Don't use GLINK_CALL_STUB_SIZE
in glink_vma calculation.
(struct ppc_link_hash_table): Add global_entry section pointer.
(create_linkage_sections): Create separate section for global
entry stubs.
(PPC_LO, PPC_HI, PPC_HA): Move earlier.
(size_global_entry_stubs): Handle sizing for aligned stubs.
(ppc64_elf_size_dynamic_sections): Handle global_entry alloc,
and don't stash end of glink branch table in rawsize.
(ppc_build_one_stub): Rewrite stub size calculations.
(build_global_entry_stubs): Use new section.
(ppc64_elf_build_stubs): Don't pad __glink_PLTresolve with nops.
Build lazy link stubs out to end of section. Build global entry
stubs in new section.
gold/
* options.h (plt_align): Support for PowerPC32 too.
* powerpc.cc (Stub_table::stub_align): Heed --plt-align for 32-bit.
(Stub_table::plt_call_size, branch_stub_size): Tidy.
(Stub_table::plt_call_align): Implement using stub_align.
(Output_data_glink::global_entry_align): New function.
(Output_data_glink::global_entry_off): New function.
(Output_data_glink::global_entry_address): Use global_entry_off.
(Output_data_glink::pltresolve_size): New function, replacing
pltresolve_size_ constant. Update all uses.
(Output_data_glink::add_global_entry): Align offset.
(Output_data_glink::set_final_data_size): Use global_entry_align.
(Stub_table::do_write): Don't pad __glink_PLTrelsolve with nops.
Tidy stub output. Use global_entry_off.
ld/
* emultempl/ppc32elf.em (params): Init new field.
(enum ppc32_opt): New enum to define OPTION_* values. Add
OPTION_PLT_ALIGN and OPTION_NO_PLT_ALIGN.
(PARSE_AND_LIST_LONGOPTS): Handle new options.
(PARSE_AND_LIST_ARGS_CASES): Likewise.
(PARSE_AND_LIST_OPTIONS): Likewise. Break up help output.
* emultempl/ppc64elf.em (ppc_add_stub_section): Init alignment
correctly for negative --plt-stub-align.
* testsuite/ld-powerpc/elfv2exe.d,
* testsuite/ld-powerpc/elfv2so.d,
* testsuite/ld-powerpc/relbrlt.d,
* testsuite/ld-powerpc/relbrlt.s,
* testsuite/ld-powerpc/tlsexe.d,
* testsuite/ld-powerpc/tlsexe.r,
* testsuite/ld-powerpc/tlsexe32.d,
* testsuite/ld-powerpc/tlsexe32.g,
* testsuite/ld-powerpc/tlsexe32.r,
* testsuite/ld-powerpc/tlsexetoc.d,
* testsuite/ld-powerpc/tlsexetoc.r,
* testsuite/ld-powerpc/tlsopt5_32.d,
* testsuite/ld-powerpc/tlsso.d,
* testsuite/ld-powerpc/tlstocso.d: Update for changed stub order.
Currently we have no obvious way to revert the action of the "-z defs"
command line option. The "--unresolved-symbols=ignore-in-object-files"
does pretty much what is needed, but it is non-obvious and it also
touches the setting for reporting unresolved symbol references from
shared libraries. So I am proposing adding a "-z undefs" option to be
the inverse of "-z defs". (I thought that "-z nodefs" might be
confusing since it implies banning all definitions, rather than
allowing them).
In addition the description of the "-z defs" option in the linker
documentation is misleading in one place, where it says:
'defs'
Disallows undefined symbols in object files. Undefined
symbols in shared libraries are still allowed.
whereas later on it gets it right:
'-z defs'
Report unresolved symbol references from regular object files.
This is done even if the linker is creating a non-symbolic shared
library. The switch '--[no-]allow-shlib-undefined' controls the
behaviour for reporting unresolved references found in shared
libraries being linked in.
* emultempl/elf32.em (_handle_option): Add support for "-z undefs"
as the opposite of "-z defs".
* ld.texinfo: Document the new option. Update the description of
the -z defs option to make it clear that it does generate an error
if an undefined symbol reference is found in an object file whilst
creating a shared library.
* NEWS: Document this new feature.
The new "-z separate-code" option will generate separate code LOAD
segment which must be in wholly disjoint pages from any other data.
include/
PR ld/22393
* bfdlink.h (bfd_link_info): Add separate_code.
ld/
PR ld/22393
* NEWS: Mention "-z separate-code".
* emultempl/elf32.em (gld${EMULATION_NAME}_get_script): Get
builtin linker scripts and return linker scripts from disk for
"-z separate-code".
(gld${EMULATION_NAME}_handle_option): Handle "-z separate-code"
and "-z noseparate-code".
* genscripts.sh: Generate linker scripts for "-z separate-code".
(LD_FLAG): Set to *textonly for "-z separate-code".
* ld.texinfo: Document "-z separate-code".
* lexsup.c (elf_shlib_list_options): Add linker help messsages
for "-z separate-code" and "-z noseparate-code".
* scripttempl/elf.sc (SEPARATE_TEXT): New
(TEXT_SEGMENT_ALIGN): Likewise.
Use ${TEXT_SEGMENT_ALIGN} to align and pad text segment to
${MAXPAGESIZE}.
PR 22419
* emultempl/v850elf.em (v850_create_output_section_statements):
New function. Generate an error if attempting to convert the
format of the output file.
* testsuite/ld-unique/pr21529.d: Skip for the V850.
* testsuite/ld-elf/pr21884.d: Skip for the V850.
We currently delete bytes by shifting an entire BFD backwards to
overwrite the bytes we no longer need. The result is that relaxing a
BFD is quadratic time.
This patch adds an additional relocation that specifies a byte range
that will be deleted from the final object file, and adds a relaxation
pass (between the existing passes that delete bytes and the alignment
pass) that actually deletes the bytes. Note that deletion is still
quadratic time, and nothing uses R_RISCV_DELETE yet.
I've been meaning to go convert all the other relaxations to use
R_RISCV_DELETE and then make it faster, but this patch has been sitting
around for months so it looks like that won't happen for a bit. The
PCREL->GPREL relaxation that comes next uses this, and since we've been
using these two patches out of tree since I wrote them months ago I
figure it's better to just get them in now. I (or someone else :)) can
convert all the relocations later...
R_RISCV_DELETE will never be emitted into ELF objects, so therefor isn't
exposed to the rest of binutils. As such, we're not considering this as
part of the ABI.
bfd/ChangeLog
2017-10-19 Palmer Dabbelt <palmer@dabbelt.com>
* elfnn-riscv (R_RISCV_DELETE): New define.
(_bfd_riscv_relax_delete): New function.
(perform_relocation): Handle R_RISCV_DELETE.
(_bfd_riscv_relax_section): Likewise.
ld/ChangeLog
2017-10-19 Palmer Dabbelt <palmer@dabbelt.com>
* emultempl/riscvelf.em (riscv_elf_before_allocation): Add a
third relaxation pass.
I believe we should be warning if ld is given both --no-dynamic-linker
and -z dynamic-undefined-weak. The two options are contradictory, the
first says an executable has no dynamic interpreter to resolve dynamic
symbols, while the second is asking for dynamic symbols to be emitted.
(And even if a static PIE's relocation code, which is needed to
process R_*_RELATIVE relocs, could process symbols, there are no
DT_NEEDED dynamic objects to define such symbols.)
I also think that dynamic_undefined_weak is the right flag to control
whether undefined weaks are made dynamic, whether in static PIEs or
anywhere else. So force it to 0 for static PIEs, fixing PR 22269 for
powerpc and any other target where the backend usually defaults to
undefined weaks being made dynamic.
This patch introduces regressions. I'd normally not do that, but
these are all in very recently added test cases, or expose bugs in the
x86 backend. The test cases were added after I'd made it known that
this patch or one like it was imminent.
PR 22269
* emultempl/elf32.em (after_parse): Warn on --no-dynamic-linker
-z dynamic-undefined-weak combination. Set dynamic_undefined_weak
to zero when nointerp.
This function shouldn't be called directly, except from backend code.
bfd/
* elflink.c (_bfd_elf_adjust_dynamic_symbol): Call
elf_backend_hide_symbol, not _bfd_elf_link_hash_hide_symbol.
(bfd_elf_define_start_stop): Likewise.
ld/
* emultempl/elf32.em (before_allocation): Call
elf_backend_hide_symbol, not _bfd_elf_link_hash_hide_symbol.
Formatting.
This changes the PowerPC64 --plt-align option to perform the usual
alignment of code as suggested by its name, as well as the previous
behaviour of padding so as to reduce boundary crossing. The old
behaviour is had by using a negative parameter.
The default is also changed to align plt stub code by default to 32
byte boundaries, the point being to get better bctr branch prediction
on power8 and power9 hardware.
bfd/
* elf64-ppp.c (plt_stub_pad): Handle positive and negative
plt_stub_align.
ld/
* ld.texinfo (--plt-align): Describe new behaviour of option.
* emultempl/ppc64elf.em (params): Default plt_stub_align to 5.
* testsuite/ld-powerpc/powerpc.exp: Pass --no-plt-align for
selected tests.
* testsuite/ld-powerpc/relbrlt.d: Pass --no-plt-align.
* testsuite/ld-powerpc/elfv2so.d: Adjust expected output.
* emultempl/elf32.em (handle_option): Accept the -z globalaudit
command line option.
* lexsup.c (elf_static_list_options): Add -z globalaudit.
* ld.texinfo: Document the support for the new command line
option.
* NEWS: Mention the new feature.
* testsuite/ld-elf/audit.exp: Add a test of the -z globalaudit
command line option.
* testsuite/ld-elf/globalaudit.rd: New file: Expected output from
readelf.
PR ld/21884
* testsuite/ld-elf/pr21884.d: Add AVR, HPPA, IA64, M68HC1x and
SCORE to list of targets not supporting file format changes during
linking.
* testsuite/ld-unique/pr21529.d: Likewise.
* emultempl/avrelf.em (_before_allocation): Skip for non-ELF
output formats.
(avr_elf_create_output_section_statements): Fail if the output
format is not ELF.
(avr_finish): Do not access the ELF header in non-ELF format
output bfds.
* emultempl/m68hc1xelf.em (_before_allocation): Skip for non-ELF
output formats.
(m68hc11elf_create_output_section_statements): Fail if the putput
format is not ELF.
(m68hc11elf_after_allocation): Skip for non-ELF output formats.
The loop checking for previous orphan placement should run even when
the output is non-ELF.
PR ld/21884
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Revert
last change. Rename iself to elfinput. Expand comments. Condition
ELF checks on having both input and output ELF files. Extract..
(elf_orphan_compatible): ..this new function.
Fix a commit 861fb55ab5 ("Defer allocation of R_MIPS_REL32 GOT
slots"), <https://sourceware.org/ml/binutils/2008-08/msg00096.html>,
regression and a more recent:
FAIL: ld-unique/pr21529
new LD test case failure, observed with all the relevant MIPS targets
whenever the linker is invoked with one or more ELF inputs and the
output format set to `binary'.
The culprit is a segmentation fault caused in `mips_before_allocation'
by a null pointer dereference, where an attempt is made to access the
ELF file header's `e_flags' member, for the purpose of determining
whether to produce a PLT and copy relocations, without first checking
that the output BFD is ELF. The `e_flags' member is stored in BFD's
private data pointed to by `tdep', which in the case of the `binary' BFD
is null, causing the segmentation fault. With other non-ELF BFDs such
as SREC `tdep' is not null and consequently no crash may happen and in
that case random data will be interpreted as it was `e_flags'.
Disable the access to `e_flags' then and all the associated checks and
consequently never produce a PLT and copy relocations if output is not a
MIPS ELF BFD, matching `_bfd_mips_elf_merge_private_bfd_data' that does
not process `e_flags' in that case either and therefore does not let us
decide here anyway if all the input objects included in the link are
suitable for use with a PLT and copy relocations.
ld/
* emultempl/mipself.em (mips_before_allocation): Avoid ELF
processing if not MIPS ELF.
* testsuite/ld-mips-elf/binary.d: New test.
* testsuite/ld-mips-elf/binary.ld: New test linker script.
* testsuite/ld-mips-elf/binary.s: New test source.
* testsuite/ld-mips-elf/mips-elf.exp: Run the new test.
All sections on a --just-syms bfd are discarded from the output, so
attaching linker created sections to such a bfd results in errors.
In other cases, like the .note.GNU-stack check, it's wrong to have a
--just-syms object potentially affect the output.
bfd/
* elflink.c (_bfd_elf_link_create_dynstrtab): Don't make dynobj
a --just-syms bfd.
(_bfd_elf_size_group_sections): Skip --just-syms bfds.
(bfd_elf_size_dynamic_sections): Ignore .note.GNU-stack and
.preinit_array on --just-syms bfds.
(_bfd_elf_gc_mark_extra_sections): Skip --just-syms bfds.
(elf_gc_sweep, bfd_elf_parse_eh_frame_entries): Likewise.
(bfd_elf_gc_sections, bfd_elf_discard_info): Likewise.
ld/
* emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Skip
--just-syms bfds when looking for a place to attach .note.gnu.build-id
and .eh_frame_hdr sections. Delete dead code.
This patch adds a new S/390 specific segment type: PT_S390_PGSTE. For
binaries marked with that segment the kernel will allocate 4k page
tables. The only user so far will be qemu.
ld/ChangeLog:
2017-06-23 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* Makefile.in: Add s390.em as build dependency.
* emulparams/elf64_s390.sh (EXTRA_EM_FILE): Add s390.em.
* emultempl/s390.em: New file.
* gen-doc.texi: Add documentation for --s390-pgste option.
* ld.texinfo: Likewise.
include/ChangeLog:
2017-06-23 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elf/s390.h (PT_S390_PGSTE): Define macro.
binutils/ChangeLog:
2017-06-23 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* readelf.c (get_s390_segment_type): Add support for the new
segment type PT_S390_PGSTE.
(get_segment_type): Call get_s390_segment_type.
elfcpp/ChangeLog:
2017-06-23 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elfcpp.h (enum PT): Add PT_S390_PGSTE to enum.
bfd/ChangeLog:
2017-06-23 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elf-s390.h: New file.
* elf64-s390.c (struct elf_s390_link_hash_table): Add params
field.
(elf_s390_additional_program_headers): New function.
(elf_s390_modify_segment_map): New function.
(bfd_elf_s390_set_options): New function.
(elf_backend_additional_program_headers)
(elf_backend_modify_segment_map): Add macro definitions.
Currently, linker will define __start_SECNAME and __stop_SECNAME symbols
only for orphaned sections.
However, during garbage collection, ELF linker marks all sections with
references to __start_SECNAME and __stop_SECNAME symbols as used even
when section SECNAME isn't an orphaned section and linker won't define
__start_SECNAME nor __stop_SECNAME. And ELF linker stores the first
input section whose name matches __start_SECNAME or __stop_SECNAME in
u.undef.section for garbage collection. If these symbols are provided
in linker script, u.undef.section is set to the section where they will
defined by linker script, which leads to the incorrect output.
This patch changes linker to always define referenced __start_SECNAME and
__stop_SECNAME if the input section name is the same as the output section
name, which is always true for orphaned sections, and SECNAME is a C
identifier. Also __start_SECNAME and __stop_SECNAME symbols are marked
as hidden by ELF linker so that __start_SECNAME and __stop_SECNAME symbols
for section SECNAME in different modules are unique. For garbage
collection, ELF linker stores the first matched input section in the
unused vtable field.
bfd/
PR ld/20022
PR ld/21557
PR ld/21562
PR ld/21571
* elf-bfd.h (elf_link_hash_entry): Add start_stop. Change the
vtable field to a union.
(_bfd_elf_is_start_stop): Removed.
* elf32-i386.c (elf_i386_convert_load_reloc): Also check for
__start_SECNAME and __stop_SECNAME symbols.
* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Likewise.
* elflink.c (_bfd_elf_is_start_stop): Removed.
(_bfd_elf_gc_mark_rsec): Check start_stop instead of calling
_bfd_elf_is_start_stop.
(elf_gc_propagate_vtable_entries_used): Skip __start_SECNAME and
__stop_SECNAME symbols. Updated.
(elf_gc_smash_unused_vtentry_relocs): Likewise.
(bfd_elf_gc_record_vtinherit): Likewise.
(bfd_elf_gc_record_vtentry): Likewise.
ld/
PR ld/20022
PR ld/21557
PR ld/21562
PR ld/21571
* ld.texinfo: Update __start_SECNAME/__stop_SECNAME symbols.
* ldlang.c (lang_insert_orphan): Move handling of __start_SECNAME
and __stop_SECNAME symbols to ...
(lang_set_startof): Here. Also define __start_SECNAME and
__stop_SECNAME for -Ur.
* emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Mark
referenced __start_SECNAME and __stop_SECNAME symbols as hidden
and set start_stop for garbage collection.
* testsuite/ld-elf/pr21562a.d: New file.
* testsuite/ld-elf/pr21562a.s: Likewise.
* testsuite/ld-elf/pr21562a.t: Likewise.
* testsuite/ld-elf/pr21562b.d: Likewise.
* testsuite/ld-elf/pr21562b.s: Likewise.
* testsuite/ld-elf/pr21562b.t: Likewise.
* testsuite/ld-elf/pr21562c.d: Likewise.
* testsuite/ld-elf/pr21562c.t: Likewise.
* testsuite/ld-elf/pr21562d.d: Likewise.
* testsuite/ld-elf/pr21562d.t: Likewise.
* testsuite/ld-elf/pr21562e.d: Likewise.
* testsuite/ld-elf/pr21562f.d: Likewise.
* testsuite/ld-elf/pr21562g.d: Likewise.
* testsuite/ld-elf/pr21562h.d: Likewise.
* testsuite/ld-elf/pr21562i.d: Likewise.
* testsuite/ld-elf/pr21562j.d: Likewise.
* testsuite/ld-elf/pr21562k.d: Likewise.
* testsuite/ld-elf/pr21562l.d: Likewise.
* testsuite/ld-elf/pr21562m.d: Likewise.
* testsuite/ld-elf/pr21562n.d: Likewise.
* testsuite/ld-gc/pr20022.d: Likewise.
* testsuite/ld-gc/pr20022a.s: Likewise.
* testsuite/ld-gc/pr20022b.s: Likewise.
* testsuite/ld-gc/gc.exp: Run PR ld/20022 tests.
* testsuite/ld-gc/pr19161.d: Also accept local __start_SECNAME
symbol.
* testsuite/ld-gc/start.d: Likewise.
* testsuite/ld-x86-64/lea1a.d: Updated.
* testsuite/ld-x86-64/lea1b.d: Updated.
* testsuite/ld-x86-64/lea1d.d: Updated.
* testsuite/ld-x86-64/lea1e.d: Likewise.
ELFv2 functions with localentry:0 are those with a single entry point,
ie. global entry == local entry, and that have no requirement on r2 or
r12, and guarantee r2 is unchanged on return. Such an external
function can be called via the PLT without saving r2 or restoring it
on return, avoiding a common load-hit-store for small functions. The
optimization is attractive. The TOC pointer load-hit-store is a major
reason why calls to small functions that need no register saves, or
with shrink-wrap, no register saves on a fast path, are slow on
powerpc64le.
To be safe, this optimization needs ld.so support to check that the
run-time matches link-time function implementation. If a function
in a shared library with st_other localentry non-zero is called
without saving and restoring r2, r2 will be trashed on return, leading
to segfaults. For that reason the optimization does not happen for
weak functions since a weak definition is a fairly solid hint that the
function will likely be overridden. I'm also not enabling the
optimization by default unless glibc-2.26 is detected, which should
have the ld.so checks implemented.
bfd/
* elf64-ppc.c (struct ppc_link_hash_table): Add has_plt_localentry0.
(ppc64_elf_merge_symbol_attribute): Merge localentry bits from
dynamic objects.
(is_elfv2_localentry0): New function.
(ppc64_elf_tls_setup): Default params->plt_localentry0.
(plt_stub_size): Adjust size for tls_get_addr_opt stub.
(build_tls_get_addr_stub): Use a simpler stub when r2 is not saved.
(ppc64_elf_size_stubs): Leave stub_type as ppc_stub_plt_call for
optimized localentry:0 stubs.
(ppc64_elf_build_stubs): Save r2 in ELFv2 __glink_PLTresolve.
(ppc64_elf_relocate_section): Leave nop unchanged for optimized
localentry:0 stubs.
(ppc64_elf_finish_dynamic_sections): Set PPC64_OPT_LOCALENTRY in
DT_PPC64_OPT.
* elf64-ppc.h (struct ppc64_elf_params): Add plt_localentry0.
include/
* elf/ppc64.h (PPC64_OPT_LOCALENTRY): Define.
ld/
* emultempl/ppc64elf.em (params): Init plt_localentry0 field.
(enum ppc64_opt): New, replacing OPTION_* defines. Add
OPTION_PLT_LOCALENTRY, and OPTION_NO_PLT_LOCALENTRY.
(PARSE_AND_LIST_*): Support --plt-localentry and --no-plt-localentry.
* testsuite/ld-powerpc/elfv2so.d: Update.
* testsuite/ld-powerpc/powerpc.exp (TLS opt 5): Use --no-plt-localentry.
* testsuite/ld-powerpc/tlsopt5.d: Update.
Don't use fixed size buffers for symbol names.
PR 21274
PR 18466
* emultempl/pe.em (pe_find_data_imports): Don't use fixed size
symbol buffer. Instead, xmalloc max size needed with space for
prefix. Wrap overlong lines. Formatting. Pass symbol buffer
copy of name to pe_walk_relocs_of_symbol.
(make_inport_fixup): Add "name" param, pass to pe_create_import_fixup.
* emultempl/pe.em (pep_find_data_imports): As for pe_find_data_imports.
(make_import_fixup): Add "name" param, pass to pep_create_import_fixup.
Use bfd_get_signed_* and remove unnecessary casts. Formatting.
* pe-dll.c (pe_walk_relocs_of_symbol): Add "name" param. Pass to
callback.
(make_import_fixup_mark): Add "name" param. Make use of prefix
space rather than xmalloc here.
(pe_create_import_fixup): Likewise.
* pe-dll.h (pe_walk_relocs_of_symbol): Update prototype.
(pe_create_import_fixup): Likewise.
* pep-dll.h (pep_walk_relocs_of_symbol): Likewise.
(pep_create_import_fixup): Likewise.
Mark an ALLOC section, which should be placed in special memory area,
with SHF_GNU_MBIND. Its sh_info field indicates the special memory
type. GNU_MBIND section names start with ".mbind" so that they are
placed as orphan sections by linker. All input GNU_MBIND sections
with the same sh_type, sh_flags and sh_info are placed in one output
GNU_MBIND section. In executable and shared object, create a
GNU_MBIND segment for each GNU_MBIND section and its segment type is
PT_GNU_MBIND_LO plus the sh_info value. Each GNU_MBIND segment is
aligned at page boundary.
The assembler syntax:
.section .mbind.foo,"adx",%progbits
^ 0: Special memory type.
|
'd' for SHF_GNU_MBIND.
.section .mbind.foo,"adx",%progbits,0x1
^ 1: Special memory type.
|
'd' for SHF_GNU_MBIND.
.section .mbind.bar,"adG",%progbits,.foo_group,comdat,0x2
^ 2: Special memory type.
|
'd' for SHF_GNU_MBIND.
bfd/
* elf.c (get_program_header_size): Add a GNU_MBIND segment for
each GNU_MBIND section and align GNU_MBIND section to page size.
(_bfd_elf_map_sections_to_segments): Create a GNU_MBIND
segment for each GNU_MBIND section.
(_bfd_elf_init_private_section_data): Copy sh_info from input
for GNU_MBIND section.
binutils/
* NEWS: Mention support for ELF SHF_GNU_MBIND and
PT_GNU_MBIND_XXX.
* readelf.c (get_segment_type): Handle PT_GNU_MBIND_XXX.
(get_elf_section_flags): Handle SHF_GNU_MBIND.
(process_section_headers): Likewise.
* testsuite/binutils-all/mbind1.s: New file.
* testsuite/binutils-all/objcopy.exp: Run readelf test on
mbind1.s.
gas/
* NEWS: Mention support for ELF SHF_GNU_MBIND.
* config/obj-elf.c (section_match): New.
(get_section): Match both sh_info and group name.
(obj_elf_change_section): Add argument for sh_info. Pass both
sh_info and group name to get_section. Issue an error for
SHF_GNU_MBIND section without SHF_ALLOC. Set sh_info.
(obj_elf_parse_section_letters): Set SHF_GNU_MBIND for 'd'.
(obj_elf_section): Support SHF_GNU_MBIND section info.
* config/obj-elf.h (obj_elf_change_section): Add argument for
sh_info.
* config/tc-arm.c (start_unwind_section): Pass 0 as sh_info to
obj_elf_change_section.
* config/tc-ia64.c (obj_elf_vms_common): Likewise.
* config/tc-microblaze.c (microblaze_s_data): Likewise.
(microblaze_s_sdata): Likewise.
(microblaze_s_rdata): Likewise.
(microblaze_s_bss): Likewise.
* config/tc-mips.c (s_change_section): Likewise.
* config/tc-msp430.c (msp430_profiler): Likewise.
* config/tc-rx.c (parse_rx_section): Likewise.
* config/tc-tic6x.c (tic6x_start_unwind_section): Likewise.
* doc/as.texinfo: Document 'd' for SHF_GNU_MBIND.
* testsuite/gas/elf/elf.exp: Run section12a, section12b and
section13.
* testsuite/gas/elf/section10.d: Updated.
* testsuite/gas/elf/section10.s: Likewise.
* testsuite/gas/elf/section12.s: New file.
* testsuite/gas/elf/section12a.d: Likewise.
* testsuite/gas/elf/section12b.d: Likewise.
* testsuite/gas/elf/section13.l: Likewise.
* testsuite/gas/elf/section13.d: Likewise.
* testsuite/gas/elf/section13.s: Likewise.
include/
* elf/common.h (PT_GNU_MBIND_NUM): New.
(PT_GNU_MBIND_LO): Likewise.
(PT_GNU_MBIND_HI): Likewise.
(SHF_GNU_MBIND): Likewise.
ld/
* NEWS: Mention support for ELF SHF_GNU_MBIND and
PT_GNU_MBIND_XXX.
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Place
input GNU_MBIND sections with the same type, attributes and
sh_info field into a single output GNU_MBIND section.
* testsuite/ld-elf/elf.exp: Run mbind2a and mbind2b.
* testsuite/ld-elf/mbind1.s: New file.
* testsuite/ld-elf/mbind1a.d: Likewise.
* testsuite/ld-elf/mbind1b.d: Likewise.
* testsuite/ld-elf/mbind1c.d: Likewise.
* testsuite/ld-elf/mbind2a.s: Likewise.
* testsuite/ld-elf/mbind2b.c: Likewise.
Relative paths shouldn't have the sysroot prefix added. The patch
also makes some attempt at supporting DOS paths, and tidies code using
the new add_sysroot.
* emultempl/elf32.em (gld${EMULATION_NAME}_add_sysroot): Rewrite.
Only prefix absolute paths with sysroot. Handle DOS paths.
(gld${EMULATION_NAME}_check_ld_elf_hints): Constify variable.
(gld${EMULATION_NAME}_check_ld_so_conf): Likewise.
(gld${EMULATION_NAME}_after_open): Short-circuit NULL path
searches. Rename variable. Simplify get_runpath search.
Complement commit 9d862524f6 ("MIPS: Verify the ISA mode and alignment
of branch and jump targets") and add GAS and LD options to control the
checks for invalid branches between ISA modes introduced there, to help
with some handwritten code lacking `.insn' annotation for labels used as
branch targets and code produced by older versions of GCC which suffers
from the issue with branches to code that has been optimized away,
addressed with GCC commit 242424 ("MIPS/GCC: Mark trailing labels with
`.insn'"), <https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01061.html>.
bfd/
* elfxx-mips.h (_bfd_mips_elf_insn32): Rename prototype to...
(_bfd_mips_elf_linker_flags): ... this. Add another parameter.
* elfxx-mips.c (mips_elf_link_hash_table): Add
`ignore_branch_isa' member.
(mips_elf_perform_relocation): Do not treat an ISA mode mismatch
in branch relocation calculation as an error if
`ignore_branch_isa' has been set.
(_bfd_mips_elf_insn32): Rename to...
(_bfd_mips_elf_linker_flags): ... this. Rename the `on'
parameter to `insn32' and add an `ignore_branch_isa' parameter.
Handle the new parameter.
gas/
* config/tc-mips.c (mips_ignore_branch_isa): New variable.
(options): Add OPTION_IGNORE_BRANCH_ISA and
OPTION_NO_IGNORE_BRANCH_ISA enum values.
(md_longopts): Add "mignore-branch-isa" and
"mno-ignore-branch-isa" options.
(md_parse_option): Handle OPTION_IGNORE_BRANCH_ISA and
OPTION_NO_IGNORE_BRANCH_ISA.
(fix_bad_cross_mode_branch_p): Return FALSE if
`mips_ignore_branch_isa' has been set.
(md_show_usage): Add `-mignore-branch-isa' and
`-mno-ignore-branch-isa'.
* doc/as.texinfo (Target MIPS options): Add
`-mignore-branch-isa' and `-mno-ignore-branch-isa' options.
(-mignore-branch-isa, -mno-ignore-branch-isa): New options.
* doc/c-mips.texi (MIPS Options): Add `-mignore-branch-isa' and
`-mno-ignore-branch-isa' options.
* testsuite/gas/mips/branch-local-ignore-2.d: New test.
* testsuite/gas/mips/branch-local-ignore-3.d: New test.
* testsuite/gas/mips/branch-local-ignore-n32-2.d: New test.
* testsuite/gas/mips/branch-local-ignore-n32-3.d: New test.
* testsuite/gas/mips/branch-local-ignore-n64-2.d: New test.
* testsuite/gas/mips/branch-local-ignore-n64-3.d: New test.
* testsuite/gas/mips/mips.exp: Run the new tests.
ld/
* emultempl/mipself.em (ignore_branch_isa): New variable.
(mips_create_output_section_statements): Rename
`_bfd_mips_elf_insn32' called to `_bfd_mips_elf_linker_flags',
add `ignore_branch_isa' argument.
(PARSE_AND_LIST_PROLOGUE): Add OPTION_IGNORE_BRANCH_ISA and
OPTION_NO_IGNORE_BRANCH_ISA enum values.
(PARSE_AND_LIST_LONGOPTS): Add "ignore-branch-isa" and
"no-ignore-branch-isa" options.
(PARSE_AND_LIST_OPTIONS): Add `--ignore-branch-isa' and
`--no-ignore-branch-isa'.
(PARSE_AND_LIST_ARGS_CASES): Handle OPTION_IGNORE_BRANCH_ISA and
OPTION_NO_IGNORE_BRANCH_ISA.
* ld.texinfo (Options specific to MIPS targets): Add
`--ignore-branch-isa' and `--no-ignore-branch-isa' options.
(ld and the MIPS family): Likewise.
* testsuite/ld-mips-elf/bal-jalx-pic-ignore.d: New test.
* testsuite/ld-mips-elf/bal-jalx-pic-ignore-n32.d: New test.
* testsuite/ld-mips-elf/bal-jalx-pic-ignore-n64.d: New test.
* testsuite/ld-mips-elf/unaligned-branch-ignore-2.d: New test.
* testsuite/ld-mips-elf/unaligned-branch-ignore-r6-1: New test.
* testsuite/ld-mips-elf/unaligned-branch-ignore-mips16: New
test.
* testsuite/ld-mips-elf/unaligned-branch-ignore-micromips: New
test.
* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.
Correct a bug in Solaris 2 linker emulation code triggered by a test
introduced with commit 81ff47b3a5 ("PR ld/20828: Fix linker script
symbols wrongly forced local with section GC") and only create implicit
version nodes if versioning is actually introduced with a version script
(or VERSION command) rather than only global vs local symbol visibility
selected, fixing an:
ld: anonymous version tag cannot be combined with other version tags
linker error produced whenever a version script (or VERSION command) is
used that does not assign symbol versions, such as:
{ global: foo; bar; local: *; };
and consequently removing a:
FAIL: PR ld/20828 dynamic symbols with section GC (version script)
test suite failure with the `x86_64-solaris2' target.
ld/
* emultempl/solaris2.em (elf_solaris2_before_allocation): Do not
add implicit version nodes if an anonymous version tag is being
used.
Lots of fixes for the compatibility code that handles linking of
-mcall-aixdesc code (or that generated by 12 year old gcc) with
current ELFv1 ABI code.
1) A reference to a dot-symbol in an object file wasn't satisfied by a
function descriptor in later object files.
2) The as-needed code had bit-rotted; Shared libs now need a strong
reference to be counted as needed.
3) --gc-sections involving dot-symbols was broken, needing
func_desc_adjust to be run early and lots of other fixes.
bfd/
* elf64-ppc.c (struct ppc_link_hash_entry): Delete "was_undefined".
(struct ppc_link_hash_table): Delete "twiddled_syms". Add
"need_func_desc_adj".
(lookup_fdh): Link direct fdh sym via oh field and set flags.
(make_fdh): Make strong and weak undefined function descriptor
symbols.
(ppc64_elf_merge_symbol): New function.
(elf_backend_merge_symbol): Define.
(ppc64_elf_archive_symbol_lookup): Don't test undefweak for fake
function descriptors.
(add_symbol_adjust): Don't twiddle symbols to undefweak.
Propagate more ref flags to function descriptor symbol. Make
some function descriptor symbols dynamic.
(ppc64_elf_before_check_relocs): Only run add_symbol_adjust for
ELFv1. Set need_func_desc_adj. Don't fix undefs list.
(ppc64_elf_check_relocs): Set non_ir_ref for descriptors.
Don't call lookup_fdh here.
(ppc64_elf_gc_sections): New function.
(bfd_elf64_bfd_gc_sections): Define.
(ppc64_elf_gc_mark_hook): Mark descriptor.
(func_desc_adjust): Don't make fake function descriptor syms strong
here. Exit earlier on non-dotsyms. Take note of elf.dynamic
flag when deciding whether a dynamic function descriptor might
be needed. Transfer elf.dynamic and set elf.needs_plt. Move
plt regardless of visibility. Make descriptor dynamic if
entry sym is dynamic, not for other cases.
(ppc64_elf_func_desc_adjust): Don't run func_desc_adjust if
already done.
(ppc64_elf_edit_opd): Use oh field rather than lookup_fdh.
(ppc64_elf_size_stubs): Likewise.
(ppc_build_one_stub): Don't clear was_undefined. Only set sym
undefweak if stub symbol is defined.
(undo_symbol_twiddle, ppc64_elf_restore_symbols): Delete.
* elf64-ppc.h (ppc64_elf_restore_symbols): Don't declare.
ld/
* emultempl/ppc64elf.em (gld${EMULATION_NAME}_finish): Don't call
ppc64_elf_restore_symbols.
* testsuite/ld-powerpc/dotsym1.d: New.
* testsuite/ld-powerpc/dotsym2.d: New.
* testsuite/ld-powerpc/dotsym3.d: New.
* testsuite/ld-powerpc/dotsym4.d: New.
* testsuite/ld-powerpc/dotsymref.s: New.
* testsuite/ld-powerpc/nodotsym.s: New.
* testsuite/ld-powerpc/powerpc.exp: Run new tests.
H.J. Lu