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${EMULATION_NAME}_before_parse): Set
link_info.separate_code DEFAULT_LD_Z_SEPARATE_CODE.
Currently we have no obvious way to revert the action of the "-z defs"
command line option. The "--unresolved-symbols=ignore-in-object-files"
does pretty much what is needed, but it is non-obvious and it also
touches the setting for reporting unresolved symbol references from
shared libraries. So I am proposing adding a "-z undefs" option to be
the inverse of "-z defs". (I thought that "-z nodefs" might be
confusing since it implies banning all definitions, rather than
allowing them).
In addition the description of the "-z defs" option in the linker
documentation is misleading in one place, where it says:
'defs'
Disallows undefined symbols in object files. Undefined
symbols in shared libraries are still allowed.
whereas later on it gets it right:
'-z defs'
Report unresolved symbol references from regular object files.
This is done even if the linker is creating a non-symbolic shared
library. The switch '--[no-]allow-shlib-undefined' controls the
behaviour for reporting unresolved references found in shared
libraries being linked in.
* emultempl/elf32.em (_handle_option): Add support for "-z undefs"
as the opposite of "-z defs".
* ld.texinfo: Document the new option. Update the description of
the -z defs option to make it clear that it does generate an error
if an undefined symbol reference is found in an object file whilst
creating a shared library.
* NEWS: Document this new feature.
The new "-z separate-code" option will generate separate code LOAD
segment which must be in wholly disjoint pages from any other data.
include/
PR ld/22393
* bfdlink.h (bfd_link_info): Add separate_code.
ld/
PR ld/22393
* NEWS: Mention "-z separate-code".
* emultempl/elf32.em (gld${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}.
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.
* 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.
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.
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.
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.
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.
PR ld/20784
* emultempl/elf32.em (search_needed): Fix infinite loop when
unable to process a token. Add support for curly braced enclosed
tokens.
* ld.texinfo (--rpath-link): Document supprot for $ORIGIN and
$LIB.
* emultempl/elf32.em (search_needed): Remove use of getauxval and
inclusion of <sys/auxv.h>. Replace support for $PLATFORM with a
warning message.
* configure.ac (AC_CHECK_FUNCS): Remove getauxval.
* configure: Regenerate.
* config.in: Regenerate.
SEC_EXCLUDE is ignored when doing a relocatable link. But we can't
merge 2 input sections with the same name when only one of them has
SHF_EXCLUDE.
PR ld/20528
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Don't
merge 2 sections with different SHF_EXCLUDE.
* testsuite/ld-elf/pr20528a.d: New file.
* testsuite/ld-elf/pr20528a.s: Likewise.
* testsuite/ld-elf/pr20528b.d: Likewise.
* testsuite/ld-elf/pr20528b.s: Likewise.
PR ld/20537
* emultempl/elf32.em: More OPTION_xxx values into an enum. Add
OPTION_NO_EH_FRAME_HDR.
(_add_options): Add support for --no-eh-frame-hdr.
* ld.texinfo: Document new option.
* lexsup.c (elf_shlib_list_options): List new option.
* NEWS: Mention the new option.
Add a configure option --enable-relro to decide whether -z relro should
be enabled in ELF linker by default. Default to yes for all Linux
targets, except FRV, HPPA, IA64 and MIPS, since many relro tests fail
on these targets.
PR ld/20283
* NEWS: Mention --enable-relro.
* configure.ac: Add --enable-relro.
(DEFAULT_LD_Z_RELRO): New. Set by --enable-relro.
* configure.tgt (ac_default_ld_z_relro): Default it to 1 for
some Linux targets.
* config.in: Regenerated.
* configure: Likewise.
* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse): Set
link_info.relro to DEFAULT_LD_Z_RELRO.
* testsuite/config/default.exp (ld_elf_shared_opt): New.
* testsuite/lib/ld-lib.exp (run_dump_test): Pass
$ld_elf_shared_opt to ld for ELF targets with shared object
support.
(run_ld_link_tests): Likewise.
Move ELF relocation check after lang_gc_sections so that all the
reference counting code for plt and got relocs can be removed. This
only affects ELF targets which check relocations after opening all
input file.
* ldlang.c (lang_check_relocs): New function.
(lang_process): Call lang_check_relocs after lang_gc_sections.
* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse): Don't
call _bfd_elf_link_check_relocs here.
Delaying checking ELF relocations until opening all input files so
that symbol information is final when relocations are checked. This
is only enabled for x86 targets.
bfd/
* elf-bfd.h (_bfd_elf_link_check_relocs): New.
* elflink.c (_bfd_elf_link_check_relocs): New function.
(elf_link_add_object_symbols): Call _bfd_elf_link_check_relocs
if check_relocs_after_open_input is FALSE.
include/
* bfdlink.h (bfd_link_info): Add check_relocs_after_open_input.
ld/
* emulparams/elf32_x86_64.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
New.
* emulparams/elf_i386.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/elf_i386_be.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/elf_i386_chaos.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/elf_i386_ldso.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/elf_i386_vxworks.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/elf_x86_64.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emulparams/i386nto.sh (CHECK_RELOCS_AFTER_OPEN_INPUT):
Likewise.
* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse):
Set check_relocs_after_open_input to TRUE if
CHECK_RELOCS_AFTER_OPEN_INPUT is yes.
(gld${EMULATION_NAME}_after_open): Call
_bfd_elf_link_check_relocs on all inputs if
check_relocs_after_open_input is TRUE.
Since there is no need to place output sections in specific order for
relocatable link, we can skip merging flags of other input sections.
PR ld/19739
* ld/emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Don't
merge flags of other input sections for relocatable link.
The last patch missed handling the case where the ideal place to put
an orphan was after a non-existent output section statement, as can
happen when not using the builtin linker scripts. This patch uses the
updated flags for that case too, and extends the support to mmo and pe.
PR ld/19162
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Pass
updated flags to lang_output_section_find_by_flags.
* emultempl/mmo.em (mmo_place_orphan): Merge flags for any
other input sections that might match a new output section to
decide placement.
* emultempl/pe.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
* emultempl/pep.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
* ldlang.c (lang_output_section_find_by_flags): Add sec_flags param.
* ldlang.h (lang_output_section_find_by_flags): Update prototype.
If given input sections with differing flags, we'd like to place the
section according to the final output section flags.
bfd/
PR ld/19162
* elflink.c (_bfd_elf_gc_mark_reloc): Move code iterating over
linker input bfds..
* section.c (bfd_get_next_section_by_name): ..to here. Add ibfd param.
(bfd_get_linker_section): Adjust bfd_get_next_section_by_name call.
* tekhex.c (first_phase): Likewise.
* elflink.c (bfd_elf_gc_sections): Likewise.
* bfd-in2.h: Regenerate.
ld/
PR ld/19162
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Check flags
before calling _bfd_elf_match_sections_by_type. Merge flags for
any other input sections that might match a new output section to
decide placement.
This fixes two problems. First, the --sysroot option wasn't available
with a ld configured without --with-sysroot, a historical accident.
This led to people configuring binutils with --with-sysroot=/ in order
to enable sysroot support, which exposes a case where ld wrongly
prepends the sysroot to a relative path.
PR ld/18992
* ldmain.c (main): Always enable --sysroot.
* emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Don't
prepend sysroot to relative rpath/runpath.
