Currently on S/390 the .got.plt always comes first which prevents the
GNU_RELRO segment from being extended across the non-plt GOT entries.
Just swapping both unfortunately is not that simple since our ABI
requires the _GLOBAL_OFFSET_TABLE_ symbol to point to the very
beginning of the entire GOT. Of the 3 magic GOT entries the first is
accessed via got pointer while second and third are being accessed via
DT_PLTGOT. In order to keep them together we make DT_PLTGOT to point
to the .got instead of .got.plt. However, this violates an assumption
in the dynamic linker prelink undo code about the GOTPLT entries
starting at DT_PLTGOT + 3. We got rid of this requirement with a
Glibc patch already in version 2.24:
https://sourceware.org/ml/libc-alpha/2016-06/msg01302.html
So the S/390 relro GOT layout will look like this with this patch:
+----------------------------------+
|got[0]: DYNAMIC | <--- _GLOBAL_OFFSET_TABLE_ == DT_PLTGOT .got
|got[1]: link_map parm |
|got[2]: &_dl_runtime_resolve |
+----------------------------------+
| | non-plt GOT entries
| |
| |
+----------------------------------+
| | <--- .gotplt, PLT GOT entries
| |
| |
| |
+----------------------------------+
The patch detects the current layout in size_dynamic_section in order
to deal also with linker scripts not generated by this ld version.
With partial relro enabled we pick a linker script where .got and
.got.plt are swapped which then triggers the rest of the logic.
ld/ChangeLog:
2018-07-18 Andreas Krebbel <krebbel@linux.ibm.com>
* emulparams/elf64_s390.sh: Define GENERATE_RELRO_SCRIPT and
SEPARATE_GOTPLT.
* testsuite/ld-s390/gotreloc_64-relro-1.dd: New test.
* testsuite/ld-s390/gotreloc_64-norelro-1.dd: Renamed from ...
* testsuite/ld-s390/gotreloc_64-1.dd: ... this.
* testsuite/ld-s390/s390.exp: Split the GOT testcase into two.
bfd/ChangeLog:
2018-07-18 Andreas Krebbel <krebbel@linux.ibm.com>
* elf-s390-common.c (s390_gotplt_after_got_p): New function.
(s390_got_pointer): New function.
(s390_got_offset): New function.
(s390_gotplt_offset): New function.
* elf64-s390.c (allocate_dynrelocs): Adjust comment.
(elf_s390_size_dynamic_sections): Move space for magic GOT entries
from .got.plt to .got if necessary and pick the right location for
_GLOBAL_OFFSET_TABLE_.
(elf_s390_relocate_section): Use the wrapper functions from
elf-s390-common.c to deal with both possible layouts (either .got
or .got.plt first).
(elf_s390_finish_dynamic_sections): Likewise.
(elf_s390_finish_dynamic_symbol): Make the location of the GOT
magic entries conditional.
This fixes a problem with a missing R_390_64 reloc against .data for a
function pointer to an ifunc function.
No regressions on s390x.
Pushed to mainline.
bfd/ChangeLog:
2017-05-08 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elf-s390-common.c: Don't check non_got_ref flag.
* elf32-s390.c (elf_s390_relocate_section): Likewise.
* elf64-s390.c (elf_s390_relocate_section): Likewise.
This steals _doprnt from libiberty, extended to handle %A and %B.
Which lets us do away with the current horrible %A and %B handling
that requires all %A and %B arguments to be passed first, rather than
in the natural order.
* bfd.c (PRINT_TYPE): Define.
(_doprnt): New function.
(error_handler_internal): Use _doprnt.
* coff-arm.c: Put %A and %B arguments to _bfd_error_handler
calls in their natural order, throughout file.
* coff-mcore.c: Likewise.
* coff-ppc.c: Likewise.
* coff-tic80.c: Likewise.
* cofflink.c: Likewise.
* elf-s390-common.c: Likewise.
* elf.c: Likewise.
* elf32-arm.c: Likewise.
* elf32-i386.c: Likewise.
* elf32-m32r.c: Likewise.
* elf32-msp430.c: Likewise.
* elf32-spu.c: Likewise.
* elf64-ia64-vms.c: Likewise.
* elf64-sparc.c: Likewise.
* elf64-x86-64.c: Likewise.
* elflink.c: Likewise.
* elfnn-aarch64.c: Likewise.
* elfnn-ia64.c: Likewise.
* elfxx-mips.c: Likewise.
Since the backend elf_add_symbol_hook isn't called on local symbols,
the EI_OSABI field isn't to ELFOSABI_GNU where are local IFUNC symbols.
This patch changes the x86 backends to set has_gnu_symbols if there are
relocations against IFUNC symbols. Other backends with IFUNC support
may need a similar change.
This patch also changes the type of has_gnu_symbols from bfd_boolean to
enum elf_gnu_symbols.
bfd/
PR ld/18815
* elf-bfd.h (elf_gnu_symbols): New enum.
(elf_obj_tdata): Use elf_gnu_symbols on has_gnu_symbols.
* elf-s390-common.c (elf_s390_add_symbol_hook): Set
has_gnu_symbols to elf_gnu_symbol_any.
* elf32-arm.c (elf32_arm_add_symbol_hook): Likewise.
* elf32-m68k.c (elf_m68k_add_symbol_hook): Likewise.
* elf32-ppc.c (ppc_elf_add_symbol_hook): Likewise.
* elf32-sparc.c (elf32_sparc_add_symbol_hook): Likewise.
* elf64-ppc.c (ppc64_elf_add_symbol_hook): Likewise.
* elf64-sparc.c (elf64_sparc_add_symbol_hook): Likewise.
* lfxx-aarch64.c (_bfd_aarch64_elf_add_symbol_hook): Likewise.
* elf32-i386.c (elf_i386_check_relocs): Update has_gnu_symbols
if there are relocations against IFUNC symbols.
(elf_i386_add_symbol_hook): Don't check STT_GNU_IFUNC here.
* elf64-x86-64. (elf_x86_64_check_relocs): Update has_gnu_symbols
if there are relocations against IFUNC symbols.
(elf_x86_64_add_symbol_hook): Don't check STT_GNU_IFUNC here.
ld/testsuite/
PR ld/18815
* ld-i386/i386.exp: Run pr18815.
* ld-x86-64/x86-64.exp: Likewise.
* ld-i386/pr18815.d: New file.
* ld-i386/pr18815.s: Likewise.
* ld-x86-64/pr18815.d: Likewise.
* ld-x86-64/pr18815.s: Likewise.
When downgrading from GD to IE model we rewrite the call to
__tls_get_offset to a 64 bit load instruction. This relies on the fact
that the additional relocation for the call target has already been
executed when doing the rewrite.
f1018: e3 20 d0 00 00 04 lg %r2,0(%r13)
f101e: c0 e5 00 00 00 00 brasl %r14,f101e <__res_init+0x1e>
f101e: R_390_TLS_GDCALL __libc_resp
f1020: R_390_PLT32DBL __tls_get_offset+0x2
0000000f1020 39f6c00000014 R_390_PLT32DBL 0000000000000000 __tls_get_offset + 2
0000000f101e 3afb700000026 R_390_TLS_GDCALL 0000000000000008 __libc_resp + 0
Due to the reloc sorting the order changed an the PLT32DBL reloc is
executed after the rewrite and overwrites part of the load instruction
with garbage.
bfd/
2015-03-14 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elf-s390-common.c (elf_s390_elf_sort_relocs_p): Don't sort
relocs against code sections.
* elf32-s390.c: Define elf_backend_sort_relocs_p.
* elf64-s390.c: Likewise.
* elf64-s390.c: Include elf-s390-common.c.
(R_390_IRELATIVE): New reloc.
(elf_s390_reloc_type_lookup): Support R_390_IRELATIVE.
(RELA_ENTRY_SIZE): New macro.
(elf_s390_link_hash_entry): New fields ifunc_resolver_address and
*ifunc_resolver_section.
(struct plt_entry): New struct.
(struct elf_s390_obj_tdata): New field local_plt.
(elf_s390_local_plt): New macro.
(struct elf_s390_link_hash_table): New field irelifunc.
(ELF64): New macro.
(link_hash_newfunc): Initialize new fields.
(elf_s390_check_relocs): Handle IFUNC symbols.
(elf_s390_adjust_dynamic_symbol): Don't do anything for IFUNC
symbols.
(allocate_dynrelocs): Call s390_elf_allocate_ifunc_dyn_relocs for
IFUNC symbols.
(elf_s390_size_dynamic_sections): Handle IFUNC symbols.
(elf_s390_relocate_section): Likewise.
(elf_s390_finish_dynamic_symbol): Likewise.
(elf_s390_finish_dynamic_sections): Handle local IFUNC symbols.
(elf_s390_finish_ifunc_symbol): New function.
(elf_s390_gc_sweep_hook): Handle local plt entries.
(elf_backend_add_symbol_hook): Define.
* elf32-s390.c: See elf64-s390.c changes.
* elf-s390-common.c: New file.
* bfd-in2.h (BFD_RELOC_390_IRELATIVE): New enum field.
* libbfd.h (BFD_RELOC_390_IRELATIVE): New entry for
BFD_RELOC_390_IRELATIVE.
* reloc.c (BFD_RELOC_390_IRELATIVE): Document new relocation.
2012-07-13 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
* elf/s390.h (START_RELOC_NUMBERS): Define R_390_IRELATIVE reloc.
2012-07-13 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
* emulparams/elf_s390.sh (IREL_IN_PLT): Define.
* emulparams/elf64_s390.sh (IREL_IN_PLT): Define.
