A recent bug (RH BZ 1931344) has exposed a bug in the core file
build-ID support that I introduced a while ago. It is pretty
easy to demonstate the problem following a simplified procedure
outlined in that bug:
[shell1]
shell1$ /usr/libexec/qemu-kvm
[shell2]
shell2$ pkill -SEGV -x qemu-kvm
[shell1]
Segmentation fault (core dumped)
Load this core file into GDB without specifying an executable
(an unfortunate Fedora/RHEL-ism), and GDB will inform the user
to install debuginfo for the "missing" executable:
$ gdb -nx -q core.12345
...
Missing separate debuginfo for the main executable file
Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/e2/e9c66d3117fb2bbb5b2be122f04f2664e5df54
Core was generated by `/usr/libexec/qemu-kvm'.
Program terminated with signal SIGSEGV, Segmentation fault.
...
The suggested build-ID is actaully for gmp not qemu-kvm. The problem
lies in _bfd_elf_core_find_build_id, where we loop over program headers
looking for note segments:
/* Read in program headers and parse notes. */
for (i = 0; i < i_ehdr.e_phnum; ++i, ++i_phdr)
{
Elf_External_Phdr x_phdr;
if (bfd_bread (&x_phdr, sizeof (x_phdr), abfd) != sizeof (x_phdr))
goto fail;
elf_swap_phdr_in (abfd, &x_phdr, i_phdr);
if (i_phdr->p_type == PT_NOTE && i_phdr->p_filesz > 0)
{
elf_read_notes (abfd, offset + i_phdr->p_offset,
i_phdr->p_filesz, i_phdr->p_align);
if (abfd->build_id != NULL)
return TRUE;
}
elf_read_notes uses bfd_seek to forward the stream to the location of
the note segment. When control returns to _bfd_elf_core_fild_build_id,
the stream is no longer in the location looking at program headers, and
all subsequent reads will read from the wrong file offset.
To fix this, this patch marks the stream location and ensures
that it is restored after elf_read_notes is called.
bfd/ChangeLog
2021-03-26 Keith Seitz <keiths@redhat.com>
* elfcore.h (_bfd_elf_core_find_build_id): Seek file
offset of program headers after calling elf_read_notes.
bfd/
* bfd-in.h (startswith): New inline.
(CONST_STRNEQ): Use startswith.
* bfd-in2.h: Regenerate.
gdbsupport/
* common-utils.h (startswith): Delete version now supplied by bfd.h.
libctf/
* ctf-impl.h: Include string.h.
The exception for debug sections in clearing SEC_EXCLUDE when
relocatable was really for one specific debug section, so let's make
it do just that.
bfd/
PR 27590
* elf.c (_bfd_elf_make_section_from_shdr): Remove SHF_EXCLUDE
test for .gnu.debuglto*.
ld/
PR 27590
* ldlang.c (lang_gc_sections): Clear SEC_EXCLUDE when relocatable
for all sections except .stabstr.
commit 994b251328
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Sun Jan 17 20:01:16 2021 -0800
ld/elf: Ignore section symbols when matching linkonce with comdat
ignored section symbols when comparing symbols in 2 sections. Since all
references to debugging sections are done with section symbols, symbols
in debugging sections are ignored and we fail to match symbols in comdat
debugging sections. Also .gnu.debuglto_.debug_* sections aren't treated
as debugging sections.
1. Treate .gnu.debuglto_.debug_ section as debugging section unless it
is marked with SHF_EXCLUDE.
2. Revert commit 994b251328 in elf_create_symbuf.
3. Ignore section symbols only when matching non-debugging sections or
linkonce section with comdat section.
bfd/
PR ld/27590
* elf.c (_bfd_elf_make_section_from_shdr): Treate
.gnu.debuglto_.debug_ section as debugging section unless it is
marked with SHF_EXCLUDE.
* elflink.c (elf_create_symbuf): Revert commit 994b251328.
(bfd_elf_match_symbols_in_sections): Ignore section symbols when
matching non-debugging sections or linkonce section with comdat
section.
ld/
PR ld/27590
* testsuite/ld-elf/pr27590.s: New file.
* testsuite/ld-elf/pr27590a.d: Likewise.
* testsuite/ld-elf/pr27590b.d: Likewise.
* testsuite/ld-i386/i386.exp: Also run ld/27193 test with
--reduce-memory-overheads.
* peXXigen.c (_bfd_XXi_swap_aux_out): Avoid potential buffer
overrun by using sizeof of the destination x_fname field as the
limit for a memcpy.
* coff/internal.h (struct internal_auxent): Fix a couple of typos
in comment describing the x_fname field.
Add support for TLS in XCOFF. Amongst the things done by this commit:
- Update XCOFF auxialiary header to match new version and allow TLS
sections.
- Add TLS sections (.tdata and .tbss) support in gas and ld.
- Add support for the TLS relocations in gas and ld.
Two different types BFD_RELOC are created for PPC and PPC64 as
the size is a pointer, thus distinct in 32 or 64bit.
The addresses given by ld to .tdata and .tbss is a bit special. In
XCOFF, these addresses are actually offsets from the TLS pointer
computed at runtime. AIX assembly and linker does the same. In
top of that, the .tdata must be before .data (this is mandatory for AIX
loader). Thus, the aix ld script is recomputing "." before .data to restore
its original value. There might be a simpler way, but this one is working.
Optimisation linked to TLS relocations aren't yet implemented.
bfd/
* reloc.c (BFD_RELOC_PPC_TLS_LE, BFD_RELOC_PPC_TLS_IE,
BFD_RELOC_PPC_TLS_M, BFD_RELOC_PPC_TLS_ML, BFD_RELOC_PPC64_TLS_GD,
BFD_RELOC_PPC64_TLS_LD, BFD_RELOC_PPC64_TLS_LE,
BFD_RELOC_PPC64_TLS_IE, BFD_RELOC_PPC64_TLS_M,
BFD_RELOC_PPC64_TLS_ML): New relocations.
* bfd-in2.h: Regenerate.
* libbfd.h: Regenerate.
* coff-rs6000.c (xcoff_calculate_relocation): Call
xcoff_reloc_type_tls for TLS relocations.
(xcoff_howto_table): Implement TLS relocations.
(_bfd_xcoff_reloc_type_lookup): Add cases TLS relocations.
(xcoff_reloc_type_tls): New function.
* coff64-rs6000.c (xcoff_calculate_relocation): Likewise.
(xcoff_howto_table): Likewise.
(_bfd_xcoff_reloc_type_lookup): Likewise.
* coffcode.h (sec_to_styp_flags): Handle TLS sections.
(styp_to_sec_flags): Likewise.
(coff_compute_section_file_positions): Avoid file offset
optimisation for .data when the previous section is .tdata.
(coff_write_object_contents): Handle TLS sections.
* coffswap.h (coff_swap_aouthdr_out): Add support for
new fields in aouthdr.
* libxcoff.h (xcoff_reloc_type_tls): Add prototype.
* xcofflink.c (xcoff_link_add_symbols): Handle XMC_UL.
(xcoff_need_ldrel_p): Add cases for TLS relocations.
(xcoff_create_ldrel): Add l_symndx for TLS sections.
gas/
* config/tc-ppc.c (ppc_xcoff_text_section, ppc_xcoff_data_section,
(ppc_xcoff_bss_section, ppc_xcoff_tdata_section,
(ppc_xcoff_tbss_section): New variables.
(ppc_text_subsegment, ppc_text_csects, ppc_data_subgments,
(ppc_data_csects): Removed.
(ppc_xcoff_section_is_initialized, ppc_init_xcoff_section,
ppc_xcoff_parse_cons): New functions.
(md_being): Initialize XCOFF sections.
(ppc_xcoff_suffix): Add support for TLS relocations
(fixup_size, md_apply_fix): Add support for new BFD_RELOC.
(ppc_change_csect): Handle XMC_TL, XMC_UL. Correctly, add XMC_BS
to .bss section. Handle new XCOFF section variables.
(ppc_comm): Likewise.
(ppc_toc): Likewise.
(ppc_symbol_new_hook): Likewise.
(ppc_frob_symbol): Likewise.
(ppc_fix_adjustable): Add tbss support.
* config/tc-ppc.h (TC_PARSE_CONS_EXPRESSION): New define.
(ppc_xcoff_parse_cons): Add prototype.
(struct ppc_xcoff_section): New structure.
ld/
* emultempl/aix.em: Ensure .tdata section is removed
if empty, even with -r flag.
* scripttempl/aix.sc: Handle TLS sections.
* testsuite/ld-powerpc/aix52.exp: Add new tests.
* testsuite/ld-powerpc/aix-tls-reloc-32.d: New test.
* testsuite/ld-powerpc/aix-tls-reloc-64.d: New test.
* testsuite/ld-powerpc/aix-tls-reloc.ex: New test.
* testsuite/ld-powerpc/aix-tls-reloc.s: New test.
* testsuite/ld-powerpc/aix-tls-section-32.d: New test.
* testsuite/ld-powerpc/aix-tls-section-64.d: New test.
* testsuite/ld-powerpc/aix-tls-section.ex: New test.
* testsuite/ld-powerpc/aix-tls-section.s: New test.
include/
* coff/internal.h (struct internal_aouthdr): Add new fields.
* coff/rs6000.h (AOUTHDRÃ): Add new fields.
* coff/rs6k64.h (struct external_filehdr): Likewise.
* coff/xcoff.h (_TDATA), _TBSS): New defines
(RS6K_AOUTHDR_TLS_LE, RS6K_AOUTHDR_RAS, RS6K_AOUTHDR_ALGNTDATA,
RS6K_AOUTHDR_SHR_SYMTAB, RS6K_AOUTHDR_FORK_POLICY,
RS6K_AOUTHDR_FORK_COR): New defines.
(XMC_TU): Removed.
(XMC_UL): New define.
Implement support for largetoc on XCOFF.
R_TOCU and R_TOCL are referenced by the new BFD defines:
BFD_RELOC_PPC_TOC16_HI and BFD_RELOC_PPC_TOC16_LO.
A new toc storage class is added XMC_TE.
In order to correctly handle R_TOCU, the logic behind
xcoff_reloc_type_toc is changed to compute the whole TOC offset
instead of just the difference between the "link" offset and the
"assembly" offset.
In gas, add a function to transform addis format used by AIX
"addis RT, D(RA)" into the ELF format "addis RT, RA, SI".
bfd/
* reloc.c (BFD_RELOC_PPC_TOC16_HI, BFD_RELOC_PPC_TOC16_LO):
New relocations.
* bfd-in2.h: Regenerate.
* libbfd.h: Regenerate.
* coff-rs6000.c (xcoff_calculate_relocation): Call
xcoff_reloc_type_toc for R_TOCU and R_TOCL.
(xcoff_howto_table): Remove src_mask for TOC relocations.
Add R_TOCU and R_TOCL howtos.
(_bfd_xcoff_reloc_type_lookup): Add cases for
BFD_RELOC_PPC_TOC16_HI and BFD_RELOC_PPC_TOC16_LO.
(xcoff_reloc_type_toc): Compute the whole offset.
Implement R_TOCU and R_TOCL.
* coff64-rs6000.c (xcoff64_calculate_relocation):
Likewise.
(xcoff64_howto_table): Likewise.
(xcoff64_reloc_type_lookup): Likewise.
gas/
* config/tc-ppc.c (ppc_xcoff_suffix): New function.
(MAP, MAP32, MAP64): New macros for XCOFF.
(ppc_xcoff_fixup_addis): New function.
(ppc_is_toc_sym): Handle XMC_TE.
(fixup_size): Add cases for BFD_RELOC_PPC_TOC16_HI and
BFD_RELOC_PPC_TOC16_LO.
(md_assemble): Call ppc_xcoff_fixup_addis for XCOFF.
(ppc_change_csect): Handle XMC_TE.
(ppc_tc): Enable .tc symbols to have only a XMC_TC or XMC_TE
storage class.
(ppc_symbol_new_hook): Handle XMC_TE.
(ppc_frob_symbol): Likewise.
(ppc_fix_adjustable): Likewise.
(md_apply_fix): Handle BFD_RELOC_PPC_TOC16_HI and
BFD_RELOC_PPC_TOC16_LO.
ld/
* scripttempl/aix.sc: Add .te to .data section.
* testsuite/ld-powerpc/aix52.exp: Add test structure for AIX7+.
Add aix-largetoc-1 test.
* testsuite/ld-powerpc/aix-largetoc-1-32.d: New test.
* testsuite/ld-powerpc/aix-largetoc-1-64.d: New test.
* testsuite/ld-powerpc/aix-largetoc-1.ex: New test.
* testsuite/ld-powerpc/aix-largetoc-1.s: New test.
Since the last time AIX HOWTO table was modified, IBM has now
released an official documentation about XCOFF relocations.
This commit corrects the wrong ones and add some missing.
For now, the "custom" relocations made for xcoff_rtype2howto have
been kept.
The new relocations are still set as EMPTY_HOWTO because they will
be implemented in later commits.
In xcoff[64]_ppc_relocate_section, instead of recreating howto
from scratch, it's better to use the existing howto from the
table and fixing it according to r_size field.
bfd/
* coff-rs6000.c (xcoff_calculate_relocation): Correct and
add new relocations.
(xcoff_howto_table): Likewise.
(xcoff_rtype2howto): Increase r_type maximum value.
(xcoff_ppc_relocate_section): Reuse predefined HOWTOs instead
of create a new one from scratch. Enable only some relocations
to have a changing r_size.
* coff64-rs6000.c (xcoff64_calculate_relocation): Likewise.
(xcoff64_howto_table): Likewise.
(xcoff64_rtype2howto): Likewise.
(xcoff64_ppc_relocate_section): Likewise.
* libxcoff.h (XCOFF_MAX_CALCULATE_RELOCATION): Fix value.
binutils/
* od-xcoff.c: Replace RTB by TRL entry.
include/
* coff/xcoff.h (R_RTB): Remove.
(R_TRL): Fix value.
This will be needed for later commits, as xcoff64_ppc_relocate_section
will use the HOWTO table unlike now.
* coff64-rs6000.c (xcoff64_ppc_relocate_section): Move.
There is no need for XCOFF64 to have is own write_object_contents.
* coff64-rs6000.c (xcoff64_write_object_contents): Remove.
* coffcode.h (coff_write_object_contents): Add bfd_mach_ppc_620
support for o_cputype field. Avoid creating an empty a.out header
for XCOFF64.
According to the commit abd20cb637, an
intersting thing is that - the more relax passes, the more chances of
relaxations are reduced [1]. Originally, we set the boolean `again`
to TRUE once the code is actually deleted, and then we run the relaxations
repeatedly if `again` is still TRUE. But `again` only works for the
relax pass itself, and won't affect others. That is - we can not use
`again` to re-run the relax pass when we already enter into the following
passes (can not run the relax passes backwards). Besides, we must seperate
the PCREL relaxations into two relax passes for some reasons [2], it make
us lose some relax opportunities.
This patch try to fix the problem, and the basic idea was come from Jim
Wilson - we use a new boolean, restart_relax, to determine if we need to
run the whole relax passes again from 0 to 2. Once we have deleted the
code between relax pass 0 to 2, the restart_relax will be set to TRUE,
we should run the whole relaxations again to give them more chances to
shorten the code. We will only enter into the relax pass 3 when the
restart_relax is FALSE, since we can't relax anything else once we start
to handle the alignments.
I have passed the gcc/binutils regressions by riscv-gnu-toolchain, and
looks fine for now.
[1] https://sourceware.org/pipermail/binutils/2020-November/114223.html
[2] https://sourceware.org/pipermail/binutils/2020-November/114235.html
bfd/
* elfnn-riscv.c (riscv_elf_link_hash_table): New boolean restart_relax,
used to check if we need to run the whole relaxations from relax pass 0
to 2 again.
(riscv_elf_link_hash_table_create): Init restart_relax to FALSE.
(_bfd_riscv_relax_align): Remove obsolete sec_flg0 set.
(_bfd_riscv_relax_delete): Set again to TRUE if we do delete the code.
(bfd_elfNN_riscv_restart_relax_sections): New function. Called by
after_allocation to check if we need to run the whole relaxations again.
(_bfd_riscv_relax_section): We will only enter into the relax pass 3 when
the restart_relax is FALSE; At last set restart_relax to TRUE if again is
TRUE, too.
* elfxx-riscv.h (bfd_elf32_riscv_restart_relax_sections): Declaration.
(bfd_elf64_riscv_restart_relax_sections): Likewise.
ld/
* emultempl/riscvelf.em (after_allocation): Run ldelf_map_segments many
times if riscv_restart_relax_sections returns TRUE.
* testsuite/ld-riscv-elf/restart-relax.d: New testcase. Before applying
this patch, the call won't be relaxed to jal; But now we have more chances
to do relaxations.
* testsuite/ld-riscv-elf/restart-relax.s: Likewise.
* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.
The offset-within-section field in the symbol table entry is only 32
bits wide, so rather than emitting bogus entries omit them, and issue
a diagnostic identifying the issue.
This requires adjusting the PR/22267 test to no longer produce symbols
with out of range values on 64-bit BFD. This also depends on
adjustments to testsuite/ld-scripts/map-address.* made by an earlier
patch. The purpose of the test can very well be achieved nevertheless.
In PE images section addresses get expressed as addresses relative to
the image base. Therefore the VA of a section must be no less than the
image base, and after subtraction of the image base the resulting value
should fit in 32 bits. (The issue is particularly obvious to notice when
sections, perhaps because of ELF assumptions, get placed at VA 0 by
default. Debugging info sections as well as .comment, when input files
are ELF, are a good example. All such sections need proper mentioning in
the linker script to avoid this warning.)
There are a number of test cases which previously produced bogus images,
yet still declared the test a success. Like done for other tests
already, force a zero image base for these. This then also allows (and
requires) dropping again xfail-s which 39a7b38fac ("Fix linker tests
to work with 16-bit targets") had added to ld-scripts/default-script*.d
(originally as skip-s). This also depends on similar adjustments to
testsuite/ld-scripts/map-address.* made by an earlier patch.
For ld-scripts/print-memory-usage.* I suppose xcoff could be dropped
from the exclusion list by suppressing garbage collection, just like
already done in e.g. (as seen in the diff here) ld-scripts/data.*, but I
didn't want to make unrelated adjustments.
When linking Windows x86-64 relocatable object files to generate x86-64
ELF executable, we need to subtract __ImageBase, aka __executable_start,
for R_AMD64_IMAGEBASE relocation:
1. Add link_info to struct output_elf_obj_tdata to store linker info and
_bfd_get_link_info() to retrieve it.
2. Add ldelf_set_output_arch to set up link_info.
3. Add pex64_link_add_symbols to create an indirect reference to
__executable_start for __ImageBase to support R_AMD64_IMAGEBASE relocation
when adding symbols from Windows x86-64 relocatable object files to
generate x86-64 ELF executable.
4. Also subtract __ImageBase for R_AMD64_IMAGEBASE when generating x86-64
ELF executable.
bfd/
PR ld/27425
PR ld/27432
* bfd.c (_bfd_get_link_info): New function.
* elf-bfd.h (output_elf_obj_tdata): Add link_info.
(elf_link_info): New.
* libbfd-in.h (_bfd_get_link_info): New prototype.
* coff-x86_64.c (coff_amd64_reloc): Also subtract __ImageBase for
R_AMD64_IMAGEBASE when generating x86-64 ELF executable.
* pe-x86_64.c: Include "coff/internal.h" and "libcoff.h".
(pex64_link_add_symbols): New function.
(coff_bfd_link_add_symbols): New macro.
* libbfd.h: Regenerated.
ld/
PR ld/27425
PR ld/27432
* ldelf.c (ldelf_set_output_arch): New function.
* ldelf.h (ldelf_set_output_arch): New prototype.
* emultempl/elf.em (LDEMUL_SET_OUTPUT_ARCH): Default to
ldelf_set_output_arch.
* ld-x86-64/pe-x86-64-1.od: Expect __executable_start.
* testsuite/ld-x86-64/pe-x86-64-2.od: Likewise.
* testsuite/ld-x86-64/pe-x86-64-3.od: Likewise.
* testsuite/ld-x86-64/pe-x86-64-4.od: Likewise.
* testsuite/ld-x86-64/pe-x86-64-5.od: Likewise.
* testsuite/ld-x86-64/pe-x86-64-5.rd: Likewise.
* testsuite/ld-x86-64/pe-x86-64-6.obj.bz2: New file.
* testsuite/ld-x86-64/pe-x86-64-6.od: Likewise.
* testsuite/ld-x86-64/pe-x86-64.exp: Run ld/27425 test.
Adds support for including RISC-V control and status registers into
core files.
The value for the define NT_RISCV_CSR is set to 0x900, this
corresponds to a patch I have proposed for the Linux kernel here:
http://lists.infradead.org/pipermail/linux-riscv/2020-December/003910.html
As I have not yet heard if the above patch will be accepted into the
kernel or not I have set the note name string to "GDB", and the note
type to NT_RISCV_CSR.
This means that if the above patch is rejected from the kernel, and
the note type number 0x900 is assigned to some other note type, we
will still be able to distinguish between the GDB produced
NT_RISCV_CSR, and the kernel produced notes, where the name would be
set to "CORE".
bfd/ChangeLog:
* elf-bfd.h (elfcore_write_riscv_csr): Declare.
* elf.c (elfcore_grok_riscv_csr): New function.
(elfcore_grok_note): Handle NT_RISCV_CSR.
(elfcore_write_riscv_csr): New function.
(elfcore_write_register_note): Handle '.reg-riscv-csr'.
binutils/ChangeLog:
* readelf.c (get_note_type): Handle NT_RISCV_CSR.
include/ChangeLog:
* elf/common.h (NT_RISCV_CSR): Define.
When creating a core file GDB will call the function
elfcore_write_prstatus to write out the general purpose registers
along with the pid/tid for the thread (into a prstatus structure) and
the executable name and arguments (into a prpsinfo_t structure).
However, for a bare metal RISC-V tool chain the prstatus_t and
prpsinfo_t types are not defined so the elfcore_write_prstatus
function will return NULL, preventing core file creation.
This commit provides the `elf_backend_write_core_note' hook and uses
the provided function to write out the required information.
In order to keep changes in the non bare metal tools to a minimum, the
provided backend function will itself return NULL when the prstatus_t
or pspsinfo_t types are available, the consequence of this is that the
generic code in elfcore_write_prstatus will be used just as before.
But, when prstatus_t or prpsinfo_t is not available, the new backend
function will write out the information using predefined offsets.
This new functionality will be used by a later GDB commit that will
add bare metal core dumps for RISC-V.
bfd/ChangeLog:
* elfnn-riscv.c (PRPSINFO_PR_FNAME_LENGTH): Define.
(PRPSINFO_PR_PSARGS_LENGTH): Define.
(riscv_write_core_note): New function.
(riscv_elf_grok_psinfo): Make use of two new length defines.
(elf_backend_write_core_note): Define.
This commit lays the ground work for allowing GDB to write its target
description into a generated core file.
The goal of this work is to allow a user to connect to a remote
target, capture a core file from within GDB, then pass the executable
and core file to another user and have the user be able to examine the
state of the machine without needing to connect to a running target.
Different remote targets can have different register sets and this
information is communicated from the target to GDB in the target
description.
It is possible for a user to extract the target description from GDB
and pass this along with the core file so that when the core file is
used the target description can be fed back into GDB, however this is
not a great user experience.
It would be nicer, I think, if GDB could write the target description
directly into the core file, and then make use of this description
when loading a core file.
This commit performs the binutils/bfd side of this task, adding the
boiler plate functions to access the target description from within a
core file note, and reserving a new number for a note containing the
target description. Later commits will extend GDB to make use of
this.
The new note is given the name 'GDB' and a type NT_GDB_TDESC. This
should hopefully protect us if there's ever a reuse of the number
assigned to NT_GDB_TDESC by some other core file producer. It should
also, hopefully, make it clearer to users that this note carries GDB
specific information.
bfd/ChangeLog:
* elf-bfd.h (elfcore_write_gdb_tdesc): Declare new function.
* elf.c (elfcore_grok_gdb_tdesc): New function.
(elfcore_grok_note): Handle NT_GDB_TDESC.
(elfcore_write_gdb_tdesc): New function.
(elfcore_write_register_note): Handle NT_GDB_TDESC.
binutils/ChangeLog:
* readelf.c (get_note_type): Handle NT_GDB_TDESC.
include/ChangeLog:
* elf/common.h (NT_GDB_TDESC): Define.
bfd_perform_relocation should not have special case target code. This
patch moves the code that was there for x86_64 PE linking to ELF
output into the x86_64 PE howto special function, correcting that
function for linking to targets other than ELF too. The fixes in
bfd_perform_relocation were over-complicated due to needing to
compensate for things that had already gone wrong in coff_amd64_reloc.
In particular, an adjustment for pc-relative relocs was done in a way
that meant adjustment for things related to symbol offsets was lost.
I think those two things are orthogonal, but who knows with COFF where
addends and symbol values are found randomly in the section contents.
Note that linking natively to an x86_64 PE output relocates by
coff_pe_amd64_relocate_section, which does not use arelent relocs or
bfd_perform_relocation, but be aware of coff_amd64_rtype_to_howto
hacking addends for relocations. The adjustments for a particular
relocation type there and in coff_amd64_reloc ought to match after
taking into consideration CALC_ADDEND. They don't. For example,
the pc-relative adjustment for R_PCRWORD is 2 bytes in
coff_amd64_reloc and 4 bytes in coff_amd64_rtype_to_howto.
* reloc.c (bfd_perform_relocation): Revert 2021-01-12 and
2020-09-16 changes.
* coff-x86_64.c (coff_amd64_reloc): Do more or less the same
adjustments here instead. Separate pc-relative adjustments
from symbol related adjustments. Tidy comments and formatting.
It is my understanding that IMAGE_SCN_LNK_* are supposed to communicate
information to the (static) linker, and become at best meaningless in PE
images. I wouldn't call loaders wrong which would refuse to process
sections with any of these bits set. While there's no replacement for
IMAGE_SCN_LNK_COMDAT, use IMAGE_SCN_MEM_DISCARDABLE in place of
IMAGE_SCN_LNK_REMOVE in this case.
