Some DW_CFA_* and DW_OP_* take wider than byte, but non-LEB128 operands.
Having to hand-encode such when needing to resort to .cfi_escape isn't
very helpful.
These are data generating directives not overly different from e.g.
.byte and .long. Whatever (directly) results from should also be
represented in the listing, if one was requested. It's just that the
output data is generated much later than the parsing of the directive
arguments.
Ignoring return values often isn't a good idea. The Sparc assembler in
particular would report an internal error if an expression with
relocation specifier is used with .cfi_escape, when the same works fine
with .byte. Propagate the relocation indicator up from
do_parse_cons_expression(), and eventually into emit_expr_with_reloc().
dot_cfi_fde_data(), only retaining the expression's X_add_number, would
require further work. Simply report the lack of support there. While
there, also check that what we were dealt is actually a constant.
CFI_escape is most commonly used to include DWARF expressions in the
unwind information. One may also use CFI_escape to add OS-specific CFI
opcodes. Up until now, SFrame generation process would skip generating
SFrame FDE at the mere sight of a CFI_escape opcode.
Fine tune the handling of CFI_escape for SFrame generation by explicitly
checking for few "harmless" (in context of SFrame generation)
CFI_escape DWARF info:
- DW_CFA_expression affecting registers of no significance to SFrame
stack trace info
- DW_CFA_value_offset affecting registers of no significance to SFrame
stack trace info
Expose the current cfi_escape_data structure in dw2gencfi.c to the
relevant header file to allow SFrame generation APIs to use it too.
Valid unwind info may be split across multiple .cfi_escape directives.
Conversely, it is also allowed to simply put multiple DWARF expressions
and/or operations in a single .cfi_escape directive. Handling all of
these cases correctly will need parsing/processing that is not deemed
worth the effort in context of SFrame generation; We continue to skip
generating SFrame FDE for these cases and warn the user.
In future, SFrame stack trace format may support non-SP/FP as base
register (albeit in limited form). Add an explicit check in
sframe_xlate_do_escape_expr (to test against the current CFA register)
to ensure the functionality continues to work.
Use differentiated warning text in sframe_xlate_do_val_offset to avoid
confusion to the user as the same function is used for handling
.cfi_val_offset and .cfi_escape DW_CFA_val_offset,...
Also, add a common test with DWARF reg 12 which is non SP / FP on x86_64
and aarch64 (and s390x too).
gas/
* gas/dw2gencfi.c (struct cfi_escape_data): Move from ...
* gas/dw2gencfi.h (struct cfi_escape_data): ... to.
* gas/gen-sframe.c (sframe_xlate_do_val_offset): Include string
for .cfi_escape conditionally.
(sframe_xlate_do_escape_expr): New definition.
(sframe_xlate_do_escape_val_offset): Likewise.
(sframe_xlate_do_cfi_escape): Likewise.
(sframe_do_cfi_insn): Handle CFI_escape explicitly.
gas/testsuite/
* gas/cfi-sframe/cfi-sframe.exp: Add new tests.
* gas/cfi-sframe/cfi-sframe-common-9.d: New test.
* gas/cfi-sframe/cfi-sframe-common-9.s: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-1.d: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-1.s: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-2.d: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-2.s: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-3.d: New test.
* gas/cfi-sframe/cfi-sframe-x86_64-empty-3.s: New test.
scfidw2gen will use this for processing the .cfi_sections directive.
gas/
* dw2gencfi.c (dot_cfi_sections): Not static anymore.
* dw2gencfi.h (dot_cfi_sections): Mark as extern.
Move the following three defines to the header file, so the SCFI
machinery can use them:
- tc_cfi_frame_initial_instructions
- tc_cfi_startproc
- tc_cfi_endproc
gas/
* dw2gencfi.c: Move from ...
* dw2gencfi.h: ... to here.
Adds two new external authors to etc/update-copyright.py to cover
bfd/ax_tls.m4, and adds gprofng to dirs handled automatically, then
updates copyright messages as follows:
1) Update cgen/utils.scm emitted copyrights.
2) Run "etc/update-copyright.py --this-year" with an extra external
author I haven't committed, 'Kalray SA.', to cover gas testsuite
files (which should have their copyright message removed).
3) Build with --enable-maintainer-mode --enable-cgen-maint=yes.
4) Check out */po/*.pot which we don't update frequently.
The newer update-copyright.py fixes file encoding too, removing cr/lf
on binutils/bfdtest2.c and ld/testsuite/ld-cygwin/exe-export.exp, and
embedded cr in binutils/testsuite/binutils-all/ar.exp string match.
Currently supported for x86_64 and aarch64 only.
[PS: Currently, the compiler has not been adapted to generate
".cfi_sections" with ".sframe" in it. The newly added command line
option of --gsframe provides an easy way to try out .sframe support
in the toolchain.]
gas interprets the CFI directives to generate DWARF-based .eh_frame
info. These internal DWARF structures are now consumed by
gen-sframe.[ch] sub-system to, in turn, create the SFrame unwind
information. These internal DWARF structures are read-only for the
purpose of SFrame unwind info generation.
SFrame unwind info generation does not impact .eh_frame unwind info
generation. Both .eh_frame and .sframe can co-exist in an ELF file,
if so desired by the user.
Recall that SFrame unwind information only contains the minimal
necessary information to generate backtraces and does not provide
information to recover all callee-saved registers. The reason being
that callee-saved registers other than FP are not needed for stack
unwinding, and hence are not included in the .sframe section.
Consequently, gen-sframe.[ch] only needs to interpret a subset of
DWARF opcodes in gas. More details follow.
[Set 1, Interpreted] The following opcodes are interpreted:
- DW_CFA_advance_loc
- DW_CFA_def_cfa
- DW_CFA_def_cfa_register
- DW_CFA_def_cfa_offset
- DW_CFA_offset
- DW_CFA_remember_state
- DW_CFA_restore_state
- DW_CFA_restore
[Set 2, Bypassed] The following opcodes are acknowledged but are not
necessary for generating SFrame unwind info:
- DW_CFA_undefined
- DW_CFA_same_value
Anything else apart from the two above-mentioned sets is skipped
altogether. This means that any function containing a CFI directive not
in Set 1 or Set 2 above, will not have any SFrame unwind information
generated for them. Holes in instructions covered by FREs of a single
FDE are not representable in the SFrame unwind format.
As few examples, following opcodes are not processed for .sframe
generation, and are skipped:
- .cfi_personality*
- .cfi_*lsda
- .cfi_escape
- .cfi_negate_ra_state
- ...
Not processing .cfi_escape, .cfi_negate_ra_state will cause SFrame
unwind information to be absent for SFrame FDEs that contain these CFI
directives, hence affecting the asynchronicity.
x86-64 and aarch64 backends need to have a few new definitions and
functions for .sframe generation. These provide gas with architecture
specific information like the SP/FP/RA register numbers and an
SFrame-specific ABI marker.
Lastly, the patch also implements an optimization for size, where
specific fragments containing SFrame FRE start address and SFrame FDE
function are fixed up. This is similar to other similar optimizations
in gas, where fragments are sized and fixed up when the associated
symbols can be resolved. This optimization is controlled by a #define
SFRAME_FRE_TYPE_SELECTION_OPT and should be easy to turn off if needed.
The optimization is on by default for both x86_64 and aarch64.
ChangeLog:
* gas/Makefile.am: Include gen-sframe.c and sframe-opt.c.
* gas/Makefile.in: Regenerated.
* gas/as.h (enum _relax_state): Add new state rs_sframe.
(sframe_estimate_size_before_relax): New function.
(sframe_relax_frag): Likewise.
(sframe_convert_frag): Likewise.
* gas/config/tc-aarch64.c (aarch64_support_sframe_p): New
definition.
(aarch64_sframe_ra_tracking_p): Likewise.
(aarch64_sframe_cfa_ra_offset): Likewise.
(aarch64_sframe_get_abi_arch): Likewise.
(md_begin): Set values of sp/fp/ra registers.
* gas/config/tc-aarch64.h (aarch64_support_sframe_p): New
declaration.
(support_sframe_p): Likewise.
(SFRAME_CFA_SP_REG): Likewise.
(SFRAME_CFA_FP_REG): Likewise.
(SFRAME_CFA_RA_REG): Likewise.
(aarch64_sframe_ra_tracking_p): Likewise.
(sframe_ra_tracking_p): Likewise.
(aarch64_sframe_cfa_ra_offset): Likewise.
(sframe_cfa_ra_offset): Likewise.
(aarch64_sframe_get_abi_arch): Likewise.
(sframe_get_abi_arch): Likewise.
* gas/config/tc-i386.c (x86_support_sframe_p): New definition.
(x86_sframe_ra_tracking_p): Likewise.
(x86_sframe_cfa_ra_offset): Likewise.
(x86_sframe_get_abi_arch): Likewise.
* gas/config/tc-i386.h (x86_support_sframe_p): New declaration.
(support_sframe_p): Likewise.
(SFRAME_CFA_SP_REG): Likewise.
(SFRAME_CFA_FP_REG): Likewise.
(x86_sframe_ra_tracking_p): Likewise.
(sframe_ra_tracking_p): Likewise.
(x86_sframe_cfa_ra_offset): Likewise.
(sframe_cfa_ra_offset): Likewise.
(x86_sframe_get_abi_arch): Likewise.
(sframe_get_abi_arch): Likewise.
* gas/config/tc-xtensa.c (unrelaxed_frag_max_size): Add case for
rs_sframe.
* gas/doc/as.texi: Add .sframe to the documentation for
.cfi_sections.
* gas/dw2gencfi.c (cfi_finish): Create a .sframe section.
* gas/dw2gencfi.h (CFI_EMIT_sframe): New definition.
* gas/write.c (cvt_frag_to_fill): Handle rs_sframe.
(relax_segment): Likewise.
* gas/gen-sframe.c: New file.
* gas/gen-sframe.h: New file.
* gas/sframe-opt.c: New file.
This patch is based on MULTIPLE_FRAME_SECTIONS and EH_FRAME_LINKONCE,
it allows backend to enable this feature and use '--gc-sections' simply.
* gas/dw2gencfi.h (TARGET_MULTIPLE_EH_FRAME_SECTIONS): New.
(MULTIPLE_FRAME_SECTIONS): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS.
* gas/dw2gencfi.c (EH_FRAME_LINKONCE): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS.
(is_now_linkonce_segment): Likewise.
(get_cfi_seg): Create relocation info between .eh_frame.* and .text.* section.
* bfd/elf-bfd.h (elf_backend_can_make_multiple_eh_frame): New.
* bfd/elfxx-target.h (elf_backend_can_make_multiple_eh_frame): Likewise.
* bfd/elflink.c (_bfd_elf_default_action_discarded): Add checking for
elf_backend_can_make_multiple_eh_frame.
The result of running etc/update-copyright.py --this-year, fixing all
the files whose mode is changed by the script, plus a build with
--enable-maintainer-mode --enable-cgen-maint=yes, then checking
out */po/*.pot which we don't update frequently.
The copy of cgen was with commit d1dd5fcc38ead reverted as that commit
breaks building of bfp opcodes files.
Armv8.3-A has another key used in pointer authentication called the
B-key (other than the A-key that is already supported). In order for
stack unwinders to work it is necessary to be able to identify frames
that have been signed with the B-key rather than the A-key and it was
felt that keeping this as an augmentation character in the CIE was the
best bet. The DWARF extensions for ARM therefore propose to add a new
augmentation character 'B' to the CIE augmentation string and the
corresponding cfi directive ".cfi_b_key_frame". I've made the relevant
changes to GAS and LD to add support for B-key unwinding, which required
modifying LD to check for 'B' in the augmentation string, adding the
".cfi_b_key_frame" directive to GAS and adding a "pauth_key" field to
GAS's fde_entry and cie_entry structs.
The pointer authentication instructions will behave as NOPs on
architectures that don't support them, and so a check for the
architecture being assembled for is not necessary since there will be no
behavioural difference between augmentation strings with and without the
'B' character on such architectures.
2018-12-05 Sam Tebbs <sam.tebbs@arm.com>
bfd/
* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Add check for 'B'.
gas/
* dw2gencfi.c (struct cie_entry): Add tc_cie_entry_extras invocation.
(alloc_fde_entry): Add tc_fde_entry_init_extra invocation.
(output_cie): Add tc_output_cie_extra invocation.
(select_cie_for_fde): Add tc_cie_fde_equivalent_extra and
tc_cie_entry_init_extra invocation.
(frch_cfi_data, cfa_save_data): Move to dwgencfi.h.
* config/tc-aarch64.c (s_aarch64_cfi_b_key_frame): Declare.
(md_pseudo_table): Add "cfi_b_key_frame".
* config/tc-aarch64.h (tc_fde_entry_extras, tc_cie_entry_extras,
tc_fde_entry_init_extra, tc_output_cie_extra,
tc_cie_fde_equivalent_extra, tc_cie_entry_init_extra): Define.
* dw2gencfi.h (struct fde_entry): Add tc_fde_entry_extras invocation.
(pointer_auth_key): Define.
(frch_cfi_data, cfa_save_data): Move from dwgencfi.c.
* doc/c-aarch64.texi (.cfi_b_key_frame): Add documentation.
* testsuite/gas/aarch64/(pac_ab_key.d, pac_ab_key.s): New file.
This patch adds support for .cfi_val_offset GAS pseudo command which
maps to DW_CFA_val_offset and DW_CFA_val_offset_sf.
gas/ChangeLog:
2016-09-29 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* doc/as.texinfo: Add docu for .cfi_val_offset.
* dw2gencfi.c (cfi_add_CFA_val_offset): New function.
(dot_cfi): Add case for DW_CFA_val_offset.
(output_cfi_insn): Likewise.
(cfi_pseudo_table): Add entry for cfi_val_offset.
* dw2gencfi.h: Add prototype for cfi_add_CFA_val_offset.
* testsuite/gas/cfi/cfi-common-8.d: New test.
* testsuite/gas/cfi/cfi-common-8.s: New test.
* testsuite/gas/cfi/cfi.exp: Run cfi-common-8 testcase.
binutils/ChangeLog:
2016-09-29 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* dwarf.c (display_debug_frames): Adjust output line.
When runtime patching code (like e.g. done by the Linux kernel) there
may be cases where the set of stack frame alterations differs between
unpatched and patched code. Consequently the corresponding unwind data
needs patching too. Locating the right places within an FDE, however,
is rather cumbersome without a way to insert labels in the resulting
section. Hence this patch introduces a new directive, .cfi_label. Note
that with the way CFI data gets emitted currently (at the end of the
assembly process) this can't support local FB- and dollar-labels.
gas/
2015-01-12 Jan Beulich <jbeulich@suse.com>
* gas/dw2gencfi.c (cfi_add_label, dot_cfi_label): New.
(cfi_pseudo_table): Add "cfi_label".
(output_cfi_insn): Handle CFI_label.
(select_cie_for_fde): Als terminate CIE when encountering
CFI_label.
* dw2gencfi.h (cfi_add_label): Declare.
(struct cfi_insn_data): New member "sym_name".
(CFI_label): New.
* read.c (read_symbol_name): Drop "static".
* read.h (read_symbol_name): Declare.
gas/testsuite/
2015-01-12 Jan Beulich <jbeulich@suse.com>
gas/cfi/cfi-label.d, gas/cfi/cfi-label.s: New.
gas/cfi/cfi.exp: Run new tests.
* dw2gencfi.h (all_fde_data): Declare.
* config/tc-alpha.c (alpha_elf_md_end): Don't convert legacy unwind
info to cfi unwind info if the user already has supplied some.
