[RFD 0/5] Add support for MTE stack tagging.

[Luis Machado]

Hi,

On 12/5/24 22:58, Indu Bhagat wrote:
> Hello,
> 
> I am sending some WIP patches to follow up on some of the questions I
> have had with regard to Binutils support for MTE stack tagging.
> https://gcc.gnu.org/pipermail/gcc-patches/2024-November/670319.html
> 
> Since sending of the above message to gcc-patches mailing list, I
> changed the command line options a bit.  I also realised that some text
> in the gcc-patches message was a bit incorrect.  So I am sending the
> patches, hopefully that conveys the picture better.
> 
> The commit log of each commit has some of the above questions listed
> too.  Most of the questions are around the implementation of the two
> dynamic tags (related to MTE stack tagging).  Although the patchset
> addresses three different aspects (i.e., .cfi_mte_tagged_frame CFI
> directive, DT_AARCH64_MEMTAG_MODE and DT_AARCH64_MEMTAG_STACK), I am
> sending them together for discussion/coordination for next steps.
> 
> (PS: I can get rid of the ChangeLog in the commit message later when the
> patches are more mature. Also, I have an erratic and sparse work
> schedule for December, my responses may be slow.)
> 
> Thanks,
> 
> Indu Bhagat (5):
>   binutils: make read_cie aware of new augmentation char 'G'
>   gas: aarch64: suppport CFI directive .cfi_mte_tagged_frame
>   ld: aarch64: make EH Frame parsing aware of augmentation char 'G'
>   ld/aarch64elf: add support for DT_AARCH64_MEMTAG_MODE dynamic tag
>   ld/aarch64elf: add support for DT_AARCH64_MEMTAG_STACK dynamic tag
> 
>  bfd/elf-eh-frame.c                            |  2 +
>  bfd/elfnn-aarch64.c                           | 21 ++++++++-
>  bfd/elfxx-aarch64.h                           | 27 ++++++++++-
>  binutils/dwarf.c                              |  2 +
>  binutils/readelf.c                            |  3 ++
>  gas/config/tc-aarch64.c                       |  9 ++++
>  gas/config/tc-aarch64.h                       | 17 +++++--
>  gas/doc/c-aarch64.texi                        | 10 ++++
>  gas/testsuite/gas/aarch64/mte_tagged_stack.d  | 47 +++++++++++++++++++
>  gas/testsuite/gas/aarch64/mte_tagged_stack.s  | 24 ++++++++++
>  include/elf/aarch64.h                         |  2 +
>  ld/emultempl/aarch64elf.em                    | 47 ++++++++++++++++++-
>  ld/ld.texi                                    | 14 ++++++
>  ld/testsuite/ld-aarch64/aarch64-elf.exp       |  4 ++
>  ld/testsuite/ld-aarch64/dt-memtag-mode.d      |  7 +++
>  ld/testsuite/ld-aarch64/dt-memtag-stack.d     |  7 +++
>  ld/testsuite/ld-aarch64/dt-memtag.s           |  7 +++
>  .../ld-aarch64/mte-tagged-frame-bar.s         | 17 +++++++
>  .../ld-aarch64/mte-tagged-frame-foo.s         | 16 +++++++
>  ld/testsuite/ld-aarch64/mte-tagged-frame.d    | 29 ++++++++++++
>  20 files changed, 303 insertions(+), 9 deletions(-)
>  create mode 100644 gas/testsuite/gas/aarch64/mte_tagged_stack.d
>  create mode 100644 gas/testsuite/gas/aarch64/mte_tagged_stack.s
>  create mode 100644 ld/testsuite/ld-aarch64/dt-memtag-mode.d
>  create mode 100644 ld/testsuite/ld-aarch64/dt-memtag-stack.d
>  create mode 100644 ld/testsuite/ld-aarch64/dt-memtag.s
>  create mode 100644 ld/testsuite/ld-aarch64/mte-tagged-frame-bar.s
>  create mode 100644 ld/testsuite/ld-aarch64/mte-tagged-frame-foo.s
>  create mode 100644 ld/testsuite/ld-aarch64/mte-tagged-frame.d
> 

Do you envision gdb having to know any of this for debugging purposes? I know
gdb parses the augmentation character, but it is not clear gdb can do anything
useful with it.