Re: [PATCH 0/2] Support HWASAN with Intel LAM

[Hongtao Liu <crazylht@gmail.com>]

On Wed, Nov 30, 2022 at 10:07 PM Martin Liška <mliska@suse.cz> wrote:
>
> On 11/29/22 03:37, Hongtao Liu wrote:
> > On Mon, Nov 28, 2022 at 10:40 PM Martin Liška <mliska@suse.cz> wrote:
> >>
> >> On 11/11/22 02:26, liuhongt via Gcc-patches wrote:
> >>>    2 years ago, ARM folks support HWASAN[1] in GCC[2], and introduced several
> >>> target hooks(Many thanks to their work) so other backends can do similar
> >>> things if they have similar feature.
> >>>    Intel LAM(linear Address Masking)[3 Charpter 14] supports similar feature with
> >>> the upper bits of pointers can be used as metadata, LAM support two modes:
> >>>    LAM_U48:bits 48-62 can be used as metadata
> >>>    LAM_U57:bits 57-62 can be used as metedata.
> >>>
> >>> These 2 patches mainly support those target hooks, but HWASAN is not really
> >>> enabled until the final decision for the LAM kernel interface which may take
> >>> quite a long time. We have verified our patches with a "fake" interface locally[4], and
> >>> decided to push the backend patches to the GCC13 to make other HWASAN developper's work
> >>> easy.
I've committed 2 patches.
> >>
> >> Hello.
> >>
> >> A few random comments I noticed:
> >>
> >> 1) please document the new target -mlam in extend.texi
> > I will.
>
> Thanks.
>
> >> 2) the description speaks about bits [48-62] or [57-62], can explain why the patch contains:
> >>
> > Kernel will use bit 63 for special purposes, and here we want to
> > extract the tag by shifting right the pointer 57 bits, and need to
> > manually mask off bit63.
>
> And thanks for the explanation.
>
> Martin
>
> >> +  /* Mask off bit63 when LAM_U57.  */
> >> +  if (ix86_lam_type == lam_u57)
> >> ?
> >>
> >> 3) Shouldn't the -lman option emit GNU_PROPERTY_X86_FEATURE_1_LAM_U57 or GNU_PROPERTY_X86_FEATURE_1_LAM_U48
> >> .gnu.property note?
> >>
> >> 4) Can you please explain Florian's comment here:
> >> https://gitlab.com/x86-psABIs/x86-64-ABI/-/merge_requests/13#note_1181396487
> >>
> >> Thanks,
> >> Martin
> >>
> >>>
> >>> [1] https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
> >>> [2] https://gcc.gnu.org/pipermail/gcc-patches/2020-November/557857.html
> >>> [3] https://www.intel.com/content/dam/develop/external/us/en/documents/architecture-instruction-set-extensions-programming-reference.pdf
> >>> [4] https://gitlab.com/x86-gcc/gcc/-/tree/users/intel/lam/master
> >>>
> >>>
> >>> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> >>> Ok for trunk?
> >>>
> >>> liuhongt (2):
> >>>    Implement hwasan target_hook.
> >>>    Enable hwasan for x86-64.
> >>>
> >>>   gcc/config/i386/i386-expand.cc  |  12 ++++
> >>>   gcc/config/i386/i386-options.cc |   3 +
> >>>   gcc/config/i386/i386-opts.h     |   6 ++
> >>>   gcc/config/i386/i386-protos.h   |   2 +
> >>>   gcc/config/i386/i386.cc         | 123 ++++++++++++++++++++++++++++++++
> >>>   gcc/config/i386/i386.opt        |  16 +++++
> >>>   libsanitizer/configure.tgt      |   1 +
> >>>   7 files changed, 163 insertions(+)
> >>>
> >>
> >
> >
>


-- 
BR,
Hongtao