Indu Bhagat <indu.bha...@oracle.com> writes:
> In context of stack tagging, the AArch64 Memtag ABI Extension to ELF
> specifies the usage of two dynamic tags for the dynamic loader to do the
> necessary tasks:
> - If DT_AARCH64_MEMTAG_MODE is present, the dynamic loader should (in
> a platform-specific specific way) enable MTE for the process.
> - If DT_AARCH64_MEMTAG_STACK is present, the dynamic loader should
> enable tagging for the main stack and thread stacks.
>
> Make changes in the link spec so appropriate command line options can be
> passed to ld.
>
> The two (proposed) command line options added to ld are:
> -z memtag-mode=<mode>
> -z memtag-stack
>
> On the GCC side, the user can:
> - Enable MTE stack tagging using -fsanitize=memtag
> - Select the MTE mode by using -fsanitize-memtag-mode=mode.
>
> TBD:
> - We need to check explicitly for stack tagging; sanitize(memtag) does
> not appear to be enough. Because -fsanitize=memtag will also be used
> for MTE tagging of globals later. On a related note, clang has two
> explicit options: -fsanitize=memtag-stack and -fsanitize=memtag-globals.
Yeah, I think we should aim for option compatibility with Clang unless
there's a specific reason not to. In a way, getting rid of the associated
--params is a feature, since --params are supposed to be developer options
that can go away at any time.
Thanks,
Richard
> gcc/ChangeLog:
>
> * config/aarch64/aarch64-linux.h: Update LINUX_TARGET_LINK_SPEC
> macro.
> * gcc.cc (sanitize_spec_function): Add check for memtag.
>
> ---
> [New in RFC V2]
> ---
> gcc/config/aarch64/aarch64-linux.h | 4 +++-
> gcc/gcc.cc | 2 ++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/aarch64/aarch64-linux.h
> b/gcc/config/aarch64/aarch64-linux.h
> index 116bb4e69f37..a5e5f8bb5ac5 100644
> --- a/gcc/config/aarch64/aarch64-linux.h
> +++ b/gcc/config/aarch64/aarch64-linux.h
> @@ -48,7 +48,9 @@
> %{static-pie:-Bstatic -pie --no-dynamic-linker -z text} \
> -X \
> %{mbig-endian:-EB} %{mlittle-endian:-EL} \
> - -maarch64linux%{mabi=ilp32:32}%{mbig-endian:b}"
> + -maarch64linux%{mabi=ilp32:32}%{mbig-endian:b} \
> + %{%:sanitize(memtag):%{!fsanitize-memtag-mode:-z memtag-stack -z
> memtag-mode=sync}} \
> + %{%:sanitize(memtag):%{fsanitize-memtag-mode=*:-z memtag-stack -z
> memtag-mode=%}}"
>
>
> #define LINK_SPEC LINUX_TARGET_LINK_SPEC AARCH64_ERRATA_LINK_SPEC
> diff --git a/gcc/gcc.cc b/gcc/gcc.cc
> index aac33e91a9a0..5beb793b075c 100644
> --- a/gcc/gcc.cc
> +++ b/gcc/gcc.cc
> @@ -10443,6 +10443,8 @@ sanitize_spec_function (int argc, const char **argv)
> return (flag_sanitize & SANITIZE_KERNEL_ADDRESS) ? "" : NULL;
> if (strcmp (argv[0], "kernel-hwaddress") == 0)
> return (flag_sanitize & SANITIZE_KERNEL_HWADDRESS) ? "" : NULL;
> + if (strcmp (argv[0], "memtag") == 0)
> + return (flag_sanitize & SANITIZE_MEMTAG) ? "" : NULL;
> if (strcmp (argv[0], "thread") == 0)
> return (flag_sanitize & SANITIZE_THREAD) ? "" : NULL;
> if (strcmp (argv[0], "undefined") == 0)
