[PATCH] x86: Set header.feature_1 in TCB for always-on CET

[H.J. Lu]

On Wed, Jan 13, 2021 at 4:09 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Update dl_cet_check() to set header.feature_1 in TCB when both IBT and
> SHSTK are always on.
> ---
>  sysdeps/x86/Makefile         | 6 ++++++
>  sysdeps/x86/dl-cet.c         | 5 ++++-
>  sysdeps/x86/tst-setjmp-cet.c | 1 +
>  3 files changed, 11 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/x86/tst-setjmp-cet.c
>
> diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
> index c814d5a195..adaa2a92cd 100644
> --- a/sysdeps/x86/Makefile
> +++ b/sysdeps/x86/Makefile
> @@ -48,6 +48,12 @@ endif # $(subdir) == math
>  ifeq ($(subdir),setjmp)
>  gen-as-const-headers += jmp_buf-ssp.sym
>  sysdep_routines += __longjmp_cancel
> +ifneq ($(enable-cet),no)
> +ifneq ($(have-tunables),no)
> +tests += tst-setjmp-cet
> +tst-setjmp-cet-ENV = GLIBC_TUNABLES=glibc.cpu.x86_ibt=on:glibc.cpu.x86_shstk=on
> +endif
> +endif
>  endif
>
>  ifeq ($(subdir),string)
> diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
> index ed7fd6d10d..a63b9c7164 100644
> --- a/sysdeps/x86/dl-cet.c
> +++ b/sysdeps/x86/dl-cet.c
> @@ -47,7 +47,10 @@ dl_cet_check (struct link_map *m, const char *program)
>    /* No legacy object check if both IBT and SHSTK are always on.  */
>    if (enable_ibt_type == cet_always_on
>        && enable_shstk_type == cet_always_on)
> -    return;
> +    {
> +      THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
> +      return;
> +    }
>
>    /* Check if IBT is enabled by kernel.  */
>    bool ibt_enabled
> diff --git a/sysdeps/x86/tst-setjmp-cet.c b/sysdeps/x86/tst-setjmp-cet.c
> new file mode 100644
> index 0000000000..42c795d2a8
> --- /dev/null
> +++ b/sysdeps/x86/tst-setjmp-cet.c
> @@ -0,0 +1 @@
> +#include <setjmp/tst-setjmp.c>
> --
> 2.29.2
>

This fixed:

https://sourceware.org/bugzilla/show_bug.cgi?id=27177

I'd like to fix it for 2.33.

Thanks.

-- 
H.J.