[PATCH v3 2/2] x32/cet: Support shadow stack during startup for Linux 6.10

[Noah Goldstein]

On Tue, Jul 23, 2024 at 8:47 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Use RXX_LP in RTLD_START_ENABLE_X86_FEATURES.  Support shadow stack during
> startup for Linux 6.10:
>
> commit 2883f01ec37dd8668e7222dfdb5980c86fdfe277
> Author: H.J. Lu <hjl.tools@gmail.com>
> Date:   Fri Mar 15 07:04:33 2024 -0700
>
>     x86/shstk: Enable shadow stacks for x32
>
>     1. Add shadow stack support to x32 signal.
>     2. Use the 64-bit map_shadow_stack syscall for x32.
>     3. Set up shadow stack for x32.
>
> Add the map_shadow_stack system call to <fixup-asm-unistd.h> and regenerate
> arch-syscall.h.  Tested on Intel Tiger Lake with CET enabled x32.  There
> are no regressions with CET enabled x86-64.  There are no changes in CET
> enabled x86-64 _dl_start_user.
>
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> ---
>  sysdeps/unix/sysv/linux/x86_64/dl-cet.h               | 6 +++---
>  sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h     | 1 +
>  sysdeps/unix/sysv/linux/x86_64/x32/fixup-asm-unistd.h | 4 ++++
>  3 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/x86_64/dl-cet.h b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> index 1fe3133406..b4f7e6c9cd 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> +++ b/sysdeps/unix/sysv/linux/x86_64/dl-cet.h
> @@ -92,9 +92,9 @@ dl_cet_ibt_enabled (void)
>         # Pass GL(dl_x86_feature_1) to _dl_cet_setup_features.\n\
>         movl %edx, %edi\n\
>         # Align stack for the _dl_cet_setup_features call.\n\
> -       andq $-16, %rsp\n\
> +       and $-16, %" RSP_LP "\n\
>         call _dl_cet_setup_features\n\
>         # Restore %rax and %rsp from %r12 and %r13.\n\
> -       movq %r12, %rax\n\
> -       movq %r13, %rsp\n\
> +       mov %" R12_LP ", %" RAX_LP "\n\
> +       mov %" R13_LP ", %" RSP_LP "\n\
>  "
> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h b/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
> index 3040a47d72..df3e22236d 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/arch-syscall.h
> @@ -155,6 +155,7 @@
>  #define __NR_lsm_set_self_attr 1073742284
>  #define __NR_lstat 1073741830
>  #define __NR_madvise 1073741852
> +#define __NR_map_shadow_stack 1073742277
>  #define __NR_mbind 1073742061
>  #define __NR_membarrier 1073742148
>  #define __NR_memfd_create 1073742143
> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/fixup-asm-unistd.h b/sysdeps/unix/sysv/linux/x86_64/x32/fixup-asm-unistd.h
> index 98124169e6..47fa8af4ce 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/x32/fixup-asm-unistd.h
> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/fixup-asm-unistd.h
> @@ -15,6 +15,10 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>
> +#ifndef __NR_map_shadow_stack
> +# define __NR_map_shadow_stack 1073742277
> +#endif
> +
>  /* X32 uses the same 64-bit syscall interface for set_thread_area.   */
>  #ifndef __NR_set_thread_area
>  # define __NR_set_thread_area 1073742029
> --
> 2.45.2
>
LGTM
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>