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.

Tested with shadow stack enabled x32 glibc on Intel Tiger Lake:

I configured x32 glibc with --enable-cet, build glibc and
run all glibc tests with shadow stack enabled.  There are
no regressions.  I verified that shadow stack is enabled
via /proc/pid/status.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: H.J. Lu <hjl.tools@gmail.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20240315140433.1966543-1-hjl.tools@gmail.com

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 7e8d46f4147f574111962c214119af2dd2b62b4a..cc78226ffc359357d994f8242ed94879114e122f 100644 (file)
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -374,7 +374,7 @@
 450    common  set_mempolicy_home_node sys_set_mempolicy_home_node
 451    common  cachestat               sys_cachestat
 452    common  fchmodat2               sys_fchmodat2
-453    64      map_shadow_stack        sys_map_shadow_stack
+453    common  map_shadow_stack        sys_map_shadow_stack
 454    common  futex_wake              sys_futex_wake
 455    common  futex_wait              sys_futex_wait
 456    common  futex_requeue           sys_futex_requeue

diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 59e15dd8d0f86665ef0949b1c7072b9d25205c5e..6f1e9883f07425e87d2ee7c4366ed284a8051ee7 100644 (file)
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c
@@ -163,8 +163,8 @@ static int shstk_setup(void)
        if (features_enabled(ARCH_SHSTK_SHSTK))
                return 0;
 
-       /* Also not supported for 32 bit and x32 */
-       if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK) || in_32bit_syscall())
+       /* Also not supported for 32 bit */
+       if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK) || in_ia32_syscall())
                return -EOPNOTSUPP;
 
        size = adjust_shstk_size(0);

diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 23d8aaf8d9fd1950fcd6c3a43f5af4a013d57a31..8a94053c5444659123f07e680700d9096defa4bc 100644 (file)
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -315,6 +315,9 @@ int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 
        uc_flags = frame_uc_flags(regs);
 
+       if (setup_signal_shadow_stack(ksig))
+               return -EFAULT;
+
        if (!user_access_begin(frame, sizeof(*frame)))
                return -EFAULT;
 
@@ -377,6 +380,9 @@ COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
        if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
                goto badframe;
 
+       if (restore_signal_shadow_stack())
+               goto badframe;
+
        if (compat_restore_altstack(&frame->uc.uc_stack))
                goto badframe;