x86/ibt: Fix hibernate

Todd reported, and Len confirmed, that commit 582077c94052 ("x86/cfi:
Clean up linkage") broke S4 hiberate on a fair number of machines.

Turns out these machines trip #CP when trying to restore the image.

As it happens, the commit in question removes two ENDBR instructions
in the hibernate code, and clearly got it wrong.

Notably restore_image() does an indirect jump to
relocated_restore_code(), which is a relocated copy of
core_restore_code().

In turn, core_restore_code(), will at the end do an indirect jump to
restore_jump_address (r8), which is pointing at a relocated
restore_registers().

So both sites do indeed need to be ENDBR.

Fixes: 582077c94052 ("x86/cfi: Clean up linkage")
Reported-by: Todd Brandt <todd.e.brandt@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Todd Brandt <todd.e.brandt@intel.com>
Tested-by: Len Brown <len.brown@intel.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219998
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219998

diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
index 8c534c36adfa2865349f1d4c202345abdc721a7e..66f066b8fedad226234a61be0c7069540ed024c7 100644 (file)
--- a/arch/x86/power/hibernate_asm_64.S
+++ b/arch/x86/power/hibernate_asm_64.S
@@ -26,7 +26,7 @@
         /* code below belongs to the image kernel */
        .align PAGE_SIZE
 SYM_FUNC_START(restore_registers)
-       ANNOTATE_NOENDBR
+       ENDBR
        /* go back to the original page tables */
        movq    %r9, %cr3
 
@@ -120,7 +120,7 @@ SYM_FUNC_END(restore_image)
 
        /* code below has been relocated to a safe page */
 SYM_FUNC_START(core_restore_code)
-       ANNOTATE_NOENDBR
+       ENDBR
        /* switch to temporary page tables */
        movq    %rax, %cr3
        /* flush TLB */