| From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 |
| From: Sami Tolvanen <samitolvanen@google.com> |
| Date: Wed, 2 Oct 2019 13:37:45 -0700 |
| Subject: FROMLIST: arm64: efi: restore x18 if it was corrupted |
| |
| If we detect a corrupted x18 and SCS is enabled, restore the register |
| before jumping back to instrumented code. This is safe, because the |
| wrapper is called with preemption disabled and a separate shadow stack |
| is used for interrupt handling. |
| |
| Bug: 145210207 |
| Change-Id: Idb75117e38c895231a14f5573261861e722c1264 |
| (am from https://lore.kernel.org/patchwork/patch/1149060/) |
| Reviewed-by: Kees Cook <keescook@chromium.org> |
| Signed-off-by: Sami Tolvanen <samitolvanen@google.com> |
| --- |
| arch/arm64/kernel/efi-rt-wrapper.S | 11 ++++++++++- |
| 1 file changed, 10 insertions(+), 1 deletion(-) |
| |
| diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S |
| index 3fc71106cb2b..62f0260f5c17 100644 |
| --- a/arch/arm64/kernel/efi-rt-wrapper.S |
| +++ b/arch/arm64/kernel/efi-rt-wrapper.S |
| @@ -34,5 +34,14 @@ ENTRY(__efi_rt_asm_wrapper) |
| ldp x29, x30, [sp], #32 |
| b.ne 0f |
| ret |
| -0: b efi_handle_corrupted_x18 // tail call |
| +0: |
| +#ifdef CONFIG_SHADOW_CALL_STACK |
| + /* |
| + * Restore x18 before returning to instrumented code. This is |
| + * safe because the wrapper is called with preemption disabled and |
| + * a separate shadow stack is used for interrupts. |
| + */ |
| + mov x18, x2 |
| +#endif |
| + b efi_handle_corrupted_x18 // tail call |
| ENDPROC(__efi_rt_asm_wrapper) |
