Re: [PATCH v6 11/15] arm64: efi: restore x18 if it was corrupted
From: Will Deacon <will@kernel.org>
Date: 2020-01-16 17:53:44
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On Fri, Dec 06, 2019 at 02:13:47PM -0800, Sami Tolvanen wrote:
quoted hunk ↗ jump to hunk
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. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <redacted> --- 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
Why not restore it regardless of CONFIG_SHADOW_CALL_STACK? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel