Re: [PATCH v6 14/15] arm64: implement Shadow Call Stack
From: Will Deacon <will@kernel.org>
Date: 2020-01-16 18:24:25
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On Fri, Dec 06, 2019 at 02:13:50PM -0800, Sami Tolvanen wrote:
This change implements shadow stack switching, initial SCS set-up, and interrupt shadow stacks for arm64. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <redacted> --- arch/arm64/Kconfig | 5 ++++ arch/arm64/include/asm/scs.h | 37 +++++++++++++++++++++++++ arch/arm64/include/asm/thread_info.h | 3 +++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/entry.S | 31 +++++++++++++++++++-- arch/arm64/kernel/head.S | 9 +++++++ arch/arm64/kernel/irq.c | 2 ++ arch/arm64/kernel/process.c | 2 ++ arch/arm64/kernel/scs.c | 40 ++++++++++++++++++++++++++++ arch/arm64/kernel/smp.c | 4 +++ 11 files changed, 135 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c
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quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 583f71abbe98..7aa2d366b2df 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S@@ -172,6 +172,10 @@ alternative_cb_end apply_ssbd 1, x22, x23 +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack + str xzr, [tsk, #TSK_TI_SCS] // Limit visibility of saved SCS +#endif .else add x21, sp, #S_FRAME_SIZE get_current_task tsk@@ -280,6 +284,12 @@ alternative_else_nop_endif ct_user_enter .endif +#ifdef CONFIG_SHADOW_CALL_STACK + .if \el == 0 + str x18, [tsk, #TSK_TI_SCS] // Save shadow call stack + .endif +#endif + #ifdef CONFIG_ARM64_SW_TTBR0_PAN /* * Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR@@ -385,6 +395,9 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 .macro irq_stack_entry mov x19, sp // preserve the original sp +#ifdef CONFIG_SHADOW_CALL_STACK + mov x20, x18 // preserve the original shadow stack +#endif
Hmm, not sure about corrupting x20 here. Doesn't it hold the PMR value from kernel_entry? Rest of the patch looks ok, but I'll do a proper review when it's closer to being merged as we've got a bunch of other entry changes in the pipeline. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel