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@xxxxxxxxxx> > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > 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 [...] > 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
