On Tue, Nov 5, 2019 at 3:56 PM Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote: > > Don't lose the current task's shadow stack when the CPU is suspended. > > Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Re-LGTM > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > arch/arm64/include/asm/suspend.h | 2 +- > arch/arm64/mm/proc.S | 14 ++++++++++++++ > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h > index 8939c87c4dce..0cde2f473971 100644 > --- a/arch/arm64/include/asm/suspend.h > +++ b/arch/arm64/include/asm/suspend.h > @@ -2,7 +2,7 @@ > #ifndef __ASM_SUSPEND_H > #define __ASM_SUSPEND_H > > -#define NR_CTX_REGS 12 > +#define NR_CTX_REGS 13 > #define NR_CALLEE_SAVED_REGS 12 > > /* > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index fdabf40a83c8..5c8219c55948 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -49,6 +49,8 @@ > * cpu_do_suspend - save CPU registers context > * > * x0: virtual address of context pointer > + * > + * This must be kept in sync with struct cpu_suspend_ctx in <asm/suspend.h>. > */ > ENTRY(cpu_do_suspend) > mrs x2, tpidr_el0 > @@ -73,6 +75,11 @@ alternative_endif > stp x8, x9, [x0, #48] > stp x10, x11, [x0, #64] > stp x12, x13, [x0, #80] > + /* > + * Save x18 as it may be used as a platform register, e.g. by shadow > + * call stack. > + */ > + str x18, [x0, #96] > ret > ENDPROC(cpu_do_suspend) > > @@ -89,6 +96,13 @@ ENTRY(cpu_do_resume) > ldp x9, x10, [x0, #48] > ldp x11, x12, [x0, #64] > ldp x13, x14, [x0, #80] > + /* > + * Restore x18, as it may be used as a platform register, and clear > + * the buffer to minimize the risk of exposure when used for shadow > + * call stack. > + */ > + ldr x18, [x0, #96] > + str xzr, [x0, #96] > msr tpidr_el0, x2 > msr tpidrro_el0, x3 > msr contextidr_el1, x4 > -- > 2.24.0.rc1.363.gb1bccd3e3d-goog > -- Thanks, ~Nick Desaulniers
