from zephyr.c:78
static const struct stack_register_offset arm_callee_saved[] = {
{ ARMV7M_R13, 32, 32 },
{ ARMV7M_R4, 0, 32 },
{ ARMV7M_R5, 4, 32 },
{ ARMV7M_R6, 8, 32 },
{ ARMV7M_R7, 12, 32 },
{ ARMV7M_R8, 16, 32 },
{ ARMV7M_R9, 20, 32 },
{ ARMV7M_R10, 24, 32 },
{ ARMV7M_R11, 28, 32 },
};