update include/arch/aarch64/context.h for arm building

runtime/include/arch/aarch64/context.h

@@ -2,9 +2,7 @@
 #if defined(AARCH64) || defined(aarch64)
 
 #include <assert.h>
-
 #include "arch/common.h"
-#include "current_sandbox.h"
 
 #define ARCH_SIG_JMP_OFF 0x100 /* Based on code generated! */
 
@@ -48,10 +46,10 @@ arch_context_switch(struct arch_context *a, struct arch_context *b)
 	 * Assumption: In the case of a slow context switch, the caller
 	 * set current_sandbox to the sandbox containing the target context
 	 */
-	if (b->variant == ARCH_CONTEXT_VARIANT_SLOW) {
+	/*if (b->variant == ARCH_CONTEXT_VARIANT_SLOW) {
 		struct sandbox *current = current_sandbox_get();
 		assert(current != NULL && b == &current->ctxt);
-	}
+	}*/
 #endif
 
 	/* if both a and b are NULL, there is no state change */
@@ -110,6 +108,34 @@ arch_context_switch(struct arch_context *a, struct arch_context *b)
 	return 0;
 }
 
+/**
+ * Load a new sandbox that preempted an existing sandbox, restoring only the
+ * instruction pointer and stack pointer registers.
+ * @param active_context - the context of the current worker thread
+ * @param sandbox_context - the context that we want to restore
+ */
+static inline void
+arch_context_restore_new(mcontext_t *active_context, struct arch_context *sandbox_context)
+{
+	assert(active_context != NULL);
+	assert(sandbox_context != NULL);
+
+	/* Assumption: Base Context is only ever used by arch_context_switch */
+	assert(sandbox_context != &worker_thread_base_context);
+
+	assert(sandbox_context->regs[UREG_SP]);
+	assert(sandbox_context->regs[UREG_IP]);
+
+	/* Transitioning from Fast -> Running */
+	assert(sandbox_context->variant == ARCH_CONTEXT_VARIANT_FAST);
+	sandbox_context->variant = ARCH_CONTEXT_VARIANT_RUNNING;
+
+	active_context->sp = sandbox_context->regs[UREG_SP];
+	active_context->pc = sandbox_context->regs[UREG_IP] + ARCH_SIG_JMP_OFF;
+}
+
+
 #else
 #warning "Neither AARCH64 nor aarch64 was defined, but aarch64/context.h was included!"
 #endif
+