i#1569 AArch64: Implement dynamorio_app_take_over.

Review-URL: https://codereview.appspot.com/301790043

core/arch/aarch64/aarch64.asm

@@ -130,7 +130,7 @@ GLOBAL_LABEL(dr_app_start:)
 
         DECLARE_EXPORTED_FUNC(dr_app_take_over)
 GLOBAL_LABEL(dr_app_take_over:)
-        bl       GLOBAL_REF(unexpected_return) /* FIXME i#1569: NYI */
+        b        GLOBAL_REF(dynamorio_app_take_over)
         END_FUNC(dr_app_take_over)
 
         DECLARE_EXPORTED_FUNC(dr_app_running_under_dynamorio)
@@ -139,9 +139,53 @@ GLOBAL_LABEL(dr_app_running_under_dynamorio:)
         END_FUNC(dr_app_running_under_dynamorio)
 #endif /* DR_APP_EXPORTS */
 
+/* sizeof(priv_mcontext_t) rounded up to a multiple of 16 */
+#define PRIV_MCONTEXT_SIZE 800
+
         DECLARE_EXPORTED_FUNC(dynamorio_app_take_over)
 GLOBAL_LABEL(dynamorio_app_take_over:)
-        bl       GLOBAL_REF(unexpected_return) /* FIXME i#1569: NYI */
+        /* Save FP and LR for the case that DR is not taking over. */
+        stp      x29, x30, [sp, #-16]!
+        /* Build a priv_mcontext_t on the stack. */
+        sub      sp, sp, #PRIV_MCONTEXT_SIZE
+        stp      x0, x1, [sp, #(0 * ARG_SZ*2)]
+        stp      x2, x3, [sp, #(1 * ARG_SZ*2)]
+        stp      x4, x5, [sp, #(2 * ARG_SZ*2)]
+        stp      x6, x7, [sp, #(3 * ARG_SZ*2)]
+        stp      x8, x9, [sp, #(4 * ARG_SZ*2)]
+        stp      x10, x11, [sp, #(5 * ARG_SZ*2)]
+        stp      x12, x13, [sp, #(6 * ARG_SZ*2)]
+        stp      x14, x15, [sp, #(7 * ARG_SZ*2)]
+        stp      x16, x17, [sp, #(8 * ARG_SZ*2)]
+        stp      x18, x19, [sp, #(9 * ARG_SZ*2)]
+        stp      x20, x21, [sp, #(10 * ARG_SZ*2)]
+        stp      x22, x23, [sp, #(11 * ARG_SZ*2)]
+        stp      x24, x25, [sp, #(12 * ARG_SZ*2)]
+        stp      x26, x27, [sp, #(13 * ARG_SZ*2)]
+        stp      x28, x29, [sp, #(14 * ARG_SZ*2)]
+        add      x0, sp, #(PRIV_MCONTEXT_SIZE + 16) /* compute original SP */
+        stp      x30, x0, [sp, #(15 * ARG_SZ*2)]
+        str      x30, [sp, #(16 * ARG_SZ*2)] /* save LR as PC */
+        mrs      x1, nzcv
+        mrs      x2, fpcr
+        mrs      x3, fpsr
+        str      w1, [sp, #(16 * ARG_SZ*2 + 8)]
+        str      w2, [sp, #(16 * ARG_SZ*2 + 12)]
+        str      w3, [sp, #(16 * ARG_SZ*2 + 16)]
+        add      x4, sp, #(16 * ARG_SZ*2 + 20) /* offsetof(priv_mcontext_t, simd) */
+        st1      {v0.2d-v3.2d}, [x4], #64
+        st1      {v4.2d-v7.2d}, [x4], #64
+        st1      {v8.2d-v11.2d}, [x4], #64
+        st1      {v12.2d-v15.2d}, [x4], #64
+        st1      {v16.2d-v19.2d}, [x4], #64
+        st1      {v20.2d-v23.2d}, [x4], #64
+        st1      {v24.2d-v27.2d}, [x4], #64
+        st1      {v28.2d-v31.2d}, [x4], #64
+        CALLC1(GLOBAL_REF(dynamorio_app_take_over_helper), sp)
+        /* If we get here, DR is not taking over. */
+        add      sp, sp, #PRIV_MCONTEXT_SIZE
+        ldp      x29, x30, [sp], #16
+        ret
         END_FUNC(dynamorio_app_take_over)
 
 /*