From fe466d003a8921e83962da1634eadd4461a0ed17 Mon Sep 17 00:00:00 2001
From: Nguyen Anh Quynh <aquynh@gmail.com>
Date: Fri, 16 Jun 2017 13:22:38 +0800
Subject: [PATCH] callback to count number of instructions in uc_emu_start()
 should be executed first. fix #727

---
 include/list.h    | 10 ++++++++++
 include/uc_priv.h |  1 +
 list.c            | 22 ++++++++++++++++++++++
 uc.c              | 36 +++++++++++++++++++++++++++++-------
 4 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/include/list.h b/include/list.h
index 67734cc..84917ab 100644
--- a/include/list.h
+++ b/include/list.h
@@ -12,9 +12,19 @@ struct list {
     struct list_item *head, *tail;
 };
 
+// create a new list
 struct list *list_new(void);
+
+// removed linked list nodes but does not free their content
 void list_clear(struct list *list);
+
+// insert a new item at the begin of the list.
+void *list_insert(struct list *list, void *data);
+
+// append a new item at the end of the list.
 void *list_append(struct list *list, void *data);
+
+// returns true if entry was removed, false otherwise
 bool list_remove(struct list *list, void *data);
 
 #endif
diff --git a/include/uc_priv.h b/include/uc_priv.h
index 5c47fb9..22f494e 100644
--- a/include/uc_priv.h
+++ b/include/uc_priv.h
@@ -244,6 +244,7 @@ struct uc_struct {
     uint32_t target_page_size;
     uint32_t target_page_align;
     uint64_t next_pc;   // save next PC for some special cases
+    bool hook_insert;	// insert new hook at begin of the hook list (append by default)
 };
 
 // Metadata stub for the variable-size cpu context used with uc_context_*()
diff --git a/list.c b/list.c
index 69a6649..0703c10 100644
--- a/list.c
+++ b/list.c
@@ -22,6 +22,28 @@ void list_clear(struct list *list)
     list->tail = NULL;
 }
 
+// insert a new item at the begin of the list.
+// returns generated linked list node, or NULL on failure
+void *list_insert(struct list *list, void *data)
+{
+    struct list_item *item = malloc(sizeof(struct list_item));
+    if (item == NULL) {
+        return NULL;
+    }
+
+    item->data = data;
+    item->next = list->head;
+
+    if (list->tail == NULL) {
+        list->tail = item;
+    }
+
+    list->head = item;
+
+    return item;
+}
+
+// append a new item at the end of the list.
 // returns generated linked list node, or NULL on failure
 void *list_append(struct list *list, void *data)
 {
diff --git a/uc.c b/uc.c
index 4046694..c39ea48 100644
--- a/uc.c
+++ b/uc.c
@@ -594,7 +594,13 @@ uc_err uc_emu_start(uc_engine* uc, uint64_t begin, uint64_t until, uint64_t time
     }
     // set up count hook to count instructions.
     if (count > 0 && uc->count_hook == 0) {
+        // callback to count instructions must be run before everything else,
+        // so instead of appending, we must insert the hook at the begin
+        // of the hook list
+        uc->hook_insert = 1;
         uc_err err = uc_hook_add(uc, &uc->count_hook, UC_HOOK_CODE, hook_count_cb, NULL, 1, 0);
+        // restore to append mode for uc_hook_add()
+        uc->hook_insert = 0;
         if (err != UC_ERR_OK) {
             return err;
         }
@@ -1043,9 +1049,16 @@ uc_err uc_hook_add(uc_engine *uc, uc_hook *hh, int type, void *callback,
             }
         }
 
-        if (list_append(&uc->hook[UC_HOOK_INSN_IDX], hook) == NULL) {
-            free(hook);
-            return UC_ERR_NOMEM;
+        if (uc->hook_insert) {
+            if (list_insert(&uc->hook[UC_HOOK_INSN_IDX], hook) == NULL) {
+                free(hook);
+                return UC_ERR_NOMEM;
+            }
+        } else {
+            if (list_append(&uc->hook[UC_HOOK_INSN_IDX], hook) == NULL) {
+                free(hook);
+                return UC_ERR_NOMEM;
+            }
         }
 
         hook->refs++;
@@ -1056,11 +1069,20 @@ uc_err uc_hook_add(uc_engine *uc, uc_hook *hh, int type, void *callback,
         if ((type >> i) & 1) {
             // TODO: invalid hook error?
             if (i < UC_HOOK_MAX) {
-                if (list_append(&uc->hook[i], hook) == NULL) {
-                    if (hook->refs == 0) {
-                        free(hook);
+                if (uc->hook_insert) {
+                    if (list_insert(&uc->hook[i], hook) == NULL) {
+                        if (hook->refs == 0) {
+                            free(hook);
+                        }
+                        return UC_ERR_NOMEM;
+                    }
+                } else {
+                    if (list_append(&uc->hook[i], hook) == NULL) {
+                        if (hook->refs == 0) {
+                            free(hook);
+                        }
+                        return UC_ERR_NOMEM;
                     }
-                    return UC_ERR_NOMEM;
                 }
                 hook->refs++;
             }