Use arrays to store syscalls

Uses arrays to store configured syscalls to ensure easier memory
management and stop syscall-interceptor from segfaulting if too many
calls are configured

Author: axtloss

parse_config.py

@@ -50,11 +50,13 @@
 }} syscall_default = {{NULL, -1, false, false, NULL, -1, 0, false, NULL, -1, 0, false, NULL, -1, 0, false, NULL, -1, 0, false, NULL, -1, 0, false, NULL, -1, 0, false, NULL, NULL}};
 
 typedef struct conf_syscall conf_syscall;
+const int calls_size = {CALLLEN};
+conf_syscall calls[{CALLLEN}];
+int finishInit = 0;
 
-conf_syscall *
-get_calls() {{
+void get_calls() {{
 {PYSTRUCTBUILD}
-return {FIRSTVARNAME};
+finishInit = 1;
 }};
 """
 
@@ -67,8 +69,7 @@
     "set_arg_long": '{varname}->{argname}_long = {arg};\n',
     "set_arg_matchtype": '{varname}->{argname}_matchtype = {matchtype};\n',
     "set_arg_isfdesc": '{varname}->{argname}_fdesc = {isfdesc};\n',
-    "set_next": "{varname}->next = {nextcall};\n",
-    "set_prev": "{varname}->prev = {prevcall};\n",
+    "set_array": "calls[{num}] = *{varname};\n",
 }
 
 
@@ -205,39 +206,15 @@ def build_c_code(self) -> str:
             i = i - 1
             c_structs = c_structs + "\n"
 
-        linked_list_setup: str = ""
-        if len(self.syscalls) == 1:
-            linked_list_setup = linked_list_setup + structbuild_template["set_next"].format(varname="call1", nextcall="NULL")
-            linked_list_setup = linked_list_setup + structbuild_template["set_prev"].format(varname="call1", prevcall="NULL")
-        else:
-            for i in range(1, len(self.syscalls) + 1):
-                if i == 1:
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_next"
-                    ].format(varname="call" + str(i), nextcall="call" + str(i + 1))
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_prev"
-                    ].format(varname="call" + str(i), prevcall="NULL")
-                elif i == len(self.syscalls):
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_prev"
-                    ].format(varname="call" + str(i), prevcall="call" + str(i - 1))
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_next"
-                    ].format(varname="call" + str(i), nextcall="NULL")
-                else:
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_prev"
-                    ].format(varname="call" + str(i), prevcall="call" + str(i - 1))
-                    linked_list_setup = linked_list_setup + structbuild_template[
-                        "set_next"
-                    ].format(varname="call" + str(i), nextcall="call" + str(i + 1))
-
-        c_structs = c_structs + linked_list_setup
+        call_arr_setup: str = ""
+        for i in range(0, len(self.syscalls)):
+            call_arr_setup = call_arr_setup + structbuild_template["set_array"].format(num=str(i), varname="call"+str(i+1))
+
+        c_structs = c_structs + call_arr_setup
         c_code = header_template.format(
             PYLOGFILE=self.log_file,
             PYSTRUCTBUILD=c_structs,
-            FIRSTVARNAME="call1",
+            CALLLEN=len(self.syscalls),
         )
         return c_code
 

src/main.c

@@ -41,7 +41,6 @@ argcmp(int matchtype, long config_arg_long, char *config_arg_char, long sys_arg)
             default:
                 return_val = false;
         }
-
     return return_val;
 }
 
@@ -188,24 +187,22 @@ log_call(conf_syscall * call)
 static int
 hook(long syscall_number, long arg0, long arg1, long arg2, long arg3, long arg4, long arg5, long *result)
 {
-    conf_syscall *call = get_calls ();
-    while (true)
+    if (finishInit == 0)
+        get_calls ();
+    for (int i=0; i < calls_size; i++)
     {
-        if (call->callnum == syscall_number && match_args (call, arg0, arg1, arg2, arg3, arg4, arg5))
+        if (calls[i].callnum == syscall_number && match_args (&calls[i], arg0, arg1, arg2, arg3, arg4, arg5))
         {
-            if (call->log)
-                log_call (call);
-            if (call->block)
+            if (calls[i].log)
+                log_call (&calls[i]);
+            if (calls[i].block)
             {
                 *result = -ENOTSUP;
                 return 0;
             }
         }
-        if (!call->next)
-            return 1;
-
-        call = call->next;
     }
+    return 1;
 }
 
 static __attribute__ ((constructor))