Turn interpositions into macro, implement for read, write

Symbi-OS · Nov 15, 2022 · 42f26a6 · 42f26a6
1 parent d6d5c93
commit 42f26a6
Show file tree

Hide file tree

Showing 2 changed files with 31 additions and 107 deletions.
diff --git a/bin/shortcut/sc_lib.c b/bin/shortcut/sc_lib.c
@@ -271,107 +271,6 @@ void egress_work(struct fn_ctrl *ctrl) {
 }
 
 // This macro allocates a "real_" fn ptr, a "ksys_" fn ptr, and a fn_ctrl struct
-MAKE_STRUCTS(write, ssize_t (*write_t)(int fd, const void *buf, size_t count))
-MAKE_STRUCTS(read, ssize_t  (*read_t)(int fd, void *buf, size_t count))
-
-MAKE_INTERPOSE_FN(write, ssize_t, (int fd, const void *buf, size_t count))
-
-
-
-  // This is awkward, but it is an effort to minimize the scope of differences
-  // btw fns.
-
-  // Pointer to the ctrl struct.
-  // struct fn_ctrl *ctrl = &write_ctrl;
-
-  // Shortcut fn has same signature as write
-  // typedef write_t shortcut_fn_t;
-
-  // typedef int (*shortcut_fn_t)(unsigned int fd, const char *buf, size_t
-  // count);
-  typedef write_t real_fn_t;
-
-  // Pointer to real_write, generic version
-  real_fn_t *real_fn = &real_write;
-
-  // Pointer to shortcut_write, generic version
-  // shortcut_fn_t *shortcut_fn = &ksys_write;
-
-  // String name of shortcut target
-  char *shortcut_target = "ksys_write";
-
-  // If real_write is null, get it from dlsym
-  if (! real_write) {
-    // Place to do one time work
-    // Configs ctrl struct with envt variables, gets ptrs to real and shortcut
-    // fns
-    get_fn_config_and_targets(&write_ctrl, (void **)real_fn, (void **) &ksys_write,
-                              shortcut_target, __func__);
-  }
-
-  // Pre fn work e.g. elevation
-  ingress_work(&write_ctrl);
-
-  int ret;
-  // Call real write
-  if (write_ctrl.do_shortcut) {
-    // Awkward, but we have to deref the ptr to the fn ptr
-    ret = ksys_write(fd, buf, count);
-  } else {
-    ret = (*real_fn)(fd, buf, count);
-  }
-
-  egress_work(&write_ctrl);
-
-  return ret;
-}
-
-ssize_t read(int fd, void *buf, size_t len) {
-
-  // This is awkward, but it is an effort to minimize the scope of differences
-  // btw fns.
-
-  // Pointer to the ctrl struct.
-  struct fn_ctrl *ctrl = &read_ctrl;
-
-  // Shortcut fn has same signature as write
-  typedef read_t shortcut_fn_t;
-
-  // typedef int (*shortcut_fn_t)(unsigned int fd, const char *buf, size_t
-  // count);
-  typedef read_t real_fn_t;
-
-  // Pointer to real_write, generic version
-  real_fn_t *real_fn = &real_read;
-
-  // Pointer to shortcut_write, generic version
-  shortcut_fn_t *shortcut_fn = &ksys_read;
-
-  // String name of shortcut target
-  char *shortcut_target = "ksys_read";
-
-  // If real_write is null, get it from dlsym
-  if (!(*real_fn)) {
-    // Place to do one time work
-    // Configs ctrl struct with envt variables, gets ptrs to real and shortcut
-    // fns
-    get_fn_config_and_targets(ctrl, (void **)real_fn, (void **)shortcut_fn,
-                              shortcut_target, __func__);
-  }
-
-  // Pre fn work e.g. elevation
-  ingress_work(ctrl);
-
-  int ret;
-  // Call real write
-  if (ctrl->do_shortcut) {
-    // Awkward, but we have to deref the ptr to the fn ptr
-    ret = (*shortcut_fn)(fd, buf, len);
-  } else {
-    ret = (*real_fn)(fd, buf, len);
-  }
-
-  egress_work(ctrl);
-
-  return ret;
-}
+// Then it implements the relevant interposer fn.
+MAKE_STRUCTS_AND_FN(write, ssize_t, int, fd, const void *, buf, size_t, count)
+MAKE_STRUCTS_AND_FN(read, ssize_t, int, fd, void *, buf, size_t, count)
diff --git a/bin/shortcut/sc_lib.h b/bin/shortcut/sc_lib.h
@@ -7,6 +7,10 @@
 #include <stdbool.h>
 
 // Struct that contains all flags for function interposition
+
+// HACK: huge hack to toggle shortcut
+int master_toggle_shortcut = 0;
+
 struct fn_ctrl {
   // Do we need to run a pre/post condition around fn call?
   bool sandwich_fn;
@@ -26,10 +30,31 @@ struct fn_ctrl {
     struct fn_ctrl fn_name##_ctrl = {0, 0, 0, 0}; \
     fn_name##_t ksys_##fn_name = NULL;
 
-#define MAKE_INTERPOSE_FN(fn_name, ret_t, args) \
-    ret_t fn_name args { 
+  // If real_write is null, get it from dlsym
+  // Place to do one time work
+  // Configs ctrl struct with envt variables, gets ptrs to real and shortcut
+
+#define MAKE_INTERPOSE_FN(fn_name, ret_t, t_1, arg_1, t_2, arg_2, t_3, arg_3 ) \
+    ret_t fn_name ( t_1 arg_1, t_2 arg_2, t_3 arg_3 ) { \
+  if (! real_##fn_name ) { \
+    get_fn_config_and_targets(& fn_name##_ctrl, (void **)&real_##fn_name, (void **) &ksys_##fn_name, \
+                              "ksys_"#fn_name, __func__); \
+  } \
+  ingress_work(&fn_name##_ctrl); \
+  int ret; \
+  if (fn_name##_ctrl.do_shortcut ^ master_toggle_shortcut) { \
+    ret = ksys_##fn_name( arg_1, arg_2, arg_3 ); \
+  } else { \
+    ret = real_##fn_name( arg_1, arg_2, arg_3 ); \
+  } \
+  egress_work(&fn_name##_ctrl); \
+  return ret;\
+}
 
-    void fn(){};
+// Combine both structs, variables and fn
+#define MAKE_STRUCTS_AND_FN(fn_name, ret_t, t_1, arg_1, t_2, arg_2, t_3, arg_3 ) \
+    MAKE_STRUCTS(fn_name, ret_t (*fn_name##_t) ( t_1 arg_1, t_2 arg_2, t_3 arg_3) ) \
+    MAKE_INTERPOSE_FN(fn_name, ret_t, t_1, arg_1, t_2, arg_2, t_3, arg_3)
 
 
 #endif