VPP API: Memory trace

if you plan to put a hash into shared memory, the key sum and key
equal functions MUST be set to constants such as KEY_FUNC_STRING,
KEY_FUNC_MEM, etc. -lvppinfra is PIC, which means that the process
which set up the hash won't have the same idea where the key sum and
key compare functions live in other processes.

Change-Id: Ib3b5963a0d2fb467b91e1f16274df66ac74009e9
Signed-off-by: Ole Troan <ot@cisco.com>
Signed-off-by: Dave Barach <dave@barachs.net>
Signed-off-by: Ole Troan <ot@cisco.com>

4 files changed, 27 insertions, 3 deletions

diff --git a/src/vppinfra/hash.c b/src/vppinfra/hash.c
index 79103b6d3f4..abc7c4ce4a2 100644
--- a/src/vppinfra/hash.c
+++ b/src/vppinfra/hash.c
@@ -282,6 +282,10 @@ key_sum (hash_t * h, uword key)
       sum = string_key_sum (h, key);
       break;
 
+    case KEY_FUNC_MEM:
+      sum = mem_key_sum (h, key);
+      break;
+
     default:
       sum = h->key_sum (h, key);
       break;
@@ -312,6 +316,10 @@ key_equal1 (hash_t * h, uword key1, uword key2, uword e)
       e = string_key_equal (h, key1, key2);
       break;
 
+    case KEY_FUNC_MEM:
+      e = mem_key_equal (h, key1, key2);
+      break;
+
     default:
       e = h->key_equal (h, key1, key2);
       break;
diff --git a/src/vppinfra/hash.h b/src/vppinfra/hash.h
index 21986ea774c..de155e6ac1c 100644
--- a/src/vppinfra/hash.h
+++ b/src/vppinfra/hash.h
@@ -77,6 +77,7 @@ typedef struct hash_header
 #define KEY_FUNC_POINTER_UWORD	(1)	/*< sum = *(uword *) key */
 #define KEY_FUNC_POINTER_U32	(2)	/*< sum = *(u32 *) key */
 #define KEY_FUNC_STRING         (3)	/*< sum = string_key_sum, etc. */
+#define KEY_FUNC_MEM		(4)	/*< sum = mem_key_sum */
 
   /* key comparison function */
   hash_key_equal_function_t *key_equal;
@@ -672,6 +673,20 @@ extern uword string_key_sum (hash_t * h, uword key);
 extern uword string_key_equal (hash_t * h, uword key1, uword key2);
 extern u8 *string_key_format_pair (u8 * s, va_list * args);
 
+/*
+ * Note: if you plan to put a hash into shared memory,
+ * the key sum and key equal functions MUST be set to magic constants!
+ * PIC means that whichever process sets up the hash won't have
+ * the actual key sum functions at the same place, leading to
+ * very hard-to-find bugs...
+ */
+
+#define hash_create_shmem(elts,key_bytes,value_bytes)           \
+  hash_create2((elts),(key_bytes),(value_bytes),                \
+               (hash_key_sum_function_t *) KEY_FUNC_MEM,        \
+               (hash_key_equal_function_t *)KEY_FUNC_MEM,       \
+               0, 0)
+
 #define hash_create_string(elts,value_bytes)                    \
   hash_create2((elts),0,(value_bytes),                          \
                (hash_key_sum_function_t *) KEY_FUNC_STRING,     \
diff --git a/src/vppinfra/mheap.c b/src/vppinfra/mheap.c
index 4d27d419e64..fceca95ff7d 100644
--- a/src/vppinfra/mheap.c
+++ b/src/vppinfra/mheap.c
@@ -1512,7 +1512,7 @@ mheap_get_trace (void *v, uword offset, uword size)
 
   if (!tm->trace_by_callers)
     tm->trace_by_callers =
-      hash_create_mem (0, sizeof (trace.callers), sizeof (uword));
+      hash_create_shmem (0, sizeof (trace.callers), sizeof (uword));
 
   p = hash_get_mem (tm->trace_by_callers, &trace.callers);
   if (p)
diff --git a/src/vppinfra/test_macros.c b/src/vppinfra/test_macros.c
index de8f2c49fc1..05299b38e3f 100644
--- a/src/vppinfra/test_macros.c
+++ b/src/vppinfra/test_macros.c
@@ -26,13 +26,14 @@ test_macros_main (unformat_input_t * input)
   clib_macro_init (mm);
 
   fformat (stdout, "hostname: %s\n",
-	   clib_macro_eval_dollar (mm, "hostname", 1 /* complain */ ));
+	   clib_macro_eval_dollar (mm, (i8 *) "hostname", 1 /* complain */ ));
 
   clib_macro_set_value (mm, "foo", "this is foo which contains $(bar)");
   clib_macro_set_value (mm, "bar", "bar");
 
   fformat (stdout, "evaluate: %s\n",
-	   clib_macro_eval (mm, "returns '$(foo)'", 1 /* complain */ ));
+	   clib_macro_eval (mm, (i8 *) "returns '$(foo)'",
+			    1 /* complain */ ));
 
   clib_macro_free (mm);