[fnrec] Enhance function recording

Enhance the information collected by the function recorder to include
the call site and entry/exit counts.  This allows fnrec.pl to produce
a call tree such as:

    step (from core/getkey.c:46 = 0x17e90) {
      ref_increment (from core/process.c:93 = 0x73ec) { }
      net_step (from core/process.c:96 = 0x73f1) {
        net_poll (from net/netdevice.c:741 = 0xbce6) {
          netdev_poll (from net/netdevice.c:700 = 0xbc58) { }
          netdev_rx_dequeue (from net/netdevice.c:709 = 0xbc65) { }
        }
      }
      ref_decrement (from core/process.c:96 = 0x73f9) { }
    }

Note that inlined functions are reported, confusingly, as extra calls
to the *containing* function.  Minimise this confusion by adding the
attribute "no_instrument_function" to all functions declared as
inline.  (Static functions that have been inlined autonomously by gcc
will still be problematic, but these are far fewer in number.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/compiler.h

@@ -537,6 +537,19 @@ int __debug_disable;
 /** Declare a function to be always inline */
 #define __always_inline __attribute__ (( always_inline ))
 
+/* Force all inline functions to not be instrumented
+ *
+ * This is required to cope with what seems to be a long-standing gcc
+ * bug, in which -finstrument-functions will cause instances of
+ * inlined functions to be reported as further calls to the
+ * *containing* function.  This makes instrumentation very difficult
+ * to use.
+ *
+ * Work around this problem by adding the no_instrument_function
+ * attribute to all inlined functions.
+ */
+#define inline inline __attribute__ (( no_instrument_function ))
+
 /**
  * Shared data.
  *