This is all "#if defined(__i386__) && __GNUC__ >= 2":

Add support for GCC's --test-coverage --profile-arcs options.

Add code to call the functions listed in the .ctors section, these are
used to string the per .o file counter blocks into a linked list.

Add empty __bb_fork_func() to cope with GCC magic gandling of exec*()
named functions.

To add support for other platforms should be trivial, but involves
determining the exact data-types gcc uses on that platform.

1 files changed, 47 insertions, 0 deletions

diff --git a/sys/kern/subr_prof.c b/sys/kern/subr_prof.c
index 479d953..adb6147 100644
--- a/sys/kern/subr_prof.c
+++ b/sys/kern/subr_prof.c
@@ -157,6 +157,7 @@ kmstartup(dummy)
 	uintfptr_t tmp_addr;
 #endif
 
+	tcov_init();
 	/*
 	 * Round lowpc and highpc to multiples of the density we're using
 	 * so the rest of the scaling (here and in gprof) stays in ints.
@@ -531,3 +532,49 @@ addupc_task(ke, pc, ticks)
 	}
 	stopprofclock(p);
 }
+
+#if defined(__i386__) && __GNUC__ >= 2
+/*
+ * Support for "--test-coverage --profile-arcs" in GCC.
+ *
+ * We need to call all the functions in the .ctor section, in order
+ * to get all the counter-arrays strung into a list.
+ *
+ * XXX: the .ctors call __bb_init_func which is located in over in 
+ * XXX: i386/i386/support.s for historical reasons.  There is probably
+ * XXX: no reason for that to be assembler anymore, but doing it right
+ * XXX: in MI C code requires one to reverse-engineer the type-selection
+ * XXX: inside GCC.  Have fun.
+ *
+ * XXX: Worrisome perspective: Calling the .ctors may make C++ in the
+ * XXX: kernel feasible.  Don't.
+ */
+typedef void (*ctor_t)(void);
+extern ctor_t _start_ctors, _stop_ctors;
+
+static void
+tcov_init(void *foo __unused)
+{
+	ctor_t *p, q;
+
+	for (p = &_start_ctors; p < &_stop_ctors; p++) {
+		q = *p;
+		q();
+	}
+}
+
+SYSINIT(kmem, SI_SUB_KPROF, SI_ORDER_SECOND, tcov_init, NULL)
+
+/*
+ * GCC contains magic to recognize calls to for instance execve() and
+ * puts in calls to this function to preserve the profile counters.
+ * XXX: Put zinging punchline here.
+ */
+void __bb_fork_func(void);
+void
+__bb_fork_func(void)
+{
+}
+
+#endif
+