core: Add support for code coverage compilation

The code coverage is performed at runtime by keeping in memory
structures holding the releveant data:

In order to generate the code coverage, two steps are required:
 - Instruct the compiler to generate coverage information structure
   and functions to initialize them: flag --coverage.
 - Call the constructors added to initialize the coverage information
   and register them to the libgcov (modification of boot.c)

When an object file (.o) is created with code coverage support, a note
(.gcno) file is created with it. The note file contains informations
used when creating the code coverage report.

The support of code coverage in compiled code increases its size (~15%)
and the compilation time (~25%).

Signed-off-by: Franck LENORMAND <[email protected]>

Author: lenormandfranck

core/arch/arm/kernel/boot.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: BSD-2-Clause
 /*
  * Copyright (c) 2015-2020, Linaro Limited
+ * Copyright 2020 NXP
  */
 
 #include <arm.h>
@@ -202,15 +203,23 @@ static void secondary_init_cntfrq(void)
 }
 #endif
 
-#ifdef CFG_CORE_SANITIZE_KADDRESS
+/*
+ * Gcov needs the constructor to run at init. There is a constructor
+ * function for each function to gather coverage data.
+ * These functions are created automatically by the compiler.
+ * Each constructor function will call __gcov_int() for their function.
+ */
+#if defined(CFG_CORE_SANITIZE_KADDRESS) || defined(CFG_CORE_GCOV_SUPPORT)
 static void init_run_constructors(void)
 {
 	const vaddr_t *ctor;
 
 	for (ctor = &__ctor_list; ctor < &__ctor_end; ctor++)
 		((void (*)(void))(*ctor))();
 }
+#endif /* CFG_CORE_SANITIZE_KADDRESS || CFG_CORE_GCOV_SUPPORT */
 
+#ifdef CFG_CORE_SANITIZE_KADDRESS
 static void init_asan(void)
 {
 
@@ -260,6 +269,9 @@ static void init_asan(void)
 #else /*CFG_CORE_SANITIZE_KADDRESS*/
 static void init_asan(void)
 {
+#ifdef CFG_CORE_GCOV_SUPPORT
+	init_run_constructors();
+#endif
 }
 #endif /*CFG_CORE_SANITIZE_KADDRESS*/
 

core/core.mk

@@ -63,6 +63,12 @@ endif
 cppflags$(sm)	+= -Ildelf/include
 cppflags$(sm)	+= -Ilib/libutee/include
 
+ifeq ($(CFG_CORE_GCOV_SUPPORT),y)
+cppflags$(sm) += --coverage
+cflags$(sm) += --coverage
+aflags$(sm) += --coverage
+endif
+
 ifeq ($(filter y, $(CFG_CORE_DYN_SHM) $(CFG_CORE_RESERVED_SHM)),)
 $(error error: No shared memory configured)
 endif

mk/compile.mk

@@ -9,6 +9,7 @@
 #
 # set	  objs
 # update  cleanfiles
+# update  gcnofiles if CFG_GCOV_SUPPORT is enabled
 #
 # Generates explicit rules for all objs
 
@@ -83,6 +84,15 @@ echo-check-$2 := $(cmd-echo-silent)
 echo-check-cmd-$2 = $(cmd-echo) $$(subst \",\\\",$$(check-cmd-$2))
 endif
 
+ifeq ($(CFG_GCOV_SUPPORT),y)
+ifeq ($$(findstring --coverage, $$(comp-flags-$2)), --coverage)
+gcnofile := $(basename $2).gcno
+cleanfiles := $$(cleanfiles) $(gcnofile)
+gcnofiles := $$(gcnofiles) $(gcnofile)
+$(basename $2).gcno: $2
+endif
+endif
+
 else ifeq ($$(filter %.S,$1),$1)
 comp-q-$2 := AS # one trailing space
 comp-compiler-$2 := $$(CC$(sm))

ta/arch/arm/link.mk

@@ -47,6 +47,10 @@ link-ldflags += --dynamic-list $(link-out-dir$(sm))/dyn_list
 dynlistdep = $(link-out-dir$(sm))/dyn_list
 cleanfiles += $(link-out-dir$(sm))/dyn_list
 
+ifeq ($(CFG_GCOV_SUPPORT),y)
+	libnames += gcov
+endif
+
 link-ldadd  = $(user-ta-ldadd) $(addprefix -L,$(libdirs))
 link-ldadd += --start-group
 link-ldadd += $(addprefix -l,$(libnames))

ta/ta.mk

@@ -83,6 +83,13 @@ endif
 
 base-prefix := $(sm)-
 
+ifeq ($(CFG_GCOV_SUPPORT),y)
+libname = gcov
+libdir = lib/libgcov
+libuuid = a97851f6-c80e-11ea-87d0-0242ac130003
+include mk/lib.mk
+endif
+
 libname = utils
 libdir = lib/libutils
 libuuid = 71855bba-6055-4293-a63f-b0963a737360