Implement GCC code coverage analysis

In order to provide some insight on what code is executed during
coreboot's run time and how well our test scenarios work, this
adds code coverage support to coreboot's ram stage. This should
be easily adaptable for payloads, and maybe even romstage.

See http://gcc.gnu.org/onlinedocs/gcc/Gcov.html for
more information.

To instrument coreboot, select CONFIG_COVERAGE ("Code coverage
support") in Kconfig, and recompile coreboot. coreboot will then
store its code coverage information into CBMEM, if possible.
Then, run "cbmem -CV" as root on the target system running the
instrumented coreboot binary. This will create a whole bunch of
.gcda files that contain coverage information. Tar them up, copy
them to your build system machine, and untar them. Then you can
use your favorite coverage utility (gcov, lcov, ...) to visualize
code coverage.

For a sneak peak of what will expect you, please take a look
at http://www.coreboot.org/~stepan/coreboot-coverage/

Change-Id: Ib287d8309878a1f5c4be770c38b1bc0bb3aa6ec7
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2052
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Martin Roth <martin@se-eng.com>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 177 insertions, 0 deletions

diff --git a/documentation/gcov.txt b/documentation/gcov.txt
new file mode 100644
index 0000000000..795f827707
--- /dev/null
+++ b/documentation/gcov.txt
@@ -0,0 +1,177 @@
+This patch contains our local modifications for gcov-io.h and libgcov.c.
+The file gcov-iov.h is taken from a gcc build (produced at compile
+time). The file gcov-io.c is unchanged.
+
+--- gcc-4.7.2/gcc/gcov-io.h	2011-12-04 10:27:19.000000000 -0800
++++ coreboot/src/lib/gcov-io.h	2013-01-09 15:29:19.000000000 -0800
+@@ -163,6 +163,24 @@
+ #ifndef GCC_GCOV_IO_H
+ #define GCC_GCOV_IO_H
+ 
++#ifdef __COREBOOT__
++#define GCOV_LINKAGE /* nothing */
++/* We need the definitions for
++    BITS_PER_UNIT and
++    LONG_LONG_TYPE_SIZE
++   They are defined in gcc/defaults.h and gcc/config/<arch_depend_files>
++   (like, gcc/config/i386/i386.h). And it can be overridden by setting
++   in build scripts. Here I hardcoded the value for x86. */
++#define BITS_PER_UNIT 8
++#define LONG_LONG_TYPE_SIZE 64
++
++/* There are many gcc_assertions. Set the vaule to 1 if we want a warning
++   message if the assertion fails.  */
++#ifndef ENABLE_ASSERT_CHECKING
++#define ENABLE_ASSERT_CHECKING 1
++#endif
++#endif /* __COREBOOT__ */
++
+ #if IN_LIBGCOV
+ /* About the target */
+ 
+@@ -232,7 +250,9 @@
+    is not also used in a DSO.  */
+ #if IN_LIBGCOV
+ 
++#ifndef __COREBOOT__
+ #include "tconfig.h"
++#endif /* __COREBOOT__ */
+ 
+ #define gcov_var __gcov_var
+ #define gcov_open __gcov_open
+@@ -455,8 +475,10 @@
+ /* Register a new object file module.  */
+ extern void __gcov_init (struct gcov_info *) ATTRIBUTE_HIDDEN;
+ 
++#ifndef __COREBOOT__
+ /* Called before fork, to avoid double counting.  */
+ extern void __gcov_flush (void) ATTRIBUTE_HIDDEN;
++#endif
+ 
+ /* The merge function that just sums the counters.  */
+ extern void __gcov_merge_add (gcov_type *, unsigned) ATTRIBUTE_HIDDEN;
+--- gcc-4.7.2/libgcc/libgcov.c	2012-01-11 10:50:21.000000000 -0800
++++ coreboot/src/lib/libgcov.c	2013-01-09 15:32:37.000000000 -0800
+@@ -25,12 +25,41 @@
+ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+ <http://www.gnu.org/licenses/>.  */
+ 
++#define __COREBOOT__
++#ifdef __COREBOOT__
++#include <stdlib.h>
++#include <string.h>
++#include <console/console.h>
++#include <assert.h>
++typedef s32 pid_t;
++#define gcc_assert(x) ASSERT(x)
++#define fprintf(file, x...) printk(BIOS_ERR, x)
++#define alloca(size)   __builtin_alloca (size)
++#include "gcov-glue.c"
++
++/* Define MACROs to be used by coreboot compilation.  */
++# define L_gcov
++# define L_gcov_interval_profiler
++# define L_gcov_pow2_profiler
++# define L_gcov_one_value_profiler
++# define L_gcov_indirect_call_profiler
++# define L_gcov_average_profiler
++# define L_gcov_ior_profiler
++
++# define HAVE_CC_TLS 0
++# define __GCOV_KERNEL__
++
++# define IN_LIBGCOV 1
++# define IN_GCOV 0
++#else /* __COREBOOT__ */
+ #include "tconfig.h"
+ #include "tsystem.h"
+ #include "coretypes.h"
+ #include "tm.h"
+ #include "libgcc_tm.h"
++#endif /* __COREBOOT__ */
+ 
++#ifndef __COREBOOT__
+ #if defined(inhibit_libc)
+ #define IN_LIBGCOV (-1)
+ #else
+@@ -41,6 +70,7 @@
+ #define GCOV_LINKAGE /* nothing */
+ #endif
+ #endif
++#endif /* __COREBOOT__ */
+ #include "gcov-io.h"
+ 
+ #if defined(inhibit_libc)
+@@ -68,12 +98,17 @@
+ 
+ #else
+ 
++#ifndef __COREBOOT__
+ #include <string.h>
+ #if GCOV_LOCKED
+ #include <fcntl.h>
+ #include <errno.h>
+ #include <sys/stat.h>
+ #endif
++#else
++void __gcov_merge_add(gcov_type *counters  __attribute__ ((unused)),
++			unsigned n_counters __attribute__ ((unused))) {}
++#endif /* __COREBOOT__ */
+ 
+ #ifdef L_gcov
+ #include "gcov-io.c"
+@@ -99,6 +134,10 @@
+ static int
+ create_file_directory (char *filename)
+ {
++#ifdef __COREBOOT__
++  (void) filename;
++  return 0;
++#else
+ #if !defined(TARGET_POSIX_IO) && !defined(_WIN32)
+   (void) filename;
+   return -1;
+@@ -137,6 +176,7 @@
+       };
+   return 0;
+ #endif
++#endif
+ }
+ 
+ static struct gcov_fn_buffer *
+@@ -279,7 +319,7 @@
+   struct gcov_ctr_summary *cs_ptr;
+   const struct gcov_ctr_info *ci_ptr;
+   unsigned t_ix;
+-  int f_ix;
++  int f_ix = 0;
+   gcov_unsigned_t c_num;
+   const char *gcov_prefix;
+   int gcov_prefix_strip = 0;
+@@ -329,6 +369,7 @@
+ 	}
+     }
+ 
++#ifndef __COREBOOT__
+   {
+     /* Check if the level of dirs to strip off specified. */
+     char *tmp = getenv("GCOV_PREFIX_STRIP");
+@@ -352,6 +393,7 @@
+ 	prefix_length--;
+     }
+   else
++#endif
+     prefix_length = 0;
+ 
+   /* If no prefix was specified and a prefix stip, then we assume
+@@ -696,8 +738,10 @@
+       if (filename_length > gcov_max_filename)
+         gcov_max_filename = filename_length;
+ 
++#ifndef __COREBOOT__
+       if (!gcov_list)
+ 	atexit (gcov_exit);
++#endif
+ 
+       info->next = gcov_list;
+       gcov_list = info;