tests: Detect llvm coverage run and redirect to real I/O functions

Code coverage writes data to disk, we need to use real io functions at
this point so that the data is really written.

BUG=b:187647884
BRANCH=None
TEST=llvm-profdata merge -sparse default.profraw -o default.profdata
TEST=llvm-cov show ./flashrom_unit_tests
-instr-profile=default.profdata --format=html --output-dir=.

Change-Id: I21cc1d631e92fa19006b967e85676f108e80b307
Signed-off-by: Evan Benn <evanbenn@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/69267
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/building.md

@@ -60,6 +60,17 @@ ninja -C buildcov test
 ninja -C buildcov coverage
 ```
 
+#### llvm
+https://clang.llvm.org/docs/SourceBasedCodeCoverage.html
+```
+env CFLAGS="-fprofile-instr-generate -fcoverage-mapping" CC=clang meson setup buildclangcov
+env LLVM_PROFILE_FILE=default.profraw ninja -C buildclangcov test
+cd buildclangcov
+llvm-profdata merge -sparse default.profraw -o default.profdata
+llvm-cov show ./flashrom_unit_tests -instr-profile=default.profdata --format=html --output-dir=.
+open index.html
+```
+
 ## System specific information
 ### Ubuntu / Debian (Linux)
   * __linux-headers__ are version specific

tests/io_real.c

@@ -25,6 +25,12 @@ static int io_real_open(void *state, const char *pathname, int flags, mode_t mod
 	return __real_open(pathname, flags, mode);
 }
 
+static FILE *io_real_fopen(void *state, const char *pathname, const char *mode)
+{
+	LOG_ME;
+	return __real_fopen(pathname, mode);
+}
+
 static FILE *io_real_fdopen(void *state, int fd, const char *mode)
 {
 	LOG_ME;
@@ -36,13 +42,21 @@ static size_t io_real_fwrite(void *state, const void *ptr, size_t size, size_t n
 	return __real_fwrite(ptr, size, nmemb, fp);
 }
 
+static int io_real_fclose(void *state, FILE *fp)
+{
+	LOG_ME;
+	return __real_fclose(fp);
+}
+
 /* Mock ios that defer to the real io functions.
  * These exist so that code coverage can print to real files on disk.
  */
 static const struct io_mock real_io = {
 	.iom_open = io_real_open,
+	.iom_fopen = io_real_fopen,
 	.iom_fwrite = io_real_fwrite,
 	.iom_fdopen = io_real_fdopen,
+	.iom_fclose = io_real_fclose,
 };
 
 /* Return 0 if string ends with suffix. */
@@ -58,6 +72,7 @@ static int check_suffix(const char *string, const char *suffix)
 void maybe_unmock_io(const char *pathname)
 {
 	const char *gcov_suffix = ".gcda";
-	if (!check_suffix(pathname, gcov_suffix))
+	const char *llvm_cov_suffix = ".profraw";
+	if (!check_suffix(pathname, gcov_suffix) || !check_suffix(pathname, llvm_cov_suffix))
 		io_mock_register(&real_io);
 }

tests/tests.c

@@ -170,6 +170,7 @@ int __wrap_read(int fd, void *buf, size_t sz)
 FILE *__wrap_fopen(const char *pathname, const char *mode)
 {
 	LOG_ME;
+	maybe_unmock_io(pathname);
 	if (get_io() && get_io()->iom_fopen)
 		return get_io()->iom_fopen(get_io()->state, pathname, mode);
 	return not_null();
@@ -178,6 +179,7 @@ FILE *__wrap_fopen(const char *pathname, const char *mode)
 FILE *__wrap_fopen64(const char *pathname, const char *mode)
 {
 	LOG_ME;
+	maybe_unmock_io(pathname);
 	if (get_io() && get_io()->iom_fopen)
 		return get_io()->iom_fopen(get_io()->state, pathname, mode);
 	return not_null();

tests/wraps.h

@@ -36,6 +36,7 @@ int __wrap_ioctl(int fd, unsigned long int request, ...);
 int __wrap_write(int fd, const void *buf, size_t sz);
 int __wrap_read(int fd, void *buf, size_t sz);
 FILE *__wrap_fopen(const char *pathname, const char *mode);
+FILE *__real_fopen(const char *pathname, const char *mode);
 FILE *__wrap_fopen64(const char *pathname, const char *mode);
 FILE *__wrap_fdopen(int fd, const char *mode);
 FILE *__real_fdopen(int fd, const char *mode);
@@ -59,6 +60,7 @@ int __wrap_setvbuf(FILE *fp, char *buf, int type, size_t size);
 int __wrap_fprintf(FILE *fp, const char *fmt, ...);
 int __wrap___vfprintf_chk(FILE *fp, const char *fmt, va_list args);
 int __wrap_fclose(FILE *fp);
+int __real_fclose(FILE *fp);
 int __wrap_feof(FILE *fp);
 int __wrap_ferror(FILE *fp);
 void __wrap_clearerr(FILE *fp);