programs: make the test programs show libfsverity error messages

Signed-off-by: Eric Biggers <ebiggers@google.com>

programs/fsverity.c

@@ -200,16 +200,11 @@ u32 get_default_block_size(void)
 	return n;
 }
 
-static void print_libfsverity_error(const char *msg)
-{
-	error_msg("%s", msg);
-}
-
 int main(int argc, char *argv[])
 {
 	const struct fsverity_command *cmd;
 
-	libfsverity_set_error_callback(print_libfsverity_error);
+	install_libfsverity_error_handler();
 
 	if (argc < 2) {
 		error_msg("no command specified");

programs/test_compute_digest.c

@@ -4,6 +4,7 @@
  *
  * Copyright 2020 Google LLC
  */
+
 #include "utils.h"
 
 #define SHA256_DIGEST_SIZE 32
@@ -43,6 +44,8 @@ int main(void)
 		"\x86\x52";
 	int err;
 
+	install_libfsverity_error_handler();
+
 	f.data = xmalloc(f.size);
 	for (i = 0; i < f.size; i++)
 		f.data[i] = (i % 11) + (i % 439) + (i % 1103);

programs/test_hash_algs.c

@@ -4,6 +4,7 @@
  *
  * Copyright 2020 Google LLC
  */
+
 #include "utils.h"
 
 #define SHA256_DIGEST_SIZE 32
@@ -11,6 +12,8 @@
 
 int main(void)
 {
+	install_libfsverity_error_handler();
+
 	ASSERT(libfsverity_get_digest_size(0) == -1);
 	ASSERT(libfsverity_get_hash_name(0) == NULL);
 	ASSERT(libfsverity_find_hash_alg_by_name("bad") == 0);

programs/test_sign_digest.c

@@ -4,6 +4,7 @@
  *
  * Copyright 2020 Google LLC
  */
+
 #include "utils.h"
 
 #include <fcntl.h>
@@ -24,6 +25,8 @@ int main(void)
 	u64 expected_sig_size;
 	int err;
 
+	install_libfsverity_error_handler();
+
 	d->digest_algorithm = FS_VERITY_HASH_ALG_SHA256;
 	d->digest_size = SHA256_DIGEST_SIZE;
 	memcpy(d->digest,

programs/utils.c

@@ -84,6 +84,16 @@ __noreturn void assertion_failed(const char *expr, const char *file, int line)
 	fatal_error("Assertion failed: %s at %s:%d", expr, file, line);
 }
 
+static void print_libfsverity_error(const char *msg)
+{
+	error_msg("%s", msg);
+}
+
+void install_libfsverity_error_handler(void)
+{
+	libfsverity_set_error_callback(print_libfsverity_error);
+}
+
 /* ========== File utilities ========== */
 
 bool open_file(struct filedes *file, const char *filename, int flags, int mode)

programs/utils.h

@@ -27,6 +27,8 @@ __cold __noreturn void assertion_failed(const char *expr,
 
 #define ASSERT(e) ({ if (!(e)) assertion_failed(#e, __FILE__, __LINE__); })
 
+void install_libfsverity_error_handler(void);
+
 struct filedes {
 	int fd;
 	char *name;		/* filename, for logging or error messages */