netdev - [PATCH net-next v3 2/8] selftests/net: Provide test

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Message-Id: <20240815-tcp-ao-selftests-upd-6-12-v3-2-7bd2e22bb81c@gmail.com>
Date: Thu, 15 Aug 2024 22:32:27 +0100
From: Dmitry Safonov via B4 Relay <devnull+0x7f454c46.gmail.com@...nel.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>
Cc: Mohammad Nassiri <mnassiri@...na.com>, netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Dmitry Safonov <0x7f454c46@...il.com>
Subject: [PATCH net-next v3 2/8] selftests/net: Provide test_snprintf()
 helper

From: Dmitry Safonov <0x7f454c46@...il.com>

Instead of pre-allocating a fixed-sized buffer of TEST_MSG_BUFFER_SIZE
and printing into it, call vsnprintf() with str = NULL, which will
return the needed size of the buffer. This hack is documented in
man 3 vsnprintf.

Essentially, in C++ terms, it re-invents std::stringstream, which is
going to be used to print different tracing paths and formatted strings.
Use it straight away in __test_print() - which is thread-safe version of
printing in selftests.

Signed-off-by: Dmitry Safonov <0x7f454c46@...il.com>
---
 tools/testing/selftests/net/tcp_ao/lib/aolib.h | 59 ++++++++++++++++++++++----
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_ao/lib/aolib.h b/tools/testing/selftests/net/tcp_ao/lib/aolib.h
index fbc7f6111815..60a63419cabb 100644
--- a/tools/testing/selftests/net/tcp_ao/lib/aolib.h
+++ b/tools/testing/selftests/net/tcp_ao/lib/aolib.h
@@ -37,17 +37,58 @@ extern void __test_xfail(const char *buf);
 extern void __test_error(const char *buf);
 extern void __test_skip(const char *buf);

-__attribute__((__format__(__printf__, 2, 3)))
-static inline void __test_print(void (*fn)(const char *), const char *fmt, ...)
+static inline char *test_snprintf(const char *fmt, va_list vargs)
 {
-#define TEST_MSG_BUFFER_SIZE 4096
-	char buf[TEST_MSG_BUFFER_SIZE];
-	va_list arg;
+	char *ret = NULL;
+	size_t size = 0;
+	va_list tmp;
+	int n = 0;

-	va_start(arg, fmt);
-	vsnprintf(buf, sizeof(buf), fmt, arg);
-	va_end(arg);
-	fn(buf);
+	va_copy(tmp, vargs);
+	n = vsnprintf(ret, size, fmt, tmp);
+	if (n < 0)
+		return NULL;
+
+	size = (size_t) n + 1;
+	ret = malloc(size);
+	if (ret == NULL)
+		return NULL;
+
+	n = vsnprintf(ret, size, fmt, vargs);
+	if (n < 0 || n > size - 1) {
+		free(ret);
+		return NULL;
+	}
+	return ret;
+}
+
+static __printf(1, 2) inline char *test_sprintf(const char *fmt, ...)
+{
+	va_list vargs;
+	char *ret;
+
+	va_start(vargs, fmt);
+	ret = test_snprintf(fmt, vargs);
+	va_end(vargs);
+
+	return ret;
+}
+
+static __printf(2, 3) inline void __test_print(void (*fn)(const char *),
+					       const char *fmt, ...)
+{
+	va_list vargs;
+	char *msg;
+
+	va_start(vargs, fmt);
+	msg = test_snprintf(fmt, vargs);
+	va_end(vargs);
+
+	if (!msg)
+		return;
+
+	fn(msg);
+	free(msg);
 }

 #define test_print(fmt, ...)						\

-- 
2.42.2