linux-kernel - [PATCH RFC v8 09/10] kselftest: save-and-restore errno to allow for %m formatting

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Message-Id: <20190520133305.11925-10-cyphar@cyphar.com>
Date:   Mon, 20 May 2019 23:33:04 +1000
From:   Aleksa Sarai <cyphar@...har.com>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...nel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     Aleksa Sarai <cyphar@...har.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Drysdale <drysdale@...gle.com>,
        Chanho Min <chanho.min@....com>,
        Oleg Nesterov <oleg@...hat.com>, Aleksa Sarai <asarai@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        containers@...ts.linux-foundation.org,
        linux-kselftest@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [PATCH RFC v8 09/10] kselftest: save-and-restore errno to allow for %m formatting

Previously, using "%m" in a ksft_* format string can result in strange
output because the errno value wasn't saved before calling other libc
functions. The solution is to simply save and restore the errno before
we format the user-supplied format string.

Signed-off-by: Aleksa Sarai <cyphar@...har.com>
---
 tools/testing/selftests/kselftest.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index 47e1d995c182..ce049af7415b 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -10,6 +10,7 @@
 #ifndef __KSELFTEST_H
 #define __KSELFTEST_H
 
+#include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdarg.h>
@@ -72,58 +73,68 @@ static inline void ksft_print_cnts(void)
 
 static inline void ksft_print_msg(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	va_start(args, msg);
 	printf("# ");
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 }
 
 static inline void ksft_test_result_pass(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	ksft_cnt.ksft_pass++;
 
 	va_start(args, msg);
 	printf("ok %d ", ksft_test_num());
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 }
 
 static inline void ksft_test_result_fail(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	ksft_cnt.ksft_fail++;
 
 	va_start(args, msg);
 	printf("not ok %d ", ksft_test_num());
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 }
 
 static inline void ksft_test_result_skip(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	ksft_cnt.ksft_xskip++;
 
 	va_start(args, msg);
 	printf("ok %d # skip ", ksft_test_num());
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 }
 
 static inline void ksft_test_result_error(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	ksft_cnt.ksft_error++;
 
 	va_start(args, msg);
 	printf("not ok %d # error ", ksft_test_num());
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 }
@@ -143,10 +154,12 @@ static inline int ksft_exit_fail(void)
 
 static inline int ksft_exit_fail_msg(const char *msg, ...)
 {
+	int saved_errno = errno;
 	va_list args;
 
 	va_start(args, msg);
 	printf("Bail out! ");
+	errno = saved_errno;
 	vprintf(msg, args);
 	va_end(args);
 
@@ -169,10 +182,12 @@ static inline int ksft_exit_xpass(void)
 static inline int ksft_exit_skip(const char *msg, ...)
 {
 	if (msg) {
+		int saved_errno = errno;
 		va_list args;
 
 		va_start(args, msg);
 		printf("1..%d # Skipped: ", ksft_test_num());
+		errno = saved_errno;
 		vprintf(msg, args);
 		va_end(args);
 	} else {
-- 
2.21.0