linux-kernel - [PATCH] x86: vdso: change time() prototype to match __vdso

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Message-Id: <20171204150203.852959-1-arnd@arndb.de>
Date:   Mon,  4 Dec 2017 16:01:55 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:     Arnd Bergmann <arnd@...db.de>, Mark Rutland <mark.rutland@....com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86: vdso: change time() prototype to match __vdso_time()

gcc-8 warns that time() is an alias for __vdso_time() but the two
have different prototypes:

arch/x86/entry/vdso/vclock_gettime.c:327:5: error: 'time' alias between functions of incompatible types 'int(time_t *)' {aka 'int(long int *)'} and 'time_t(time_t *)' {aka 'long int(long int *)'} [-Werror=attribute-alias]
 int time(time_t *t)
     ^~~~
arch/x86/entry/vdso/vclock_gettime.c:318:16: note: aliased declaration here

I could not figure out whether this is intentional, but I see that
changing it to return time_t avoids the warning.

Returning 'int' from time() is also a bit questionable, as it causes an
overflow in y2038 even on 64-bit architectures that use a 64-bit time_t
type. On 32-bit architecture with 64-bit time_t, time() should always
be implement by the C library by calling a (to be added) clock_gettime()
variant that takes a sufficiently wide argument.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/entry/vdso/vclock_gettime.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index b179d73c53bf..ebd1ab0b21a2 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -324,5 +324,5 @@ notrace time_t __vdso_time(time_t *t)
 		*t = result;
 	return result;
 }
-int time(time_t *t)
+time_t time(time_t *t)
 	__attribute__((weak, alias("__vdso_time")));
-- 
2.9.0