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Message-Id: <a0bd708c70118fd0b767a9fd04c61129c8255f9a.1579196675.git.christophe.leroy@c-s.fr>
In-Reply-To: <cover.1579196675.git.christophe.leroy@c-s.fr>
References: <cover.1579196675.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [RFC PATCH v4 05/11] lib: vdso: allow arches to provide vdso data
 pointer
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, nathanl@linux.ibm.com,
        arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com,
        luto@kernel.org
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
        x86@kernel.org
Date:   Thu, 16 Jan 2020 17:58:29 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On powerpc, __arch_get_vdso_data() clobbers the link register,
requiring the caller to save it.

As the parent function already has to set a stack frame and saves
the link register before calling the C vdso function, retriving the
vdso data pointer there is lighter.

Give arches the opportunity to hand the vdso data pointer
to C vdso functions.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 lib/vdso/gettimeofday.c | 83 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 67 insertions(+), 16 deletions(-)

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index 8b3084d9a3ec..9fa249809399 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -219,9 +219,9 @@ static __always_inline int do_coarse(const struct vdso_data *vd, clockid_t clk,
 }
 
 static __maybe_unused int
-__cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
+__cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t clock,
+			     struct __kernel_timespec *ts)
 {
-	const struct vdso_data *vd = __arch_get_vdso_data();
 	u32 msk;
 
 	/* Check for negative values or invalid clocks */
@@ -246,23 +246,33 @@ __cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
 }
 
 static __maybe_unused int
-__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+__cvdso_clock_gettime_data(const struct vdso_data *vd, clockid_t clock,
+			   struct __kernel_timespec *ts)
 {
-	int ret = __cvdso_clock_gettime_common(clock, ts);
+	int ret = __cvdso_clock_gettime_common(vd, clock, ts);
 
 	if (unlikely(ret))
 		return clock_gettime_fallback(clock, ts);
 	return 0;
 }
 
+static __maybe_unused int
+__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+
+	return __cvdso_clock_gettime_data(vd, clock, ts);
+}
+
 #ifdef BUILD_VDSO32
 static __maybe_unused int
-__cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
+__cvdso_clock_gettime32_data(const struct vdso_data *vd, clockid_t clock,
+			     struct old_timespec32 *res)
 {
 	struct __kernel_timespec ts;
 	int ret;
 
-	ret = __cvdso_clock_gettime_common(clock, &ts);
+	ret = __cvdso_clock_gettime_common(vd, clock, &ts);
 
 	if (unlikely(ret))
 		return clock_gettime32_fallback(clock, res);
@@ -273,13 +283,21 @@ __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
 
 	return ret;
 }
-#endif /* BUILD_VDSO32 */
 
 static __maybe_unused int
-__cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
+__cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
 
+	return __cvdso_clock_gettime32_data(vd, clock, res);
+}
+#endif /* BUILD_VDSO32 */
+
+static __maybe_unused int
+__cvdso_gettimeofday_data(const struct vdso_data *vd,
+			  struct __kernel_old_timeval *tv, struct timezone *tz)
+{
+
 	if (likely(tv != NULL)) {
 		struct __kernel_timespec ts;
 
@@ -302,10 +320,18 @@ __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 	return 0;
 }
 
-#ifdef VDSO_HAS_TIME
-static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time)
+static __maybe_unused int
+__cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
+
+	return __cvdso_gettimeofday_data(vd, tv, tz);
+}
+
+#ifdef VDSO_HAS_TIME
+static __maybe_unused __kernel_old_time_t
+__cvdso_time_data(const struct vdso_data *vd, __kernel_old_time_t *time)
+{
 	__kernel_old_time_t t;
 
 	if (IS_ENABLED(CONFIG_TIME_NS) &&
@@ -319,13 +345,20 @@ static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time
 
 	return t;
 }
+
+static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+
+	return __cvdso_time_data(vd, time);
+}
 #endif /* VDSO_HAS_TIME */
 
 #ifdef VDSO_HAS_CLOCK_GETRES
 static __maybe_unused
-int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
+int __cvdso_clock_getres_common(const struct vdso_data *vd, clockid_t clock,
+				struct __kernel_timespec *res)
 {
-	const struct vdso_data *vd = __arch_get_vdso_data();
 	u32 msk;
 	u64 ns;
 
@@ -364,23 +397,33 @@ int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 }
 
 static __maybe_unused
-int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
+int __cvdso_clock_getres_data(const struct vdso_data *vd, clockid_t clock,
+			      struct __kernel_timespec *res)
 {
-	int ret = __cvdso_clock_getres_common(clock, res);
+	int ret = __cvdso_clock_getres_common(vd, clock, res);
 
 	if (unlikely(ret))
 		return clock_getres_fallback(clock, res);
 	return 0;
 }
 
+static __maybe_unused
+int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+
+	return __cvdso_clock_getres_data(vd, clock, res);
+}
+
 #ifdef BUILD_VDSO32
 static __maybe_unused int
-__cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
+__cvdso_clock_getres_time32_data(const struct vdso_data *vd, clockid_t clock,
+				 struct old_timespec32 *res)
 {
 	struct __kernel_timespec ts;
 	int ret;
 
-	ret = __cvdso_clock_getres_common(clock, &ts);
+	ret = __cvdso_clock_getres_common(vd, clock, &ts);
 
 	if (unlikely(ret))
 		return clock_getres32_fallback(clock, res);
@@ -391,5 +434,13 @@ __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
 	}
 	return ret;
 }
+
+static __maybe_unused int
+__cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+
+	return __cvdso_clock_getres_time32_data(vd, clock, res);
+}
 #endif /* BUILD_VDSO32 */
 #endif /* VDSO_HAS_CLOCK_GETRES */
-- 
2.13.3