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Message-Id: <381e547dbb3c48fd39d6cf208033bba38ad048fb.1578934751.git.christophe.leroy@c-s.fr>
In-Reply-To: <cover.1578934751.git.christophe.leroy@c-s.fr>
References: <cover.1578934751.git.christophe.leroy@c-s.fr>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [RFC PATCH v3 08/12] 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>, 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:   Mon, 13 Jan 2020 17:08:46 +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 | 56 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index da15a8842825..ea1a55507af5 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -104,9 +104,15 @@ static __always_inline int do_coarse(const struct vdso_data *vd, clockid_t clk,
 }
 
 static __maybe_unused int
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+__cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t clock,
+		      struct __kernel_timespec *ts)
+{
+#else
 __cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
+#endif
 	u32 msk;
 
 	/* Check for negative values or invalid clocks */
@@ -131,9 +137,16 @@ __cvdso_clock_gettime_common(clockid_t clock, struct __kernel_timespec *ts)
 }
 
 static __maybe_unused int
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+__cvdso_clock_gettime(const struct vdso_data *vd, clockid_t clock,
+		      struct __kernel_timespec *ts)
+{
+	int ret = __cvdso_clock_gettime_common(vd, clock, ts);
+#else
 __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
 {
 	int ret = __cvdso_clock_gettime_common(clock, ts);
+#endif
 
 	if (unlikely(ret))
 		return clock_gettime_fallback(clock, ts);
@@ -141,12 +154,21 @@ __cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
 }
 
 static __maybe_unused int
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+__cvdso_clock_gettime32(const struct vdso_data *vd, clockid_t clock,
+			struct old_timespec32 *res)
+#else
 __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
+#endif
 {
 	struct __kernel_timespec ts;
 	int ret;
 
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+	ret = __cvdso_clock_gettime_common(vd, clock, &ts);
+#else
 	ret = __cvdso_clock_gettime_common(clock, &ts);
+#endif
 
 #ifdef VDSO_HAS_32BIT_FALLBACK
 	if (unlikely(ret))
@@ -164,9 +186,15 @@ __cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
 }
 
 static __maybe_unused int
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+__cvdso_gettimeofday(const struct vdso_data *vd, struct __kernel_old_timeval *tv,
+		     struct timezone *tz)
+{
+#else
 __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
+#endif
 
 	if (likely(tv != NULL)) {
 		struct __kernel_timespec ts;
@@ -187,9 +215,15 @@ __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
 }
 
 #ifdef VDSO_HAS_TIME
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+static __maybe_unused __kernel_old_time_t
+__cvdso_time(const struct vdso_data *vd, __kernel_old_time_t *time)
+{
+#else
 static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
+#endif
 	__kernel_old_time_t t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec);
 
 	if (time)
@@ -201,9 +235,15 @@ static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time
 
 #ifdef VDSO_HAS_CLOCK_GETRES
 static __maybe_unused
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+int __cvdso_clock_getres_common(const struct vdso_data *vd, clockid_t clock,
+				struct __kernel_timespec *res)
+{
+#else
 int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
+#endif
 	u32 msk;
 	u64 ns;
 
@@ -238,9 +278,16 @@ int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 }
 
 static __maybe_unused
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+int __cvdso_clock_getres(const struct vdso_data *vd, clockid_t clock,
+			 struct __kernel_timespec *res)
+{
+	int ret = __cvdso_clock_getres_common(vd, clock, res);
+#else
 int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
 {
 	int ret = __cvdso_clock_getres_common(clock, res);
+#endif
 
 	if (unlikely(ret))
 		return clock_getres_fallback(clock, res);
@@ -248,12 +295,21 @@ int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
 }
 
 static __maybe_unused int
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+__cvdso_clock_getres_time32(const struct vdso_data *vd, clockid_t clock,
+			    struct old_timespec32 *res)
+#else
 __cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
+#endif
 {
 	struct __kernel_timespec ts;
 	int ret;
 
+#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
+	ret = __cvdso_clock_getres_common(vd, clock, &ts);
+#else
 	ret = __cvdso_clock_getres_common(clock, &ts);
+#endif
 
 #ifdef VDSO_HAS_32BIT_FALLBACK
 	if (unlikely(ret))
-- 
2.13.3