linux-kernel - [patch 2/5] lib/vdso: Move fallback invocation to the callers

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Message-Id: <20190728131648.695579736@linutronix.de>
Date:   Sun, 28 Jul 2019 15:12:53 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Bolle <pebolle@...cali.nl>, Will Deacon <will@...nel.org>
Subject: [patch 2/5] lib/vdso: Move fallback invocation to the callers

To allow syscall fallbacks using the legacy 32bit syscall for 32bit VDSO
builds, move the fallback invocation out into the callers.

Split the common code out of __cvdso_clock_gettime/getres() and invoke the
syscall fallback in the 64bit and 32bit variants.

Preparatory work for using legacy syscalls in 32bit VDSO. No functional
change.

Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 lib/vdso/gettimeofday.c |   53 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 17 deletions(-)

--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -51,7 +51,7 @@ static int do_hres(const struct vdso_dat
 		ns = vdso_ts->nsec;
 		last = vd->cycle_last;
 		if (unlikely((s64)cycles < 0))
-			return clock_gettime_fallback(clk, ts);
+			return -1;
 
 		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
 		ns >>= vd->shift;
@@ -82,14 +82,14 @@ static void do_coarse(const struct vdso_
 }
 
 static __maybe_unused int
-__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+__cvdso_clock_gettime_common(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 */
 	if (unlikely((u32) clock >= MAX_CLOCKS))
-		goto fallback;
+		return -1;
 
 	/*
 	 * Convert the clockid to a bitmask and use it to check which
@@ -104,9 +104,17 @@ static __maybe_unused int
 	} else if (msk & VDSO_RAW) {
 		return do_hres(&vd[CS_RAW], clock, ts);
 	}
+	return -1;
+}
 
-fallback:
-	return clock_gettime_fallback(clock, ts);
+static __maybe_unused int
+__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
+{
+	int ret = __cvdso_clock_gettime_common(clock, ts);
+
+	if (unlikely(ret))
+		return clock_gettime_fallback(clock, ts);
+	return 0;
 }
 
 static __maybe_unused int
@@ -115,9 +123,12 @@ static __maybe_unused int
 	struct __kernel_timespec ts;
 	int ret;
 
-	ret = __cvdso_clock_gettime(clock, &ts);
+	ret = __cvdso_clock_gettime_common(clock, &ts);
 
-	if (ret == 0) {
+	if (unlikely(ret))
+		ret = clock_gettime_fallback(clock, &ts);
+
+	if (likely(!ret)) {
 		res->tv_sec = ts.tv_sec;
 		res->tv_nsec = ts.tv_nsec;
 	}
@@ -163,17 +174,18 @@ static __maybe_unused time_t __cvdso_tim
 
 #ifdef VDSO_HAS_CLOCK_GETRES
 static __maybe_unused
-int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
+int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
-	u64 ns;
+	u64 hrtimer_res;
 	u32 msk;
-	u64 hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
+	u64 ns;
 
 	/* Check for negative values or invalid clocks */
 	if (unlikely((u32) clock >= MAX_CLOCKS))
-		goto fallback;
+		return -1;
 
+	hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
 	/*
 	 * Convert the clockid to a bitmask and use it to check which
 	 * clocks are handled in the VDSO directly.
@@ -195,16 +207,22 @@ int __cvdso_clock_getres(clockid_t clock
 		 */
 		ns = hrtimer_res;
 	} else {
-		goto fallback;
+		return -1;
 	}
 
 	res->tv_sec = 0;
 	res->tv_nsec = ns;
 
 	return 0;
+}
+
+int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
+{
+	int ret = __cvdso_clock_getres_common(clock, res);
 
-fallback:
-	return clock_getres_fallback(clock, res);
+	if (unlikely(ret))
+		return clock_getres_fallback(clock, res);
+	return 0;
 }
 
 static __maybe_unused int
@@ -213,13 +231,14 @@ static __maybe_unused int
 	struct __kernel_timespec ts;
 	int ret;
 
-	ret = __cvdso_clock_getres(clock, &ts);
+	ret = __cvdso_clock_getres_common(clock, &ts);
+	if (unlikely(ret))
+		ret = clock_getres_fallback(clock, &ts);
 
-	if (ret == 0) {
+	if (likely(!ret)) {
 		res->tv_sec = ts.tv_sec;
 		res->tv_nsec = ts.tv_nsec;
 	}
-
 	return ret;
 }
 #endif /* VDSO_HAS_CLOCK_GETRES */