vdso: Consolidate nanoseconds calculation

Consolidate nanoseconds calculation to simplify and reduce code
duplication.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240325064023.2997-3-adrian.hunter@intel.com

1 files changed, 19 insertions, 24 deletions

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index faccf12f7c03..9fa90e0794c9 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -5,31 +5,32 @@
 #include <vdso/datapage.h>
 #include <vdso/helpers.h>
 
-#ifndef vdso_calc_delta
+#ifndef vdso_calc_ns
 
 #ifdef VDSO_DELTA_NOMASK
-# define VDSO_DELTA_MASK(mask)	U64_MAX
+# define VDSO_DELTA_MASK(vd)	U64_MAX
 #else
-# define VDSO_DELTA_MASK(mask)	(mask)
+# define VDSO_DELTA_MASK(vd)	(vd->mask)
+#endif
+
+#ifndef vdso_shift_ns
+static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
+{
+	return ns >> shift;
+}
 #endif
 
 /*
  * Default implementation which works for all sane clocksources. That
  * obviously excludes x86/TSC.
  */
-static __always_inline
-u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
+static __always_inline u64 vdso_calc_ns(const struct vdso_data *vd, u64 cycles, u64 base)
 {
-	return ((cycles - last) & VDSO_DELTA_MASK(mask)) * mult;
-}
-#endif
+	u64 delta = (cycles - vd->cycle_last) & VDSO_DELTA_MASK(vd);
 
-#ifndef vdso_shift_ns
-static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
-{
-	return ns >> shift;
+	return vdso_shift_ns((delta * vd->mult) + base, vd->shift);
 }
-#endif
+#endif /* vdso_calc_ns */
 
 #ifndef __arch_vdso_hres_capable
 static inline bool __arch_vdso_hres_capable(void)
@@ -56,10 +57,10 @@ static inline bool vdso_cycles_ok(u64 cycles)
 static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
 					  struct __kernel_timespec *ts)
 {
-	const struct vdso_data *vd;
 	const struct timens_offset *offs = &vdns->offset[clk];
 	const struct vdso_timestamp *vdso_ts;
-	u64 cycles, last, ns;
+	const struct vdso_data *vd;
+	u64 cycles, ns;
 	u32 seq;
 	s64 sec;
 
@@ -80,10 +81,7 @@ static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_
 		cycles = __arch_get_hw_counter(vd->clock_mode, vd);
 		if (unlikely(!vdso_cycles_ok(cycles)))
 			return -1;
-		ns = vdso_ts->nsec;
-		last = vd->cycle_last;
-		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
-		ns = vdso_shift_ns(ns, vd->shift);
+		ns = vdso_calc_ns(vd, cycles, vdso_ts->nsec);
 		sec = vdso_ts->sec;
 	} while (unlikely(vdso_read_retry(vd, seq)));
 
@@ -118,7 +116,7 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
 				   struct __kernel_timespec *ts)
 {
 	const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
-	u64 cycles, last, sec, ns;
+	u64 cycles, sec, ns;
 	u32 seq;
 
 	/* Allows to compile the high resolution parts out */
@@ -151,10 +149,7 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
 		cycles = __arch_get_hw_counter(vd->clock_mode, vd);
 		if (unlikely(!vdso_cycles_ok(cycles)))
 			return -1;
-		ns = vdso_ts->nsec;
-		last = vd->cycle_last;
-		ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
-		ns = vdso_shift_ns(ns, vd->shift);
+		ns = vdso_calc_ns(vd, cycles, vdso_ts->nsec);
 		sec = vdso_ts->sec;
 	} while (unlikely(vdso_read_retry(vd, seq)));