vdso/gettimeofday: Add support for auxiliary clocks

Expose the auxiliary clocks through the vDSO.

Architectures not using the generic vDSO time framework,
namely SPARC64, are not supported.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-12-df7d9f87b9b8@linutronix.de

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index f4c96d9ce674abb07ccd8703f1a04da7631c1677..02533038640e53c40291c7e09139e0f9b32f502a 100644 (file)
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -5,6 +5,7 @@
 #ifndef __ASSEMBLY__
 
 #include <linux/compiler.h>
+#include <uapi/linux/bits.h>
 #include <uapi/linux/time.h>
 #include <uapi/linux/types.h>
 #include <uapi/asm-generic/errno-base.h>
@@ -46,6 +47,7 @@ struct vdso_arch_data {
 #define VDSO_COARSE    (BIT(CLOCK_REALTIME_COARSE)     | \
                         BIT(CLOCK_MONOTONIC_COARSE))
 #define VDSO_RAW       (BIT(CLOCK_MONOTONIC_RAW))
+#define VDSO_AUX       __GENMASK(CLOCK_AUX_LAST, CLOCK_AUX)
 
 #define CS_HRES_COARSE 0
 #define CS_RAW         1

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index fc0038e83b5c736eedce8a30ec2c6923cadf18ff..02ea19f671647e9a1b8c3e7ea0cbff33b4024711 100644 (file)
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -2,6 +2,7 @@
 /*
  * Generic userspace implementations of gettimeofday() and similar.
  */
+#include <vdso/auxclock.h>
 #include <vdso/datapage.h>
 #include <vdso/helpers.h>
 
@@ -74,7 +75,7 @@ static inline bool vdso_cycles_ok(u64 cycles)
 static __always_inline bool vdso_clockid_valid(clockid_t clock)
 {
        /* Check for negative values or invalid clocks */
-       return likely((u32) clock < MAX_CLOCKS);
+       return likely((u32) clock <= CLOCK_AUX_LAST);
 }
 
 /*
@@ -268,6 +269,48 @@ bool do_coarse(const struct vdso_time_data *vd, const struct vdso_clock *vc,
        return true;
 }
 
+static __always_inline
+bool do_aux(const struct vdso_time_data *vd, clockid_t clock, struct __kernel_timespec *ts)
+{
+       const struct vdso_clock *vc;
+       u32 seq, idx;
+       u64 sec, ns;
+
+       if (!IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))
+               return false;
+
+       idx = clock - CLOCK_AUX;
+       vc = &vd->aux_clock_data[idx];
+
+       do {
+               /*
+                * Open coded function vdso_read_begin() to handle
+                * VDSO_CLOCK_TIMENS. See comment in do_hres().
+                */
+               while ((seq = READ_ONCE(vc->seq)) & 1) {
+                       if (IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS) {
+                               vd = __arch_get_vdso_u_timens_data(vd);
+                               vc = &vd->aux_clock_data[idx];
+                               /* Re-read from the real time data page */
+                               continue;
+                       }
+                       cpu_relax();
+               }
+               smp_rmb();
+
+               /* Auxclock disabled? */
+               if (vc->clock_mode == VDSO_CLOCKMODE_NONE)
+                       return false;
+
+               if (!vdso_get_timestamp(vd, vc, VDSO_BASE_AUX, &sec, &ns))
+                       return false;
+       } while (unlikely(vdso_read_retry(vc, seq)));
+
+       vdso_set_timespec(ts, sec, ns);
+
+       return true;
+}
+
 static __always_inline bool
 __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,
                             struct __kernel_timespec *ts)
@@ -289,6 +332,8 @@ __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,
                return do_coarse(vd, &vc[CS_HRES_COARSE], clock, ts);
        else if (msk & VDSO_RAW)
                vc = &vc[CS_RAW];
+       else if (msk & VDSO_AUX)
+               return do_aux(vd, clock, ts);
        else
                return false;
 
@@ -433,6 +478,8 @@ bool __cvdso_clock_getres_common(const struct vdso_time_data *vd, clockid_t cloc
                 * Preserves the behaviour of posix_get_coarse_res().
                 */
                ns = LOW_RES_NSEC;
+       } else if (msk & VDSO_AUX) {
+               ns = aux_clock_resolution_ns();
        } else {
                return false;
        }