vdso: Add vdso_data:: Max_cycles

Add vdso_data::max_cycles in preparation to use it to detect potential
multiplication overflow.

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/20240325064023.2997-7-adrian.hunter@intel.com

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index c71ddb6d46914be3d91758608e92248aea98fcba..d04d394db064aec1283366e5abf57bc4c010d9ea 100644 (file)
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -61,6 +61,7 @@ struct vdso_timestamp {
  * @seq:               timebase sequence counter
  * @clock_mode:                clock mode
  * @cycle_last:                timebase at clocksource init
+ * @max_cycles:                maximum cycles which won't overflow 64bit multiplication
  * @mask:              clocksource mask
  * @mult:              clocksource multiplier
  * @shift:             clocksource shift
@@ -92,6 +93,9 @@ struct vdso_data {
 
        s32                     clock_mode;
        u64                     cycle_last;
+#ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT
+       u64                     max_cycles;
+#endif
        u64                     mask;
        u32                     mult;
        u32                     shift;

diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
index f0d5062d9cbc621a2ab32141b53c2f1f8cba0337..9193d6133e5d688342be8485b9a0efb7af9ee148 100644 (file)
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -22,10 +22,16 @@ static inline void update_vdso_data(struct vdso_data *vdata,
        u64 nsec, sec;
 
        vdata[CS_HRES_COARSE].cycle_last        = tk->tkr_mono.cycle_last;
+#ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT
+       vdata[CS_HRES_COARSE].max_cycles        = tk->tkr_mono.clock->max_cycles;
+#endif
        vdata[CS_HRES_COARSE].mask              = tk->tkr_mono.mask;
        vdata[CS_HRES_COARSE].mult              = tk->tkr_mono.mult;
        vdata[CS_HRES_COARSE].shift             = tk->tkr_mono.shift;
        vdata[CS_RAW].cycle_last                = tk->tkr_raw.cycle_last;
+#ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT
+       vdata[CS_RAW].max_cycles                = tk->tkr_raw.clock->max_cycles;
+#endif
        vdata[CS_RAW].mask                      = tk->tkr_raw.mask;
        vdata[CS_RAW].mult                      = tk->tkr_raw.mult;
        vdata[CS_RAW].shift                     = tk->tkr_raw.shift;