Add vdso_data::max_cycles in preparation to use it to detect potential
multiplication overflow.
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
include/vdso/datapage.h | 4 ++++
kernel/time/vsyscall.c | 6 ++++++
2 files changed, 10 insertions(+)
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 5d5c0b8efff2..6c3d67d6b758 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -67,6 +67,7 @@ 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
@@ -98,6 +99,9 @@ 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 f0d5062d9cbc..9193d6133e5d 100644
--- 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;
--
2.34.1
