[tip: timers/core] vdso: Add vdso_data:: Max_cycles

[tip-bot2 for Adrian Hunter]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     d2e58ab5cda2a225c406ac10d0a8b960bc5a39b6
Gitweb:        https://git.kernel.org/tip/d2e58ab5cda2a225c406ac10d0a8b960bc5a39b6
Author:        Adrian Hunter <adrian.hunter@xxxxxxxxx>
AuthorDate:    Mon, 25 Mar 2024 08:40:10 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 08 Apr 2024 15:03:07 +02:00

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@xxxxxxxxxxxxx>
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240325064023.2997-7-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 c71ddb6..d04d394 100644
--- 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 f0d5062..9193d61 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;