From 1beb35ec615f676d49d68b6dc23c7418ba8ff145 Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Mon, 25 Mar 2024 08:40:09 +0200 Subject: vdso, math64: Provide mul_u64_u32_add_u64_shr() Provide mul_u64_u32_add_u64_shr() which is a calculation that will be used by timekeeping and VDSO. Place #include after #include to allow architecture-specific overrides, at least for the kernel. Signed-off-by: Adrian Hunter Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240325064023.2997-6-adrian.hunter@intel.com --- include/vdso/math64.h | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) (limited to 'include/vdso') diff --git a/include/vdso/math64.h b/include/vdso/math64.h index 7da703ee5561..22ae212f8b28 100644 --- a/include/vdso/math64.h +++ b/include/vdso/math64.h @@ -21,4 +21,42 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) return ret; } +#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__) + +#ifndef mul_u64_u32_add_u64_shr +static __always_inline u64 mul_u64_u32_add_u64_shr(u64 a, u32 mul, u64 b, unsigned int shift) +{ + return (u64)((((unsigned __int128)a * mul) + b) >> shift); +} +#endif /* mul_u64_u32_add_u64_shr */ + +#else + +#ifndef mul_u64_u32_add_u64_shr +#ifndef mul_u32_u32 +static inline u64 mul_u32_u32(u32 a, u32 b) +{ + return (u64)a * b; +} +#define mul_u32_u32 mul_u32_u32 +#endif +static __always_inline u64 mul_u64_u32_add_u64_shr(u64 a, u32 mul, u64 b, unsigned int shift) +{ + u32 ah = a >> 32, al = a; + bool ovf; + u64 ret; + + ovf = __builtin_add_overflow(mul_u32_u32(al, mul), b, &ret); + ret >>= shift; + if (ovf && shift) + ret += 1ULL << (64 - shift); + if (ah) + ret += mul_u32_u32(ah, mul) << (32 - shift); + + return ret; +} +#endif /* mul_u64_u32_add_u64_shr */ + +#endif + #endif /* __VDSO_MATH64_H */ -- cgit v1.2.3 From d2e58ab5cda2a225c406ac10d0a8b960bc5a39b6 Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Mon, 25 Mar 2024 08:40:10 +0200 Subject: 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 Signed-off-by: Adrian Hunter Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240325064023.2997-7-adrian.hunter@intel.com --- include/vdso/datapage.h | 4 ++++ kernel/time/vsyscall.c | 6 ++++++ 2 files changed, 10 insertions(+) (limited to 'include/vdso') diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h index c71ddb6d4691..d04d394db064 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 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; -- cgit v1.2.3