linux-kernel - [RFC][PATCH 5/9] loongarch: Provide noinstr sched_clock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 08 May 2023 23:19:56 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     bigeasy@...utronix.de
Cc:     mark.rutland@....com, maz@...nel.org, catalin.marinas@....com,
        will@...nel.org, chenhuacai@...nel.org, kernel@...0n.name,
        hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
        pbonzini@...hat.com, wanpengli@...cent.com, vkuznets@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        jgross@...e.com, boris.ostrovsky@...cle.com,
        daniel.lezcano@...aro.org, kys@...rosoft.com,
        haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
        rafael@...nel.org, peterz@...radead.org, longman@...hat.com,
        boqun.feng@...il.com, pmladek@...e.com, senozhatsky@...omium.org,
        rostedt@...dmis.org, john.ogness@...utronix.de,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, jstultz@...gle.com,
        sboyd@...nel.org, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: [RFC][PATCH 5/9] loongarch: Provide noinstr sched_clock_read()

With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by providing a noinstr sched_clock_read() function.

Specifically, preempt_enable_*() calls out to schedule(), which upsets
noinstr validation efforts.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/loongarch/include/asm/loongarch.h |    2 +-
 arch/loongarch/kernel/time.c           |    6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -1167,7 +1167,7 @@ static __always_inline void iocsr_write6
 
 #ifndef __ASSEMBLY__
 
-static inline u64 drdtime(void)
+static __always_inline u64 drdtime(void)
 {
 	int rID = 0;
 	u64 val = 0;
--- a/arch/loongarch/kernel/time.c
+++ b/arch/loongarch/kernel/time.c
@@ -190,9 +190,9 @@ static u64 read_const_counter(struct clo
 	return drdtime();
 }
 
-static u64 native_sched_clock(void)
+static noinstr u64 sched_clock_read(void)
 {
-	return read_const_counter(NULL);
+	return drdtime();
 }
 
 static struct clocksource clocksource_const = {
@@ -211,7 +211,7 @@ int __init constant_clocksource_init(voi
 
 	res = clocksource_register_hz(&clocksource_const, freq);
 
-	sched_clock_register(native_sched_clock, 64, freq);
+	sched_clock_register(sched_clock_read, 64, freq);
 
 	pr_info("Constant clock source device register\n");