linux-kernel - [RFC][PATCH 0/9] local

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20230508211951.901961964@infradead.org>
Date:   Mon, 08 May 2023 23:19:51 +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 0/9] local_clock() vs noinstr

Hi all!

A recent commit of mine marked local_clock() as noinstr.

  776f22913b8e ("sched/clock: Make local_clock() noinstr")

Sadly both me and objtool missed the fact that this is subly broken; but
Sebastian tripped over it [*]:

| vmlinux.o: warning: objtool: native_sched_clock+0x97: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: local_clock+0xb4: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section

Specifically, local_clock() (and many of the sched_clock() implementation is
relies upon) use preempt_{dis,en}able_notrace() which obviously calls out to
schedule().

Now, noinstr code *should* never trigger this and already run in
non-preemptible code. Specifically entry code should have IRQs disabled while
__cpuidle code should have preemption disabled.

So while it is mostly harmless, I figured it wouldn't be too hard to clean this
up a little -- but that was ~10 patches. Anyway, here goes...

Compile tested only on x86_64/s390/arm64 -- I've just fed it to the
robots.

---
 arch/arm64/include/asm/arch_timer.h    |  8 +----
 arch/arm64/include/asm/io.h            | 12 +++----
 arch/loongarch/include/asm/loongarch.h |  2 +-
 arch/loongarch/kernel/time.c           |  6 ++--
 arch/s390/include/asm/timex.h          | 13 +++++---
 arch/s390/kernel/time.c                | 11 ++++++-
 arch/x86/kernel/kvmclock.c             |  4 +--
 arch/x86/kernel/tsc.c                  | 38 ++++++++++++++++-----
 arch/x86/xen/time.c                    |  3 +-
 drivers/clocksource/arm_arch_timer.c   | 60 ++++++++++++++++++++++++++--------
 drivers/clocksource/hyperv_timer.c     |  4 +--
 drivers/cpuidle/cpuidle.c              |  8 ++---
 drivers/cpuidle/poll_state.c           |  4 +--
 include/clocksource/hyperv_timer.h     |  4 +--
 include/linux/rbtree_latch.h           |  2 +-
 include/linux/sched/clock.h            | 17 +++++++++-
 include/linux/seqlock.h                | 15 +++++----
 kernel/printk/printk.c                 |  2 +-
 kernel/sched/clock.c                   | 19 +++++++----
 kernel/time/sched_clock.c              | 24 ++++++++++----
 kernel/time/timekeeping.c              |  4 +--
 21 files changed, 176 insertions(+), 84 deletions(-)


* https://lkml.kernel.org/r/20230309072724.3F6zRkvw@linutronix.de
  TL;DR: PREEMPT_DYNAMIC=n PREEMPT=y DEBUG_ENTRY=y