From: Alexandre Chartre <alexandre.chartre@oracle.com>
To: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
Brian Gerst <brgerst@gmail.com>, Juergen Gross <jgross@suse.com>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [patch part-II V2 01/13] context_tracking: Ensure that the critical path cannot be instrumented
Date: Tue, 10 Mar 2020 11:12:12 +0100 [thread overview]
Message-ID: <ca03a66a-a632-e646-ed3d-d350f78f7d79@oracle.com> (raw)
In-Reply-To: <20200308222609.017810037@linutronix.de>
On 3/8/20 11:24 PM, Thomas Gleixner wrote:
> context tracking lacks a few protection mechanisms against instrumentation:
>
> - While the core functions are marked NOKPROBE they lack protection
> against function tracing which is required as the function entry/exit
> points can be utilized by BPF.
>
> - static functions invoked from the protected functions need to be marked
> as well as they can be instrumented otherwise.
>
> - using plain inline allows the compiler to emit traceable and probable
> functions.
>
> Fix this by adding the missing notrace/NOKPROBE annotations and converting
> the plain inlines to __always_inline.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> include/linux/context_tracking.h | 14 +++++++-------
> include/linux/context_tracking_state.h | 6 +++---
> kernel/context_tracking.c | 9 +++++----
> 3 files changed, 15 insertions(+), 14 deletions(-)
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
alex.
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -20,32 +20,32 @@ extern void context_tracking_exit(enum c
> extern void context_tracking_user_enter(void);
> extern void context_tracking_user_exit(void);
>
> -static inline void user_enter(void)
> +static __always_inline void user_enter(void)
> {
> if (context_tracking_enabled())
> context_tracking_enter(CONTEXT_USER);
>
> }
> -static inline void user_exit(void)
> +static __always_inline void user_exit(void)
> {
> if (context_tracking_enabled())
> context_tracking_exit(CONTEXT_USER);
> }
>
> /* Called with interrupts disabled. */
> -static inline void user_enter_irqoff(void)
> +static __always_inline void user_enter_irqoff(void)
> {
> if (context_tracking_enabled())
> __context_tracking_enter(CONTEXT_USER);
>
> }
> -static inline void user_exit_irqoff(void)
> +static __always_inline void user_exit_irqoff(void)
> {
> if (context_tracking_enabled())
> __context_tracking_exit(CONTEXT_USER);
> }
>
> -static inline enum ctx_state exception_enter(void)
> +static __always_inline enum ctx_state exception_enter(void)
> {
> enum ctx_state prev_ctx;
>
> @@ -59,7 +59,7 @@ static inline enum ctx_state exception_e
> return prev_ctx;
> }
>
> -static inline void exception_exit(enum ctx_state prev_ctx)
> +static __always_inline void exception_exit(enum ctx_state prev_ctx)
> {
> if (context_tracking_enabled()) {
> if (prev_ctx != CONTEXT_KERNEL)
> @@ -75,7 +75,7 @@ static inline void exception_exit(enum c
> * is enabled. If context tracking is disabled, returns
> * CONTEXT_DISABLED. This should be used primarily for debugging.
> */
> -static inline enum ctx_state ct_state(void)
> +static __always_inline enum ctx_state ct_state(void)
> {
> return context_tracking_enabled() ?
> this_cpu_read(context_tracking.state) : CONTEXT_DISABLED;
> --- a/include/linux/context_tracking_state.h
> +++ b/include/linux/context_tracking_state.h
> @@ -26,12 +26,12 @@ struct context_tracking {
> extern struct static_key_false context_tracking_key;
> DECLARE_PER_CPU(struct context_tracking, context_tracking);
>
> -static inline bool context_tracking_enabled(void)
> +static __always_inline bool context_tracking_enabled(void)
> {
> return static_branch_unlikely(&context_tracking_key);
> }
>
> -static inline bool context_tracking_enabled_cpu(int cpu)
> +static __always_inline bool context_tracking_enabled_cpu(int cpu)
> {
> return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
> }
> @@ -41,7 +41,7 @@ static inline bool context_tracking_enab
> return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
> }
>
> -static inline bool context_tracking_in_user(void)
> +static __always_inline bool context_tracking_in_user(void)
> {
> return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
> }
> --- a/kernel/context_tracking.c
> +++ b/kernel/context_tracking.c
> @@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(context_tracking_key);
> DEFINE_PER_CPU(struct context_tracking, context_tracking);
> EXPORT_SYMBOL_GPL(context_tracking);
>
> -static bool context_tracking_recursion_enter(void)
> +static notrace bool context_tracking_recursion_enter(void)
> {
> int recursion;
>
> @@ -44,8 +44,9 @@ static bool context_tracking_recursion_e
>
> return false;
> }
> +NOKPROBE_SYMBOL(context_tracking_recursion_enter);
>
> -static void context_tracking_recursion_exit(void)
> +static __always_inline void context_tracking_recursion_exit(void)
> {
> __this_cpu_dec(context_tracking.recursion);
> }
> @@ -59,7 +60,7 @@ static void context_tracking_recursion_e
> * instructions to execute won't use any RCU read side critical section
> * because this function sets RCU in extended quiescent state.
> */
> -void __context_tracking_enter(enum ctx_state state)
> +void notrace __context_tracking_enter(enum ctx_state state)
> {
> /* Kernel threads aren't supposed to go to userspace */
> WARN_ON_ONCE(!current->mm);
> @@ -142,7 +143,7 @@ NOKPROBE_SYMBOL(context_tracking_user_en
> * This call supports re-entrancy. This way it can be called from any exception
> * handler without needing to know if we came from userspace or not.
> */
> -void __context_tracking_exit(enum ctx_state state)
> +void notrace __context_tracking_exit(enum ctx_state state)
> {
> if (!context_tracking_recursion_enter())
> return;
>
next prev parent reply other threads:[~2020-03-10 10:12 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-08 22:23 [patch part-II V2 00/13] x86/entry: Consolidation - Part II (syscalls) Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 01/13] context_tracking: Ensure that the critical path cannot be instrumented Thomas Gleixner
2020-03-09 14:22 ` Frederic Weisbecker
2020-03-09 14:40 ` Thomas Gleixner
2020-03-10 10:12 ` Alexandre Chartre [this message]
2020-03-08 22:24 ` [patch part-II V2 02/13] x86/entry: Mark enter_from_user_mode() notrace and NOKPROBE Thomas Gleixner
2020-03-09 15:14 ` Frederic Weisbecker
2020-03-09 15:40 ` Thomas Gleixner
2020-03-11 22:21 ` Frederic Weisbecker
2020-03-10 10:15 ` Alexandre Chartre
2020-03-08 22:24 ` [patch part-II V2 03/13] x86/entry/32: Remove unused label restore_nocheck Thomas Gleixner
2020-03-10 10:16 ` Alexandre Chartre
2020-03-10 13:02 ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 04/13] x86/entry/64: Trace irqflags unconditionally as ON when returning to user space Thomas Gleixner
2020-03-10 10:25 ` Alexandre Chartre
2020-03-10 13:02 ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 05/13] x86/entry/common: Consolidate syscall entry code Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 06/13] x86/entry/common: Mark syscall entry points notrace and NOKPROBE Thomas Gleixner
2020-03-13 15:12 ` Frederic Weisbecker
2020-03-08 22:24 ` [patch part-II V2 07/13] x86/entry: Move irq tracing on syscall entry to C-code Thomas Gleixner
2020-03-13 15:16 ` Frederic Weisbecker
2020-03-13 23:17 ` Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 08/13] tracing: Provide lockdep less trace_hardirqs_on/off() variants Thomas Gleixner
2020-03-10 10:55 ` Alexandre Chartre
2020-03-10 11:08 ` Borislav Petkov
2020-03-10 11:21 ` Alexandre Chartre
2020-03-08 22:24 ` [patch part-II V2 09/13] x86/entry/common: Split hardirq tracing into lockdep and ftrace parts Thomas Gleixner
2020-03-10 11:20 ` Borislav Petkov
2020-03-10 13:40 ` Steven Rostedt
2020-03-10 13:28 ` Alexandre Chartre
2020-03-23 9:08 ` [x86/entry/common] bae397f6e7: WARNING:at_kernel/sched/cputime.c:#get_vtime_delta kernel test robot
2020-03-08 22:24 ` [patch part-II V2 10/13] x86/entry/common: Split prepare_exit_to_usermode() and syscall_return_slowpath() Thomas Gleixner
2020-03-10 13:37 ` Alexandre Chartre
2020-03-08 22:24 ` [patch part-II V2 11/13] x86/speculation/mds: Mark mds_user_clear_cpu_buffers() __always_inline Thomas Gleixner
2020-03-10 13:48 ` Alexandre Chartre
2020-03-10 16:38 ` Thomas Gleixner
2020-03-08 22:24 ` [patch part-II V2 12/13] x86/entry: Move irq flags tracing to prepare_exit_to_usermode() Thomas Gleixner
2020-03-10 14:03 ` Alexandre Chartre
2020-03-08 22:24 ` [patch part-II V2 13/13] x86/entry/common: Split irq tracing in prepare_exit_to_usermode() Thomas Gleixner
2020-03-10 14:09 ` Alexandre Chartre
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ca03a66a-a632-e646-ed3d-d350f78f7d79@oracle.com \
--to=alexandre.chartre@oracle.com \
--cc=brgerst@gmail.com \
--cc=frederic@kernel.org \
--cc=jgross@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).