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 10/13] x86/entry/common: Split prepare_exit_to_usermode() and syscall_return_slowpath()
Date: Tue, 10 Mar 2020 14:37:30 +0100 [thread overview]
Message-ID: <66bc932f-3ef7-1bcd-c5bc-c546036e2f3f@oracle.com> (raw)
In-Reply-To: <20200308222609.932307492@linutronix.de>
On 3/8/20 11:24 PM, Thomas Gleixner wrote:
> Split the functions into traceable and probale parts and a part protected
typo: probale -> probeable ?
> from instrumentation.
>
> This is required because after calling user_exit_irqsoff() kprobes and
> tracepoints/function entry/exit which can be utilized by e.g. BPF are not
> longer safe vs. RCU.
>
> Preparatory step to move irq flags tracing to C code.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> V2: New patch to reduce the churn
> ---
> arch/x86/entry/common.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
>
> --- a/arch/x86/entry/common.c
> +++ b/arch/x86/entry/common.c
> @@ -206,7 +206,7 @@ static void exit_to_usermode_loop(struct
> }
>
> /* Called with IRQs disabled. */
> -__visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
> +static noinline void __prepare_exit_to_usermode(struct pt_regs *regs)
Why noinline?
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
alex.
> {
> struct thread_info *ti = current_thread_info();
> u32 cached_flags;
> @@ -245,11 +245,16 @@ static void exit_to_usermode_loop(struct
> */
> ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
> #endif
> +}
>
> - user_enter_irqoff();
> +__visible inline notrace void prepare_exit_to_usermode(struct pt_regs *regs)
> +{
> + __prepare_exit_to_usermode(regs);
>
> + user_enter_irqoff();
> mds_user_clear_cpu_buffers();
> }
> +NOKPROBE_SYMBOL(prepare_exit_to_usermode);
>
> #define SYSCALL_EXIT_WORK_FLAGS \
> (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
> @@ -277,11 +282,7 @@ static void syscall_slow_exit_work(struc
> tracehook_report_syscall_exit(regs, step);
> }
>
> -/*
> - * Called with IRQs on and fully valid regs. Returns with IRQs off in a
> - * state such that we can immediately switch to user mode.
> - */
> -__visible inline void syscall_return_slowpath(struct pt_regs *regs)
> +static void __syscall_return_slowpath(struct pt_regs *regs)
> {
> struct thread_info *ti = current_thread_info();
> u32 cached_flags = READ_ONCE(ti->flags);
> @@ -302,8 +303,18 @@ static void syscall_slow_exit_work(struc
> syscall_slow_exit_work(regs, cached_flags);
>
> local_irq_disable();
> +}
> +
> +/*
> + * Called with IRQs on and fully valid regs. Returns with IRQs off in a
> + * state such that we can immediately switch to user mode.
> + */
> +__visible inline notrace void syscall_return_slowpath(struct pt_regs *regs)
> +{
> + __syscall_return_slowpath(regs);
> prepare_exit_to_usermode(regs);
> }
> +NOKPROBE_SYMBOL(syscall_return_slowpath);
>
> #ifdef CONFIG_X86_64
> static __always_inline
>
next prev parent reply other threads:[~2020-03-10 13:38 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
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 [this message]
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
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