linux-kernel - Re: [PATCH 03/10] kernel: entry: Wire up syscall

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Date:   Sun, 15 Nov 2020 19:38:42 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     mingo@...hat.com, keescook@...omium.org, arnd@...db.de,
        luto@...capital.net, wad@...omium.org, rostedt@...dmis.org,
        paul@...l-moore.com, eparis@...hat.com, oleg@...hat.com,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: Re: [PATCH 03/10] kernel: entry: Wire up syscall_work in common entry code

On Fri, Nov 13 2020 at 22:29, Gabriel Krisman Bertazi wrote:

"kernel: entry:" is not the right subsystem prefix.

git log kernel/entry/ might give you a hint.

> Prepares the common entry code to use the SYSCALL_WORK flags. They
> will

s/Prepares/Prepare/

> be defined in subsequent patches for each type of syscall
> work. SYSCALL_WORK_ENTRY/EXIT are defined for the transition, as they
> will replace the TIF_ equivalent defines.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  include/linux/entry-common.h |  3 +++
>  kernel/entry/common.c        | 15 +++++++++------
>  2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index 1a128baf3628..cbc5c702ee4d 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -64,6 +64,9 @@
>  	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |			\
>  	 _TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
>  
> +#define SYSCALL_WORK_ENTER	(0)
> +#define SYSCALL_WORK_EXIT	(0)
> +
>  /*
>   * TIF flags handled in exit_to_user_mode_loop()
>   */
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index bc75c114c1b3..5a4bb72ff28e 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -42,7 +42,7 @@ static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
>  }
>  
>  static long syscall_trace_enter(struct pt_regs *regs, long syscall,
> -				unsigned long ti_work)
> +				unsigned long ti_work, unsigned long work)
>  {
>  	long ret = 0;
>  
> @@ -75,10 +75,11 @@ static __always_inline long
>  __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
>  {
>  	unsigned long ti_work;
> +	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);

Even if this is temporary this code uses reverse fir tree ordering of
variable declarations:

	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	unsigned long ti_work;

Thanks,

        tglx