linux-kernel - Re: [PATCH 1/1] powerpc/debug: implement HAVE_USER_RETURN

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Message-ID: <894d6819-c8d8-4929-81c1-323724f62b80@csgroup.eu>
Date:   Mon, 11 Dec 2023 06:34:04 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Luming Yu <luming.yu@...ngroup.cn>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>
CC:     "luming.yu@...il.com" <luming.yu@...il.com>,
        "ke.zhao@...ngroup.cn" <ke.zhao@...ngroup.cn>,
        "dawei.li@...ngroup.cn" <dawei.li@...ngroup.cn>,
        "shenghui.qu@...ngroup.cn" <shenghui.qu@...ngroup.cn>
Subject: Re: [PATCH 1/1] powerpc/debug: implement HAVE_USER_RETURN_NOTIFIER



Le 11/12/2023 à 03:50, Luming Yu a écrit :
> [Vous ne recevez pas souvent de courriers de luming.yu@...ngroup.cn. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> 
> The support for user return notifier infrastructure
> is hooked into powerpc architecture.

"The support ... is hooked". So what ? It's like saying "The sky is 
blue". Ok, and then ? What's the link between that statement and the patch ?

I don't understand what you mean. Please provide more details, tell what 
this patch does and how.

Christophe


> ---
>   arch/powerpc/Kconfig                    |  1 +
>   arch/powerpc/include/asm/entry-common.h | 16 ++++++++++++++++
>   arch/powerpc/include/asm/thread_info.h  |  2 ++
>   arch/powerpc/kernel/process.c           |  2 ++
>   4 files changed, 21 insertions(+)
>   create mode 100644 arch/powerpc/include/asm/entry-common.h
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index c10229c0243c..b968068cc04a 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -277,6 +277,7 @@ config PPC
>          select HAVE_STACKPROTECTOR              if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
>          select HAVE_STATIC_CALL                 if PPC32
>          select HAVE_SYSCALL_TRACEPOINTS
> +       select HAVE_USER_RETURN_NOTIFIER
>          select HAVE_VIRT_CPU_ACCOUNTING
>          select HAVE_VIRT_CPU_ACCOUNTING_GEN
>          select HOTPLUG_SMT                      if HOTPLUG_CPU
> diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
> new file mode 100644
> index 000000000000..51f1eb767696
> --- /dev/null
> +++ b/arch/powerpc/include/asm/entry-common.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef ARCH_POWERPC_ENTRY_COMMON_H
> +#define ARCH_POWERPC_ENTRY_COMMON_H
> +
> +#include <linux/user-return-notifier.h>
> +
> +static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
> +                                                 unsigned long ti_work)
> +{
> +       if (ti_work & _TIF_USER_RETURN_NOTIFY)
> +               fire_user_return_notifiers();
> +}
> +
> +#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
> +
> +#endif
> diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> index bf5dde1a4114..47e226032f9c 100644
> --- a/arch/powerpc/include/asm/thread_info.h
> +++ b/arch/powerpc/include/asm/thread_info.h
> @@ -117,6 +117,7 @@ void arch_setup_new_exec(void);
>   #endif
>   #define TIF_POLLING_NRFLAG     19      /* true if poll_idle() is polling TIF_NEED_RESCHED */
>   #define TIF_32BIT              20      /* 32 bit binary */
> +#define TIF_USER_RETURN_NOTIFY 21      /* notify kernel of userspace return */
> 
>   /* as above, but as bit values */
>   #define _TIF_SYSCALL_TRACE     (1<<TIF_SYSCALL_TRACE)
> @@ -125,6 +126,7 @@ void arch_setup_new_exec(void);
>   #define _TIF_NOTIFY_SIGNAL     (1<<TIF_NOTIFY_SIGNAL)
>   #define _TIF_POLLING_NRFLAG    (1<<TIF_POLLING_NRFLAG)
>   #define _TIF_32BIT             (1<<TIF_32BIT)
> +#define _TIF_USER_RETURN_NOTIFY        (1<<TIF_USER_RETURN_NOTIFY)
>   #define _TIF_RESTORE_TM                (1<<TIF_RESTORE_TM)
>   #define _TIF_PATCH_PENDING     (1<<TIF_PATCH_PENDING)
>   #define _TIF_SYSCALL_AUDIT     (1<<TIF_SYSCALL_AUDIT)
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 392404688cec..70a9ea949798 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -38,6 +38,7 @@
>   #include <linux/uaccess.h>
>   #include <linux/pkeys.h>
>   #include <linux/seq_buf.h>
> +#include <linux/user-return-notifier.h>
> 
>   #include <asm/interrupt.h>
>   #include <asm/io.h>
> @@ -1386,6 +1387,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
>          if (current->thread.regs)
>                  restore_math(current->thread.regs);
>   #endif /* CONFIG_PPC_BOOK3S_64 */
> +       propagate_user_return_notify(prev, new);
> 
>          return last;
>   }
> --
> 2.42.0.windows.2
>