From nobody Fri Dec 19 03:44:43 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B27F6EEB562 for ; Fri, 8 Sep 2023 18:57:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242912AbjIHS5t (ORCPT ); Fri, 8 Sep 2023 14:57:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234527AbjIHS5s (ORCPT ); Fri, 8 Sep 2023 14:57:48 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D0351BF for ; Fri, 8 Sep 2023 11:57:13 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1694199014; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zsoNHH89SNtOZCvpJWTZfwP83WCUYW1q+GgTPpFsUgQ=; b=hIWEQ7KuQv9FBY8NoQ+5XKehruQdzQOY55LvRTXxGX4SGujykUUa1B/ClZ/Mn49g5RXb/9 LWAHpzRxfgkFq1sFL5FppACC23jdXqbjJo+jAaUqkZr/2mL0QW5BHNIBmyT+mBg4ZpGWms 0M9Ywr+5eVkynAG7O6Sq25+nUcpvMAMEzVHnrvdyZ4pJLHGsD2UuCMdyvgxf43cqVieNqH HpsA1FKG/EPbjrIJstDWnX3ETm+pvDoLh2L1qQozW/rweGvfL/5xlaUGgSJg3HMv642sUY fdf6a51GtTkFJlKlat7ZS77vRTAElyHQGQCScCaSnwAVH6BwziThTVA/WIHD1w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1694199014; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zsoNHH89SNtOZCvpJWTZfwP83WCUYW1q+GgTPpFsUgQ=; b=g1Fp77vT+dxtiKsbcMzs7QqKe5l15ACNRRe27b4h77Hye7mUVYYM2gq7t/4hR0Dq59vzf3 Obbx5joHPKcxFqAA== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH printk v4 8/8] printk: nbcon: Allow drivers to mark unsafe regions and check state Date: Fri, 8 Sep 2023 20:56:08 +0206 Message-Id: <20230908185008.468566-9-john.ogness@linutronix.de> In-Reply-To: <20230908185008.468566-1-john.ogness@linutronix.de> References: <20230908185008.468566-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Thomas Gleixner For the write_atomic callback, the console driver may have unsafe regions that need to be appropriately marked. Provide functions that accept the nbcon_write_context struct to allow for the driver to enter and exit unsafe regions. Also provide a function for drivers to check if they are still the owner of the console. Co-developed-by: John Ogness Signed-off-by: John Ogness Signed-off-by: Thomas Gleixner (Intel) Reviewed-by: Petr Mladek --- include/linux/console.h | 10 +++++++ kernel/printk/nbcon.c | 66 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 76 insertions(+) diff --git a/include/linux/console.h b/include/linux/console.h index 0ce7a2a856ab..de8fd92a960b 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -454,6 +454,16 @@ static inline bool console_is_registered(const struct = console *con) lockdep_assert_console_list_lock_held(); \ hlist_for_each_entry(con, &console_list, node) =20 +#ifdef CONFIG_PRINTK +extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt); +extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt); +extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt); +#else +static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { = return false; } +static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) {= return false; } +static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { = return false; } +#endif + extern int console_set_on_cmdline; extern struct console *early_console; =20 diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index e2c274f4142e..04fac73c6e96 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -660,6 +660,32 @@ static bool nbcon_context_can_proceed(struct nbcon_con= text *ctxt, struct nbcon_s return false; } =20 +/** + * nbcon_can_proceed - Check whether ownership can proceed + * @wctxt: The write context that was handed to the write function + * + * Return: True if this context still owns the console. False if + * ownership was handed over or taken. + * + * Must be invoked at appropriate safe places in the driver. + * + * When this function returns false then the calling context no longer owns + * the console and is no longer allowed to go forward. In this case it must + * back out immediately and carefully. The buffer content is also no longer + * trusted since it no longer belongs to the calling context. + */ +bool nbcon_can_proceed(struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt =3D &ACCESS_PRIVATE(wctxt, ctxt); + struct console *con =3D ctxt->console; + struct nbcon_state cur; + + nbcon_state_read(con, &cur); + + return nbcon_context_can_proceed(ctxt, &cur); +} +EXPORT_SYMBOL_GPL(nbcon_can_proceed); + #define nbcon_context_enter_unsafe(c) __nbcon_context_update_unsafe(c, tru= e) #define nbcon_context_exit_unsafe(c) __nbcon_context_update_unsafe(c, fals= e) =20 @@ -710,6 +736,46 @@ static bool __nbcon_context_update_unsafe(struct nbcon= _context *ctxt, bool unsaf return nbcon_context_can_proceed(ctxt, &cur); } =20 +/** + * nbcon_enter_unsafe - Enter an unsafe region in the driver + * @wctxt: The write context that was handed to the write function + * + * Return: True if this context still owns the console. False if + * ownership was handed over or taken. + * + * When this function returns false then the calling context no longer owns + * the console and is no longer allowed to go forward. In this case it must + * back out immediately and carefully. The buffer content is also no longer + * trusted since it no longer belongs to the calling context. + */ +bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt =3D &ACCESS_PRIVATE(wctxt, ctxt); + + return nbcon_context_enter_unsafe(ctxt); +} +EXPORT_SYMBOL_GPL(nbcon_enter_unsafe); + +/** + * nbcon_exit_unsafe - Exit an unsafe region in the driver + * @wctxt: The write context that was handed to the write function + * + * Return: True if this context still owns the console. False if + * ownership was handed over or taken. + * + * When this function returns false then the calling context no longer owns + * the console and is no longer allowed to go forward. In this case it must + * back out immediately and carefully. The buffer content is also no longer + * trusted since it no longer belongs to the calling context. + */ +bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt =3D &ACCESS_PRIVATE(wctxt, ctxt); + + return nbcon_context_exit_unsafe(ctxt); +} +EXPORT_SYMBOL_GPL(nbcon_exit_unsafe); + /** * nbcon_emit_next_record - Emit a record in the acquired context * @wctxt: The write context that will be handed to the write function --=20 2.39.2