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[23.128.96.35]) by mx.google.com with ESMTPS id n5-20020a632705000000b005c665c81b7bsi510776pgn.36.2023.12.06.13.33.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Dec 2023 13:33:37 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35; Authentication-Results: mx.google.com; dkim=pass header.i=@amazon.com header.s=amazon201209 header.b=Yxvzotlq; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=amazon.com Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by groat.vger.email (Postfix) with ESMTP id 971EB80D6507; Wed, 6 Dec 2023 13:33:30 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at groat.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230340AbjLFVdW (ORCPT + 99 others); Wed, 6 Dec 2023 16:33:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229679AbjLFVdV (ORCPT ); Wed, 6 Dec 2023 16:33:21 -0500 Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E65ACD5C; Wed, 6 Dec 2023 13:33:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1701898408; x=1733434408; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=olXMY6IT8d9dmgacsnRgFeTZm0WgXJ1U7yVx5NNY3To=; b=YxvzotlqmijvJgPVVPwxfkQbUystmXG3eLx/7xmblqPL4tGk6E3KCrU8 JvuqXH2aDvDVhsVM0EnYOYjFvWpinKe4sP8HCtVMrC3HG7SJBbhrOGU9X HfRPRyI3681O3GRWMnMgLRdwyZA6RUyTqsI/VC3Hur4Gydyq3kNxgX6nj s=; X-IronPort-AV: E=Sophos;i="6.04,256,1695686400"; d="scan'208";a="257298916" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-m6i4x-ed19f671.us-west-2.amazon.com) ([10.25.36.214]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Dec 2023 21:33:28 +0000 Received: from smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev (pdx2-ws-svc-p26-lb5-vlan3.pdx.amazon.com [10.39.38.70]) by email-inbound-relay-pdx-2b-m6i4x-ed19f671.us-west-2.amazon.com (Postfix) with ESMTPS id 32CEA82660; Wed, 6 Dec 2023 21:33:27 +0000 (UTC) Received: from EX19MTAUWA002.ant.amazon.com [10.0.7.35:14806] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.56.214:2525] with esmtp (Farcaster) id 9e65d653-7053-45d0-8def-e5b76986597e; Wed, 6 Dec 2023 21:33:26 +0000 (UTC) X-Farcaster-Flow-ID: 9e65d653-7053-45d0-8def-e5b76986597e Received: from EX19D020UWC004.ant.amazon.com (10.13.138.149) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Wed, 6 Dec 2023 21:33:26 +0000 Received: from dev-dsk-graf-1a-5ce218e4.eu-west-1.amazon.com (10.253.83.51) by EX19D020UWC004.ant.amazon.com (10.13.138.149) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Wed, 6 Dec 2023 21:33:25 +0000 From: Alexander Graf To: CC: , Andrew Morton , Jonathan Corbet , Greg Kroah-Hartman , =?utf-8?q?Jan_H_=2E_Sch?= =?utf-8?q?=C3=B6nherr?= , James Gowans Subject: [PATCH v2] initramfs: Expose retained initrd as sysfs file Date: Wed, 6 Dec 2023 21:33:23 +0000 Message-ID: <20231206213323.78233-1-graf@amazon.com> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-Originating-IP: [10.253.83.51] X-ClientProxiedBy: EX19D036UWB004.ant.amazon.com (10.13.139.170) To EX19D020UWC004.ant.amazon.com (10.13.138.149) X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE, UNPARSEABLE_RELAY autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Wed, 06 Dec 2023 13:33:31 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784542346505758322 X-GMAIL-MSGID: 1784569834296303487 When the kernel command line option "retain_initrd" is set, we do not free the initrd memory. However, we also don't expose it to anyone for consumption. That leaves us in a weird situation where the only user of this feature is ppc64 and arm64 specific kexec tooling. To make it more generally useful, this patch adds a kobject to the firmware object that contains the initrd context when "retain_initrd" is set. That way, we can access the initrd any time after boot from user space and for example hand it into kexec as --initrd parameter if we want to reboot the same initrd. Or inspect it directly locally. With this patch applied, there is a new /sys/firmware/initrd file when the kernel was booted with an initrd and "retain_initrd" command line option is set. Signed-off-by: Alexander Graf Tested-by: Bagas Sanjaya --- v1 -> v2: - Reword commit message to explain the new file path - Add a Documentation/ABI/testing/sysfs-firmware-initrd file --- .../ABI/testing/sysfs-firmware-initrd | 8 ++++++++ .../admin-guide/kernel-parameters.txt | 5 +++-- init/initramfs.c | 18 +++++++++++++++++- 3 files changed, 28 insertions(+), 3 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-firmware-initrd diff --git a/Documentation/ABI/testing/sysfs-firmware-initrd b/Documentation/ABI/testing/sysfs-firmware-initrd new file mode 100644 index 000000000000..20bf7cf77a19 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-firmware-initrd @@ -0,0 +1,8 @@ +What: /sys/firmware/initrd +Date: December 2023 +Contact: Alexander Graf +Description: + When the kernel was booted with an initrd and the + "retain_initrd" option is set on the kernel command + line, /sys/firmware/initrd contains the contents of the + initrd that the kernel was booted with. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 65731b060e3f..51575cd31741 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2438,7 +2438,7 @@ between unregistering the boot console and initializing the real console. - keepinitrd [HW,ARM] + keepinitrd [HW,ARM] See retain_initrd. kernelcore= [KNL,X86,IA-64,PPC] Format: nn[KMGTPE] | nn% | "mirror" @@ -5580,7 +5580,8 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). - retain_initrd [RAM] Keep initrd memory after extraction + retain_initrd [RAM] Keep initrd memory after extraction. After boot, it will + be accessible via /sys/firmware/initrd. retbleed= [X86] Control mitigation of RETBleed (Arbitrary Speculative Code Execution with Return Instructions) diff --git a/init/initramfs.c b/init/initramfs.c index 8d0fd946cdd2..25244e2a5739 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -574,6 +574,16 @@ extern unsigned long __initramfs_size; #include #include +static ssize_t raw_read(struct file *file, struct kobject *kobj, + struct bin_attribute *attr, char *buf, + loff_t pos, size_t count) +{ + memcpy(buf, attr->private + pos, count); + return count; +} + +static BIN_ATTR(initrd, 0440, raw_read, NULL, 0); + void __init reserve_initrd_mem(void) { phys_addr_t start; @@ -715,8 +725,14 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie) * If the initrd region is overlapped with crashkernel reserved region, * free only memory that is not part of crashkernel region. */ - if (!do_retain_initrd && initrd_start && !kexec_free_initrd()) + if (!do_retain_initrd && initrd_start && !kexec_free_initrd()) { free_initrd_mem(initrd_start, initrd_end); + } else if (do_retain_initrd) { + bin_attr_initrd.size = initrd_end - initrd_start; + bin_attr_initrd.private = (void *)initrd_start; + if (sysfs_create_bin_file(firmware_kobj, &bin_attr_initrd)) + pr_err("Failed to create initrd sysfs file"); + } initrd_start = 0; initrd_end = 0;