From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FORGED_YAHOO_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68591C433DF for ; Wed, 5 Aug 2020 21:54:09 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B0F0C206F6 for ; Wed, 5 Aug 2020 21:54:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=yahoo.com header.i=@yahoo.com header.b="Ar0AGd4L" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B0F0C206F6 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=yahoo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BMQPT72DrzDqdM for ; Thu, 6 Aug 2020 07:54:05 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=yahoo.com (client-ip=66.163.190.32; helo=sonic307-9.consmr.mail.ne1.yahoo.com; envelope-from=ecs_dn@yahoo.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=reject dis=none) header.from=yahoo.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=yahoo.com header.i=@yahoo.com header.a=rsa-sha256 header.s=s2048 header.b=Ar0AGd4L; dkim-atps=neutral Received: from sonic307-9.consmr.mail.ne1.yahoo.com (sonic307-9.consmr.mail.ne1.yahoo.com [66.163.190.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4BMQMQ2S3CzDqd0 for ; Thu, 6 Aug 2020 07:52:15 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048; t=1596664330; bh=IKr+A8SMCtydYzCmcfJVV74xj/D6IbcnYDNHPp3I+Ww=; h=Date:From:To:In-Reply-To:Subject:References:From:Subject; b=Ar0AGd4L44AzNJDQjHiAFN/nkoGlVJqtXHW7KFFhOYWXcI87q+D5cA9Par/iRGAIGeFETQEzFBa3n7/tfKQGYagWQUEBAx3EgRrOt6EeKBfOko+gLiorP3BX7GyA9HFO6yv5VymkgRsKpMOmGcq06AG1wWSd+Tr/sYMqFx09XAKoiB/Y86bdt+0aVi8U5eGcUfP1Ul1ReaPP4X8BfzAjppnkRKM4oevhogWQA4VNqAOefLl047GhNK1/r2+0V2hRox+cMqhUxMJB2Vkwe4YLCvpxtwTKdPcRw4DCDKCgYxZzXRhxo/qukFkn68vA3wOC26M0qXsW8ULtbNeTxZY3EA== X-YMail-OSG: 8mrt9YEVM1l3q0B6P3BYMWhpA6EkM_qwuOeVzamd_ocXvlTDMTKGBASOeoxJQTI PZTqvYIMuwz8xcjfvC8fpNntwzBMyVAfjw_uLZP4u9yltYiHwMARaicAeAqQbNx2tnrNbtq4rOcI F4pkXeModow.u6kCLYHeq9E6EHjzjtMfVFzcyD261sZTSKWhtTR3zVtBWNp_ZT5oM1s_BdKSamHs 4dtqUFiVehZAnfbAj7BypTkzb6TZGpoYSVSK9rUWEkAnYrdfC_KqRgjN_kddL0kKgPOpsQ4xXniz m.HiF_ZdLGeSCjDFpghKl5y4Y6wIpHa1SyWxa4wYHwVGT5UjYnFonipmuGcoFzwdtsmeoMInXbAF 1kdmtK3.W.BN6Te4DOYogLuXv2MX1ytmwbBWVDoqaCu3NJn4DMRWmgkBa_OSS.g9TiyjM2uci0kX oqev8s5O.zpILI8TVkHNI.wrHBE3azvw.8ilzx44SyGfwY6fBuEYfF0XW3BuMxxDxclt2T1QX4If m9sgxgAmHhRphkst8fMx.SZLvT9EhariKpCBqJd1k7E3B2wn.8RnNDUEY2keCv749P062EJkUqVC sE1ejxvCohGmIvKqjSCZdDi0m5vORnN_exiBuAg0vJRLmcDMOT19rK9HB4M7k2ciybP7K.M_MjjS jNIJxBHlH5YMlXkJdGLJWDNvfcP4MWurCakCqphtqgdYlZ.oZnJg2yhjNzrlMbKxvHAMx3.UUjWc ocIDfYEtSknvXrPt.Hjys7gZk9fX9oCySWhNvfI9GVJUywl5j2AmP1sqyFpwSAv3TVYipWvld5Wz cMqvGHfMz0CvR0Z1xZkaKhAbzSmmL6EARxWfoI8yikiucmR2vLrLBNVKnruFus6Iui5MNMw7WJf_ FQsZh2xVQMgcR4Py5oZ1NdwBI3LwSSjOAmM5D5ykeyKXp.QpJucyjqRrikJ5dlm_xBIWQzDrYzNe iq9EN42x1.tKnsW4kNopgSeC2eC.fedwts2baaPop6EJCONVAIbXnuXGD1h0XPSAj7tyD1afMdkZ UzW6a7ji34DkfsQOOtALaR5yyVb4xw77rdh5O29_QNnp6XJXhcpeBXVgmTABdgsFh3ucwjtFygw7 sGYZ6mUf5NE2IWCGYAfhmt4VKVo.OsFph3.Y7AjG2F1GQuFFyo5nVd3cTQt3QuilrXYyeiSsiBEZ PXLDf9ERGsLCkx0BPL1k1fAzqXdKWXMHcUtYTyOTetcUUY5ueDWij1j1AEHLjzYqVEVksOVxwlK0 JwJ0tgclfD981LQLIClOKD6cTU0RMqp54qvtmH1rgApLZ4PJZTZRNXN1afZU1EI4TH6nDAlP4Wty TfvhsWLnTzhRh7SjD7Sw92.ln Received: from sonic.gate.mail.ne1.yahoo.com by sonic307.consmr.mail.ne1.yahoo.com with HTTP; Wed, 5 Aug 2020 21:52:10 +0000 Received: by smtp409.mail.ne1.yahoo.com (VZM Hermes SMTP Server) with ESMTPA ID 7d2658b8c0bb2faf86b243b1b22b29e0; Wed, 05 Aug 2020 21:52:06 +0000 (UTC) Date: Wed, 5 Aug 2020 14:52:58 -0700 (PDT) From: thefirst ECS To: linuxppc-dev@lists.ozlabs.org Message-ID: <32112832.26959.1596664366002.JavaMail.Dan@DanHP> In-Reply-To: <3103222.25048.1596318084416.JavaMail.Dan@DanHP> Subject: How would I code a Write to a proc file from within the kernel without reading anything from user space? MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit References: <32112832.26959.1596664366002.JavaMail.Dan.ref@DanHP> X-Mailer: WebService/1.1.16436 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo Apache-HttpAsyncClient/4.1.4 (Java/11.0.7) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" In order to help debug a certain discrepancy, I need to "simulate" an "echo 1 > /proc/file" but doing it from kernel even when root file system is unavailable. I have simulated it just fine via call_usermodehelper (with argv etc of "echo 1 > /proc/file") from inside the kernel which triggers: [ee897ec0] [c0122704] proc_reg_write+0x80/0xb4 [ee897ef0] [c00d3b7c] vfs_write+0xb4/0x184 just as I had wanted. But now I need to trigger the "vfs_write" and "proc_reg_write" but without using call_usermodehelper since I will be doing it when root "/" is unavailable and so I can no longer access /bin/echo and call the usermodehelper etc. So my question is how can I do that in kernel? Not sure if I'm supposed to look in fs read_write.c and fs.h and write a method based on those or if there's some other way etc. Thanks, -Dan