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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=ham 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 632DEC433DB for ; Mon, 1 Feb 2021 13:58:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D0D964EA2 for ; Mon, 1 Feb 2021 13:58:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232303AbhBAN6G (ORCPT ); Mon, 1 Feb 2021 08:58:06 -0500 Received: from foss.arm.com ([217.140.110.172]:60624 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232157AbhBAN6E (ORCPT ); Mon, 1 Feb 2021 08:58:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DEE01101E; Mon, 1 Feb 2021 05:57:18 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.41.104]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 50AB83F71A; Mon, 1 Feb 2021 05:57:17 -0800 (PST) Date: Mon, 1 Feb 2021 13:57:14 +0000 From: Mark Rutland To: Russell King - ARM Linux admin Cc: Giancarlo Ferrari , linux-kernel@vger.kernel.org, penberg@kernel.org, geert@linux-m68k.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, rppt@kernel.org, giancarlo.ferrari@nokia.com Subject: Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated Message-ID: <20210201135714.GB66060@C02TD0UTHF1T.local> References: <1612140296-12546-1-git-send-email-giancarlo.ferrari89@gmail.com> <20210201124720.GA66060@C02TD0UTHF1T.local> <20210201130344.GF1463@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210201130344.GF1463@shell.armlinux.org.uk> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 01, 2021 at 01:03:45PM +0000, Russell King - ARM Linux admin wrote: > On Mon, Feb 01, 2021 at 12:47:20PM +0000, Mark Rutland wrote: > > 1. copy reloc code into buffer > > 2. alter variables in copy of reloc code > > 3. branch to buffer > > > > ... which would avoid this class of problem too. > > Yep, slightly messy to do though: > > diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c > index 5d84ad333f05..6058e0d3a40d 100644 > --- a/arch/arm/kernel/machine_kexec.c > +++ b/arch/arm/kernel/machine_kexec.c > @@ -174,18 +174,27 @@ void machine_kexec(struct kimage *image) > > reboot_code_buffer = page_address(image->control_code_page); > > - /* Prepare parameters for reboot_code_buffer*/ > - set_kernel_text_rw(); > - kexec_start_address = image->start; > - kexec_indirection_page = page_list; > - kexec_mach_type = machine_arch_type; > - kexec_boot_atags = image->arch.kernel_r2; > - > /* copy our kernel relocation code to the control code page */ > reboot_entry = fncpy(reboot_code_buffer, > &relocate_new_kernel, > relocate_new_kernel_size); > > +#define set(what, val) \ > + do { \ > + uintptr_t __funcp_address; \ > + int __offset; \ > + void *__ptr; \ > + asm("" : "=r" (__funcp_address) : "0" (&relocate_new_kernel)); \ > + __offset = (uintptr_t)&(what) - (__funcp_address & ~1); \ > + __ptr = reboot_code_buffer + __offset; \ > + *(__typeof__(&(what)))__ptr = val; \ > + } while (0) > + > + set(kexec_start_address, image->start); > + set(kexec_indirection_page, page_list); > + set(kexec_mach_type, machine_arch_type); > + set(kexec_boot_atags, image->arch.kernel_r2); We could simplify this slightly if we moved the kexec_& variables into a struct (using asm-offset KEXEC_VAR_* offsets and a KEXEC_VAR_SIZE region reserved in the asm), then here we could do something like: static struct kexec_vars *kexec_buffer_vars(void *buffer) { unsigned long code = ((unisigned long)relocate_new_kernel) & ~1; unsigned long vars - (unsigned long)relocate_vars; unsigned long offset = vars - code; return buffer + offset; } ... and in machine_kexec() do: struct kexec_vars *kv = kexec_buffer_vars(reboot_code_buffer); kv->start_address = image->start; kv->indirection_page = page_list; kv->mach_type = machine-arch_type; kv->boot_atags = arch.kernel_r2; ... if that looks any better to you? Mark.