Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754401AbdHYBty (ORCPT ); Thu, 24 Aug 2017 21:49:54 -0400 Received: from mail-pg0-f41.google.com ([74.125.83.41]:37478 "EHLO mail-pg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754066AbdHYBtx (ORCPT ); Thu, 24 Aug 2017 21:49:53 -0400 Date: Fri, 25 Aug 2017 10:49:46 +0900 From: AKASHI Takahiro To: Mark Rutland Cc: catalin.marinas@arm.com, will.deacon@arm.com, bauerman@linux.vnet.ibm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, akpm@linux-foundation.org, mpe@ellerman.id.au, dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de, ard.biesheuvel@linaro.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 13/14] arm64: kexec_file: add Image format support Message-ID: <20170825014942.GB7282@akashi-kouhiroshi-no-MacBook-Air.local> Mail-Followup-To: AKASHI Takahiro , Mark Rutland , catalin.marinas@arm.com, will.deacon@arm.com, bauerman@linux.vnet.ibm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, akpm@linux-foundation.org, mpe@ellerman.id.au, dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de, ard.biesheuvel@linaro.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20170824081811.19299-1-takahiro.akashi@linaro.org> <20170824081811.19299-14-takahiro.akashi@linaro.org> <20170824172337.GF29665@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170824172337.GF29665@leverpostej> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3190 Lines: 107 On Thu, Aug 24, 2017 at 06:23:37PM +0100, Mark Rutland wrote: > On Thu, Aug 24, 2017 at 05:18:10PM +0900, AKASHI Takahiro wrote: > > The "Image" binary will be loaded at the offset of TEXT_OFFSET from > > the start of system memory. TEXT_OFFSET is basically determined from > > the header of the image. > > What's the policy for the binary types kexec_file_load() will load, and > how are these identified? AFAICT, there are no flags, so it looks like > we're just checking the magic and hoping. Yes, please see image_probe(). > > Regarding kernel verification, it will be done through > > verify_pefile_signature() as arm64's "Image" binary can be seen as > > in PE format. This approach is consistent with x86 implementation. > > This will not work for kernels built without CONFIG_EFI, where we don't > have a PE header. Right. > What happens in that case? In this case, we cannot find a signature in the binary when loading, so kexec just fails. Signature is a must if the kernel is configured with KEXEC_FILE_VERIFY. Thanks, -Takahiro AKASHI > [...] > > > +/** > > + * arm64_header_check_msb - Helper to check the arm64 image header. > > + * > > + * Returns non-zero if the image was built as big endian. > > + */ > > + > > +static inline int arm64_header_check_msb(const struct arm64_image_header *h) > > +{ > > + if (!h) > > + return 0; > > + > > + return !!(h->flags[7] & arm64_image_flag_7_be); > > +} > > What are we going to use this for? Nowhere. I forgot to remove it. > In kernel, we use the term "BE" rather than "MSB", and it's unfortunate > to have code with varying naming conventions. > > [...] > > > +static void *image_load(struct kimage *image, char *kernel, > > + unsigned long kernel_len, char *initrd, > > + unsigned long initrd_len, char *cmdline, > > + unsigned long cmdline_len) > > +{ > > + struct kexec_buf kbuf; > > + struct arm64_image_header *h = (struct arm64_image_header *)kernel; > > + unsigned long text_offset, kernel_load_addr; > > + int ret; > > + > > + /* Create elf core header segment */ > > + ret = load_crashdump_segments(image); > > + if (ret) > > + goto out; > > + > > + /* Load the kernel */ > > + kbuf.image = image; > > + if (image->type == KEXEC_TYPE_CRASH) { > > + kbuf.buf_min = crashk_res.start; > > + kbuf.buf_max = crashk_res.end + 1; > > + } else { > > + kbuf.buf_min = 0; > > + kbuf.buf_max = ULONG_MAX; > > + } > > + kbuf.top_down = 0; > > + > > + kbuf.buffer = kernel; > > + kbuf.bufsz = kernel_len; > > + if (h->image_size) { > > + kbuf.memsz = le64_to_cpu(h->image_size); > > + text_offset = le64_to_cpu(h->text_offset); > > + } else { > > + /* v3.16 or older */ > > + kbuf.memsz = kbuf.bufsz; /* NOTE: not including BSS */ > > Why bother supporting < 3.16 kernels? Because kexec-tools does :) > They predate regulate kexec, we know we don't have enough information to > boot such kernels reliably, and arguably attempting to load one would > indicate some kind of rollback attack. Around the time when Geoff were originally working on kexec, there might be some possibility that people might want to boot a bit older kernel, I guess. Thanks, -Takahiro AKASHI > Thanks, > Mark.