From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752062AbeCUL2e (ORCPT ); Wed, 21 Mar 2018 07:28:34 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:34746 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751907AbeCUL2N (ORCPT ); Wed, 21 Mar 2018 07:28:13 -0400 From: Philipp Rudo To: kexec@lists.infradead.org, linux-s390@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Biederman , Vivek Goyal , Michael Ellerman , Thiago Jung Bauermann , Martin Schwidefsky , Heiko Carstens , Andrew Morton , x86@kernel.org, Dave Young , AKASHI Takahiro , Ingo Molnar Subject: [PATCH v2 09/11] kexec_file: Remove mis-use of sh_offset field during purgatory load Date: Wed, 21 Mar 2018 12:27:49 +0100 X-Mailer: git-send-email 2.13.5 In-Reply-To: <20180321112751.22196-1-prudo@linux.vnet.ibm.com> References: <20180321112751.22196-1-prudo@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18032111-0020-0000-0000-00000407BAE1 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18032111-0021-0000-0000-0000429BD8F9 Message-Id: <20180321112751.22196-10-prudo@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-21_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803210139 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current code uses the sh_offset field in purgatory_info->sechdrs to store a pointer to the current load address of the section. Depending whether the section will be loaded or not this is either a pointer into purgatory_info->purgatory_buf or kexec_purgatory. This is not only a violation of the ELF standard but also makes the code very hard to understand as you cannot tell if the memory you are using is read-only or not. Remove this mis-use and store the offset of the section in pugaroty_info->purgatory_buf in sh_offset. Signed-off-by: Philipp Rudo --- arch/x86/kernel/machine_kexec_64.c | 10 ++++++---- kernel/kexec_file.c | 37 +++++++------------------------------ 2 files changed, 13 insertions(+), 34 deletions(-) diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 51667c8b5c9b..41db74bdc88b 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -457,13 +457,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, * rel[i].r_offset contains byte offset from beginning * of section to the storage unit affected. * - * This is location to update (->sh_offset). This is temporary - * buffer where section is currently loaded. This will finally - * be loaded to a different address later, pointed to by + * This is location to update. This is temporary buffer + * where section is currently loaded. This will finally be + * loaded to a different address later, pointed to by * ->sh_addr. kexec takes care of moving it * (kexec_load_segment()). */ - location = (void *)(section->sh_offset + rel[i].r_offset); + location = pi->purgatory_buf; + location += section->sh_offset; + location += rel[i].r_offset; /* Final address of the location */ address = section->sh_addr + rel[i].r_offset; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 746b91e46e34..1478766c7754 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -729,6 +729,10 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, Elf_Shdr *sechdrs; int i; + /* + * The section headers in kexec_purgatory are read-only. In order to + * have them modifiable make a temporary copy. + */ sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr)); if (!sechdrs) return -ENOMEM; @@ -736,28 +740,6 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, pi->ehdr->e_shnum * sizeof(Elf_Shdr)); pi->sechdrs = sechdrs; - /* - * We seem to have multiple copies of sections. First copy is which - * is embedded in kernel in read only section. Some of these sections - * will be copied to a temporary buffer and relocated. And these - * sections will finally be copied to their final destination at - * segment load time. - * - * Use ->sh_offset to reflect section address in memory. It will - * point to original read only copy if section is not allocatable. - * Otherwise it will point to temporary copy which will be relocated. - * - * Use ->sh_addr to contain final address of the section where it - * will go during execution time. - */ - for (i = 0; i < pi->ehdr->e_shnum; i++) { - if (sechdrs[i].sh_type == SHT_NOBITS) - continue; - - sechdrs[i].sh_offset = (unsigned long)pi->ehdr + - sechdrs[i].sh_offset; - } - offset = 0; bss_addr = kbuf->mem + kbuf->bufsz; kbuf->image->start = pi->ehdr->e_entry; @@ -786,17 +768,12 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, kbuf->image->start += kbuf->mem + offset; } - src = (void *)sechdrs[i].sh_offset; + src = (void *)pi->ehdr + sechdrs[i].sh_offset; dst = pi->purgatory_buf + offset; memcpy(dst, src, sechdrs[i].sh_size); sechdrs[i].sh_addr = kbuf->mem + offset; - - /* - * This section got copied to temporary buffer. Update - * ->sh_offset accordingly. - */ - sechdrs[i].sh_offset = (unsigned long)dst; + sechdrs[i].sh_offset = offset; offset += sechdrs[i].sh_size; } @@ -1006,7 +983,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, return -EINVAL; } - sym_buf = (char *)sec->sh_offset + sym->st_value; + sym_buf = (char *)pi->purgatory_buf + sec->sh_offset + sym->st_value; if (get_value) memcpy((void *)buf, sym_buf, size); -- 2.13.5