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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 A87F2C433E1 for ; Mon, 29 Jun 2020 18:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 94BE52063A for ; Mon, 29 Jun 2020 18:42:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729119AbgF2Smv (ORCPT ); Mon, 29 Jun 2020 14:42:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729011AbgF2Smm (ORCPT ); Mon, 29 Jun 2020 14:42:42 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 808C9C033C09; Mon, 29 Jun 2020 11:26:30 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jpyU9-002DtD-0S; Mon, 29 Jun 2020 18:26:29 +0000 From: Al Viro To: Linus Torvalds Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, David Miller , Tony Luck , Will Deacon Subject: [PATCH 04/41] [ia64] sanitize elf_access_gpreg() Date: Mon, 29 Jun 2020 19:25:51 +0100 Message-Id: <20200629182628.529995-4-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20200629182628.529995-1-viro@ZenIV.linux.org.uk> References: <20200629182349.GA2786714@ZenIV.linux.org.uk> <20200629182628.529995-1-viro@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro The function takes the register number, finds the corresponding field of pt_regs for registers that are saved there or does the unwind for the registers that end up spilled on the kernel stack. Then it reads from or writes to the resulting location. Unfortunately, finding the required pt_regs field is done by rather horrible switch. It's microoptimized in all the wrong places - it even uses the knowledge that fields for r8..r11 follow each other in pt_regs layout, while r12..r13 are not adjacent to those, etc. All of that is to encode the mapping from register numbers to offsets + the information that r4..r7 are not to be found in pt_regs. It's deeply in nasal demon territory, at that - the games it plays with pointer arithmetics on addresses of structure members are undefined behaviour. Valid C ends up with better code in this case: just initialize a constant array with offsets of relevant pt_regs fields and we don't need that switch anymore. Signed-off-by: Al Viro --- arch/ia64/kernel/ptrace.c | 57 +++++++++++++++++++---------------------------- 1 file changed, 23 insertions(+), 34 deletions(-) diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c index 82aaacf64583..b9d068903b98 100644 --- a/arch/ia64/kernel/ptrace.c +++ b/arch/ia64/kernel/ptrace.c @@ -1273,52 +1273,41 @@ struct regset_getset { int ret; }; +static const ptrdiff_t pt_offsets[16] = +{ +#define R(n) offsetof(struct pt_regs, r##n) + [0] = -1, R(1), R(2), R(3), + [4] = -1, [5] = -1, [6] = -1, [7] = -1, + R(8), R(9), R(10), R(11), R(12), R(13), R(14), R(15), +#undef R +}; + static int access_elf_gpreg(struct task_struct *target, struct unw_frame_info *info, unsigned long addr, unsigned long *data, int write_access) { - struct pt_regs *pt; - unsigned long *ptr = NULL; - int ret; - char nat = 0; + struct pt_regs *pt = task_pt_regs(target); + unsigned reg = addr / sizeof(unsigned long); + ptrdiff_t d = pt_offsets[reg]; - pt = task_pt_regs(target); - switch (addr) { - case ELF_GR_OFFSET(1): - ptr = &pt->r1; - break; - case ELF_GR_OFFSET(2): - case ELF_GR_OFFSET(3): - ptr = (void *)&pt->r2 + (addr - ELF_GR_OFFSET(2)); - break; - case ELF_GR_OFFSET(4) ... ELF_GR_OFFSET(7): + if (d >= 0) { + unsigned long *ptr = (void *)pt + d; + if (write_access) + *ptr = *data; + else + *data = *ptr; + return 0; + } else { + char nat = 0; if (write_access) { /* read NaT bit first: */ unsigned long dummy; - - ret = unw_get_gr(info, addr/8, &dummy, &nat); + int ret = unw_get_gr(info, reg, &dummy, &nat); if (ret < 0) return ret; } - return unw_access_gr(info, addr/8, data, &nat, write_access); - case ELF_GR_OFFSET(8) ... ELF_GR_OFFSET(11): - ptr = (void *)&pt->r8 + addr - ELF_GR_OFFSET(8); - break; - case ELF_GR_OFFSET(12): - case ELF_GR_OFFSET(13): - ptr = (void *)&pt->r12 + addr - ELF_GR_OFFSET(12); - break; - case ELF_GR_OFFSET(14): - ptr = &pt->r14; - break; - case ELF_GR_OFFSET(15): - ptr = &pt->r15; + return unw_access_gr(info, reg, data, &nat, write_access); } - if (write_access) - *ptr = *data; - else - *data = *ptr; - return 0; } static int -- 2.11.0