Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752881Ab2BCMBs (ORCPT ); Fri, 3 Feb 2012 07:01:48 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:44754 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750798Ab2BCMBr (ORCPT ); Fri, 3 Feb 2012 07:01:47 -0500 X-AuditID: b753bd60-a1286ba000000655-99-4f2bcca72e0f X-AuditID: b753bd60-a1286ba000000655-99-4f2bcca72e0f Message-ID: <4F2BCCA4.7040002@hitachi.com> Date: Fri, 03 Feb 2012 21:01:40 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:9.0) Gecko/20111222 Thunderbird/9.0.1 MIME-Version: 1.0 To: Srikar Dronamraju Cc: Peter Zijlstra , Linus Torvalds , Oleg Nesterov , Ingo Molnar , Andrew Morton , LKML , Linux-mm , Andi Kleen , Christoph Hellwig , Steven Rostedt , Roland McGrath , Thomas Gleixner , Arnaldo Carvalho de Melo , Anton Arapov , Ananth N Mavinakayanahalli , Jim Keniston , Stephen Rothwell Subject: Re: [PATCH v10 3.3-rc2 1/9] uprobes: Install and remove breakpoints. References: <20120202141840.5967.39687.sendpatchset@srdronam.in.ibm.com> <20120202141851.5967.68000.sendpatchset@srdronam.in.ibm.com> In-Reply-To: <20120202141851.5967.68000.sendpatchset@srdronam.in.ibm.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2833 Lines: 87 (2012/02/02 23:18), Srikar Dronamraju wrote: > > Changelog: (Since v9) : Use insn_offset_modrm as suggested by Masami Hiramatsu. Would you add REX.B clearing code to handle_riprel_insn() too? Of course, that might not happen because it's a non-effective bit, however user can program it and pass it to uprobes. > +static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe, > + struct insn *insn) > +{ > + u8 *cursor; > + u8 reg; > + > + if (mm->context.ia32_compat) > + return; > + > + uprobe->arch_info.rip_rela_target_address = 0x0; > + if (!insn_rip_relative(insn)) > + return; > + So, here you need a REX.B clearing, like below. insn_get_length(insn); if (insn->rex_prefix.nbytes) { cursor = uprobe->insn + insn_offset_rex_prefix(insn); *cursor &= 0xfe; /* Clearing REX.B bit */ } > + /* > + * Point cursor at the modrm byte. The next 4 bytes are the > + * displacement. Beyond the displacement, for some instructions, > + * is the immediate operand. > + */ > + cursor = uprobe->insn + insn_offset_modrm(insn); > + insn_get_length(insn); > + > + /* > + * Convert from rip-relative addressing to indirect addressing > + * via a scratch register. Change the r/m field from 0x5 (%rip) > + * to 0x0 (%rax) or 0x1 (%rcx), and squeeze out the offset field. > + */ > + reg = MODRM_REG(insn); > + if (reg == 0) { > + /* > + * The register operand (if any) is either the A register > + * (%rax, %eax, etc.) or (if the 0x4 bit is set in the > + * REX prefix) %r8. In any case, we know the C register > + * is NOT the register operand, so we use %rcx (register > + * #1) for the scratch register. > + */ > + uprobe->arch_info.fixups = UPROBES_FIX_RIP_CX; > + /* Change modrm from 00 000 101 to 00 000 001. */ > + *cursor = 0x1; > + } else { > + /* Use %rax (register #0) for the scratch register. */ > + uprobe->arch_info.fixups = UPROBES_FIX_RIP_AX; > + /* Change modrm from 00 xxx 101 to 00 xxx 000 */ > + *cursor = (reg << 3); > + } > + > + /* Target address = address of next instruction + (signed) offset */ > + uprobe->arch_info.rip_rela_target_address = (long)insn->length > + + insn->displacement.value; > + /* Displacement field is gone; slide immediate field (if any) over. */ > + if (insn->immediate.nbytes) { > + cursor++; > + memmove(cursor, cursor + insn->displacement.nbytes, > + insn->immediate.nbytes); > + } > + return; > +} Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/