Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934480AbZDBR0h (ORCPT ); Thu, 2 Apr 2009 13:26:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764126AbZDBRYk (ORCPT ); Thu, 2 Apr 2009 13:24:40 -0400 Received: from mx2.redhat.com ([66.187.237.31]:43053 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764524AbZDBRYh (ORCPT ); Thu, 2 Apr 2009 13:24:37 -0400 Message-ID: <49D4F4E9.2030809@redhat.com> Date: Thu, 02 Apr 2009 13:24:57 -0400 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Ingo Molnar , Ananth N Mavinakayanahalli , Jim Keniston CC: LKML , systemtap-ml , kvm@vger.kernel.org, Andi Kleen , Andrew Morton , Arnaldo Carvalho de Melo , Steven Rostedt , Frederic Weisbecker Subject: [PATCH -tip 4/6 V4] x86: kprobes checks safeness of insertion address. X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2986 Lines: 110 Ensure safeness of inserting kprobes by checking whether the specified address is at the first byte of a instruction. This is done by decoding probed function from its head to the probe point. Signed-off-by: Masami Hiramatsu Cc: Ananth N Mavinakayanahalli Cc: Jim Keniston Cc: Ingo Molnar --- arch/x86/kernel/kprobes.c | 51 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 51 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 7b5169d..39c79cc 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -48,12 +48,14 @@ #include #include #include +#include #include #include #include #include #include +#include void jprobe_return_end(void); @@ -244,6 +246,53 @@ retry: } } +/* Recover original instruction */ +static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) +{ + struct kprobe *kp; + kp = get_kprobe((void *)addr); + if (!kp) + return -EINVAL; + + /* Don't use p->ainsn.insn; which will be modified by fix_riprel */ + memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); + buf[0] = kp->opcode; + return 0; +} + +/* Dummy buffers for lookup_symbol_attrs */ +static char __dummy_buf[KSYM_NAME_LEN]; + +/* Check whether the address can be probed */ +static int __kprobes can_probe(unsigned long paddr) +{ + int ret; + unsigned long addr, offset = 0; + struct insn insn; + kprobe_opcode_t buf[MAX_INSN_SIZE]; + + /* Lookup symbol including addr */ + if (!kallsyms_lookup(paddr, NULL, &offset, NULL, __dummy_buf)) + return 0; + + /* Decode instructions */ + addr = paddr - offset; + while (addr < paddr) { + insn_init_kernel(&insn, (void *)addr); + insn_get_opcode(&insn); + if (OPCODE1(&insn) == BREAKPOINT_INSTRUCTION) { + ret = recover_probed_instruction(buf, addr); + if (ret) + return 0; + insn_init_kernel(&insn, buf); + } + insn_get_length(&insn); + addr += insn.length; + } + + return (addr == paddr); +} + /* * Returns non-zero if opcode modifies the interrupt flag. */ @@ -359,6 +408,8 @@ static void __kprobes arch_copy_kprobe(struct kprobe *p) int __kprobes arch_prepare_kprobe(struct kprobe *p) { + if (!can_probe((unsigned long)p->addr)) + return -EILSEQ; /* insn: must be on special executable page on x86. */ p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn) -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@redhat.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/