Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759769AbXEWQkV (ORCPT ); Wed, 23 May 2007 12:40:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934235AbXEWQjy (ORCPT ); Wed, 23 May 2007 12:39:54 -0400 Received: from [198.99.130.12] ([198.99.130.12]:34972 "EHLO saraswathi.solana.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1765588AbXEWQjx (ORCPT ); Wed, 23 May 2007 12:39:53 -0400 Date: Wed, 23 May 2007 12:33:01 -0400 From: Jeff Dike To: Andrew Morton Cc: LKML , uml-devel , balajig81@gmail.com Subject: [PATCH 1/2] UML - Improve PTRACE_SYSEMU checking Message-ID: <20070523163301.GA5558@c2.user-mode-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2539 Lines: 65 Make the PTRACE_SYSEMU checking more robust. It will make sure that system call numbers are reported correctly. If there is a problem, it will disable PTRACE_SYSEMU use and use PTRACE_SYSCALL instead. Thanks to Balaji G for helping reproduce this problem. Signed-off-by: Jeff Dike -- arch/um/os-Linux/start_up.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) Index: linux-2.6.21-mm/arch/um/os-Linux/start_up.c =================================================================== --- linux-2.6.21-mm.orig/arch/um/os-Linux/start_up.c 2007-05-16 18:23:49.000000000 -0400 +++ linux-2.6.21-mm/arch/um/os-Linux/start_up.c 2007-05-22 17:47:57.000000000 -0400 @@ -144,9 +144,7 @@ static int stop_ptraced_child(int pid, v int exit_with = WEXITSTATUS(status); if (exit_with == 2) non_fatal("check_ptrace : child exited with status 2. " - "Serious trouble happening! Try updating " - "your host skas patch!\nDisabling SYSEMU " - "support."); + "\nDisabling SYSEMU support.\n"); non_fatal("check_ptrace : child exited with exitcode %d, while " "expecting %d; status 0x%x\n", exit_with, exitcode, status); @@ -209,6 +207,7 @@ __uml_setup("nosysemu", nosysemu_cmd_par static void __init check_sysemu(void) { void *stack; + unsigned long regs[MAX_REG_NR]; int pid, n, status, count=0; non_fatal("Checking syscall emulation patch for ptrace..."); @@ -225,11 +224,20 @@ static void __init check_sysemu(void) fatal("check_sysemu : expected SIGTRAP, got status = %d", status); - n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, - os_getpid()); - if(n < 0) - fatal_perror("check_sysemu : failed to modify system call " - "return"); + if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0) + fatal_perror("check_sysemu : PTRACE_GETREGS failed"); + if(PT_SYSCALL_NR(regs) != __NR_getpid){ + non_fatal("check_sysemu got system call number %d, " + "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid); + goto fail; + } + + n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, os_getpid()); + if(n < 0){ + non_fatal("check_sysemu : failed to modify system call " + "return"); + goto fail; + } if (stop_ptraced_child(pid, stack, 0, 0) < 0) goto fail_stopped; - 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/