From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Cipher TLSv1:DES-CBC3-SHA:168) (Exim 3.31-VA-mm2 #1 (Debian)) id 19zKgt-00078a-00 for ; Tue, 16 Sep 2003 11:36:43 -0700 Received: from smtp101.mail.sc5.yahoo.com ([216.136.174.139]) by sc8-sf-mx1.sourceforge.net with smtp (Exim 4.22) id 19zKgs-00044l-VG for user-mode-linux-devel@lists.sourceforge.net; Tue, 16 Sep 2003 11:36:42 -0700 From: BlaisorBlade Subject: Re: [uml-devel] [PATCH] Starting a command inside UML from mconsole References: <200309131820.45833.blaisorblade_spam@yahoo.it> In-Reply-To: <200309131820.45833.blaisorblade_spam@yahoo.it> MIME-Version: 1.0 Content-Type: Multipart/Mixed; boundary="Boundary-00=_JY1Z/ASpVgDlYwv" Message-Id: <200309162027.22242.blaisorblade_spam@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: Date: Tue, 16 Sep 2003 20:27:21 +0200 To: user-mode-linux-devel@lists.sourceforge.net --Boundary-00=_JY1Z/ASpVgDlYwv Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi, I have finally some working code. I've cleaned it up and it works quite well, now I only need to setup the file handling. Also, it can be configured with CONFIG_MCONSOLE_EXEC. Note that if disabled, for header issues, it defines the exec command anyway but it pretends not to exist(and is not showed in the However, there is a problem I'm investigating on. Even if the execve fails, it reports success. I've debugged it and it showed up that threads synchronize properly(i.e. CLONE_VFORK works) and that the fault seems to be in kmod.c:exec_usermodehelper. It seems that this code, at the end of the function: if (execve(program_path, argv, envp) < 0) return -errno; return 0; is wrong. Execve returns -2(i.e. -ENOENT), but I've not found a place where errno is set. It seems that it's not a UML problem, either: simply that code should be: return execve(program_path, argv, envp); because kernel functions don't set errno. However I need confirms on this. -- cat <= - Add a new device to UML; \n\ same syntax as command line \n\ config - Query the configuration of a device \n\ @@ -265,6 +272,149 @@ reactivate_fd(req->originating_fd, MCONSOLE_IRQ); mconsole_reply(req, "", 0, 0); } +#ifdef CONFIG_MCONSOLE_EXEC +/* This is the focal point of the exec patch. Much code comes from + * kernel/kmod.c. But I just couldn't use call_usermodehelper, because it must be + * called from process context.*/ +struct subprocess_info { + char *command; + int retval; +}; + +/* This function parses arguments from buf to the argv array. + * When it goes on a space, starts a new arguments. If it starts with a quote, + * it will end at the first matching quote(of the same tipe) which is not escaped with a \. + * Otherwise, the arg ends at the first space and can freely contain quotes. + * After this, in each argument \ is replaced by char.*/ +static void parse_args(char *buf, size_t size, char **argv) { + char *start_arg = buf, *end_arg; + int i = 0, must_not_break = 1; + + start_arg += strlen("exec"); + + while (i < size - 1 && must_not_break) { + while(isspace(*start_arg)) + start_arg++; + + if (*start_arg == '\0') + break; + + end_arg = start_arg; + if (*start_arg == '\"' || *start_arg == '\'') { /*quoted arg*/ + end_arg++; + /*while (1) { + while (*end_arg != *start_arg && *end_arg != '\0') + end_arg++; + if (*(end_arg - 1) != '\\' || *end_arg == '\0') + break; + end_arg++; + }*/ + while ((*end_arg != *start_arg || *(end_arg - 1) == '\\') + && *end_arg != '\0') + end_arg++; + start_arg++; /*skips the first quote*/ + } else { + while(!isspace(*end_arg) && *end_arg != '\0') + end_arg++; + } + argv[i++] = start_arg; + + if (*end_arg == '\0') + must_not_break = 0; /*we have finished, but the break must + be done after we strip '\' out.*/ + *end_arg = '\0'; + + /*let's remove those '\'! The text is shifted back to cover the \'s*/ + char *curs = start_arg; + int displacement = 0; + while (*curs != '\\' && *curs != '\0') + curs++; + while (*curs != '\0') { + displacement++; + curs++; + do { + *(curs-displacement) = *curs; + curs++; + } while (*curs != '\\' && *curs != '\0'); + } + *(curs - displacement) = '\0'; + start_arg = end_arg + 1; + } + + argv[i] = NULL; +} + +/* This code must be called in a new thread, and uses 2.4 exec_usermodehelper + * (which seems to be gone inside 2.6) to start the specified program. + * This function is like ____call_usermodehelper*/ +static int runner_thread(void * data) +{ + struct subprocess_info *sub_info = data; + + char *envp[] = { "HOME=/", "TERM=linux", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL }; + + char *path, *argv[MCONSOLE_MAX_DATA / 2 + 1]; + char buf[MCONSOLE_MAX_DATA]; + int retval; + + strcpy(buf, sub_info->command); + + parse_args(buf, MCONSOLE_MAX_DATA / 2 + 1, argv); + if (*argv[0] == '\0') + sub_info->retval = -EINVAL; /*invalid command to execute, though this maybe + is not needed.*/ + path = argv[0]; + + retval = exec_usermodehelper(path, argv, envp); + + /* Exec failed? */ + sub_info->retval = retval; + do_exit(0); +} + +/* This is like __call_usermodehelper. Only exception is that it's not a callback of keventd, and that + * it bundles the declaration of sub_info from call_usermodehelper.*/ +void mconsole_exec(struct mc_request *req) +{ + pid_t pid; + + struct subprocess_info sub_info = { + command: req->request.data, + retval: 0, + }; + + /* + * CLONE_VFORK: wait until the usermode helper has execve'd successfully + * We need the data structures to stay around until that is done. + */ + pid = kernel_thread(runner_thread, &sub_info, CLONE_VFORK | SIGCHLD); + + if (pid < 0) { + char buf[60]; + snprintf(buf, 60, "kernel_thread failed in mconsole_exec with error code: %d", -pid); + mconsole_reply(req, buf, 1, 0); + return; + } + if (sub_info.retval < 0) { + char buf[50]; + snprintf(buf, 50, "execve failed in mconsole_exec with errno = %d", -sub_info.retval); + mconsole_reply(req, buf, 1, 0); + return; + } + + mconsole_reply(req, "The command has been started successfully.", 0, 0); +} +#else +/* I must put mconsole_exec in the commands table always, because there + * linux/config.h cannot be included. So I pretend it doesn't exist by hiding + * it in the help text*/ +void mconsole_exec(struct mc_request *req) +{ + mconsole_reply(req, "Unknown command", 1, 0); + /*must be the same as in mconsole_reply*/ +} +/* Patch end */ +#endif /*CONFIG_MCONSOLE_EXEC*/ /* This list is populated by __initcall routines. */ --- linuxUm/arch/um/config.in.saved 2003-09-13 20:22:06.000000000 +0200 +++ linuxUm/arch/um/config.in 2003-09-16 16:31:13.000000000 +0200 @@ -40,6 +40,7 @@ tristate 'Host filesystem' CONFIG_HOSTFS tristate 'Honeypot proc filesystem' CONFIG_HPPFS bool 'Management console' CONFIG_MCONSOLE +dep_bool 'Execution through management console' CONFIG_MCONSOLE_EXEC $CONFIG_MCONSOLE dep_bool 'Magic SysRq key' CONFIG_MAGIC_SYSRQ $CONFIG_MCONSOLE bool '2G/2G host address space split' CONFIG_HOST_2G_2G bool 'Symmetric multi-processing support' CONFIG_UML_SMP --- linuxUm/arch/um/include/mconsole.h.saved 2003-09-13 20:22:07.000000000 +0200 +++ linuxUm/arch/um/include/mconsole.h 2003-09-16 18:11:48.000000000 +0200 @@ -73,6 +73,7 @@ extern void mconsole_help(struct mc_request *req); extern void mconsole_halt(struct mc_request *req); extern void mconsole_reboot(struct mc_request *req); +extern void mconsole_exec(struct mc_request *req); extern void mconsole_config(struct mc_request *req); extern void mconsole_remove(struct mc_request *req); extern void mconsole_sysrq(struct mc_request *req); --Boundary-00=_JY1Z/ASpVgDlYwv-- ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel