uml: mconsole exec support

Adds the "exec" command to mconsole; the command is passed to /bin/sh -c, so
you know its syntax, and can freely use redirections and so on. It uses
call_usermodehelper().

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Index: linux-2.6.19/arch/um/drivers/mconsole_kern.c
===================================================================
--- linux-2.6.19.orig/arch/um/drivers/mconsole_kern.c
+++ linux-2.6.19/arch/um/drivers/mconsole_kern.c
@@ -23,6 +23,7 @@
 #include "linux/list.h"
 #include "linux/mm.h"
 #include "linux/console.h"
+#include "linux/kmod.h"
 #include "asm/irq.h"
 #include "asm/uaccess.h"
 #include "user_util.h"
@@ -209,6 +210,26 @@ void mconsole_proc(struct mc_request *re
 }
 #endif
 
+#ifdef CONFIG_MCONSOLE_EXEC
+void mconsole_exec(struct mc_request *req)
+{
+	int res;
+
+	char *envp[] = { "HOME=/", "TERM=linux", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
+	char *argv[] = { "/bin/sh", "-c", req->request.data + strlen("exec "), NULL };
+	res = call_usermodehelper("/bin/sh", argv, envp, 0);
+
+	if (res < 0) {
+		char buf[60];
+		snprintf(buf, 60, "call_usermodehelper failed in mconsole_exec with error code: %d", -res);
+		mconsole_reply(req, buf, 1, 0);
+		return;
+	}
+
+	mconsole_reply(req, "The command has been started successfully.", 0, 0);
+}
+#endif
+
 void mconsole_proc(struct mc_request *req)
 {
 	char path[64];
@@ -264,6 +285,14 @@ void mconsole_proc(struct mc_request *re
 	/* nothing */;
 }
 
+#ifdef CONFIG_MCONSOLE_EXEC
+#  define EXEC_HELPTEXT "\
+    exec <command> - runs the specified command through /bin/sh -c\n"
+#else
+#  define EXEC_HELPTEXT ""
+#endif
+
+    /*exec - execute a command as root inside the UML\n"*/
 #define UML_MCONSOLE_HELPTEXT \
 "Commands: \n\
     version - Get kernel version \n\
@@ -278,7 +307,7 @@ void mconsole_proc(struct mc_request *re
     cad - invoke the Ctrl-Alt-Del handler \n\
     stop - pause the UML; it will do nothing until it receives a 'go' \n\
     go - continue the UML after a 'stop' \n\
-    log <string> - make UML enter <string> into the kernel log\n\
+    log <string> - make UML enter <string> into the kernel log\n" EXEC_HELPTEXT "\
     proc <file> - returns the contents of the UML's /proc/<file>\n\
     stack <pid> - returns the stack of the specified pid\n\
 "
Index: linux-2.6.19/arch/um/drivers/mconsole_user.c
===================================================================
--- linux-2.6.19.orig/arch/um/drivers/mconsole_user.c
+++ linux-2.6.19/arch/um/drivers/mconsole_user.c
@@ -18,6 +18,7 @@
 #include "mconsole.h"
 #include "umid.h"
 #include "user_util.h"
+#include "uml-config.h"
 
 static struct mconsole_command commands[] = {
 	/* With uts namespaces, uts information becomes process-specific, so
@@ -38,6 +39,9 @@ static struct mconsole_command commands[
 	{ "log", mconsole_log, MCONSOLE_INTR },
 	{ "proc", mconsole_proc, MCONSOLE_PROC },
         { "stack", mconsole_stack, MCONSOLE_INTR },
+#ifdef UML_CONFIG_MCONSOLE_EXEC
+	{ "exec", mconsole_exec, MCONSOLE_PROC },
+#endif
 };
 
 /* Initialized in mconsole_init, which is an initcall */
Index: linux-2.6.19/arch/um/Kconfig
===================================================================
--- linux-2.6.19.orig/arch/um/Kconfig
+++ linux-2.6.19/arch/um/Kconfig
@@ -189,6 +189,15 @@ config MCONSOLE
 
         It is safe to say 'Y' here.
 
+config MCONSOLE_EXEC
+	bool "Management console 'exec' support"
+	depends on MCONSOLE
+	help
+	Adds the 'exec' command to mconsole, which allows execution of arbitrary command
+	inside UML.
+	All its parameters are passed to /bin/sh -c inside UML, so you can use the full
+	shell syntax, especially redirections.
+
 config MAGIC_SYSRQ
 	bool "Magic SysRq key"
 	depends on MCONSOLE
Index: linux-2.6.19/arch/um/include/mconsole.h
===================================================================
--- linux-2.6.19.orig/arch/um/include/mconsole.h
+++ linux-2.6.19/arch/um/include/mconsole.h
@@ -83,6 +83,7 @@ extern void mconsole_cad(struct mc_reque
 extern void mconsole_stop(struct mc_request *req);
 extern void mconsole_go(struct mc_request *req);
 extern void mconsole_log(struct mc_request *req);
+extern void mconsole_exec(struct mc_request *req);
 extern void mconsole_proc(struct mc_request *req);
 extern void mconsole_stack(struct mc_request *req);