usermodehelper: split setup from execution
Rather than having hundreds of variations of call_usermodehelper for
various pieces of usermode state which could be set up, split the
info allocation and initialization from the actual process execution.
This means the general pattern becomes:
info = call_usermodehelper_setup(path, argv, envp); /* basic state */
call_usermodehelper_<SET EXTRA STATE>(info, stuff...); /* extra state */
call_usermodehelper_exec(info, wait); /* run process and free info */
This patch introduces wrappers for all the existing calling styles for
call_usermodehelper_*, but folds their implementations into one.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Bj?rn Steinbrink <B.Steinbrink@gmx.de>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 4d32eb0..d2dce71 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -122,6 +122,7 @@
int wait;
int retval;
struct file *stdin;
+ void (*cleanup)(char **argv, char **envp);
};
/*
@@ -180,6 +181,14 @@
do_exit(0);
}
+void call_usermodehelper_freeinfo(struct subprocess_info *info)
+{
+ if (info->cleanup)
+ (*info->cleanup)(info->argv, info->envp);
+ kfree(info);
+}
+EXPORT_SYMBOL(call_usermodehelper_freeinfo);
+
/* Keventd can't block, but this (a child) can. */
static int wait_for_helper(void *data)
{
@@ -217,7 +226,7 @@
}
if (sub_info->wait < 0)
- kfree(sub_info);
+ call_usermodehelper_freeinfo(sub_info);
else
complete(sub_info->complete);
return 0;
@@ -252,79 +261,75 @@
}
/**
- * call_usermodehelper_keys - start a usermode application
- * @path: pathname for the application
- * @argv: null-terminated argument list
- * @envp: null-terminated environment list
- * @session_keyring: session keyring for process (NULL for an empty keyring)
- * @wait: wait for the application to finish and return status.
- * when -1 don't wait at all, but you get no useful error back when
- * the program couldn't be exec'ed. This makes it safe to call
- * from interrupt context.
+ * call_usermodehelper_setup - prepare to call a usermode helper
+ * @path - path to usermode executable
+ * @argv - arg vector for process
+ * @envp - environment for process
*
- * Runs a user-space application. The application is started
- * asynchronously if wait is not set, and runs as a child of keventd.
- * (ie. it runs with full root capabilities).
- *
- * Must be called from process context. Returns a negative error code
- * if program was not execed successfully, or 0.
+ * Returns either NULL on allocation failure, or a subprocess_info
+ * structure. This should be passed to call_usermodehelper_exec to
+ * exec the process and free the structure.
*/
-int call_usermodehelper_keys(char *path, char **argv, char **envp,
- struct key *session_keyring, int wait)
+struct subprocess_info *call_usermodehelper_setup(char *path,
+ char **argv, char **envp)
{
- DECLARE_COMPLETION_ONSTACK(done);
struct subprocess_info *sub_info;
- int retval;
-
- if (!khelper_wq)
- return -EBUSY;
-
- if (path[0] == '\0')
- return 0;
-
sub_info = kzalloc(sizeof(struct subprocess_info), GFP_ATOMIC);
if (!sub_info)
- return -ENOMEM;
+ goto out;
INIT_WORK(&sub_info->work, __call_usermodehelper);
- sub_info->complete = &done;
sub_info->path = path;
sub_info->argv = argv;
sub_info->envp = envp;
- sub_info->ring = session_keyring;
- sub_info->wait = wait;
- queue_work(khelper_wq, &sub_info->work);
- if (wait < 0) /* task has freed sub_info */
- return 0;
- wait_for_completion(&done);
- retval = sub_info->retval;
- kfree(sub_info);
- return retval;
+ out:
+ return sub_info;
}
-EXPORT_SYMBOL(call_usermodehelper_keys);
+EXPORT_SYMBOL(call_usermodehelper_setup);
-int call_usermodehelper_pipe(char *path, char **argv, char **envp,
- struct file **filp)
+/**
+ * call_usermodehelper_setkeys - set the session keys for usermode helper
+ * @info: a subprocess_info returned by call_usermodehelper_setup
+ * @session_keyring: the session keyring for the process
+ */
+void call_usermodehelper_setkeys(struct subprocess_info *info,
+ struct key *session_keyring)
{
- DECLARE_COMPLETION(done);
- struct subprocess_info sub_info = {
- .work = __WORK_INITIALIZER(sub_info.work,
- __call_usermodehelper),
- .complete = &done,
- .path = path,
- .argv = argv,
- .envp = envp,
- .retval = 0,
- };
+ info->ring = session_keyring;
+}
+EXPORT_SYMBOL(call_usermodehelper_setkeys);
+
+/**
+ * call_usermodehelper_setcleanup - set a cleanup function
+ * @info: a subprocess_info returned by call_usermodehelper_setup
+ * @cleanup: a cleanup function
+ *
+ * The cleanup function is just befor ethe subprocess_info is about to
+ * be freed. This can be used for freeing the argv and envp. The
+ * Function must be runnable in either a process context or the
+ * context in which call_usermodehelper_exec is called.
+ */
+void call_usermodehelper_setcleanup(struct subprocess_info *info,
+ void (*cleanup)(char **argv, char **envp))
+{
+ info->cleanup = cleanup;
+}
+EXPORT_SYMBOL(call_usermodehelper_setcleanup);
+
+/**
+ * call_usermodehelper_stdinpipe - set up a pipe to be used for stdin
+ * @sub_info: a subprocess_info returned by call_usermodehelper_setup
+ * @filp: set to the write-end of a pipe
+ *
+ * This constructs a pipe, and sets the read end to be the stdin of the
+ * subprocess, and returns the write-end in *@filp.
+ */
+int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
+ struct file **filp)
+{
struct file *f;
- if (!khelper_wq)
- return -EBUSY;
-
- if (path[0] == '\0')
- return 0;
-
f = create_write_pipe();
if (IS_ERR(f))
return PTR_ERR(f);
@@ -335,11 +340,85 @@
free_write_pipe(*filp);
return PTR_ERR(f);
}
- sub_info.stdin = f;
+ sub_info->stdin = f;
- queue_work(khelper_wq, &sub_info.work);
+ return 0;
+}
+EXPORT_SYMBOL(call_usermodehelper_stdinpipe);
+
+/**
+ * call_usermodehelper_exec - start a usermode application
+ * @sub_info: information about the subprocessa
+ * @wait: wait for the application to finish and return status.
+ * when -1 don't wait at all, but you get no useful error back when
+ * the program couldn't be exec'ed. This makes it safe to call
+ * from interrupt context.
+ *
+ * Runs a user-space application. The application is started
+ * asynchronously if wait is not set, and runs as a child of keventd.
+ * (ie. it runs with full root capabilities).
+ */
+int call_usermodehelper_exec(struct subprocess_info *sub_info,
+ int wait)
+{
+ DECLARE_COMPLETION_ONSTACK(done);
+ int retval;
+
+ if (sub_info->path[0] == '\0') {
+ retval = 0;
+ goto out;
+ }
+
+ if (!khelper_wq) {
+ retval = -EBUSY;
+ goto out;
+ }
+
+ sub_info->complete = &done;
+ sub_info->wait = wait;
+
+ queue_work(khelper_wq, &sub_info->work);
+ if (wait < 0) /* task has freed sub_info */
+ return 0;
wait_for_completion(&done);
- return sub_info.retval;
+ retval = sub_info->retval;
+
+ out:
+ call_usermodehelper_freeinfo(sub_info);
+ return retval;
+}
+EXPORT_SYMBOL(call_usermodehelper_exec);
+
+/**
+ * call_usermodehelper_pipe - call a usermode helper process with a pipe stdin
+ * @path: path to usermode executable
+ * @argv: arg vector for process
+ * @envp: environment for process
+ * @filp: set to the write-end of a pipe
+ *
+ * This is a simple wrapper which executes a usermode-helper function
+ * with a pipe as stdin. It is implemented entirely in terms of
+ * lower-level call_usermodehelper_* functions.
+ */
+int call_usermodehelper_pipe(char *path, char **argv, char **envp,
+ struct file **filp)
+{
+ struct subprocess_info *sub_info;
+ int ret;
+
+ sub_info = call_usermodehelper_setup(path, argv, envp);
+ if (sub_info == NULL)
+ return -ENOMEM;
+
+ ret = call_usermodehelper_stdinpipe(sub_info, filp);
+ if (ret < 0)
+ goto out;
+
+ return call_usermodehelper_exec(sub_info, 1);
+
+ out:
+ call_usermodehelper_freeinfo(sub_info);
+ return ret;
}
EXPORT_SYMBOL(call_usermodehelper_pipe);