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authorPeter Rajnoha <prajnoha@redhat.com>2017-05-09 15:22:30 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-05-25 18:30:51 +0200
commitf36776fafbaa0094390dd4e7e3e29805e0b82730 (patch)
treecc7d6eac4fc119b41179288c55ed8c04d12e1d0c /lib
parent6265539776a0810b7ce6398c27866ddb9c6bd154 (diff)
kobject: support passing in variables for synthetic uevents
This patch makes it possible to pass additional arguments in addition to uevent action name when writing /sys/.../uevent attribute. These additional arguments are then inserted into generated synthetic uevent as additional environment variables. Before, we were not able to pass any additional uevent environment variables for synthetic uevents. This made it hard to identify such uevents properly in userspace to make proper distinction between genuine uevents originating from kernel and synthetic uevents triggered from userspace. Also, it was not possible to pass any additional information which would make it possible to optimize and change the way the synthetic uevents are processed back in userspace based on the originating environment of the triggering action in userspace. With the extra additional variables, we are able to pass through this extra information needed and also it makes it possible to synchronize with such synthetic uevents as they can be clearly identified back in userspace. The format for writing the uevent attribute is following: ACTION [UUID [KEY=VALUE ...] There's no change in how "ACTION" is recognized - it stays the same ("add", "change", "remove"). The "ACTION" is the only argument required to generate synthetic uevent, the rest of arguments, that this patch adds support for, are optional. The "UUID" is considered as transaction identifier so it's possible to use the same UUID value for one or more synthetic uevents in which case we logically group these uevents together for any userspace listeners. The "UUID" is expected to be in "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" format where "x" is a hex digit. The value appears in uevent as "SYNTH_UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" environment variable. The "KEY=VALUE" pairs can contain alphanumeric characters only. It's possible to define zero or more more pairs - each pair is then delimited by a space character " ". Each pair appears in synthetic uevents as "SYNTH_ARG_KEY=VALUE" environment variable. That means the KEY name gains "SYNTH_ARG_" prefix to avoid possible collisions with existing variables. To pass the "KEY=VALUE" pairs, it's also required to pass in the "UUID" part for the synthetic uevent first. If "UUID" is not passed in, the generated synthetic uevent gains "SYNTH_UUID=0" environment variable automatically so it's possible to identify this situation in userspace when reading generated uevent and so we can still make a difference between genuine and synthetic uevents. Signed-off-by: Peter Rajnoha <prajnoha@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/kobject_uevent.c167
1 files changed, 154 insertions, 13 deletions
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 9a2b811966eb..719c155fce20 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -23,6 +23,8 @@
#include <linux/socket.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
+#include <linux/uuid.h>
+#include <linux/ctype.h>
#include <net/sock.h>
#include <net/net_namespace.h>
@@ -52,19 +54,13 @@ static const char *kobject_actions[] = {
[KOBJ_OFFLINE] = "offline",
};
-/**
- * kobject_action_type - translate action string to numeric type
- *
- * @buf: buffer containing the action string, newline is ignored
- * @count: length of buffer
- * @type: pointer to the location to store the action type
- *
- * Returns 0 if the action string was recognized.
- */
-int kobject_action_type(const char *buf, size_t count,
- enum kobject_action *type)
+static int kobject_action_type(const char *buf, size_t count,
+ enum kobject_action *type,
+ const char **args)
{
enum kobject_action action;
+ size_t count_first;
+ const char *args_start;
int ret = -EINVAL;
if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
@@ -73,11 +69,20 @@ int kobject_action_type(const char *buf, size_t count,
if (!count)
goto out;
+ args_start = strnchr(buf, count, ' ');
+ if (args_start) {
+ count_first = args_start - buf;
+ args_start = args_start + 1;
+ } else
+ count_first = count;
+
for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
- if (strncmp(kobject_actions[action], buf, count) != 0)
+ if (strncmp(kobject_actions[action], buf, count_first) != 0)
continue;
- if (kobject_actions[action][count] != '\0')
+ if (kobject_actions[action][count_first] != '\0')
continue;
+ if (args)
+ *args = args_start;
*type = action;
ret = 0;
break;
@@ -86,6 +91,142 @@ out:
return ret;
}
+static const char *action_arg_word_end(const char *buf, const char *buf_end,
+ char delim)
+{
+ const char *next = buf;
+
+ while (next <= buf_end && *next != delim)
+ if (!isalnum(*next++))
+ return NULL;
+
+ if (next == buf)
+ return NULL;
+
+ return next;
+}
+
+static int kobject_action_args(const char *buf, size_t count,
+ struct kobj_uevent_env **ret_env)
+{
+ struct kobj_uevent_env *env = NULL;
+ const char *next, *buf_end, *key;
+ int key_len;
+ int r = -EINVAL;
+
+ if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
+ count--;
+
+ if (!count)
+ return -EINVAL;
+
+ env = kzalloc(sizeof(*env), GFP_KERNEL);
+ if (!env)
+ return -ENOMEM;
+
+ /* first arg is UUID */
+ if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
+ add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
+ goto out;
+
+ /*
+ * the rest are custom environment variables in KEY=VALUE
+ * format with ' ' delimiter between each KEY=VALUE pair
+ */
+ next = buf + UUID_STRING_LEN;
+ buf_end = buf + count - 1;
+
+ while (next <= buf_end) {
+ if (*next != ' ')
+ goto out;
+
+ /* skip the ' ', key must follow */
+ key = ++next;
+ if (key > buf_end)
+ goto out;
+
+ buf = next;
+ next = action_arg_word_end(buf, buf_end, '=');
+ if (!next || next > buf_end || *next != '=')
+ goto out;
+ key_len = next - buf;
+
+ /* skip the '=', value must follow */
+ if (++next > buf_end)
+ goto out;
+
+ buf = next;
+ next = action_arg_word_end(buf, buf_end, ' ');
+ if (!next)
+ goto out;
+
+ if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
+ key_len, key, (int) (next - buf), buf))
+ goto out;
+ }
+
+ r = 0;
+out:
+ if (r)
+ kfree(env);
+ else
+ *ret_env = env;
+ return r;
+}
+
+/**
+ * kobject_synth_uevent - send synthetic uevent with arguments
+ *
+ * @kobj: struct kobject for which synthetic uevent is to be generated
+ * @buf: buffer containing action type and action args, newline is ignored
+ * @count: length of buffer
+ *
+ * Returns 0 if kobject_synthetic_uevent() is completed with success or the
+ * corresponding error when it fails.
+ */
+int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
+{
+ char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
+ enum kobject_action action;
+ const char *action_args;
+ struct kobj_uevent_env *env;
+ const char *msg = NULL, *devpath;
+ int r;
+
+ r = kobject_action_type(buf, count, &action, &action_args);
+ if (r) {
+ msg = "unknown uevent action string\n";
+ goto out;
+ }
+
+ if (!action_args) {
+ r = kobject_uevent_env(kobj, action, no_uuid_envp);
+ goto out;
+ }
+
+ r = kobject_action_args(action_args,
+ count - (action_args - buf), &env);
+ if (r == -EINVAL) {
+ msg = "incorrect uevent action arguments\n";
+ goto out;
+ }
+
+ if (r)
+ goto out;
+
+ r = kobject_uevent_env(kobj, action, env->envp);
+ kfree(env);
+out:
+ if (r) {
+ devpath = kobject_get_path(kobj, GFP_KERNEL);
+ printk(KERN_WARNING "synth uevent: %s: %s",
+ devpath ?: "unknown device",
+ msg ?: "failed to send uevent");
+ kfree(devpath);
+ }
+ return r;
+}
+
#ifdef CONFIG_NET
static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
{