fault-injection: notifier error injection

This patchset provides kernel modules that can be used to test the error
handling of notifier call chain failures by injecting artifical errors to
the following notifier chain callbacks.

 * CPU notifier
 * PM notifier
 * memory hotplug notifier
 * powerpc pSeries reconfig notifier

Example: Inject CPU offline error (-1 == -EPERM)

# cd /sys/kernel/debug/notifier-error-inject/cpu
# echo -1 > actions/CPU_DOWN_PREPARE/error
# echo 0 > /sys/devices/system/cpu/cpu1/online
bash: echo: write error: Operation not permitted

The patchset also adds cpu and memory hotplug tests to
tools/testing/selftests These tests first do simple online and offline
test and then do fault injection tests if notifier error injection module
is available.

This patch:

The notifier error injection provides the ability to inject artifical
errors to specified notifier chain callbacks.  It is useful to test the
error handling of notifier call chain failures.

This adds common basic functions to define which type of events can be
fail and to initialize the debugfs interface to control what error code
should be returned and which event should be failed.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Greg KH <greg@kroah.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 51d5944d5f7bdce7131079d3c155b8e83a213671..f9a30579f9e6c920042af303baa3f7cd086ddb5b 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1084,6 +1084,17 @@ config LKDTM
        Documentation on how to use the module can be found in
        Documentation/fault-injection/provoke-crashes.txt
 
+config NOTIFIER_ERROR_INJECTION
+       tristate "Notifier error injection"
+       depends on DEBUG_KERNEL
+       select DEBUG_FS
+       help
+         This option provides the ability to inject artifical errors to
+         specified notifier chain callbacks. It is useful to test the error
+         handling of notifier call chain failures.
+
+         Say N if unsure.
+
 config CPU_NOTIFIER_ERROR_INJECT
        tristate "CPU notifier error injection module"
        depends on HOTPLUG_CPU && DEBUG_KERNEL

diff --git a/lib/Makefile b/lib/Makefile
index 9f396ddfcca21b0a6d8c88c20ed322f501d83348..9c7cd06a7809048d3ffe67afc83b72d7927dd14b 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -90,6 +90,7 @@ obj-$(CONFIG_AUDIT_GENERIC) += audit.o
 obj-$(CONFIG_SWIOTLB) += swiotlb.o
 obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o
 obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
+obj-$(CONFIG_NOTIFIER_ERROR_INJECTION) += notifier-error-inject.o
 obj-$(CONFIG_CPU_NOTIFIER_ERROR_INJECT) += cpu-notifier-error-inject.o
 
 lib-$(CONFIG_GENERIC_BUG) += bug.o

diff --git a/lib/notifier-error-inject.c b/lib/notifier-error-inject.c
new file mode 100644 (file)
index 0000000..44b92cb
--- /dev/null
+++ b/lib/notifier-error-inject.c
@@ -0,0 +1,112 @@
+#include <linux/module.h>
+
+#include "notifier-error-inject.h"
+
+static int debugfs_errno_set(void *data, u64 val)
+{
+       *(int *)data = clamp_t(int, val, -MAX_ERRNO, 0);
+       return 0;
+}
+
+static int debugfs_errno_get(void *data, u64 *val)
+{
+       *val = *(int *)data;
+       return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_errno, debugfs_errno_get, debugfs_errno_set,
+                       "%lld\n");
+
+static struct dentry *debugfs_create_errno(const char *name, mode_t mode,
+                               struct dentry *parent, int *value)
+{
+       return debugfs_create_file(name, mode, parent, value, &fops_errno);
+}
+
+static int notifier_err_inject_callback(struct notifier_block *nb,
+                               unsigned long val, void *p)
+{
+       int err = 0;
+       struct notifier_err_inject *err_inject =
+               container_of(nb, struct notifier_err_inject, nb);
+       struct notifier_err_inject_action *action;
+
+       for (action = err_inject->actions; action->name; action++) {
+               if (action->val == val) {
+                       err = action->error;
+                       break;
+               }
+       }
+       if (err)
+               pr_info("Injecting error (%d) to %s\n", err, action->name);
+
+       return notifier_from_errno(err);
+}
+
+struct dentry *notifier_err_inject_dir;
+EXPORT_SYMBOL_GPL(notifier_err_inject_dir);
+
+struct dentry *notifier_err_inject_init(const char *name, struct dentry *parent,
+                       struct notifier_err_inject *err_inject, int priority)
+{
+       struct notifier_err_inject_action *action;
+       mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+       struct dentry *dir;
+       struct dentry *actions_dir;
+
+       err_inject->nb.notifier_call = notifier_err_inject_callback;
+       err_inject->nb.priority = priority;
+
+       dir = debugfs_create_dir(name, parent);
+       if (!dir)
+               return ERR_PTR(-ENOMEM);
+
+       actions_dir = debugfs_create_dir("actions", dir);
+       if (!actions_dir)
+               goto fail;
+
+       for (action = err_inject->actions; action->name; action++) {
+               struct dentry *action_dir;
+
+               action_dir = debugfs_create_dir(action->name, actions_dir);
+               if (!action_dir)
+                       goto fail;
+
+               /*
+                * Create debugfs r/w file containing action->error. If
+                * notifier call chain is called with action->val, it will
+                * fail with the error code
+                */
+               if (!debugfs_create_errno("error", mode, action_dir,
+                                       &action->error))
+                       goto fail;
+       }
+       return dir;
+fail:
+       debugfs_remove_recursive(dir);
+       return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(notifier_err_inject_init);
+
+static int __init err_inject_init(void)
+{
+       notifier_err_inject_dir =
+               debugfs_create_dir("notifier-error-inject", NULL);
+
+       if (!notifier_err_inject_dir)
+               return -ENOMEM;
+
+       return 0;
+}
+
+static void __exit err_inject_exit(void)
+{
+       debugfs_remove_recursive(notifier_err_inject_dir);
+}
+
+module_init(err_inject_init);
+module_exit(err_inject_exit);
+
+MODULE_DESCRIPTION("Notifier error injection module");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");

diff --git a/lib/notifier-error-inject.h b/lib/notifier-error-inject.h
new file mode 100644 (file)
index 0000000..99b3b6f
--- /dev/null
+++ b/lib/notifier-error-inject.h
@@ -0,0 +1,24 @@
+#include <linux/atomic.h>
+#include <linux/debugfs.h>
+#include <linux/notifier.h>
+
+struct notifier_err_inject_action {
+       unsigned long val;
+       int error;
+       const char *name;
+};
+
+#define NOTIFIER_ERR_INJECT_ACTION(action)     \
+       .name = #action, .val = (action),
+
+struct notifier_err_inject {
+       struct notifier_block nb;
+       struct notifier_err_inject_action actions[];
+       /* The last slot must be terminated with zero sentinel */
+};
+
+extern struct dentry *notifier_err_inject_dir;
+
+extern struct dentry *notifier_err_inject_init(const char *name,
+               struct dentry *parent, struct notifier_err_inject *err_inject,
+               int priority);