root/lib/fault-inject.c

DEFINITIONS

1. setup_fault_attr
2. fail_dump
3. fail_task
4. fail_stacktrace
5. fail_stacktrace
6. should_fail
7. debugfs_ul_set
8. debugfs_ul_set_MAX_STACK_TRACE_DEPTH
9. debugfs_ul_get
10. debugfs_create_ul
11. debugfs_create_ul_MAX_STACK_TRACE_DEPTH
12. debugfs_atomic_t_set
13. debugfs_atomic_t_get
14. debugfs_create_atomic_t
15. cleanup_fault_attr_dentries
16. init_fault_attr_dentries

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/stat.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/unwind.h>
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <linux/fault-inject.h>

/*
 * setup_fault_attr() is a helper function for various __setup handlers, so it
 * returns 0 on error, because that is what __setup handlers do.
 */
int __init setup_fault_attr(struct fault_attr *attr, char *str)
{
        unsigned long probability;
        unsigned long interval;
        int times;
        int space;

        /* "<interval>,<probability>,<space>,<times>" */
        if (sscanf(str, "%lu,%lu,%d,%d",
                        &interval, &probability, &space, &times) < 4) {
                printk(KERN_WARNING
                        "FAULT_INJECTION: failed to parse arguments\n");
                return 0;
        }

        attr->probability = probability;
        attr->interval = interval;
        atomic_set(&attr->times, times);
        atomic_set(&attr->space, space);

        return 1;
}

static void fail_dump(struct fault_attr *attr)
{
        if (attr->verbose > 0)
                printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure\n");
        if (attr->verbose > 1)
                dump_stack();
}

#define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)

static bool fail_task(struct fault_attr *attr, struct task_struct *task)
{
        return !in_interrupt() && task->make_it_fail;
}

#define MAX_STACK_TRACE_DEPTH 32

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

static bool fail_stacktrace(struct fault_attr *attr)
{
        struct stack_trace trace;
        int depth = attr->stacktrace_depth;
        unsigned long entries[MAX_STACK_TRACE_DEPTH];
        int n;
        bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);

        if (depth == 0)
                return found;

        trace.nr_entries = 0;
        trace.entries = entries;
        trace.max_entries = depth;
        trace.skip = 1;

        save_stack_trace(&trace);
        for (n = 0; n < trace.nr_entries; n++) {
                if (attr->reject_start <= entries[n] &&
                               entries[n] < attr->reject_end)
                        return false;
                if (attr->require_start <= entries[n] &&
                               entries[n] < attr->require_end)
                        found = true;
        }
        return found;
}

#else

static inline bool fail_stacktrace(struct fault_attr *attr)
{
        return true;
}

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

/*
 * This code is stolen from failmalloc-1.0
 * http://www.nongnu.org/failmalloc/
 */

bool should_fail(struct fault_attr *attr, ssize_t size)
{
        if (attr->task_filter && !fail_task(attr, current))
                return false;

        if (atomic_read(&attr->times) == 0)
                return false;

        if (atomic_read(&attr->space) > size) {
                atomic_sub(size, &attr->space);
                return false;
        }

        if (attr->interval > 1) {
                attr->count++;
                if (attr->count % attr->interval)
                        return false;
        }

        if (attr->probability <= random32() % 100)
                return false;

        if (!fail_stacktrace(attr))
                return false;

        fail_dump(attr);

        if (atomic_read(&attr->times) != -1)
                atomic_dec_not_zero(&attr->times);

        return true;
}

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

static int debugfs_ul_set(void *data, u64 val)
{
        *(unsigned long *)data = val;
        return 0;
}

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
static int debugfs_ul_set_MAX_STACK_TRACE_DEPTH(void *data, u64 val)
{
        *(unsigned long *)data =
                val < MAX_STACK_TRACE_DEPTH ?
                val : MAX_STACK_TRACE_DEPTH;
        return 0;
}
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

static int debugfs_ul_get(void *data, u64 *val)
{
        *val = *(unsigned long *)data;
        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");

static struct dentry *debugfs_create_ul(const char *name, mode_t mode,
                                struct dentry *parent, unsigned long *value)
{
        return debugfs_create_file(name, mode, parent, value, &fops_ul);
}

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
DEFINE_SIMPLE_ATTRIBUTE(fops_ul_MAX_STACK_TRACE_DEPTH, debugfs_ul_get,
                        debugfs_ul_set_MAX_STACK_TRACE_DEPTH, "%llu\n");

static struct dentry *debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
        const char *name, mode_t mode,
        struct dentry *parent, unsigned long *value)
{
        return debugfs_create_file(name, mode, parent, value,
                                   &fops_ul_MAX_STACK_TRACE_DEPTH);
}
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

static int debugfs_atomic_t_set(void *data, u64 val)
{
        atomic_set((atomic_t *)data, val);
        return 0;
}

static int debugfs_atomic_t_get(void *data, u64 *val)
{
        *val = atomic_read((atomic_t *)data);
        return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
                        debugfs_atomic_t_set, "%lld\n");

static struct dentry *debugfs_create_atomic_t(const char *name, mode_t mode,
                                struct dentry *parent, atomic_t *value)
{
        return debugfs_create_file(name, mode, parent, value, &fops_atomic_t);
}

void cleanup_fault_attr_dentries(struct fault_attr *attr)
{
        debugfs_remove(attr->dentries.probability_file);
        attr->dentries.probability_file = NULL;

        debugfs_remove(attr->dentries.interval_file);
        attr->dentries.interval_file = NULL;

        debugfs_remove(attr->dentries.times_file);
        attr->dentries.times_file = NULL;

        debugfs_remove(attr->dentries.space_file);
        attr->dentries.space_file = NULL;

        debugfs_remove(attr->dentries.verbose_file);
        attr->dentries.verbose_file = NULL;

        debugfs_remove(attr->dentries.task_filter_file);
        attr->dentries.task_filter_file = NULL;

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

        debugfs_remove(attr->dentries.stacktrace_depth_file);
        attr->dentries.stacktrace_depth_file = NULL;

        debugfs_remove(attr->dentries.require_start_file);
        attr->dentries.require_start_file = NULL;

        debugfs_remove(attr->dentries.require_end_file);
        attr->dentries.require_end_file = NULL;

        debugfs_remove(attr->dentries.reject_start_file);
        attr->dentries.reject_start_file = NULL;

        debugfs_remove(attr->dentries.reject_end_file);
        attr->dentries.reject_end_file = NULL;

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

        if (attr->dentries.dir)
                WARN_ON(!simple_empty(attr->dentries.dir));

        debugfs_remove(attr->dentries.dir);
        attr->dentries.dir = NULL;
}

int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
{
        mode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
        struct dentry *dir;

        memset(&attr->dentries, 0, sizeof(attr->dentries));

        dir = debugfs_create_dir(name, NULL);
        if (!dir)
                goto fail;
        attr->dentries.dir = dir;

        attr->dentries.probability_file =
                debugfs_create_ul("probability", mode, dir, &attr->probability);

        attr->dentries.interval_file =
                debugfs_create_ul("interval", mode, dir, &attr->interval);

        attr->dentries.times_file =
                debugfs_create_atomic_t("times", mode, dir, &attr->times);

        attr->dentries.space_file =
                debugfs_create_atomic_t("space", mode, dir, &attr->space);

        attr->dentries.verbose_file =
                debugfs_create_ul("verbose", mode, dir, &attr->verbose);

        attr->dentries.task_filter_file = debugfs_create_bool("task-filter",
                                                mode, dir, &attr->task_filter);

        if (!attr->dentries.probability_file || !attr->dentries.interval_file ||
            !attr->dentries.times_file || !attr->dentries.space_file ||
            !attr->dentries.verbose_file || !attr->dentries.task_filter_file)
                goto fail;

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

        attr->dentries.stacktrace_depth_file =
                debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
                        "stacktrace-depth", mode, dir, &attr->stacktrace_depth);

        attr->dentries.require_start_file =
                debugfs_create_ul("require-start", mode, dir, &attr->require_start);

        attr->dentries.require_end_file =
                debugfs_create_ul("require-end", mode, dir, &attr->require_end);

        attr->dentries.reject_start_file =
                debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);

        attr->dentries.reject_end_file =
                debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);

        if (!attr->dentries.stacktrace_depth_file ||
            !attr->dentries.require_start_file ||
            !attr->dentries.require_end_file ||
            !attr->dentries.reject_start_file ||
            !attr->dentries.reject_end_file)
                goto fail;

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

        return 0;
fail:
        cleanup_fault_attr_dentries(attr);
        return -ENOMEM;
}

#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */