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#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 void debugfs_ul_set(void *data, u64 val)

{

        *(unsigned long *)data = val;

}

#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER

static void debugfs_ul_set_MAX_STACK_TRACE_DEPTH(void *data, u64 val)

{

        *(unsigned long *)data =

                val < MAX_STACK_TRACE_DEPTH ?

                val : MAX_STACK_TRACE_DEPTH;

}

#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */

static u64 debugfs_ul_get(void *data)

{

        return *(unsigned long *)data;

}

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 void debugfs_atomic_t_set(void *data, u64 val)

{

        atomic_set((atomic_t *)data, val);

}

static u64 debugfs_atomic_t_get(void *data)

{

        return atomic_read((atomic_t *)data);

}

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 */