// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Linux Kernel Dump Test Module for testing kernel crashes conditions:
 * induces system failures at predefined crashpoints and under predefined
 * operational conditions in order to evaluate the reliability of kernel
 * sanity checking and crash dumps obtained using different dumping
 * solutions.
 *
 * Copyright (C) IBM Corporation, 2006
 *
 * Author: Ankita Garg <ankita@in.ibm.com>
 *
 * It is adapted from the Linux Kernel Dump Test Tool by
 * Fernando Luis Vazquez Cao <http://lkdtt.sourceforge.net>
 *
 * Debugfs support added by Simon Kagstrom <simon.kagstrom@netinsight.net>
 *
 * See Documentation/fault-injection/provoke-crashes.rst for instructions
 */
#include "lkdtm.h"
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/buffer_head.h>
#include <linux/kprobes.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/debugfs.h>
#include <linux/utsname.h>

#define DEFAULT_COUNT 10

static int lkdtm_debugfs_open(struct inode *inode, struct file *file);
static ssize_t lkdtm_debugfs_read(struct file *f, char __user *user_buf,
                size_t count, loff_t *off);
static ssize_t direct_entry(struct file *f, const char __user *user_buf,
                            size_t count, loff_t *off);

#ifdef CONFIG_KPROBES
static int lkdtm_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
static ssize_t lkdtm_debugfs_entry(struct file *f,
                                   const char __user *user_buf,
                                   size_t count, loff_t *off);
# define CRASHPOINT_KPROBE(_symbol)                             \
                .kprobe = {                                     \
                        .symbol_name = (_symbol),               \
                        .pre_handler = lkdtm_kprobe_handler,    \
                },
# define CRASHPOINT_WRITE(_symbol)                              \
                (_symbol) ? lkdtm_debugfs_entry : direct_entry
#else
# define CRASHPOINT_KPROBE(_symbol)
# define CRASHPOINT_WRITE(_symbol)              direct_entry
#endif

/* Crash points */
struct crashpoint {
        const char *name;
        const struct file_operations fops;
        struct kprobe kprobe;
};

#define CRASHPOINT(_name, _symbol)                              \
        {                                                       \
                .name = _name,                                  \
                .fops = {                                       \
                        .read   = lkdtm_debugfs_read,           \
                        .llseek = generic_file_llseek,          \
                        .open   = lkdtm_debugfs_open,           \
                        .write  = CRASHPOINT_WRITE(_symbol)     \
                },                                              \
                CRASHPOINT_KPROBE(_symbol)                      \
        }

/* Define the possible places where we can trigger a crash point. */
static struct crashpoint crashpoints[] = {
        CRASHPOINT("DIRECT",             NULL),
#ifdef CONFIG_KPROBES
        CRASHPOINT("INT_HARDWARE_ENTRY", "do_IRQ"),
        CRASHPOINT("INT_HW_IRQ_EN",      "handle_irq_event"),
        CRASHPOINT("INT_TASKLET_ENTRY",  "tasklet_action"),
        CRASHPOINT("FS_DEVRW",           "ll_rw_block"),
        CRASHPOINT("MEM_SWAPOUT",        "shrink_inactive_list"),
        CRASHPOINT("TIMERADD",           "hrtimer_start"),
        CRASHPOINT("SCSI_QUEUE_RQ",      "scsi_queue_rq"),
#endif
};

/* List of possible types for crashes that can be triggered. */
static const struct crashtype_category *crashtype_categories[] = {
        &bugs_crashtypes,
        &heap_crashtypes,
        &perms_crashtypes,
        &refcount_crashtypes,
        &usercopy_crashtypes,
        &stackleak_crashtypes,
        &cfi_crashtypes,
        &fortify_crashtypes,
#ifdef CONFIG_PPC_64S_HASH_MMU
        &powerpc_crashtypes,
#endif
};

/* Global kprobe entry and crashtype. */
static struct kprobe *lkdtm_kprobe;
static struct crashpoint *lkdtm_crashpoint;
static const struct crashtype *lkdtm_crashtype;

/* Module parameters */
static int recur_count = -1;
module_param(recur_count, int, 0644);
MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test");

static char* cpoint_name;
module_param(cpoint_name, charp, 0444);
MODULE_PARM_DESC(cpoint_name, " Crash Point, where kernel is to be crashed");

static char* cpoint_type;
module_param(cpoint_type, charp, 0444);
MODULE_PARM_DESC(cpoint_type, " Crash Point Type, action to be taken on "\
                                "hitting the crash point");

static int cpoint_count = DEFAULT_COUNT;
module_param(cpoint_count, int, 0644);
MODULE_PARM_DESC(cpoint_count, " Crash Point Count, number of times the "\
                                "crash point is to be hit to trigger action");

/*
 * For test debug reporting when CI systems provide terse summaries.
 * TODO: Remove this once reasonable reporting exists in most CI systems:
 * https://lore.kernel.org/lkml/CAHk-=wiFvfkoFixTapvvyPMN9pq5G-+Dys2eSyBa1vzDGAO5+A@mail.gmail.com
 */
char *lkdtm_kernel_info;

/* Return the crashtype number or NULL if the name is invalid */
static const struct crashtype *find_crashtype(const char *name)
{
        int cat, idx;

        for (cat = 0; cat < ARRAY_SIZE(crashtype_categories); cat++) {
                for (idx = 0; idx < crashtype_categories[cat]->len; idx++) {
                        struct crashtype *crashtype;

                        crashtype = &crashtype_categories[cat]->crashtypes[idx];
                        if (!strcmp(name, crashtype->name))
                                return crashtype;
                }
        }

        return NULL;
}

/*
 * This is forced noinline just so it distinctly shows up in the stackdump
 * which makes validation of expected lkdtm crashes easier.
 */
static noinline void lkdtm_do_action(const struct crashtype *crashtype)
{
        if (WARN_ON(!crashtype || !crashtype->func))
                return;
        crashtype->func();
}

static int lkdtm_register_cpoint(struct crashpoint *crashpoint,
                                 const struct crashtype *crashtype)
{
        int ret;

        /* If this doesn't have a symbol, just call immediately. */
        if (!crashpoint->kprobe.symbol_name) {
                lkdtm_do_action(crashtype);
                return 0;
        }

        if (lkdtm_kprobe != NULL)
                unregister_kprobe(lkdtm_kprobe);

        lkdtm_crashpoint = crashpoint;
        lkdtm_crashtype = crashtype;
        lkdtm_kprobe = &crashpoint->kprobe;
        ret = register_kprobe(lkdtm_kprobe);
        if (ret < 0) {
                pr_info("Couldn't register kprobe %s\n",
                        crashpoint->kprobe.symbol_name);
                lkdtm_kprobe = NULL;
                lkdtm_crashpoint = NULL;
                lkdtm_crashtype = NULL;
        }

        return ret;
}

#ifdef CONFIG_KPROBES
/* Global crash counter and spinlock. */
static int crash_count = DEFAULT_COUNT;
static DEFINE_SPINLOCK(crash_count_lock);

/* Called by kprobe entry points. */
static int lkdtm_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
{
        unsigned long flags;
        bool do_it = false;

        if (WARN_ON(!lkdtm_crashpoint || !lkdtm_crashtype))
                return 0;

        spin_lock_irqsave(&crash_count_lock, flags);
        crash_count--;
        pr_info("Crash point %s of type %s hit, trigger in %d rounds\n",
                lkdtm_crashpoint->name, lkdtm_crashtype->name, crash_count);

        if (crash_count == 0) {
                do_it = true;
                crash_count = cpoint_count;
        }
        spin_unlock_irqrestore(&crash_count_lock, flags);

        if (do_it)
                lkdtm_do_action(lkdtm_crashtype);

        return 0;
}

static ssize_t lkdtm_debugfs_entry(struct file *f,
                                   const char __user *user_buf,
                                   size_t count, loff_t *off)
{
        struct crashpoint *crashpoint = file_inode(f)->i_private;
        const struct crashtype *crashtype = NULL;
        char *buf;
        int err;

        if (count >= PAGE_SIZE)
                return -EINVAL;

        buf = (char *)__get_free_page(GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        if (copy_from_user(buf, user_buf, count)) {
                free_page((unsigned long) buf);
                return -EFAULT;
        }
        /* NULL-terminate and remove enter */
        buf[count] = '\0';
        strim(buf);

        crashtype = find_crashtype(buf);
        free_page((unsigned long)buf);

        if (!crashtype)
                return -EINVAL;

        err = lkdtm_register_cpoint(crashpoint, crashtype);
        if (err < 0)
                return err;

        *off += count;

        return count;
}
#endif

/* Generic read callback that just prints out the available crash types */
static ssize_t lkdtm_debugfs_read(struct file *f, char __user *user_buf,
                size_t count, loff_t *off)
{
        int n, cat, idx;
        ssize_t out;
        char *buf;

        buf = (char *)__get_free_page(GFP_KERNEL);
        if (buf == NULL)
                return -ENOMEM;

        n = scnprintf(buf, PAGE_SIZE, "Available crash types:\n");

        for (cat = 0; cat < ARRAY_SIZE(crashtype_categories); cat++) {
                for (idx = 0; idx < crashtype_categories[cat]->len; idx++) {
                        struct crashtype *crashtype;

                        crashtype = &crashtype_categories[cat]->crashtypes[idx];
                        n += scnprintf(buf + n, PAGE_SIZE - n, "%s\n",
                                      crashtype->name);
                }
        }
        buf[n] = '\0';

        out = simple_read_from_buffer(user_buf, count, off,
                                      buf, n);
        free_page((unsigned long) buf);

        return out;
}

static int lkdtm_debugfs_open(struct inode *inode, struct file *file)
{
        return 0;
}

/* Special entry to just crash directly. Available without KPROBEs */
static ssize_t direct_entry(struct file *f, const char __user *user_buf,
                size_t count, loff_t *off)
{
        const struct crashtype *crashtype;
        char *buf;

        if (count >= PAGE_SIZE)
                return -EINVAL;
        if (count < 1)
                return -EINVAL;

        buf = (char *)__get_free_page(GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
        if (copy_from_user(buf, user_buf, count)) {
                free_page((unsigned long) buf);
                return -EFAULT;
        }
        /* NULL-terminate and remove enter */
        buf[count] = '\0';
        strim(buf);

        crashtype = find_crashtype(buf);
        free_page((unsigned long) buf);
        if (!crashtype)
                return -EINVAL;

        pr_info("Performing direct entry %s\n", crashtype->name);
        lkdtm_do_action(crashtype);
        *off += count;

        return count;
}

#ifndef MODULE
/*
 * To avoid needing to export parse_args(), just don't use this code
 * when LKDTM is built as a module.
 */
struct check_cmdline_args {
        const char *param;
        int value;
};

static int lkdtm_parse_one(char *param, char *val,
                           const char *unused, void *arg)
{
        struct check_cmdline_args *args = arg;

        /* short circuit if we already found a value. */
        if (args->value != -ESRCH)
                return 0;
        if (strncmp(param, args->param, strlen(args->param)) == 0) {
                bool bool_result;
                int ret;

                ret = kstrtobool(val, &bool_result);
                if (ret == 0)
                        args->value = bool_result;
        }
        return 0;
}

int lkdtm_check_bool_cmdline(const char *param)
{
        char *command_line;
        struct check_cmdline_args args = {
                .param = param,
                .value = -ESRCH,
        };

        command_line = kstrdup(saved_command_line, GFP_KERNEL);
        if (!command_line)
                return -ENOMEM;

        parse_args("Setting sysctl args", command_line,
                   NULL, 0, -1, -1, &args, lkdtm_parse_one);

        kfree(command_line);

        return args.value;
}
#endif

static struct dentry *lkdtm_debugfs_root;

static int __init lkdtm_module_init(void)
{
        struct crashpoint *crashpoint = NULL;
        const struct crashtype *crashtype = NULL;
        int ret;
        int i;

        /* Neither or both of these need to be set */
        if ((cpoint_type || cpoint_name) && !(cpoint_type && cpoint_name)) {
                pr_err("Need both cpoint_type and cpoint_name or neither\n");
                return -EINVAL;
        }

        if (cpoint_type) {
                crashtype = find_crashtype(cpoint_type);
                if (!crashtype) {
                        pr_err("Unknown crashtype '%s'\n", cpoint_type);
                        return -EINVAL;
                }
        }

        if (cpoint_name) {
                for (i = 0; i < ARRAY_SIZE(crashpoints); i++) {
                        if (!strcmp(cpoint_name, crashpoints[i].name))
                                crashpoint = &crashpoints[i];
                }

                /* Refuse unknown crashpoints. */
                if (!crashpoint) {
                        pr_err("Invalid crashpoint %s\n", cpoint_name);
                        return -EINVAL;
                }
        }

#ifdef CONFIG_KPROBES
        /* Set crash count. */
        crash_count = cpoint_count;
#endif

        /* Common initialization. */
        lkdtm_kernel_info = kasprintf(GFP_KERNEL, "kernel (%s %s)",
                                      init_uts_ns.name.release,
                                      init_uts_ns.name.machine);

        /* Handle test-specific initialization. */
        lkdtm_bugs_init(&recur_count);
        lkdtm_perms_init();
        lkdtm_usercopy_init();
        lkdtm_heap_init();

        /* Register debugfs interface */
        lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);

        /* Install debugfs trigger files. */
        for (i = 0; i < ARRAY_SIZE(crashpoints); i++) {
                struct crashpoint *cur = &crashpoints[i];

                debugfs_create_file(cur->name, 0644, lkdtm_debugfs_root, cur,
                                    &cur->fops);
        }

        /* Install crashpoint if one was selected. */
        if (crashpoint) {
                ret = lkdtm_register_cpoint(crashpoint, crashtype);
                if (ret < 0) {
                        pr_info("Invalid crashpoint %s\n", crashpoint->name);
                        goto out_err;
                }
                pr_info("Crash point %s of type %s registered\n",
                        crashpoint->name, cpoint_type);
        } else {
                pr_info("No crash points registered, enable through debugfs\n");
        }

        return 0;

out_err:
        debugfs_remove_recursive(lkdtm_debugfs_root);
        return ret;
}

static void __exit lkdtm_module_exit(void)
{
        debugfs_remove_recursive(lkdtm_debugfs_root);

        /* Handle test-specific clean-up. */
        lkdtm_heap_exit();
        lkdtm_usercopy_exit();

        if (lkdtm_kprobe != NULL)
                unregister_kprobe(lkdtm_kprobe);

        kfree(lkdtm_kernel_info);

        pr_info("Crash point unregistered\n");
}

module_init(lkdtm_module_init);
module_exit(lkdtm_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Kernel crash testing module");