// SPDX-License-Identifier: GPL-2.0
/*
 * Kprobes-based tracing events
 *
 * Created by Masami Hiramatsu <mhiramat@redhat.com>
 *
 */
#define pr_fmt(fmt)     "trace_kprobe: " fmt

#include <linux/bpf-cgroup.h>
#include <linux/cleanup.h>
#include <linux/error-injection.h>
#include <linux/module.h>
#include <linux/rculist.h>
#include <linux/security.h>
#include <linux/uaccess.h>

#include <asm/setup.h>  /* for COMMAND_LINE_SIZE */

#include "trace_dynevent.h"
#include "trace_kprobe_selftest.h"
#include "trace_probe.h"
#include "trace_probe_kernel.h"
#include "trace_probe_tmpl.h"

#define KPROBE_EVENT_SYSTEM "kprobes"
#define KRETPROBE_MAXACTIVE_MAX 4096

/* Kprobe early definition from command line */
static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;

static int __init set_kprobe_boot_events(char *str)
{
        strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
        disable_tracing_selftest("running kprobe events");

        return 1;
}
__setup("kprobe_event=", set_kprobe_boot_events);

static int trace_kprobe_create(const char *raw_command);
static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev);
static int trace_kprobe_release(struct dyn_event *ev);
static bool trace_kprobe_is_busy(struct dyn_event *ev);
static bool trace_kprobe_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev);

static struct dyn_event_operations trace_kprobe_ops = {
        .create = trace_kprobe_create,
        .show = trace_kprobe_show,
        .is_busy = trace_kprobe_is_busy,
        .free = trace_kprobe_release,
        .match = trace_kprobe_match,
};

/*
 * Kprobe event core functions
 */
struct trace_kprobe {
        struct dyn_event        devent;
        struct kretprobe        rp;     /* Use rp.kp for kprobe use */
        unsigned long __percpu *nhit;
        const char              *symbol;        /* symbol name */
        struct trace_probe      tp;
};

static bool is_trace_kprobe(struct dyn_event *ev)
{
        return ev->ops == &trace_kprobe_ops;
}

static struct trace_kprobe *to_trace_kprobe(struct dyn_event *ev)
{
        return container_of(ev, struct trace_kprobe, devent);
}

/**
 * for_each_trace_kprobe - iterate over the trace_kprobe list
 * @pos:        the struct trace_kprobe * for each entry
 * @dpos:       the struct dyn_event * to use as a loop cursor
 */
#define for_each_trace_kprobe(pos, dpos)        \
        for_each_dyn_event(dpos)                \
                if (is_trace_kprobe(dpos) && (pos = to_trace_kprobe(dpos)))
#define trace_kprobe_list_empty() list_empty(&dyn_event_list)

static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk)
{
        return tk->rp.handler != NULL;
}

static nokprobe_inline const char *trace_kprobe_symbol(struct trace_kprobe *tk)
{
        return tk->symbol ? tk->symbol : "unknown";
}

static nokprobe_inline unsigned long trace_kprobe_offset(struct trace_kprobe *tk)
{
        return tk->rp.kp.offset;
}

static nokprobe_inline bool trace_kprobe_has_gone(struct trace_kprobe *tk)
{
        return kprobe_gone(&tk->rp.kp);
}

static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
                                                 struct module *mod)
{
        int len = strlen(module_name(mod));
        const char *name = trace_kprobe_symbol(tk);

        return strncmp(module_name(mod), name, len) == 0 && name[len] == ':';
}

#ifdef CONFIG_MODULES
static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
{
        char *p;
        bool ret;

        if (!tk->symbol)
                return false;
        p = strchr(tk->symbol, ':');
        if (!p)
                return true;
        *p = '\0';
        scoped_guard(rcu)
                ret = !!find_module(tk->symbol);
        *p = ':';

        return ret;
}
#else
static inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
{
        return false;
}
#endif

static bool trace_kprobe_is_busy(struct dyn_event *ev)
{
        struct trace_kprobe *tk = to_trace_kprobe(ev);

        return trace_probe_is_enabled(&tk->tp);
}

static bool trace_kprobe_match_command_head(struct trace_kprobe *tk,
                                            int argc, const char **argv)
{
        char buf[MAX_ARGSTR_LEN + 1];

        if (!argc)
                return true;

        if (!tk->symbol)
                snprintf(buf, sizeof(buf), "0x%p", tk->rp.kp.addr);
        else if (tk->rp.kp.offset)
                snprintf(buf, sizeof(buf), "%s+%u",
                         trace_kprobe_symbol(tk), tk->rp.kp.offset);
        else
                snprintf(buf, sizeof(buf), "%s", trace_kprobe_symbol(tk));
        if (strcmp(buf, argv[0]))
                return false;
        argc--; argv++;

        return trace_probe_match_command_args(&tk->tp, argc, argv);
}

static bool trace_kprobe_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev)
{
        struct trace_kprobe *tk = to_trace_kprobe(ev);

        return (event[0] == '\0' ||
                strcmp(trace_probe_name(&tk->tp), event) == 0) &&
            (!system || strcmp(trace_probe_group_name(&tk->tp), system) == 0) &&
            trace_kprobe_match_command_head(tk, argc, argv);
}

static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
{
        unsigned long nhit = 0;
        int cpu;

        for_each_possible_cpu(cpu)
                nhit += *per_cpu_ptr(tk->nhit, cpu);

        return nhit;
}

static nokprobe_inline bool trace_kprobe_is_registered(struct trace_kprobe *tk)
{
        return !(list_empty(&tk->rp.kp.list) &&
                 hlist_unhashed(&tk->rp.kp.hlist));
}

/* Return 0 if it fails to find the symbol address */
static nokprobe_inline
unsigned long trace_kprobe_address(struct trace_kprobe *tk)
{
        unsigned long addr;

        if (tk->symbol) {
                addr = (unsigned long)
                        kallsyms_lookup_name(trace_kprobe_symbol(tk));
                if (addr)
                        addr += tk->rp.kp.offset;
        } else {
                addr = (unsigned long)tk->rp.kp.addr;
        }
        return addr;
}

static nokprobe_inline struct trace_kprobe *
trace_kprobe_primary_from_call(struct trace_event_call *call)
{
        struct trace_probe *tp;

        tp = trace_probe_primary_from_call(call);
        if (WARN_ON_ONCE(!tp))
                return NULL;

        return container_of(tp, struct trace_kprobe, tp);
}

bool trace_kprobe_on_func_entry(struct trace_event_call *call)
{
        struct trace_kprobe *tk = trace_kprobe_primary_from_call(call);

        return tk ? (kprobe_on_func_entry(tk->rp.kp.addr,
                        tk->rp.kp.addr ? NULL : tk->rp.kp.symbol_name,
                        tk->rp.kp.addr ? 0 : tk->rp.kp.offset) == 0) : false;
}

bool trace_kprobe_error_injectable(struct trace_event_call *call)
{
        struct trace_kprobe *tk = trace_kprobe_primary_from_call(call);

        return tk ? within_error_injection_list(trace_kprobe_address(tk)) :
               false;
}

static int register_kprobe_event(struct trace_kprobe *tk);
static int unregister_kprobe_event(struct trace_kprobe *tk);

static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
static int kretprobe_dispatcher(struct kretprobe_instance *ri,
                                struct pt_regs *regs);

static void free_trace_kprobe(struct trace_kprobe *tk)
{
        if (tk) {
                trace_probe_cleanup(&tk->tp);
                kfree(tk->symbol);
                free_percpu(tk->nhit);
                kfree(tk);
        }
}

DEFINE_FREE(free_trace_kprobe, struct trace_kprobe *,
        if (!IS_ERR_OR_NULL(_T)) free_trace_kprobe(_T))

/*
 * Allocate new trace_probe and initialize it (including kprobes).
 */
static struct trace_kprobe *alloc_trace_kprobe(const char *group,
                                             const char *event,
                                             void *addr,
                                             const char *symbol,
                                             unsigned long offs,
                                             int maxactive,
                                             int nargs, bool is_return)
{
        struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
        int ret = -ENOMEM;

        tk = kzalloc_flex(*tk, tp.args, nargs);
        if (!tk)
                return ERR_PTR(ret);

        tk->nhit = alloc_percpu(unsigned long);
        if (!tk->nhit)
                return ERR_PTR(ret);

        if (symbol) {
                tk->symbol = kstrdup(symbol, GFP_KERNEL);
                if (!tk->symbol)
                        return ERR_PTR(ret);
                tk->rp.kp.symbol_name = tk->symbol;
                tk->rp.kp.offset = offs;
        } else
                tk->rp.kp.addr = addr;

        if (is_return)
                tk->rp.handler = kretprobe_dispatcher;
        else
                tk->rp.kp.pre_handler = kprobe_dispatcher;

        tk->rp.maxactive = maxactive;
        INIT_HLIST_NODE(&tk->rp.kp.hlist);
        INIT_LIST_HEAD(&tk->rp.kp.list);

        ret = trace_probe_init(&tk->tp, event, group, false, nargs);
        if (ret < 0)
                return ERR_PTR(ret);

        dyn_event_init(&tk->devent, &trace_kprobe_ops);
        return_ptr(tk);
}

static struct trace_kprobe *find_trace_kprobe(const char *event,
                                              const char *group)
{
        struct dyn_event *pos;
        struct trace_kprobe *tk;

        for_each_trace_kprobe(tk, pos)
                if (strcmp(trace_probe_name(&tk->tp), event) == 0 &&
                    strcmp(trace_probe_group_name(&tk->tp), group) == 0)
                        return tk;
        return NULL;
}

static inline int __enable_trace_kprobe(struct trace_kprobe *tk)
{
        int ret = 0;

        if (trace_kprobe_is_registered(tk) && !trace_kprobe_has_gone(tk)) {
                if (trace_kprobe_is_return(tk))
                        ret = enable_kretprobe(&tk->rp);
                else
                        ret = enable_kprobe(&tk->rp.kp);
        }

        return ret;
}

static void __disable_trace_kprobe(struct trace_probe *tp)
{
        struct trace_kprobe *tk;

        list_for_each_entry(tk, trace_probe_probe_list(tp), tp.list) {
                if (!trace_kprobe_is_registered(tk))
                        continue;
                if (trace_kprobe_is_return(tk))
                        disable_kretprobe(&tk->rp);
                else
                        disable_kprobe(&tk->rp.kp);
        }
}

/*
 * Enable trace_probe
 * if the file is NULL, enable "perf" handler, or enable "trace" handler.
 */
static int enable_trace_kprobe(struct trace_event_call *call,
                                struct trace_event_file *file)
{
        struct trace_probe *tp;
        struct trace_kprobe *tk;
        bool enabled;
        int ret = 0;

        tp = trace_probe_primary_from_call(call);
        if (WARN_ON_ONCE(!tp))
                return -ENODEV;
        enabled = trace_probe_is_enabled(tp);

        /* This also changes "enabled" state */
        if (file) {
                ret = trace_probe_add_file(tp, file);
                if (ret)
                        return ret;
        } else
                trace_probe_set_flag(tp, TP_FLAG_PROFILE);

        if (enabled)
                return 0;

        list_for_each_entry(tk, trace_probe_probe_list(tp), tp.list) {
                if (trace_kprobe_has_gone(tk))
                        continue;
                ret = __enable_trace_kprobe(tk);
                if (ret)
                        break;
                enabled = true;
        }

        if (ret) {
                /* Failed to enable one of them. Roll back all */
                if (enabled)
                        __disable_trace_kprobe(tp);
                if (file)
                        trace_probe_remove_file(tp, file);
                else
                        trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
        }

        return ret;
}

/*
 * Disable trace_probe
 * if the file is NULL, disable "perf" handler, or disable "trace" handler.
 */
static int disable_trace_kprobe(struct trace_event_call *call,
                                struct trace_event_file *file)
{
        struct trace_probe *tp;

        tp = trace_probe_primary_from_call(call);
        if (WARN_ON_ONCE(!tp))
                return -ENODEV;

        if (file) {
                if (!trace_probe_get_file_link(tp, file))
                        return -ENOENT;
                if (!trace_probe_has_single_file(tp))
                        goto out;
                trace_probe_clear_flag(tp, TP_FLAG_TRACE);
        } else
                trace_probe_clear_flag(tp, TP_FLAG_PROFILE);

        if (!trace_probe_is_enabled(tp))
                __disable_trace_kprobe(tp);

 out:
        if (file)
                /*
                 * Synchronization is done in below function. For perf event,
                 * file == NULL and perf_trace_event_unreg() calls
                 * tracepoint_synchronize_unregister() to ensure synchronize
                 * event. We don't need to care about it.
                 */
                trace_probe_remove_file(tp, file);

        return 0;
}

#if defined(CONFIG_DYNAMIC_FTRACE) && \
        !defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE)
static bool __within_notrace_func(unsigned long addr)
{
        unsigned long offset, size;

        if (!addr || !kallsyms_lookup_size_offset(addr, &size, &offset))
                return false;

        /* Get the entry address of the target function */
        addr -= offset;

        /*
         * Since ftrace_location_range() does inclusive range check, we need
         * to subtract 1 byte from the end address.
         */
        return !ftrace_location_range(addr, addr + size - 1);
}

static bool within_notrace_func(struct trace_kprobe *tk)
{
        unsigned long addr = trace_kprobe_address(tk);
        char symname[KSYM_NAME_LEN], *p;

        if (!__within_notrace_func(addr))
                return false;

        /* Check if the address is on a suffixed-symbol */
        if (!lookup_symbol_name(addr, symname)) {
                p = strchr(symname, '.');
                if (!p)
                        return true;
                *p = '\0';
                addr = (unsigned long)kprobe_lookup_name(symname, 0);
                if (addr)
                        return __within_notrace_func(addr);
        }

        return true;
}
#else
#define within_notrace_func(tk) (false)
#endif

/* Internal register function - just handle k*probes and flags */
static int __register_trace_kprobe(struct trace_kprobe *tk)
{
        int i, ret;

        ret = security_locked_down(LOCKDOWN_KPROBES);
        if (ret)
                return ret;

        if (trace_kprobe_is_registered(tk))
                return -EINVAL;

        if (within_notrace_func(tk)) {
                pr_warn("Could not probe notrace function %ps\n",
                        (void *)trace_kprobe_address(tk));
                return -EINVAL;
        }

        for (i = 0; i < tk->tp.nr_args; i++) {
                ret = traceprobe_update_arg(&tk->tp.args[i]);
                if (ret)
                        return ret;
        }

        /* Set/clear disabled flag according to tp->flag */
        if (trace_probe_is_enabled(&tk->tp))
                tk->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
        else
                tk->rp.kp.flags |= KPROBE_FLAG_DISABLED;

        if (trace_kprobe_is_return(tk))
                ret = register_kretprobe(&tk->rp);
        else
                ret = register_kprobe(&tk->rp.kp);

        return ret;
}

/* Internal unregister function - just handle k*probes and flags */
static void __unregister_trace_kprobe(struct trace_kprobe *tk)
{
        if (trace_kprobe_is_registered(tk)) {
                if (trace_kprobe_is_return(tk))
                        unregister_kretprobe(&tk->rp);
                else
                        unregister_kprobe(&tk->rp.kp);
                /* Cleanup kprobe for reuse and mark it unregistered */
                INIT_HLIST_NODE(&tk->rp.kp.hlist);
                INIT_LIST_HEAD(&tk->rp.kp.list);
                if (tk->rp.kp.symbol_name)
                        tk->rp.kp.addr = NULL;
        }
}

/* Unregister a trace_probe and probe_event */
static int unregister_trace_kprobe(struct trace_kprobe *tk)
{
        /* If other probes are on the event, just unregister kprobe */
        if (trace_probe_has_sibling(&tk->tp))
                goto unreg;

        /* Enabled event can not be unregistered */
        if (trace_probe_is_enabled(&tk->tp))
                return -EBUSY;

        /* If there's a reference to the dynamic event */
        if (trace_event_dyn_busy(trace_probe_event_call(&tk->tp)))
                return -EBUSY;

        /* Will fail if probe is being used by ftrace or perf */
        if (unregister_kprobe_event(tk))
                return -EBUSY;

unreg:
        __unregister_trace_kprobe(tk);
        dyn_event_remove(&tk->devent);
        trace_probe_unlink(&tk->tp);

        return 0;
}

static bool trace_kprobe_has_same_kprobe(struct trace_kprobe *orig,
                                         struct trace_kprobe *comp)
{
        struct trace_probe_event *tpe = orig->tp.event;
        int i;

        list_for_each_entry(orig, &tpe->probes, tp.list) {
                if (strcmp(trace_kprobe_symbol(orig),
                           trace_kprobe_symbol(comp)) ||
                    trace_kprobe_offset(orig) != trace_kprobe_offset(comp))
                        continue;

                /*
                 * trace_probe_compare_arg_type() ensured that nr_args and
                 * each argument name and type are same. Let's compare comm.
                 */
                for (i = 0; i < orig->tp.nr_args; i++) {
                        if (strcmp(orig->tp.args[i].comm,
                                   comp->tp.args[i].comm))
                                break;
                }

                if (i == orig->tp.nr_args)
                        return true;
        }

        return false;
}

static int append_trace_kprobe(struct trace_kprobe *tk, struct trace_kprobe *to)
{
        int ret;

        ret = trace_probe_compare_arg_type(&tk->tp, &to->tp);
        if (ret) {
                /* Note that argument starts index = 2 */
                trace_probe_log_set_index(ret + 1);
                trace_probe_log_err(0, DIFF_ARG_TYPE);
                return -EEXIST;
        }
        if (trace_kprobe_has_same_kprobe(to, tk)) {
                trace_probe_log_set_index(0);
                trace_probe_log_err(0, SAME_PROBE);
                return -EEXIST;
        }

        /* Append to existing event */
        ret = trace_probe_append(&tk->tp, &to->tp);
        if (ret)
                return ret;

        /* Register k*probe */
        ret = __register_trace_kprobe(tk);
        if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) {
                pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
                ret = 0;
        }

        if (ret)
                trace_probe_unlink(&tk->tp);
        else
                dyn_event_add(&tk->devent, trace_probe_event_call(&tk->tp));

        return ret;
}

/* Register a trace_probe and probe_event */
static int register_trace_kprobe(struct trace_kprobe *tk)
{
        struct trace_kprobe *old_tk;
        int ret;

        guard(mutex)(&event_mutex);

        old_tk = find_trace_kprobe(trace_probe_name(&tk->tp),
                                   trace_probe_group_name(&tk->tp));
        if (old_tk) {
                if (trace_kprobe_is_return(tk) != trace_kprobe_is_return(old_tk)) {
                        trace_probe_log_set_index(0);
                        trace_probe_log_err(0, DIFF_PROBE_TYPE);
                        return -EEXIST;
                }
                return append_trace_kprobe(tk, old_tk);
        }

        /* Register new event */
        ret = register_kprobe_event(tk);
        if (ret) {
                if (ret == -EEXIST) {
                        trace_probe_log_set_index(0);
                        trace_probe_log_err(0, EVENT_EXIST);
                } else
                        pr_warn("Failed to register probe event(%d)\n", ret);
                return ret;
        }

        /* Register k*probe */
        ret = __register_trace_kprobe(tk);
        if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) {
                pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
                ret = 0;
        }

        if (ret < 0)
                unregister_kprobe_event(tk);
        else
                dyn_event_add(&tk->devent, trace_probe_event_call(&tk->tp));

        return ret;
}

#ifdef CONFIG_MODULES
static int validate_module_probe_symbol(const char *modname, const char *symbol);

static int register_module_trace_kprobe(struct module *mod, struct trace_kprobe *tk)
{
        const char *p;
        int ret = 0;

        p = strchr(trace_kprobe_symbol(tk), ':');
        if (p)
                ret = validate_module_probe_symbol(module_name(mod), p + 1);
        if (!ret)
                ret = __register_trace_kprobe(tk);
        return ret;
}

/* Module notifier call back, checking event on the module */
static int trace_kprobe_module_callback(struct notifier_block *nb,
                                       unsigned long val, void *data)
{
        struct module *mod = data;
        struct dyn_event *pos;
        struct trace_kprobe *tk;
        int ret;

        if (val != MODULE_STATE_COMING)
                return NOTIFY_DONE;

        /* Update probes on coming module */
        guard(mutex)(&event_mutex);
        for_each_trace_kprobe(tk, pos) {
                if (trace_kprobe_within_module(tk, mod)) {
                        /* Don't need to check busy - this should have gone. */
                        __unregister_trace_kprobe(tk);
                        ret = register_module_trace_kprobe(mod, tk);
                        if (ret)
                                pr_warn("Failed to re-register probe %s on %s: %d\n",
                                        trace_probe_name(&tk->tp),
                                        module_name(mod), ret);
                }
        }

        return NOTIFY_DONE;
}

static struct notifier_block trace_kprobe_module_nb = {
        .notifier_call = trace_kprobe_module_callback,
        .priority = 2   /* Invoked after kprobe and jump_label module callback */
};
static int trace_kprobe_register_module_notifier(void)
{
        return register_module_notifier(&trace_kprobe_module_nb);
}
#else
static int trace_kprobe_register_module_notifier(void)
{
        return 0;
}
#endif /* CONFIG_MODULES */

static int count_symbols(void *data, unsigned long unused)
{
        unsigned int *count = data;

        (*count)++;

        return 0;
}

struct sym_count_ctx {
        unsigned int count;
        const char *name;
};

static int count_mod_symbols(void *data, const char *name, unsigned long unused)
{
        struct sym_count_ctx *ctx = data;

        if (strcmp(name, ctx->name) == 0)
                ctx->count++;

        return 0;
}

static unsigned int number_of_same_symbols(const char *mod, const char *func_name)
{
        struct sym_count_ctx ctx = { .count = 0, .name = func_name };

        if (!mod)
                kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count);

        module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);

        return ctx.count;
}

static int validate_module_probe_symbol(const char *modname, const char *symbol)
{
        unsigned int count = number_of_same_symbols(modname, symbol);

        if (count > 1) {
                /*
                 * Users should use ADDR to remove the ambiguity of
                 * using KSYM only.
                 */
                return -EADDRNOTAVAIL;
        } else if (count == 0) {
                /*
                 * We can return ENOENT earlier than when register the
                 * kprobe.
                 */
                return -ENOENT;
        }
        return 0;
}

#ifdef CONFIG_MODULES
/* Return NULL if the module is not loaded or under unloading. */
static struct module *try_module_get_by_name(const char *name)
{
        struct module *mod;

        guard(rcu)();
        mod = find_module(name);
        if (mod && !try_module_get(mod))
                mod = NULL;
        return mod;
}
#else
#define try_module_get_by_name(name)    (NULL)
#endif

static int validate_probe_symbol(char *symbol)
{
        struct module *mod = NULL;
        char *modname = NULL, *p;
        int ret = 0;

        p = strchr(symbol, ':');
        if (p) {
                modname = symbol;
                symbol = p + 1;
                *p = '\0';
                mod = try_module_get_by_name(modname);
                if (!mod)
                        goto out;
        }

        ret = validate_module_probe_symbol(modname, symbol);
out:
        if (p)
                *p = ':';
        if (mod)
                module_put(mod);
        return ret;
}

static int trace_kprobe_entry_handler(struct kretprobe_instance *ri,
                                      struct pt_regs *regs);

static int trace_kprobe_create_internal(int argc, const char *argv[],
                                        struct traceprobe_parse_context *ctx)
{
        /*
         * Argument syntax:
         *  - Add kprobe:
         *      p[:[GRP/][EVENT]] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS]
         *  - Add kretprobe:
         *      r[MAXACTIVE][:[GRP/][EVENT]] [MOD:]KSYM[+0] [FETCHARGS]
         *    Or
         *      p[:[GRP/][EVENT]] [MOD:]KSYM[+0]%return [FETCHARGS]
         *
         * Fetch args:
         *  $retval     : fetch return value
         *  $stack      : fetch stack address
         *  $stackN     : fetch Nth of stack (N:0-)
         *  $comm       : fetch current task comm
         *  @ADDR       : fetch memory at ADDR (ADDR should be in kernel)
         *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)
         *  %REG        : fetch register REG
         * Dereferencing memory fetch:
         *  +|-offs(ARG) : fetch memory at ARG +|- offs address.
         * Alias name of args:
         *  NAME=FETCHARG : set NAME as alias of FETCHARG.
         * Type of args:
         *  FETCHARG:TYPE : use TYPE instead of unsigned long.
         */
        struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
        const char *event = NULL, *group = KPROBE_EVENT_SYSTEM;
        const char **new_argv __free(kfree) = NULL;
        int i, len, new_argc = 0, ret = 0;
        char *symbol __free(kfree) = NULL;
        char *ebuf __free(kfree) = NULL;
        char *gbuf __free(kfree) = NULL;
        char *abuf __free(kfree) = NULL;
        char *dbuf __free(kfree) = NULL;
        enum probe_print_type ptype;
        bool is_return = false;
        int maxactive = 0;
        void *addr = NULL;
        char *tmp = NULL;
        long offset = 0;

        switch (argv[0][0]) {
        case 'r':
                is_return = true;
                break;
        case 'p':
                break;
        default:
                return -ECANCELED;
        }
        if (argc < 2)
                return -ECANCELED;

        event = strchr(&argv[0][1], ':');
        if (event)
                event++;

        if (isdigit(argv[0][1])) {
                char *buf __free(kfree) = NULL;

                if (!is_return) {
                        trace_probe_log_err(1, BAD_MAXACT_TYPE);
                        return -EINVAL;
                }
                if (event)
                        len = event - &argv[0][1] - 1;
                else
                        len = strlen(&argv[0][1]);
                if (len > MAX_EVENT_NAME_LEN - 1) {
                        trace_probe_log_err(1, BAD_MAXACT);
                        return -EINVAL;
                }
                buf = kmemdup(&argv[0][1], len + 1, GFP_KERNEL);
                if (!buf)
                        return -ENOMEM;
                buf[len] = '\0';
                ret = kstrtouint(buf, 0, &maxactive);
                if (ret || !maxactive) {
                        trace_probe_log_err(1, BAD_MAXACT);
                        return -EINVAL;
                }
                /* kretprobes instances are iterated over via a list. The
                 * maximum should stay reasonable.
                 */
                if (maxactive > KRETPROBE_MAXACTIVE_MAX) {
                        trace_probe_log_err(1, MAXACT_TOO_BIG);
                        return -EINVAL;
                }
        }

        /* try to parse an address. if that fails, try to read the
         * input as a symbol. */
        if (kstrtoul(argv[1], 0, (unsigned long *)&addr)) {
                trace_probe_log_set_index(1);
                /* Check whether uprobe event specified */
                if (strchr(argv[1], '/') && strchr(argv[1], ':'))
                        return -ECANCELED;

                /* a symbol specified */
                symbol = kstrdup(argv[1], GFP_KERNEL);
                if (!symbol)
                        return -ENOMEM;

                tmp = strchr(symbol, '%');
                if (tmp) {
                        if (!strcmp(tmp, "%return")) {
                                *tmp = '\0';
                                is_return = true;
                        } else {
                                trace_probe_log_err(tmp - symbol, BAD_ADDR_SUFFIX);
                                return -EINVAL;
                        }
                }

                /* TODO: support .init module functions */
                ret = traceprobe_split_symbol_offset(symbol, &offset);
                if (ret || offset < 0 || offset > UINT_MAX) {
                        trace_probe_log_err(0, BAD_PROBE_ADDR);
                        return -EINVAL;
                }
                ret = validate_probe_symbol(symbol);
                if (ret) {
                        if (ret == -EADDRNOTAVAIL)
                                trace_probe_log_err(0, NON_UNIQ_SYMBOL);
                        else
                                trace_probe_log_err(0, BAD_PROBE_ADDR);
                        return -EINVAL;
                }
                if (is_return)
                        ctx->flags |= TPARG_FL_RETURN;
                ret = kprobe_on_func_entry(NULL, symbol, offset);
                if (ret == 0 && !is_return)
                        ctx->flags |= TPARG_FL_FENTRY;
                /* Defer the ENOENT case until register kprobe */
                if (ret == -EINVAL && is_return) {
                        trace_probe_log_err(0, BAD_RETPROBE);
                        return -EINVAL;
                }
        }

        trace_probe_log_set_index(0);
        if (event) {
                gbuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
                if (!gbuf)
                        return -ENOMEM;
                ret = traceprobe_parse_event_name(&event, &group, gbuf,
                                                  event - argv[0]);
                if (ret)
                        return ret;
        }

        if (!event) {
                /* Make a new event name */
                ebuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
                if (!ebuf)
                        return -ENOMEM;
                if (symbol)
                        snprintf(ebuf, MAX_EVENT_NAME_LEN, "%c_%s_%ld",
                                 is_return ? 'r' : 'p', symbol, offset);
                else
                        snprintf(ebuf, MAX_EVENT_NAME_LEN, "%c_0x%p",
                                 is_return ? 'r' : 'p', addr);
                sanitize_event_name(ebuf);
                event = ebuf;
        }

        abuf = kmalloc(MAX_BTF_ARGS_LEN, GFP_KERNEL);
        if (!abuf)
                return -ENOMEM;
        argc -= 2; argv += 2;
        ctx->funcname = symbol;
        new_argv = traceprobe_expand_meta_args(argc, argv, &new_argc,
                                               abuf, MAX_BTF_ARGS_LEN, ctx);
        if (IS_ERR(new_argv)) {
                ret = PTR_ERR(new_argv);
                new_argv = NULL;
                return ret;
        }
        if (new_argv) {
                argc = new_argc;
                argv = new_argv;
        }
        if (argc > MAX_TRACE_ARGS) {
                trace_probe_log_set_index(2);
                trace_probe_log_err(0, TOO_MANY_ARGS);
                return -E2BIG;
        }

        ret = traceprobe_expand_dentry_args(argc, argv, &dbuf);
        if (ret)
                return ret;

        /* setup a probe */
        tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive,
                                argc, is_return);
        if (IS_ERR(tk)) {
                ret = PTR_ERR(tk);
                /* This must return -ENOMEM, else there is a bug */
                WARN_ON_ONCE(ret != -ENOMEM);
                return ret;     /* We know tk is not allocated */
        }

        /* parse arguments */
        for (i = 0; i < argc; i++) {
                trace_probe_log_set_index(i + 2);
                ctx->offset = 0;
                ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], ctx);
                if (ret)
                        return ret;     /* This can be -ENOMEM */
        }
        /* entry handler for kretprobe */
        if (is_return && tk->tp.entry_arg) {
                tk->rp.entry_handler = trace_kprobe_entry_handler;
                tk->rp.data_size = traceprobe_get_entry_data_size(&tk->tp);
        }

        ptype = is_return ? PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
        ret = traceprobe_set_print_fmt(&tk->tp, ptype);
        if (ret < 0)
                return ret;

        ret = register_trace_kprobe(tk);
        if (ret) {
                trace_probe_log_set_index(1);
                if (ret == -EILSEQ)
                        trace_probe_log_err(0, BAD_INSN_BNDRY);
                else if (ret == -ENOENT)
                        trace_probe_log_err(0, BAD_PROBE_ADDR);
                else if (ret != -ENOMEM && ret != -EEXIST)
                        trace_probe_log_err(0, FAIL_REG_PROBE);
                return ret;
        }
        /*
         * Here, 'tk' has been registered to the list successfully,
         * so we don't need to free it.
         */
        tk = NULL;

        return 0;
}

static int trace_kprobe_create_cb(int argc, const char *argv[])
{
        struct traceprobe_parse_context *ctx __free(traceprobe_parse_context) = NULL;
        int ret;

        ctx = kzalloc_obj(*ctx);
        if (!ctx)
                return -ENOMEM;
        ctx->flags = TPARG_FL_KERNEL;

        trace_probe_log_init("trace_kprobe", argc, argv);

        ret = trace_kprobe_create_internal(argc, argv, ctx);

        trace_probe_log_clear();
        return ret;
}

static int trace_kprobe_create(const char *raw_command)
{
        return trace_probe_create(raw_command, trace_kprobe_create_cb);
}

static int create_or_delete_trace_kprobe(const char *raw_command)
{
        int ret;

        if (raw_command[0] == '-')
                return dyn_event_release(raw_command, &trace_kprobe_ops);

        ret = dyn_event_create(raw_command, &trace_kprobe_ops);
        return ret == -ECANCELED ? -EINVAL : ret;
}

static int trace_kprobe_run_command(struct dynevent_cmd *cmd)
{
        return create_or_delete_trace_kprobe(cmd->seq.buffer);
}

/**
 * kprobe_event_cmd_init - Initialize a kprobe event command object
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @buf: A pointer to the buffer used to build the command
 * @maxlen: The length of the buffer passed in @buf
 *
 * Initialize a synthetic event command object.  Use this before
 * calling any of the other kprobe_event functions.
 */
void kprobe_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
{
        dynevent_cmd_init(cmd, buf, maxlen, DYNEVENT_TYPE_KPROBE,
                          trace_kprobe_run_command);
}
EXPORT_SYMBOL_GPL(kprobe_event_cmd_init);

/**
 * __kprobe_event_gen_cmd_start - Generate a kprobe event command from arg list
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @kretprobe: Is this a return probe?
 * @name: The name of the kprobe event
 * @loc: The location of the kprobe event
 * @...: Variable number of arg (pairs), one pair for each field
 *
 * NOTE: Users normally won't want to call this function directly, but
 * rather use the kprobe_event_gen_cmd_start() wrapper, which automatically
 * adds a NULL to the end of the arg list.  If this function is used
 * directly, make sure the last arg in the variable arg list is NULL.
 *
 * Generate a kprobe event command to be executed by
 * kprobe_event_gen_cmd_end().  This function can be used to generate the
 * complete command or only the first part of it; in the latter case,
 * kprobe_event_add_fields() can be used to add more fields following this.
 *
 * Unlikely the synth_event_gen_cmd_start(), @loc must be specified. This
 * returns -EINVAL if @loc == NULL.
 *
 * Return: 0 if successful, error otherwise.
 */
int __kprobe_event_gen_cmd_start(struct dynevent_cmd *cmd, bool kretprobe,
                                 const char *name, const char *loc, ...)
{
        char buf[MAX_EVENT_NAME_LEN];
        struct dynevent_arg arg;
        va_list args;
        int ret;

        if (cmd->type != DYNEVENT_TYPE_KPROBE)
                return -EINVAL;

        if (!loc)
                return -EINVAL;

        if (kretprobe)
                snprintf(buf, MAX_EVENT_NAME_LEN, "r:kprobes/%s", name);
        else
                snprintf(buf, MAX_EVENT_NAME_LEN, "p:kprobes/%s", name);

        ret = dynevent_str_add(cmd, buf);
        if (ret)
                return ret;

        dynevent_arg_init(&arg, 0);
        arg.str = loc;
        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        va_start(args, loc);
        for (;;) {
                const char *field;

                field = va_arg(args, const char *);
                if (!field)
                        break;

                if (++cmd->n_fields > MAX_TRACE_ARGS) {
                        ret = -EINVAL;
                        break;
                }

                arg.str = field;
                ret = dynevent_arg_add(cmd, &arg, NULL);
                if (ret)
                        break;
        }
        va_end(args);

        return ret;
}
EXPORT_SYMBOL_GPL(__kprobe_event_gen_cmd_start);

/**
 * __kprobe_event_add_fields - Add probe fields to a kprobe command from arg list
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @...: Variable number of arg (pairs), one pair for each field
 *
 * NOTE: Users normally won't want to call this function directly, but
 * rather use the kprobe_event_add_fields() wrapper, which
 * automatically adds a NULL to the end of the arg list.  If this
 * function is used directly, make sure the last arg in the variable
 * arg list is NULL.
 *
 * Add probe fields to an existing kprobe command using a variable
 * list of args.  Fields are added in the same order they're listed.
 *
 * Return: 0 if successful, error otherwise.
 */
int __kprobe_event_add_fields(struct dynevent_cmd *cmd, ...)
{
        struct dynevent_arg arg;
        va_list args;
        int ret = 0;

        if (cmd->type != DYNEVENT_TYPE_KPROBE)
                return -EINVAL;

        dynevent_arg_init(&arg, 0);

        va_start(args, cmd);
        for (;;) {
                const char *field;

                field = va_arg(args, const char *);
                if (!field)
                        break;

                if (++cmd->n_fields > MAX_TRACE_ARGS) {
                        ret = -EINVAL;
                        break;
                }

                arg.str = field;
                ret = dynevent_arg_add(cmd, &arg, NULL);
                if (ret)
                        break;
        }
        va_end(args);

        return ret;
}
EXPORT_SYMBOL_GPL(__kprobe_event_add_fields);

/**
 * kprobe_event_delete - Delete a kprobe event
 * @name: The name of the kprobe event to delete
 *
 * Delete a kprobe event with the give @name from kernel code rather
 * than directly from the command line.
 *
 * Return: 0 if successful, error otherwise.
 */
int kprobe_event_delete(const char *name)
{
        char buf[MAX_EVENT_NAME_LEN];

        snprintf(buf, MAX_EVENT_NAME_LEN, "-:%s", name);

        return create_or_delete_trace_kprobe(buf);
}
EXPORT_SYMBOL_GPL(kprobe_event_delete);

static int trace_kprobe_release(struct dyn_event *ev)
{
        struct trace_kprobe *tk = to_trace_kprobe(ev);
        int ret = unregister_trace_kprobe(tk);

        if (!ret)
                free_trace_kprobe(tk);
        return ret;
}

static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev)
{
        struct trace_kprobe *tk = to_trace_kprobe(ev);
        int i;

        seq_putc(m, trace_kprobe_is_return(tk) ? 'r' : 'p');
        if (trace_kprobe_is_return(tk) && tk->rp.maxactive)
                seq_printf(m, "%d", tk->rp.maxactive);
        seq_printf(m, ":%s/%s", trace_probe_group_name(&tk->tp),
                                trace_probe_name(&tk->tp));

        if (!tk->symbol)
                seq_printf(m, " 0x%p", tk->rp.kp.addr);
        else if (tk->rp.kp.offset)
                seq_printf(m, " %s+%u", trace_kprobe_symbol(tk),
                           tk->rp.kp.offset);
        else
                seq_printf(m, " %s", trace_kprobe_symbol(tk));

        for (i = 0; i < tk->tp.nr_args; i++)
                seq_printf(m, " %s=%s", tk->tp.args[i].name, tk->tp.args[i].comm);
        seq_putc(m, '\n');

        return 0;
}

static int probes_seq_show(struct seq_file *m, void *v)
{
        struct dyn_event *ev = v;

        if (!is_trace_kprobe(ev))
                return 0;

        return trace_kprobe_show(m, ev);
}

static const struct seq_operations probes_seq_op = {
        .start  = dyn_event_seq_start,
        .next   = dyn_event_seq_next,
        .stop   = dyn_event_seq_stop,
        .show   = probes_seq_show
};

static int probes_open(struct inode *inode, struct file *file)
{
        int ret;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = dyn_events_release_all(&trace_kprobe_ops);
                if (ret < 0)
                        return ret;
        }

        return seq_open(file, &probes_seq_op);
}

static ssize_t probes_write(struct file *file, const char __user *buffer,
                            size_t count, loff_t *ppos)
{
        return trace_parse_run_command(file, buffer, count, ppos,
                                       create_or_delete_trace_kprobe);
}

static const struct file_operations kprobe_events_ops = {
        .owner          = THIS_MODULE,
        .open           = probes_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
        .write          = probes_write,
};

static unsigned long trace_kprobe_missed(struct trace_kprobe *tk)
{
        return trace_kprobe_is_return(tk) ?
                tk->rp.kp.nmissed + tk->rp.nmissed : tk->rp.kp.nmissed;
}

/* Probes profiling interfaces */
static int probes_profile_seq_show(struct seq_file *m, void *v)
{
        struct dyn_event *ev = v;
        struct trace_kprobe *tk;
        unsigned long nmissed;

        if (!is_trace_kprobe(ev))
                return 0;

        tk = to_trace_kprobe(ev);
        nmissed = trace_kprobe_missed(tk);
        seq_printf(m, "  %-44s %15lu %15lu\n",
                   trace_probe_name(&tk->tp),
                   trace_kprobe_nhit(tk),
                   nmissed);

        return 0;
}

static const struct seq_operations profile_seq_op = {
        .start  = dyn_event_seq_start,
        .next   = dyn_event_seq_next,
        .stop   = dyn_event_seq_stop,
        .show   = probes_profile_seq_show
};

static int profile_open(struct inode *inode, struct file *file)
{
        int ret;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        return seq_open(file, &profile_seq_op);
}

static const struct file_operations kprobe_profile_ops = {
        .owner          = THIS_MODULE,
        .open           = profile_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

/* Note that we don't verify it, since the code does not come from user space */
static int
process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
                   void *dest, void *base)
{
        struct pt_regs *regs = rec;
        unsigned long val;
        int ret;

retry:
        /* 1st stage: get value from context */
        switch (code->op) {
        case FETCH_OP_REG:
                val = regs_get_register(regs, code->param);
                break;
        case FETCH_OP_STACK:
                val = regs_get_kernel_stack_nth(regs, code->param);
                break;
        case FETCH_OP_STACKP:
                val = kernel_stack_pointer(regs);
                break;
        case FETCH_OP_RETVAL:
                val = regs_return_value(regs);
                break;
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
        case FETCH_OP_ARG:
                val = regs_get_kernel_argument(regs, code->param);
                break;
        case FETCH_OP_EDATA:
                val = *(unsigned long *)((unsigned long)edata + code->offset);
                break;
#endif
        case FETCH_NOP_SYMBOL:  /* Ignore a place holder */
                code++;
                goto retry;
        default:
                ret = process_common_fetch_insn(code, &val);
                if (ret < 0)
                        return ret;
        }
        code++;

        return process_fetch_insn_bottom(code, val, dest, base);
}
NOKPROBE_SYMBOL(process_fetch_insn)

/* Kprobe handler */
static nokprobe_inline void
__kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
                    struct trace_event_file *trace_file)
{
        struct kprobe_trace_entry_head *entry;
        struct trace_event_call *call = trace_probe_event_call(&tk->tp);
        struct trace_event_buffer fbuffer;
        int dsize;

        WARN_ON(call != trace_file->event_call);

        if (trace_trigger_soft_disabled(trace_file))
                return;

        dsize = __get_data_size(&tk->tp, regs, NULL);

        entry = trace_event_buffer_reserve(&fbuffer, trace_file,
                                           sizeof(*entry) + tk->tp.size + dsize);
        if (!entry)
                return;

        fbuffer.regs = regs;
        entry->ip = (unsigned long)tk->rp.kp.addr;
        store_trace_args(&entry[1], &tk->tp, regs, NULL, sizeof(*entry), dsize);

        trace_event_buffer_commit(&fbuffer);
}

static void
kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs)
{
        struct event_file_link *link;

        trace_probe_for_each_link_rcu(link, &tk->tp)
                __kprobe_trace_func(tk, regs, link->file);
}
NOKPROBE_SYMBOL(kprobe_trace_func);

/* Kretprobe handler */

static int trace_kprobe_entry_handler(struct kretprobe_instance *ri,
                                      struct pt_regs *regs)
{
        struct kretprobe *rp = get_kretprobe(ri);
        struct trace_kprobe *tk;

        /*
         * There is a small chance that get_kretprobe(ri) returns NULL when
         * the kretprobe is unregister on another CPU between kretprobe's
         * trampoline_handler and this function.
         */
        if (unlikely(!rp))
                return -ENOENT;

        tk = container_of(rp, struct trace_kprobe, rp);

        /* store argument values into ri->data as entry data */
        if (tk->tp.entry_arg)
                store_trace_entry_data(ri->data, &tk->tp, regs);

        return 0;
}


static nokprobe_inline void
__kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
                       struct pt_regs *regs,
                       struct trace_event_file *trace_file)
{
        struct kretprobe_trace_entry_head *entry;
        struct trace_event_buffer fbuffer;
        struct trace_event_call *call = trace_probe_event_call(&tk->tp);
        int dsize;

        WARN_ON(call != trace_file->event_call);

        if (trace_trigger_soft_disabled(trace_file))
                return;

        dsize = __get_data_size(&tk->tp, regs, ri->data);

        entry = trace_event_buffer_reserve(&fbuffer, trace_file,
                                           sizeof(*entry) + tk->tp.size + dsize);
        if (!entry)
                return;

        fbuffer.regs = regs;
        entry->func = (unsigned long)tk->rp.kp.addr;
        entry->ret_ip = get_kretprobe_retaddr(ri);
        store_trace_args(&entry[1], &tk->tp, regs, ri->data, sizeof(*entry), dsize);

        trace_event_buffer_commit(&fbuffer);
}

static void
kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
                     struct pt_regs *regs)
{
        struct event_file_link *link;

        trace_probe_for_each_link_rcu(link, &tk->tp)
                __kretprobe_trace_func(tk, ri, regs, link->file);
}
NOKPROBE_SYMBOL(kretprobe_trace_func);

/* Event entry printers */
static enum print_line_t
print_kprobe_event(struct trace_iterator *iter, int flags,
                   struct trace_event *event)
{
        struct kprobe_trace_entry_head *field;
        struct trace_seq *s = &iter->seq;
        struct trace_probe *tp;

        field = (struct kprobe_trace_entry_head *)iter->ent;
        tp = trace_probe_primary_from_call(
                container_of(event, struct trace_event_call, event));
        if (WARN_ON_ONCE(!tp))
                goto out;

        trace_seq_printf(s, "%s: (", trace_probe_name(tp));

        if (!seq_print_ip_sym_offset(s, field->ip, flags))
                goto out;

        trace_seq_putc(s, ')');

        if (trace_probe_print_args(s, tp->args, tp->nr_args,
                             (u8 *)&field[1], field) < 0)
                goto out;

        trace_seq_putc(s, '\n');
 out:
        return trace_handle_return(s);
}

static enum print_line_t
print_kretprobe_event(struct trace_iterator *iter, int flags,
                      struct trace_event *event)
{
        struct kretprobe_trace_entry_head *field;
        struct trace_seq *s = &iter->seq;
        struct trace_probe *tp;

        field = (struct kretprobe_trace_entry_head *)iter->ent;
        tp = trace_probe_primary_from_call(
                container_of(event, struct trace_event_call, event));
        if (WARN_ON_ONCE(!tp))
                goto out;

        trace_seq_printf(s, "%s: (", trace_probe_name(tp));

        if (!seq_print_ip_sym_offset(s, field->ret_ip, flags))
                goto out;

        trace_seq_puts(s, " <- ");

        if (!seq_print_ip_sym_no_offset(s, field->func, flags))
                goto out;

        trace_seq_putc(s, ')');

        if (trace_probe_print_args(s, tp->args, tp->nr_args,
                             (u8 *)&field[1], field) < 0)
                goto out;

        trace_seq_putc(s, '\n');

 out:
        return trace_handle_return(s);
}


static int kprobe_event_define_fields(struct trace_event_call *event_call)
{
        int ret;
        struct kprobe_trace_entry_head field;
        struct trace_probe *tp;

        tp = trace_probe_primary_from_call(event_call);
        if (WARN_ON_ONCE(!tp))
                return -ENOENT;

        DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);

        return traceprobe_define_arg_fields(event_call, sizeof(field), tp);
}

static int kretprobe_event_define_fields(struct trace_event_call *event_call)
{
        int ret;
        struct kretprobe_trace_entry_head field;
        struct trace_probe *tp;

        tp = trace_probe_primary_from_call(event_call);
        if (WARN_ON_ONCE(!tp))
                return -ENOENT;

        DEFINE_FIELD(unsigned long, func, FIELD_STRING_FUNC, 0);
        DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);

        return traceprobe_define_arg_fields(event_call, sizeof(field), tp);
}

#ifdef CONFIG_PERF_EVENTS

/* Kprobe profile handler */
static int
kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
{
        struct trace_event_call *call = trace_probe_event_call(&tk->tp);
        struct kprobe_trace_entry_head *entry;
        struct hlist_head *head;
        int size, __size, dsize;
        int rctx;

        if (bpf_prog_array_valid(call)) {
                unsigned long orig_ip = instruction_pointer(regs);
                int ret;

                ret = trace_call_bpf(call, regs);

                /*
                 * We need to check and see if we modified the pc of the
                 * pt_regs, and if so return 1 so that we don't do the
                 * single stepping.
                 */
                if (orig_ip != instruction_pointer(regs))
                        return 1;
                if (!ret)
                        return 0;
        }

        head = this_cpu_ptr(call->perf_events);
        if (hlist_empty(head))
                return 0;

        dsize = __get_data_size(&tk->tp, regs, NULL);
        __size = sizeof(*entry) + tk->tp.size + dsize;
        size = ALIGN(__size + sizeof(u32), sizeof(u64));
        size -= sizeof(u32);

        entry = perf_trace_buf_alloc(size, NULL, &rctx);
        if (!entry)
                return 0;

        entry->ip = (unsigned long)tk->rp.kp.addr;
        memset(&entry[1], 0, dsize);
        store_trace_args(&entry[1], &tk->tp, regs, NULL, sizeof(*entry), dsize);
        perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
                              head, NULL);
        return 0;
}
NOKPROBE_SYMBOL(kprobe_perf_func);

/* Kretprobe profile handler */
static void
kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
                    struct pt_regs *regs)
{
        struct trace_event_call *call = trace_probe_event_call(&tk->tp);
        struct kretprobe_trace_entry_head *entry;
        struct hlist_head *head;
        int size, __size, dsize;
        int rctx;

        if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
                return;

        head = this_cpu_ptr(call->perf_events);
        if (hlist_empty(head))
                return;

        dsize = __get_data_size(&tk->tp, regs, ri->data);
        __size = sizeof(*entry) + tk->tp.size + dsize;
        size = ALIGN(__size + sizeof(u32), sizeof(u64));
        size -= sizeof(u32);

        entry = perf_trace_buf_alloc(size, NULL, &rctx);
        if (!entry)
                return;

        entry->func = (unsigned long)tk->rp.kp.addr;
        entry->ret_ip = get_kretprobe_retaddr(ri);
        store_trace_args(&entry[1], &tk->tp, regs, ri->data, sizeof(*entry), dsize);
        perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
                              head, NULL);
}
NOKPROBE_SYMBOL(kretprobe_perf_func);

int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
                        const char **symbol, u64 *probe_offset,
                        u64 *probe_addr, unsigned long *missed,
                        bool perf_type_tracepoint)
{
        const char *pevent = trace_event_name(event->tp_event);
        const char *group = event->tp_event->class->system;
        struct trace_kprobe *tk;

        if (perf_type_tracepoint)
                tk = find_trace_kprobe(pevent, group);
        else
                tk = trace_kprobe_primary_from_call(event->tp_event);
        if (!tk)
                return -EINVAL;

        *fd_type = trace_kprobe_is_return(tk) ? BPF_FD_TYPE_KRETPROBE
                                              : BPF_FD_TYPE_KPROBE;
        *probe_offset = tk->rp.kp.offset;
        *probe_addr = kallsyms_show_value(current_cred()) ?
                      (unsigned long)tk->rp.kp.addr : 0;
        *symbol = tk->symbol;
        if (missed)
                *missed = trace_kprobe_missed(tk);
        return 0;
}
#endif  /* CONFIG_PERF_EVENTS */

/*
 * called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex.
 *
 * kprobe_trace_self_tests_init() does enable_trace_probe/disable_trace_probe
 * lockless, but we can't race with this __init function.
 */
static int kprobe_register(struct trace_event_call *event,
                           enum trace_reg type, void *data)
{
        struct trace_event_file *file = data;

        switch (type) {
        case TRACE_REG_REGISTER:
                return enable_trace_kprobe(event, file);
        case TRACE_REG_UNREGISTER:
                return disable_trace_kprobe(event, file);

#ifdef CONFIG_PERF_EVENTS
        case TRACE_REG_PERF_REGISTER:
                return enable_trace_kprobe(event, NULL);
        case TRACE_REG_PERF_UNREGISTER:
                return disable_trace_kprobe(event, NULL);
        case TRACE_REG_PERF_OPEN:
        case TRACE_REG_PERF_CLOSE:
        case TRACE_REG_PERF_ADD:
        case TRACE_REG_PERF_DEL:
                return 0;
#endif
        }
        return 0;
}

static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
{
        struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp);
        unsigned int flags = trace_probe_load_flag(&tk->tp);
        int ret = 0;

        raw_cpu_inc(*tk->nhit);

        if (flags & TP_FLAG_TRACE)
                kprobe_trace_func(tk, regs);
#ifdef CONFIG_PERF_EVENTS
        if (flags & TP_FLAG_PROFILE)
                ret = kprobe_perf_func(tk, regs);
#endif
        return ret;
}
NOKPROBE_SYMBOL(kprobe_dispatcher);

static int
kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
{
        struct kretprobe *rp = get_kretprobe(ri);
        struct trace_kprobe *tk;
        unsigned int flags;

        /*
         * There is a small chance that get_kretprobe(ri) returns NULL when
         * the kretprobe is unregister on another CPU between kretprobe's
         * trampoline_handler and this function.
         */
        if (unlikely(!rp))
                return 0;

        tk = container_of(rp, struct trace_kprobe, rp);
        raw_cpu_inc(*tk->nhit);

        flags = trace_probe_load_flag(&tk->tp);
        if (flags & TP_FLAG_TRACE)
                kretprobe_trace_func(tk, ri, regs);
#ifdef CONFIG_PERF_EVENTS
        if (flags & TP_FLAG_PROFILE)
                kretprobe_perf_func(tk, ri, regs);
#endif
        return 0;       /* We don't tweak kernel, so just return 0 */
}
NOKPROBE_SYMBOL(kretprobe_dispatcher);

static struct trace_event_functions kretprobe_funcs = {
        .trace          = print_kretprobe_event
};

static struct trace_event_functions kprobe_funcs = {
        .trace          = print_kprobe_event
};

static struct trace_event_fields kretprobe_fields_array[] = {
        { .type = TRACE_FUNCTION_TYPE,
          .define_fields = kretprobe_event_define_fields },
        {}
};

static struct trace_event_fields kprobe_fields_array[] = {
        { .type = TRACE_FUNCTION_TYPE,
          .define_fields = kprobe_event_define_fields },
        {}
};

static inline void init_trace_event_call(struct trace_kprobe *tk)
{
        struct trace_event_call *call = trace_probe_event_call(&tk->tp);

        if (trace_kprobe_is_return(tk)) {
                call->event.funcs = &kretprobe_funcs;
                call->class->fields_array = kretprobe_fields_array;
        } else {
                call->event.funcs = &kprobe_funcs;
                call->class->fields_array = kprobe_fields_array;
        }

        call->flags = TRACE_EVENT_FL_KPROBE;
        call->class->reg = kprobe_register;
}

static int register_kprobe_event(struct trace_kprobe *tk)
{
        init_trace_event_call(tk);

        return trace_probe_register_event_call(&tk->tp);
}

static int unregister_kprobe_event(struct trace_kprobe *tk)
{
        return trace_probe_unregister_event_call(&tk->tp);
}

#ifdef CONFIG_PERF_EVENTS

/* create a trace_kprobe, but don't add it to global lists */
struct trace_event_call *
create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
                          bool is_return)
{
        enum probe_print_type ptype;
        struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
        int ret;
        char *event;

        if (func) {
                ret = validate_probe_symbol(func);
                if (ret)
                        return ERR_PTR(ret);
        }

        /*
         * local trace_kprobes are not added to dyn_event, so they are never
         * searched in find_trace_kprobe(). Therefore, there is no concern of
         * duplicated name here.
         */
        event = func ? func : "DUMMY_EVENT";

        tk = alloc_trace_kprobe(KPROBE_EVENT_SYSTEM, event, (void *)addr, func,
                                offs, 0 /* maxactive */, 0 /* nargs */,
                                is_return);

        if (IS_ERR(tk)) {
                pr_info("Failed to allocate trace_probe.(%d)\n",
                        (int)PTR_ERR(tk));
                return ERR_CAST(tk);
        }

        init_trace_event_call(tk);

        ptype = trace_kprobe_is_return(tk) ?
                PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
        if (traceprobe_set_print_fmt(&tk->tp, ptype) < 0)
                return ERR_PTR(-ENOMEM);

        ret = __register_trace_kprobe(tk);
        if (ret < 0)
                return ERR_PTR(ret);

        return trace_probe_event_call(&(no_free_ptr(tk)->tp));
}

void destroy_local_trace_kprobe(struct trace_event_call *event_call)
{
        struct trace_kprobe *tk;

        tk = trace_kprobe_primary_from_call(event_call);
        if (unlikely(!tk))
                return;

        if (trace_probe_is_enabled(&tk->tp)) {
                WARN_ON(1);
                return;
        }

        __unregister_trace_kprobe(tk);

        free_trace_kprobe(tk);
}
#endif /* CONFIG_PERF_EVENTS */

static __init void enable_boot_kprobe_events(void)
{
        struct trace_array *tr = top_trace_array();
        struct trace_event_file *file;
        struct trace_kprobe *tk;
        struct dyn_event *pos;

        if (trace_kprobe_list_empty())
                return;

        guard(mutex)(&event_mutex);
        for_each_trace_kprobe(tk, pos) {
                list_for_each_entry(file, &tr->events, list)
                        if (file->event_call == trace_probe_event_call(&tk->tp))
                                trace_event_enable_disable(file, 1, 0);
        }
}

static __init void setup_boot_kprobe_events(void)
{
        char *p, *cmd = kprobe_boot_events_buf;
        int ret;

        strreplace(kprobe_boot_events_buf, ',', ' ');

        while (cmd && *cmd != '\0') {
                p = strchr(cmd, ';');
                if (p)
                        *p++ = '\0';

                ret = create_or_delete_trace_kprobe(cmd);
                if (ret)
                        pr_warn("Failed to add event(%d): %s\n", ret, cmd);

                cmd = p;
        }

        enable_boot_kprobe_events();
}

/*
 * Register dynevent at core_initcall. This allows kernel to setup kprobe
 * events in postcore_initcall without tracefs.
 */
static __init int init_kprobe_trace_early(void)
{
        int ret;

        ret = dyn_event_register(&trace_kprobe_ops);
        if (ret)
                return ret;

        if (trace_kprobe_register_module_notifier())
                return -EINVAL;

        return 0;
}
core_initcall(init_kprobe_trace_early);

/* Make a tracefs interface for controlling probe points */
static __init int init_kprobe_trace(void)
{
        int ret;

        ret = tracing_init_dentry();
        if (ret)
                return 0;

        /* Event list interface */
        trace_create_file("kprobe_events", TRACE_MODE_WRITE,
                          NULL, NULL, &kprobe_events_ops);

        /* Profile interface */
        trace_create_file("kprobe_profile", TRACE_MODE_READ,
                          NULL, NULL, &kprobe_profile_ops);

        /* If no 'kprobe_event=' cmd is provided, return directly. */
        if (kprobe_boot_events_buf[0] == '\0')
                return 0;

        setup_boot_kprobe_events();

        return 0;
}
fs_initcall(init_kprobe_trace);


#ifdef CONFIG_FTRACE_STARTUP_TEST
static __init struct trace_event_file *
find_trace_probe_file(struct trace_kprobe *tk, struct trace_array *tr)
{
        struct trace_event_file *file;

        list_for_each_entry(file, &tr->events, list)
                if (file->event_call == trace_probe_event_call(&tk->tp))
                        return file;

        return NULL;
}

/*
 * Nobody but us can call enable_trace_kprobe/disable_trace_kprobe at this
 * stage, we can do this lockless.
 */
static __init int kprobe_trace_self_tests_init(void)
{
        int ret, warn = 0;
        int (*target)(int, int, int, int, int, int);
        struct trace_kprobe *tk;
        struct trace_event_file *file;

        if (unlikely(tracing_disabled))
                return -ENODEV;

        if (tracing_selftest_disabled)
                return 0;

        target = kprobe_trace_selftest_target;

        pr_info("Testing kprobe tracing: ");

        ret = create_or_delete_trace_kprobe("p:testprobe kprobe_trace_selftest_target $stack $stack0 +0($stack)");
        if (WARN_ONCE(ret, "error on probing function entry.")) {
                warn++;
        } else {
                /* Enable trace point */
                tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
                if (WARN_ONCE(tk == NULL, "error on probing function entry.")) {
                        warn++;
                } else {
                        file = find_trace_probe_file(tk, top_trace_array());
                        if (WARN_ONCE(file == NULL, "error on getting probe file.")) {
                                warn++;
                        } else
                                enable_trace_kprobe(
                                        trace_probe_event_call(&tk->tp), file);
                }
        }

        ret = create_or_delete_trace_kprobe("r:testprobe2 kprobe_trace_selftest_target $retval");
        if (WARN_ONCE(ret, "error on probing function return.")) {
                warn++;
        } else {
                /* Enable trace point */
                tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
                if (WARN_ONCE(tk == NULL, "error on getting 2nd new probe.")) {
                        warn++;
                } else {
                        file = find_trace_probe_file(tk, top_trace_array());
                        if (WARN_ONCE(file == NULL, "error on getting probe file.")) {
                                warn++;
                        } else
                                enable_trace_kprobe(
                                        trace_probe_event_call(&tk->tp), file);
                }
        }

        if (warn)
                goto end;

        ret = target(1, 2, 3, 4, 5, 6);

        /*
         * Not expecting an error here, the check is only to prevent the
         * optimizer from removing the call to target() as otherwise there
         * are no side-effects and the call is never performed.
         */
        if (ret != 21)
                warn++;

        /* Disable trace points before removing it */
        tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
        if (WARN_ONCE(tk == NULL, "error on getting test probe.")) {
                warn++;
        } else {
                if (WARN_ONCE(trace_kprobe_nhit(tk) != 1,
                                 "incorrect number of testprobe hits."))
                        warn++;

                file = find_trace_probe_file(tk, top_trace_array());
                if (WARN_ONCE(file == NULL, "error on getting probe file.")) {
                        warn++;
                } else
                        disable_trace_kprobe(
                                trace_probe_event_call(&tk->tp), file);
        }

        tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
        if (WARN_ONCE(tk == NULL, "error on getting 2nd test probe.")) {
                warn++;
        } else {
                if (WARN_ONCE(trace_kprobe_nhit(tk) != 1,
                                 "incorrect number of testprobe2 hits."))
                        warn++;

                file = find_trace_probe_file(tk, top_trace_array());
                if (WARN_ONCE(file == NULL, "error on getting probe file.")) {
                        warn++;
                } else
                        disable_trace_kprobe(
                                trace_probe_event_call(&tk->tp), file);
        }

        ret = create_or_delete_trace_kprobe("-:testprobe");
        if (WARN_ONCE(ret, "error on deleting a probe."))
                warn++;

        ret = create_or_delete_trace_kprobe("-:testprobe2");
        if (WARN_ONCE(ret, "error on deleting a probe."))
                warn++;


end:
        /*
         * Wait for the optimizer work to finish. Otherwise it might fiddle
         * with probes in already freed __init text.
         */
        wait_for_kprobe_optimizer();
        if (warn)
                pr_cont("NG: Some tests are failed. Please check them.\n");
        else
                pr_cont("OK\n");
        return 0;
}

late_initcall(kprobe_trace_self_tests_init);

#endif