#include <trace/syscall.h>
#include <trace/events/syscalls.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>       /* for MODULE_NAME_LEN via KSYM_SYMBOL_LEN */
#include <linux/ftrace.h>
#include <linux/perf_event.h>
#include <asm/syscall.h>

#include "trace_output.h"
#include "trace.h"

static DEFINE_MUTEX(syscall_trace_lock);
static int sys_refcount_enter;
static int sys_refcount_exit;
static DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
static DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);

static int syscall_enter_register(struct ftrace_event_call *event,
                                 enum trace_reg type, void *data);
static int syscall_exit_register(struct ftrace_event_call *event,
                                 enum trace_reg type, void *data);

static int syscall_enter_define_fields(struct ftrace_event_call *call);
static int syscall_exit_define_fields(struct ftrace_event_call *call);

static struct list_head *
syscall_get_enter_fields(struct ftrace_event_call *call)
{
        struct syscall_metadata *entry = call->data;

        return &entry->enter_fields;
}

struct trace_event_functions enter_syscall_print_funcs = {
        .trace          = print_syscall_enter,
};

struct trace_event_functions exit_syscall_print_funcs = {
        .trace          = print_syscall_exit,
};

struct ftrace_event_class event_class_syscall_enter = {
        .system         = "syscalls",
        .reg            = syscall_enter_register,
        .define_fields  = syscall_enter_define_fields,
        .get_fields     = syscall_get_enter_fields,
        .raw_init       = init_syscall_trace,
};

struct ftrace_event_class event_class_syscall_exit = {
        .system         = "syscalls",
        .reg            = syscall_exit_register,
        .define_fields  = syscall_exit_define_fields,
        .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
        .raw_init       = init_syscall_trace,
};

extern struct syscall_metadata *__start_syscalls_metadata[];
extern struct syscall_metadata *__stop_syscalls_metadata[];

static struct syscall_metadata **syscalls_metadata;

#ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
{
        /*
         * Only compare after the "sys" prefix. Archs that use
         * syscall wrappers may have syscalls symbols aliases prefixed
         * with "SyS" instead of "sys", leading to an unwanted
         * mismatch.
         */
        return !strcmp(sym + 3, name + 3);
}
#endif

static __init struct syscall_metadata *
find_syscall_meta(unsigned long syscall)
{
        struct syscall_metadata **start;
        struct syscall_metadata **stop;
        char str[KSYM_SYMBOL_LEN];


        start = __start_syscalls_metadata;
        stop = __stop_syscalls_metadata;
        kallsyms_lookup(syscall, NULL, NULL, NULL, str);

        if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
                return NULL;

        for ( ; start < stop; start++) {
                if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
                        return *start;
        }
        return NULL;
}

static struct syscall_metadata *syscall_nr_to_meta(int nr)
{
        if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
                return NULL;

        return syscalls_metadata[nr];
}

enum print_line_t
print_syscall_enter(struct trace_iterator *iter, int flags,
                    struct trace_event *event)
{
        struct trace_seq *s = &iter->seq;
        struct trace_entry *ent = iter->ent;
        struct syscall_trace_enter *trace;
        struct syscall_metadata *entry;
        int i, ret, syscall;

        trace = (typeof(trace))ent;
        syscall = trace->nr;
        entry = syscall_nr_to_meta(syscall);

        if (!entry)
                goto end;

        if (entry->enter_event->event.type != ent->type) {
                WARN_ON_ONCE(1);
                goto end;
        }

        ret = trace_seq_printf(s, "%s(", entry->name);
        if (!ret)
                return TRACE_TYPE_PARTIAL_LINE;

        for (i = 0; i < entry->nb_args; i++) {
                /* parameter types */
                if (trace_flags & TRACE_ITER_VERBOSE) {
                        ret = trace_seq_printf(s, "%s ", entry->types[i]);
                        if (!ret)
                                return TRACE_TYPE_PARTIAL_LINE;
                }
                /* parameter values */
                ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
                                       trace->args[i],
                                       i == entry->nb_args - 1 ? "" : ", ");
                if (!ret)
                        return TRACE_TYPE_PARTIAL_LINE;
        }

        ret = trace_seq_putc(s, ')');
        if (!ret)
                return TRACE_TYPE_PARTIAL_LINE;

end:
        ret =  trace_seq_putc(s, '\n');
        if (!ret)
                return TRACE_TYPE_PARTIAL_LINE;

        return TRACE_TYPE_HANDLED;
}

enum print_line_t
print_syscall_exit(struct trace_iterator *iter, int flags,
                   struct trace_event *event)
{
        struct trace_seq *s = &iter->seq;
        struct trace_entry *ent = iter->ent;
        struct syscall_trace_exit *trace;
        int syscall;
        struct syscall_metadata *entry;
        int ret;

        trace = (typeof(trace))ent;
        syscall = trace->nr;
        entry = syscall_nr_to_meta(syscall);

        if (!entry) {
                trace_seq_printf(s, "\n");
                return TRACE_TYPE_HANDLED;
        }

        if (entry->exit_event->event.type != ent->type) {
                WARN_ON_ONCE(1);
                return TRACE_TYPE_UNHANDLED;
        }

        ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
                                trace->ret);
        if (!ret)
                return TRACE_TYPE_PARTIAL_LINE;

        return TRACE_TYPE_HANDLED;
}

extern char *__bad_type_size(void);

#define SYSCALL_FIELD(type, name)                                       \
        sizeof(type) != sizeof(trace.name) ?                            \
                __bad_type_size() :                                     \
                #type, #name, offsetof(typeof(trace), name),            \
                sizeof(trace.name), is_signed_type(type)

static
int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
{
        int i;
        int pos = 0;

        /* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)

        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
        for (i = 0; i < entry->nb_args; i++) {
                pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
                                entry->args[i], sizeof(unsigned long),
                                i == entry->nb_args - 1 ? "" : ", ");
        }
        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");

        for (i = 0; i < entry->nb_args; i++) {
                pos += snprintf(buf + pos, LEN_OR_ZERO,
                                ", ((unsigned long)(REC->%s))", entry->args[i]);
        }

#undef LEN_OR_ZERO

        /* return the length of print_fmt */
        return pos;
}

static int set_syscall_print_fmt(struct ftrace_event_call *call)
{
        char *print_fmt;
        int len;
        struct syscall_metadata *entry = call->data;

        if (entry->enter_event != call) {
                call->print_fmt = "\"0x%lx\", REC->ret";
                return 0;
        }

        /* First: called with 0 length to calculate the needed length */
        len = __set_enter_print_fmt(entry, NULL, 0);

        print_fmt = kmalloc(len + 1, GFP_KERNEL);
        if (!print_fmt)
                return -ENOMEM;

        /* Second: actually write the @print_fmt */
        __set_enter_print_fmt(entry, print_fmt, len + 1);
        call->print_fmt = print_fmt;

        return 0;
}

static void free_syscall_print_fmt(struct ftrace_event_call *call)
{
        struct syscall_metadata *entry = call->data;

        if (entry->enter_event == call)
                kfree(call->print_fmt);
}

static int syscall_enter_define_fields(struct ftrace_event_call *call)
{
        struct syscall_trace_enter trace;
        struct syscall_metadata *meta = call->data;
        int ret;
        int i;
        int offset = offsetof(typeof(trace), args);

        ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
        if (ret)
                return ret;

        for (i = 0; i < meta->nb_args; i++) {
                ret = trace_define_field(call, meta->types[i],
                                         meta->args[i], offset,
                                         sizeof(unsigned long), 0,
                                         FILTER_OTHER);
                offset += sizeof(unsigned long);
        }

        return ret;
}

static int syscall_exit_define_fields(struct ftrace_event_call *call)
{
        struct syscall_trace_exit trace;
        int ret;

        ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
        if (ret)
                return ret;

        ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
                                 FILTER_OTHER);

        return ret;
}

void ftrace_syscall_enter(void *ignore, struct pt_regs *regs, long id)
{
        struct syscall_trace_enter *entry;
        struct syscall_metadata *sys_data;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        int size;
        int syscall_nr;

        syscall_nr = syscall_get_nr(current, regs);
        if (syscall_nr < 0)
                return;
        if (!test_bit(syscall_nr, enabled_enter_syscalls))
                return;

        sys_data = syscall_nr_to_meta(syscall_nr);
        if (!sys_data)
                return;

        size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;

        event = trace_current_buffer_lock_reserve(&buffer,
                        sys_data->enter_event->event.type, size, 0, 0);
        if (!event)
                return;

        entry = ring_buffer_event_data(event);
        entry->nr = syscall_nr;
        syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);

        if (!filter_current_check_discard(buffer, sys_data->enter_event,
                                          entry, event))
                trace_current_buffer_unlock_commit(buffer, event, 0, 0);
}

void ftrace_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
{
        struct syscall_trace_exit *entry;
        struct syscall_metadata *sys_data;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        int syscall_nr;

        syscall_nr = syscall_get_nr(current, regs);
        if (syscall_nr < 0)
                return;
        if (!test_bit(syscall_nr, enabled_exit_syscalls))
                return;

        sys_data = syscall_nr_to_meta(syscall_nr);
        if (!sys_data)
                return;

        event = trace_current_buffer_lock_reserve(&buffer,
                        sys_data->exit_event->event.type, sizeof(*entry), 0, 0);
        if (!event)
                return;

        entry = ring_buffer_event_data(event);
        entry->nr = syscall_nr;
        entry->ret = syscall_get_return_value(current, regs);

        if (!filter_current_check_discard(buffer, sys_data->exit_event,
                                          entry, event))
                trace_current_buffer_unlock_commit(buffer, event, 0, 0);
}

int reg_event_syscall_enter(struct ftrace_event_call *call)
{
        int ret = 0;
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;
        if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
                return -ENOSYS;
        mutex_lock(&syscall_trace_lock);
        if (!sys_refcount_enter)
                ret = register_trace_sys_enter(ftrace_syscall_enter, NULL);
        if (!ret) {
                set_bit(num, enabled_enter_syscalls);
                sys_refcount_enter++;
        }
        mutex_unlock(&syscall_trace_lock);
        return ret;
}

void unreg_event_syscall_enter(struct ftrace_event_call *call)
{
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;
        if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
                return;
        mutex_lock(&syscall_trace_lock);
        sys_refcount_enter--;
        clear_bit(num, enabled_enter_syscalls);
        if (!sys_refcount_enter)
                unregister_trace_sys_enter(ftrace_syscall_enter, NULL);
        mutex_unlock(&syscall_trace_lock);
}

int reg_event_syscall_exit(struct ftrace_event_call *call)
{
        int ret = 0;
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;
        if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
                return -ENOSYS;
        mutex_lock(&syscall_trace_lock);
        if (!sys_refcount_exit)
                ret = register_trace_sys_exit(ftrace_syscall_exit, NULL);
        if (!ret) {
                set_bit(num, enabled_exit_syscalls);
                sys_refcount_exit++;
        }
        mutex_unlock(&syscall_trace_lock);
        return ret;
}

void unreg_event_syscall_exit(struct ftrace_event_call *call)
{
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;
        if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
                return;
        mutex_lock(&syscall_trace_lock);
        sys_refcount_exit--;
        clear_bit(num, enabled_exit_syscalls);
        if (!sys_refcount_exit)
                unregister_trace_sys_exit(ftrace_syscall_exit, NULL);
        mutex_unlock(&syscall_trace_lock);
}

int init_syscall_trace(struct ftrace_event_call *call)
{
        int id;
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;
        if (num < 0 || num >= NR_syscalls) {
                pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
                                ((struct syscall_metadata *)call->data)->name);
                return -ENOSYS;
        }

        if (set_syscall_print_fmt(call) < 0)
                return -ENOMEM;

        id = trace_event_raw_init(call);

        if (id < 0) {
                free_syscall_print_fmt(call);
                return id;
        }

        return id;
}

unsigned long __init __weak arch_syscall_addr(int nr)
{
        return (unsigned long)sys_call_table[nr];
}

int __init init_ftrace_syscalls(void)
{
        struct syscall_metadata *meta;
        unsigned long addr;
        int i;

        syscalls_metadata = kcalloc(NR_syscalls, sizeof(*syscalls_metadata),
                                    GFP_KERNEL);
        if (!syscalls_metadata) {
                WARN_ON(1);
                return -ENOMEM;
        }

        for (i = 0; i < NR_syscalls; i++) {
                addr = arch_syscall_addr(i);
                meta = find_syscall_meta(addr);
                if (!meta)
                        continue;

                meta->syscall_nr = i;
                syscalls_metadata[i] = meta;
        }

        return 0;
}
early_initcall(init_ftrace_syscalls);

#ifdef CONFIG_PERF_EVENTS

static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
static int sys_perf_refcount_enter;
static int sys_perf_refcount_exit;

static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
{
        struct syscall_metadata *sys_data;
        struct syscall_trace_enter *rec;
        struct hlist_head *head;
        int syscall_nr;
        int rctx;
        int size;

        syscall_nr = syscall_get_nr(current, regs);
        if (syscall_nr < 0)
                return;
        if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
                return;

        sys_data = syscall_nr_to_meta(syscall_nr);
        if (!sys_data)
                return;

        /* get the size after alignment with the u32 buffer size field */
        size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
        size = ALIGN(size + sizeof(u32), sizeof(u64));
        size -= sizeof(u32);

        if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
                      "perf buffer not large enough"))
                return;

        rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
                                sys_data->enter_event->event.type, regs, &rctx);
        if (!rec)
                return;

        rec->nr = syscall_nr;
        syscall_get_arguments(current, regs, 0, sys_data->nb_args,
                               (unsigned long *)&rec->args);

        head = this_cpu_ptr(sys_data->enter_event->perf_events);
        perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysenter_enable(struct ftrace_event_call *call)
{
        int ret = 0;
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;

        mutex_lock(&syscall_trace_lock);
        if (!sys_perf_refcount_enter)
                ret = register_trace_sys_enter(perf_syscall_enter, NULL);
        if (ret) {
                pr_info("event trace: Could not activate"
                                "syscall entry trace point");
        } else {
                set_bit(num, enabled_perf_enter_syscalls);
                sys_perf_refcount_enter++;
        }
        mutex_unlock(&syscall_trace_lock);
        return ret;
}

void perf_sysenter_disable(struct ftrace_event_call *call)
{
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;

        mutex_lock(&syscall_trace_lock);
        sys_perf_refcount_enter--;
        clear_bit(num, enabled_perf_enter_syscalls);
        if (!sys_perf_refcount_enter)
                unregister_trace_sys_enter(perf_syscall_enter, NULL);
        mutex_unlock(&syscall_trace_lock);
}

static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
{
        struct syscall_metadata *sys_data;
        struct syscall_trace_exit *rec;
        struct hlist_head *head;
        int syscall_nr;
        int rctx;
        int size;

        syscall_nr = syscall_get_nr(current, regs);
        if (syscall_nr < 0)
                return;
        if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
                return;

        sys_data = syscall_nr_to_meta(syscall_nr);
        if (!sys_data)
                return;

        /* We can probably do that at build time */
        size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
        size -= sizeof(u32);

        /*
         * Impossible, but be paranoid with the future
         * How to put this check outside runtime?
         */
        if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
                "exit event has grown above perf buffer size"))
                return;

        rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
                                sys_data->exit_event->event.type, regs, &rctx);
        if (!rec)
                return;

        rec->nr = syscall_nr;
        rec->ret = syscall_get_return_value(current, regs);

        head = this_cpu_ptr(sys_data->exit_event->perf_events);
        perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysexit_enable(struct ftrace_event_call *call)
{
        int ret = 0;
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;

        mutex_lock(&syscall_trace_lock);
        if (!sys_perf_refcount_exit)
                ret = register_trace_sys_exit(perf_syscall_exit, NULL);
        if (ret) {
                pr_info("event trace: Could not activate"
                                "syscall exit trace point");
        } else {
                set_bit(num, enabled_perf_exit_syscalls);
                sys_perf_refcount_exit++;
        }
        mutex_unlock(&syscall_trace_lock);
        return ret;
}

void perf_sysexit_disable(struct ftrace_event_call *call)
{
        int num;

        num = ((struct syscall_metadata *)call->data)->syscall_nr;

        mutex_lock(&syscall_trace_lock);
        sys_perf_refcount_exit--;
        clear_bit(num, enabled_perf_exit_syscalls);
        if (!sys_perf_refcount_exit)
                unregister_trace_sys_exit(perf_syscall_exit, NULL);
        mutex_unlock(&syscall_trace_lock);
}

#endif /* CONFIG_PERF_EVENTS */

static int syscall_enter_register(struct ftrace_event_call *event,
                                 enum trace_reg type, void *data)
{
        switch (type) {
        case TRACE_REG_REGISTER:
                return reg_event_syscall_enter(event);
        case TRACE_REG_UNREGISTER:
                unreg_event_syscall_enter(event);
                return 0;

#ifdef CONFIG_PERF_EVENTS
        case TRACE_REG_PERF_REGISTER:
                return perf_sysenter_enable(event);
        case TRACE_REG_PERF_UNREGISTER:
                perf_sysenter_disable(event);
                return 0;
        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 syscall_exit_register(struct ftrace_event_call *event,
                                 enum trace_reg type, void *data)
{
        switch (type) {
        case TRACE_REG_REGISTER:
                return reg_event_syscall_exit(event);
        case TRACE_REG_UNREGISTER:
                unreg_event_syscall_exit(event);
                return 0;

#ifdef CONFIG_PERF_EVENTS
        case TRACE_REG_PERF_REGISTER:
                return perf_sysexit_enable(event);
        case TRACE_REG_PERF_UNREGISTER:
                perf_sysexit_disable(event);
                return 0;
        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;
}