// SPDX-License-Identifier: GPL-2.0
/*
 * trace context switch
 *
 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/kmemleak.h>
#include <linux/ftrace.h>
#include <trace/events/sched.h>

#include "trace.h"

#define RECORD_CMDLINE  1
#define RECORD_TGID     2

static int              sched_cmdline_ref;
static int              sched_tgid_ref;
static DEFINE_MUTEX(sched_register_mutex);

static void
probe_sched_switch(void *ignore, bool preempt,
                   struct task_struct *prev, struct task_struct *next,
                   unsigned int prev_state)
{
        int flags;

        flags = (RECORD_TGID * !!sched_tgid_ref) +
                (RECORD_CMDLINE * !!sched_cmdline_ref);

        if (!flags)
                return;
        tracing_record_taskinfo_sched_switch(prev, next, flags);
}

static void
probe_sched_wakeup(void *ignore, struct task_struct *wakee)
{
        int flags;

        flags = (RECORD_TGID * !!sched_tgid_ref) +
                (RECORD_CMDLINE * !!sched_cmdline_ref);

        if (!flags)
                return;
        tracing_record_taskinfo_sched_switch(current, wakee, flags);
}

static int tracing_sched_register(void)
{
        int ret;

        ret = register_trace_sched_wakeup(probe_sched_wakeup, NULL);
        if (ret) {
                pr_info("wakeup trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_wakeup\n");
                return ret;
        }

        ret = register_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
        if (ret) {
                pr_info("wakeup trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_wakeup_new\n");
                goto fail_deprobe;
        }

        ret = register_trace_sched_switch(probe_sched_switch, NULL);
        if (ret) {
                pr_info("sched trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_switch\n");
                goto fail_deprobe_wake_new;
        }

        return ret;
fail_deprobe_wake_new:
        unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
fail_deprobe:
        unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
        return ret;
}

static void tracing_sched_unregister(void)
{
        unregister_trace_sched_switch(probe_sched_switch, NULL);
        unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
        unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
}

static void tracing_start_sched_switch(int ops)
{
        bool sched_register;

        mutex_lock(&sched_register_mutex);
        sched_register = (!sched_cmdline_ref && !sched_tgid_ref);

        switch (ops) {
        case RECORD_CMDLINE:
                sched_cmdline_ref++;
                break;

        case RECORD_TGID:
                sched_tgid_ref++;
                break;
        }

        if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
                tracing_sched_register();
        mutex_unlock(&sched_register_mutex);
}

static void tracing_stop_sched_switch(int ops)
{
        mutex_lock(&sched_register_mutex);

        switch (ops) {
        case RECORD_CMDLINE:
                sched_cmdline_ref--;
                break;

        case RECORD_TGID:
                sched_tgid_ref--;
                break;
        }

        if (!sched_cmdline_ref && !sched_tgid_ref)
                tracing_sched_unregister();
        mutex_unlock(&sched_register_mutex);
}

void tracing_start_cmdline_record(void)
{
        tracing_start_sched_switch(RECORD_CMDLINE);
}

void tracing_stop_cmdline_record(void)
{
        tracing_stop_sched_switch(RECORD_CMDLINE);
}

void tracing_start_tgid_record(void)
{
        tracing_start_sched_switch(RECORD_TGID);
}

void tracing_stop_tgid_record(void)
{
        tracing_stop_sched_switch(RECORD_TGID);
}

/*
 * The tgid_map array maps from pid to tgid; i.e. the value stored at index i
 * is the tgid last observed corresponding to pid=i.
 */
static int *tgid_map;

/* The maximum valid index into tgid_map. */
static size_t tgid_map_max;

#define SAVED_CMDLINES_DEFAULT 128
#define NO_CMDLINE_MAP UINT_MAX
/*
 * Preemption must be disabled before acquiring trace_cmdline_lock.
 * The various trace_arrays' max_lock must be acquired in a context
 * where interrupt is disabled.
 */
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
struct saved_cmdlines_buffer {
        unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
        unsigned *map_cmdline_to_pid;
        unsigned cmdline_num;
        int cmdline_idx;
        char saved_cmdlines[];
};
static struct saved_cmdlines_buffer *savedcmd;

/* Holds the size of a cmdline and pid element */
#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s)                       \
        (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))

static inline char *get_saved_cmdlines(int idx)
{
        return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
}

static inline void set_cmdline(int idx, const char *cmdline)
{
        strscpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
}

static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
{
        int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);

        kmemleak_free(s);
        free_pages((unsigned long)s, order);
}

static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
{
        struct saved_cmdlines_buffer *s;
        struct page *page;
        int orig_size, size;
        int order;

        /* Figure out how much is needed to hold the given number of cmdlines */
        orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
        order = get_order(orig_size);
        size = 1 << (order + PAGE_SHIFT);
        page = alloc_pages(GFP_KERNEL, order);
        if (!page)
                return NULL;

        s = page_address(page);
        kmemleak_alloc(s, size, 1, GFP_KERNEL);
        memset(s, 0, sizeof(*s));

        /* Round up to actual allocation */
        val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
        s->cmdline_num = val;

        /* Place map_cmdline_to_pid array right after saved_cmdlines */
        s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];

        memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
               sizeof(s->map_pid_to_cmdline));
        memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
               val * sizeof(*s->map_cmdline_to_pid));

        return s;
}

int trace_create_savedcmd(void)
{
        savedcmd = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT);

        return savedcmd ? 0 : -ENOMEM;
}

int trace_save_cmdline(struct task_struct *tsk)
{
        unsigned tpid, idx;

        /* treat recording of idle task as a success */
        if (!tsk->pid)
                return 1;

        BUILD_BUG_ON(!is_power_of_2(PID_MAX_DEFAULT));

        tpid = tsk->pid & (PID_MAX_DEFAULT - 1);

        /*
         * It's not the end of the world if we don't get
         * the lock, but we also don't want to spin
         * nor do we want to disable interrupts,
         * so if we miss here, then better luck next time.
         *
         * This is called within the scheduler and wake up, so interrupts
         * had better been disabled and run queue lock been held.
         */
        lockdep_assert_preemption_disabled();
        if (!arch_spin_trylock(&trace_cmdline_lock))
                return 0;

        idx = savedcmd->map_pid_to_cmdline[tpid];
        if (idx == NO_CMDLINE_MAP) {
                idx = (savedcmd->cmdline_idx + 1) % savedcmd->cmdline_num;

                savedcmd->map_pid_to_cmdline[tpid] = idx;
                savedcmd->cmdline_idx = idx;
        }

        savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
        set_cmdline(idx, tsk->comm);

        arch_spin_unlock(&trace_cmdline_lock);

        return 1;
}

static void __trace_find_cmdline(int pid, char comm[])
{
        unsigned map;
        int tpid;

        if (!pid) {
                strcpy(comm, "<idle>");
                return;
        }

        if (WARN_ON_ONCE(pid < 0)) {
                strcpy(comm, "<XXX>");
                return;
        }

        tpid = pid & (PID_MAX_DEFAULT - 1);
        map = savedcmd->map_pid_to_cmdline[tpid];
        if (map != NO_CMDLINE_MAP) {
                tpid = savedcmd->map_cmdline_to_pid[map];
                if (tpid == pid) {
                        strscpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
                        return;
                }
        }
        strcpy(comm, "<...>");
}

void trace_find_cmdline(int pid, char comm[])
{
        preempt_disable();
        arch_spin_lock(&trace_cmdline_lock);

        __trace_find_cmdline(pid, comm);

        arch_spin_unlock(&trace_cmdline_lock);
        preempt_enable();
}

static int *trace_find_tgid_ptr(int pid)
{
        /*
         * Pairs with the smp_store_release in set_tracer_flag() to ensure that
         * if we observe a non-NULL tgid_map then we also observe the correct
         * tgid_map_max.
         */
        int *map = smp_load_acquire(&tgid_map);

        if (unlikely(!map || pid > tgid_map_max))
                return NULL;

        return &map[pid];
}

int trace_find_tgid(int pid)
{
        int *ptr = trace_find_tgid_ptr(pid);

        return ptr ? *ptr : 0;
}

static int trace_save_tgid(struct task_struct *tsk)
{
        int *ptr;

        /* treat recording of idle task as a success */
        if (!tsk->pid)
                return 1;

        ptr = trace_find_tgid_ptr(tsk->pid);
        if (!ptr)
                return 0;

        *ptr = tsk->tgid;
        return 1;
}

static bool tracing_record_taskinfo_skip(int flags)
{
        if (unlikely(!(flags & (TRACE_RECORD_CMDLINE | TRACE_RECORD_TGID))))
                return true;
        if (!__this_cpu_read(trace_taskinfo_save))
                return true;
        return false;
}

/**
 * tracing_record_taskinfo - record the task info of a task
 *
 * @task:  task to record
 * @flags: TRACE_RECORD_CMDLINE for recording comm
 *         TRACE_RECORD_TGID for recording tgid
 */
void tracing_record_taskinfo(struct task_struct *task, int flags)
{
        bool done;

        if (tracing_record_taskinfo_skip(flags))
                return;

        /*
         * Record as much task information as possible. If some fail, continue
         * to try to record the others.
         */
        done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);

        /* If recording any information failed, retry again soon. */
        if (!done)
                return;

        __this_cpu_write(trace_taskinfo_save, false);
}

/**
 * tracing_record_taskinfo_sched_switch - record task info for sched_switch
 *
 * @prev: previous task during sched_switch
 * @next: next task during sched_switch
 * @flags: TRACE_RECORD_CMDLINE for recording comm
 *         TRACE_RECORD_TGID for recording tgid
 */
void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
                                          struct task_struct *next, int flags)
{
        bool done;

        if (tracing_record_taskinfo_skip(flags))
                return;

        /*
         * Record as much task information as possible. If some fail, continue
         * to try to record the others.
         */
        done  = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
        done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
        done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);

        /* If recording any information failed, retry again soon. */
        if (!done)
                return;

        __this_cpu_write(trace_taskinfo_save, false);
}

/* Helpers to record a specific task information */
void tracing_record_cmdline(struct task_struct *task)
{
        tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
}

void tracing_record_tgid(struct task_struct *task)
{
        tracing_record_taskinfo(task, TRACE_RECORD_TGID);
}

int trace_alloc_tgid_map(void)
{
        int *map;

        if (tgid_map)
                return 0;

        tgid_map_max = init_pid_ns.pid_max;
        map = kvzalloc_objs(*tgid_map, tgid_map_max + 1);
        if (!map)
                return -ENOMEM;

        /*
         * Pairs with smp_load_acquire() in
         * trace_find_tgid_ptr() to ensure that if it observes
         * the tgid_map we just allocated then it also observes
         * the corresponding tgid_map_max value.
         */
        smp_store_release(&tgid_map, map);
        return 0;
}

static void *saved_tgids_next(struct seq_file *m, void *v, loff_t *pos)
{
        int pid = ++(*pos);

        return trace_find_tgid_ptr(pid);
}

static void *saved_tgids_start(struct seq_file *m, loff_t *pos)
{
        int pid = *pos;

        return trace_find_tgid_ptr(pid);
}

static void saved_tgids_stop(struct seq_file *m, void *v)
{
}

static int saved_tgids_show(struct seq_file *m, void *v)
{
        int *entry = (int *)v;
        int pid = entry - tgid_map;
        int tgid = *entry;

        if (tgid == 0)
                return SEQ_SKIP;

        seq_printf(m, "%d %d\n", pid, tgid);
        return 0;
}

static const struct seq_operations tracing_saved_tgids_seq_ops = {
        .start          = saved_tgids_start,
        .stop           = saved_tgids_stop,
        .next           = saved_tgids_next,
        .show           = saved_tgids_show,
};

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

        ret = tracing_check_open_get_tr(NULL);
        if (ret)
                return ret;

        return seq_open(filp, &tracing_saved_tgids_seq_ops);
}


const struct file_operations tracing_saved_tgids_fops = {
        .open           = tracing_saved_tgids_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
{
        unsigned int *ptr = v;

        if (*pos || m->count)
                ptr++;

        (*pos)++;

        for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
             ptr++) {
                if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
                        continue;

                return ptr;
        }

        return NULL;
}

static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
{
        void *v;
        loff_t l = 0;

        preempt_disable();
        arch_spin_lock(&trace_cmdline_lock);

        v = &savedcmd->map_cmdline_to_pid[0];
        while (l <= *pos) {
                v = saved_cmdlines_next(m, v, &l);
                if (!v)
                        return NULL;
        }

        return v;
}

static void saved_cmdlines_stop(struct seq_file *m, void *v)
{
        arch_spin_unlock(&trace_cmdline_lock);
        preempt_enable();
}

static int saved_cmdlines_show(struct seq_file *m, void *v)
{
        char buf[TASK_COMM_LEN];
        unsigned int *pid = v;

        __trace_find_cmdline(*pid, buf);
        seq_printf(m, "%d %s\n", *pid, buf);
        return 0;
}

static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
        .start          = saved_cmdlines_start,
        .next           = saved_cmdlines_next,
        .stop           = saved_cmdlines_stop,
        .show           = saved_cmdlines_show,
};

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

        ret = tracing_check_open_get_tr(NULL);
        if (ret)
                return ret;

        return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
}

const struct file_operations tracing_saved_cmdlines_fops = {
        .open           = tracing_saved_cmdlines_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static ssize_t
tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
                                 size_t cnt, loff_t *ppos)
{
        char buf[64];
        int r;

        preempt_disable();
        arch_spin_lock(&trace_cmdline_lock);
        r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
        arch_spin_unlock(&trace_cmdline_lock);
        preempt_enable();

        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

void trace_free_saved_cmdlines_buffer(void)
{
        free_saved_cmdlines_buffer(savedcmd);
}

static int tracing_resize_saved_cmdlines(unsigned int val)
{
        struct saved_cmdlines_buffer *s, *savedcmd_temp;

        s = allocate_cmdlines_buffer(val);
        if (!s)
                return -ENOMEM;

        preempt_disable();
        arch_spin_lock(&trace_cmdline_lock);
        savedcmd_temp = savedcmd;
        savedcmd = s;
        arch_spin_unlock(&trace_cmdline_lock);
        preempt_enable();
        free_saved_cmdlines_buffer(savedcmd_temp);

        return 0;
}

static ssize_t
tracing_saved_cmdlines_size_write(struct file *filp, const char __user *ubuf,
                                  size_t cnt, loff_t *ppos)
{
        unsigned long val;
        int ret;

        ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
        if (ret)
                return ret;

        /* must have at least 1 entry or less than PID_MAX_DEFAULT */
        if (!val || val > PID_MAX_DEFAULT)
                return -EINVAL;

        ret = tracing_resize_saved_cmdlines((unsigned int)val);
        if (ret < 0)
                return ret;

        *ppos += cnt;

        return cnt;
}

const struct file_operations tracing_saved_cmdlines_size_fops = {
        .open           = tracing_open_generic,
        .read           = tracing_saved_cmdlines_size_read,
        .write          = tracing_saved_cmdlines_size_write,
};