// SPDX-License-Identifier: GPL-2.0
/*
 * Debug controller
 *
 * WARNING: This controller is for cgroup core debugging only.
 * Its interfaces are unstable and subject to changes at any time.
 */
#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/slab.h>

#include "cgroup-internal.h"

static struct cgroup_subsys_state *
debug_css_alloc(struct cgroup_subsys_state *parent_css)
{
        struct cgroup_subsys_state *css = kzalloc_obj(*css);

        if (!css)
                return ERR_PTR(-ENOMEM);

        return css;
}

static void debug_css_free(struct cgroup_subsys_state *css)
{
        kfree(css);
}

/*
 * debug_taskcount_read - return the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 */
static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
                                struct cftype *cft)
{
        return cgroup_task_count(css->cgroup);
}

static int current_css_set_read(struct seq_file *seq, void *v)
{
        struct kernfs_open_file *of = seq->private;
        struct css_set *cset;
        struct cgroup_subsys *ss;
        struct cgroup_subsys_state *css;
        int i, refcnt;

        if (!cgroup_kn_lock_live(of->kn, false))
                return -ENODEV;

        spin_lock_irq(&css_set_lock);
        cset = task_css_set(current);
        refcnt = refcount_read(&cset->refcount);
        seq_printf(seq, "css_set %pK %d", cset, refcnt);
        if (refcnt > cset->nr_tasks)
                seq_printf(seq, " +%d", refcnt - cset->nr_tasks);
        seq_puts(seq, "\n");

        /*
         * Print the css'es stored in the current css_set.
         */
        for_each_subsys(ss, i) {
                css = cset->subsys[ss->id];
                if (!css)
                        continue;
                seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name,
                          css, css->id);
        }
        spin_unlock_irq(&css_set_lock);
        cgroup_kn_unlock(of->kn);
        return 0;
}

static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
                                         struct cftype *cft)
{
        u64 count;

        rcu_read_lock();
        count = refcount_read(&task_css_set(current)->refcount);
        rcu_read_unlock();
        return count;
}

static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
{
        struct cgrp_cset_link *link;
        struct css_set *cset;
        char *name_buf;

        name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
        if (!name_buf)
                return -ENOMEM;

        spin_lock_irq(&css_set_lock);
        cset = task_css_set(current);
        list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
                struct cgroup *c = link->cgrp;

                cgroup_name(c, name_buf, NAME_MAX + 1);
                seq_printf(seq, "Root %d group %s\n",
                           c->root->hierarchy_id, name_buf);
        }
        spin_unlock_irq(&css_set_lock);
        kfree(name_buf);
        return 0;
}

#define MAX_TASKS_SHOWN_PER_CSS 25
static int cgroup_css_links_read(struct seq_file *seq, void *v)
{
        struct cgroup_subsys_state *css = seq_css(seq);
        struct cgrp_cset_link *link;
        int dead_cnt = 0, extra_refs = 0, threaded_csets = 0;

        spin_lock_irq(&css_set_lock);

        list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
                struct css_set *cset = link->cset;
                struct task_struct *task;
                int count = 0;
                int refcnt = refcount_read(&cset->refcount);

                /*
                 * Print out the proc_cset and threaded_cset relationship
                 * and highlight difference between refcount and task_count.
                 */
                seq_printf(seq, "css_set %pK", cset);
                if (rcu_dereference_protected(cset->dom_cset, 1) != cset) {
                        threaded_csets++;
                        seq_printf(seq, "=>%pK", cset->dom_cset);
                }
                if (!list_empty(&cset->threaded_csets)) {
                        struct css_set *tcset;
                        int idx = 0;

                        list_for_each_entry(tcset, &cset->threaded_csets,
                                            threaded_csets_node) {
                                seq_puts(seq, idx ? "," : "<=");
                                seq_printf(seq, "%pK", tcset);
                                idx++;
                        }
                } else {
                        seq_printf(seq, " %d", refcnt);
                        if (refcnt - cset->nr_tasks > 0) {
                                int extra = refcnt - cset->nr_tasks;

                                seq_printf(seq, " +%d", extra);
                                /*
                                 * Take out the one additional reference in
                                 * init_css_set.
                                 */
                                if (cset == &init_css_set)
                                        extra--;
                                extra_refs += extra;
                        }
                }
                seq_puts(seq, "\n");

                list_for_each_entry(task, &cset->tasks, cg_list) {
                        if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
                                seq_printf(seq, "  task %d\n",
                                           task_pid_vnr(task));
                }

                list_for_each_entry(task, &cset->mg_tasks, cg_list) {
                        if (count++ <= MAX_TASKS_SHOWN_PER_CSS)
                                seq_printf(seq, "  task %d\n",
                                           task_pid_vnr(task));
                }
                /* show # of overflowed tasks */
                if (count > MAX_TASKS_SHOWN_PER_CSS)
                        seq_printf(seq, "  ... (%d)\n",
                                   count - MAX_TASKS_SHOWN_PER_CSS);

                if (cset->dead) {
                        seq_puts(seq, "    [dead]\n");
                        dead_cnt++;
                }

                WARN_ON(count != cset->nr_tasks);
        }
        spin_unlock_irq(&css_set_lock);

        if (!dead_cnt && !extra_refs && !threaded_csets)
                return 0;

        seq_puts(seq, "\n");
        if (threaded_csets)
                seq_printf(seq, "threaded css_sets = %d\n", threaded_csets);
        if (extra_refs)
                seq_printf(seq, "extra references = %d\n", extra_refs);
        if (dead_cnt)
                seq_printf(seq, "dead css_sets = %d\n", dead_cnt);

        return 0;
}

static int cgroup_subsys_states_read(struct seq_file *seq, void *v)
{
        struct kernfs_open_file *of = seq->private;
        struct cgroup *cgrp;
        struct cgroup_subsys *ss;
        struct cgroup_subsys_state *css;
        char pbuf[16];
        int i;

        cgrp = cgroup_kn_lock_live(of->kn, false);
        if (!cgrp)
                return -ENODEV;

        for_each_subsys(ss, i) {
                css = rcu_dereference_check(cgrp->subsys[ss->id], true);
                if (!css)
                        continue;

                pbuf[0] = '\0';

                /* Show the parent CSS if applicable*/
                if (css->parent)
                        snprintf(pbuf, sizeof(pbuf) - 1, " P=%d",
                                 css->parent->id);
                seq_printf(seq, "%2d: %-4s\t- %p[%d] %d%s\n", ss->id, ss->name,
                          css, css->id,
                          atomic_read(&css->online_cnt), pbuf);
        }

        cgroup_kn_unlock(of->kn);
        return 0;
}

static void cgroup_masks_read_one(struct seq_file *seq, const char *name,
                                  u32 mask)
{
        struct cgroup_subsys *ss;
        int ssid;
        bool first = true;

        seq_printf(seq, "%-17s: ", name);
        for_each_subsys(ss, ssid) {
                if (!(mask & (1 << ssid)))
                        continue;
                if (!first)
                        seq_puts(seq, ", ");
                seq_puts(seq, ss->name);
                first = false;
        }
        seq_putc(seq, '\n');
}

static int cgroup_masks_read(struct seq_file *seq, void *v)
{
        struct kernfs_open_file *of = seq->private;
        struct cgroup *cgrp;

        cgrp = cgroup_kn_lock_live(of->kn, false);
        if (!cgrp)
                return -ENODEV;

        cgroup_masks_read_one(seq, "subtree_control", cgrp->subtree_control);
        cgroup_masks_read_one(seq, "subtree_ss_mask", cgrp->subtree_ss_mask);

        cgroup_kn_unlock(of->kn);
        return 0;
}

static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
        return (!cgroup_is_populated(css->cgroup) &&
                !css_has_online_children(&css->cgroup->self));
}

static struct cftype debug_legacy_files[] =  {
        {
                .name = "taskcount",
                .read_u64 = debug_taskcount_read,
        },

        {
                .name = "current_css_set",
                .seq_show = current_css_set_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "current_css_set_refcount",
                .read_u64 = current_css_set_refcount_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "current_css_set_cg_links",
                .seq_show = current_css_set_cg_links_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "cgroup_css_links",
                .seq_show = cgroup_css_links_read,
        },

        {
                .name = "cgroup_subsys_states",
                .seq_show = cgroup_subsys_states_read,
        },

        {
                .name = "cgroup_masks",
                .seq_show = cgroup_masks_read,
        },

        {
                .name = "releasable",
                .read_u64 = releasable_read,
        },

        { }     /* terminate */
};

static struct cftype debug_files[] =  {
        {
                .name = "taskcount",
                .read_u64 = debug_taskcount_read,
        },

        {
                .name = "current_css_set",
                .seq_show = current_css_set_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "current_css_set_refcount",
                .read_u64 = current_css_set_refcount_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "current_css_set_cg_links",
                .seq_show = current_css_set_cg_links_read,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        {
                .name = "css_links",
                .seq_show = cgroup_css_links_read,
        },

        {
                .name = "csses",
                .seq_show = cgroup_subsys_states_read,
        },

        {
                .name = "masks",
                .seq_show = cgroup_masks_read,
        },

        { }     /* terminate */
};

struct cgroup_subsys debug_cgrp_subsys = {
        .css_alloc      = debug_css_alloc,
        .css_free       = debug_css_free,
        .legacy_cftypes = debug_legacy_files,
};

/*
 * On v2, debug is an implicit controller enabled by "cgroup_debug" boot
 * parameter.
 */
void __init enable_debug_cgroup(void)
{
        debug_cgrp_subsys.dfl_cftypes = debug_files;
        debug_cgrp_subsys.implicit_on_dfl = true;
        debug_cgrp_subsys.threaded = true;
}