// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2012  Google, Inc.
 */

#include <linux/kernel.h>
#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/atomic.h>
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/ftrace.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/err.h>
#include <linux/cache.h>
#include <linux/slab.h>
#include <asm/barrier.h>
#include "internal.h"

/* This doesn't need to be atomic: speed is chosen over correctness here. */
static u64 pstore_ftrace_stamp;

static void notrace pstore_ftrace_call(unsigned long ip,
                                       unsigned long parent_ip,
                                       struct ftrace_ops *op,
                                       struct ftrace_regs *fregs)
{
        int bit;
        unsigned long flags;
        struct pstore_ftrace_record rec = {};
        struct pstore_record record = {
                .type = PSTORE_TYPE_FTRACE,
                .buf = (char *)&rec,
                .size = sizeof(rec),
                .psi = psinfo,
        };

        if (unlikely(oops_in_progress))
                return;

        bit = ftrace_test_recursion_trylock(ip, parent_ip);
        if (bit < 0)
                return;

        local_irq_save(flags);

        rec.ip = ip;
        rec.parent_ip = parent_ip;
        pstore_ftrace_write_timestamp(&rec, pstore_ftrace_stamp++);
        pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
        psinfo->write(&record);

        local_irq_restore(flags);
        ftrace_test_recursion_unlock(bit);
}

static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
        .func   = pstore_ftrace_call,
};

static DEFINE_MUTEX(pstore_ftrace_lock);
static bool pstore_ftrace_enabled;

static int pstore_set_ftrace_enabled(bool on)
{
        ssize_t ret;

        if (on == pstore_ftrace_enabled)
                return 0;

        if (on) {
                ftrace_ops_set_global_filter(&pstore_ftrace_ops);
                ret = register_ftrace_function(&pstore_ftrace_ops);
        } else {
                ret = unregister_ftrace_function(&pstore_ftrace_ops);
        }

        if (ret) {
                pr_err("%s: unable to %sregister ftrace ops: %zd\n",
                       __func__, on ? "" : "un", ret);
        } else {
                pstore_ftrace_enabled = on;
        }

        return ret;
}

static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
                                        size_t count, loff_t *ppos)
{
        u8 on;
        ssize_t ret;

        ret = kstrtou8_from_user(buf, count, 2, &on);
        if (ret)
                return ret;

        mutex_lock(&pstore_ftrace_lock);
        ret = pstore_set_ftrace_enabled(on);
        mutex_unlock(&pstore_ftrace_lock);

        if (ret == 0)
                ret = count;

        return ret;
}

static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
                                       size_t count, loff_t *ppos)
{
        char val[] = { '0' + pstore_ftrace_enabled, '\n' };

        return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
}

static const struct file_operations pstore_knob_fops = {
        .open   = simple_open,
        .read   = pstore_ftrace_knob_read,
        .write  = pstore_ftrace_knob_write,
};

static struct dentry *pstore_ftrace_dir;

static bool record_ftrace;
module_param(record_ftrace, bool, 0400);
MODULE_PARM_DESC(record_ftrace,
                 "enable ftrace recording immediately (default: off)");

void pstore_register_ftrace(void)
{
        if (!psinfo->write)
                return;

        pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);

        pstore_set_ftrace_enabled(record_ftrace);

        debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir, NULL,
                            &pstore_knob_fops);
}

void pstore_unregister_ftrace(void)
{
        mutex_lock(&pstore_ftrace_lock);
        if (pstore_ftrace_enabled) {
                unregister_ftrace_function(&pstore_ftrace_ops);
                pstore_ftrace_enabled = false;
        }
        mutex_unlock(&pstore_ftrace_lock);

        debugfs_remove_recursive(pstore_ftrace_dir);
}

ssize_t pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
                                  const char *src_log, size_t src_log_size)
{
        size_t dest_size, src_size, total, dest_off, src_off;
        size_t dest_idx = 0, src_idx = 0, merged_idx = 0;
        void *merged_buf;
        struct pstore_ftrace_record *drec, *srec, *mrec;
        size_t record_size = sizeof(struct pstore_ftrace_record);

        dest_off = *dest_log_size % record_size;
        dest_size = *dest_log_size - dest_off;

        src_off = src_log_size % record_size;
        src_size = src_log_size - src_off;

        total = dest_size + src_size;
        merged_buf = kmalloc(total, GFP_KERNEL);
        if (!merged_buf)
                return -ENOMEM;

        drec = (struct pstore_ftrace_record *)(*dest_log + dest_off);
        srec = (struct pstore_ftrace_record *)(src_log + src_off);
        mrec = (struct pstore_ftrace_record *)(merged_buf);

        while (dest_size > 0 && src_size > 0) {
                if (pstore_ftrace_read_timestamp(&drec[dest_idx]) <
                    pstore_ftrace_read_timestamp(&srec[src_idx])) {
                        mrec[merged_idx++] = drec[dest_idx++];
                        dest_size -= record_size;
                } else {
                        mrec[merged_idx++] = srec[src_idx++];
                        src_size -= record_size;
                }
        }

        while (dest_size > 0) {
                mrec[merged_idx++] = drec[dest_idx++];
                dest_size -= record_size;
        }

        while (src_size > 0) {
                mrec[merged_idx++] = srec[src_idx++];
                src_size -= record_size;
        }

        kfree(*dest_log);
        *dest_log = merged_buf;
        *dest_log_size = total;

        return 0;
}
EXPORT_SYMBOL_GPL(pstore_ftrace_combine_log);