// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <asm/ptrace.h>
#include <linux/uaccess.h>

#define SAMPLE_BUFFER_SIZE 8192

static char *sample_buffer;
static char *sample_buffer_pos;
static int prof_running = 0;

void cris_profile_sample(struct pt_regs *regs)
{
	if (!prof_running)
		return;

	if (user_mode(regs))
		*(unsigned int*)sample_buffer_pos = current->pid;
	else
		*(unsigned int*)sample_buffer_pos = 0;

	*(unsigned int *)(sample_buffer_pos + 4) = instruction_pointer(regs);
	sample_buffer_pos += 8;

	if (sample_buffer_pos == sample_buffer + SAMPLE_BUFFER_SIZE)
		sample_buffer_pos = sample_buffer;
}

static ssize_t
read_cris_profile(struct file *file, char __user *buf,
		  size_t count, loff_t *ppos)
{
	unsigned long p = *ppos;
	ssize_t ret;

	ret = simple_read_from_buffer(buf, count, ppos, sample_buffer,
						SAMPLE_BUFFER_SIZE);
	if (ret < 0)
		return ret;

	memset(sample_buffer + p, 0, ret);

	return ret;
}

static ssize_t
write_cris_profile(struct file *file, const char __user *buf,
		   size_t count, loff_t *ppos)
{
	sample_buffer_pos = sample_buffer;
	memset(sample_buffer, 0, SAMPLE_BUFFER_SIZE);
	return count < SAMPLE_BUFFER_SIZE ? count : SAMPLE_BUFFER_SIZE;
}

static const struct file_operations cris_proc_profile_operations = {
	.read		= read_cris_profile,
	.write		= write_cris_profile,
	.llseek		= default_llseek,
};

static int __init init_cris_profile(void)
{
	struct proc_dir_entry *entry;

	sample_buffer = kmalloc(SAMPLE_BUFFER_SIZE, GFP_KERNEL);
	if (!sample_buffer) {
		return -ENOMEM;
	}

	sample_buffer_pos = sample_buffer;

	entry = proc_create("system_profile", S_IWUSR | S_IRUGO, NULL,
			    &cris_proc_profile_operations);
	if (entry) {
		proc_set_size(entry, SAMPLE_BUFFER_SIZE);
	}
	prof_running = 1;

	return 0;
}
__initcall(init_cris_profile);