// SPDX-License-Identifier: GPL-2.0
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/setup.h>

static char new_command_line[COMMAND_LINE_SIZE];

static int cmdline_proc_show(struct seq_file *m, void *v)
{
	seq_puts(m, saved_command_line);
	seq_putc(m, '\n');
	return 0;
}

static int cmdline_proc_open(struct inode *inode, struct file *file)
{
	return single_open(file, cmdline_proc_show, NULL);
}

static const struct file_operations cmdline_proc_fops = {
	.open		= cmdline_proc_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static char *padding = "                ";

static void replace_flag(char *cmd, const char *flag, const char *flag_new)
{
	char *start_addr, *end_addr;

	/* Ensure all instances of a flag are replaced */
	while ((start_addr = strstr(cmd, flag))) {
		end_addr = strchr(start_addr, ' ');
		if (end_addr) {
			if (strlen(flag)<strlen(flag_new)) {
				// xx yy=a zz
				//    ^   ^
				// xx yy=bb zz
				int length_to_copy = strlen( start_addr + (strlen(flag) ) ) + 1; // +1 to copy trailing '/0'
				int length_diff = strlen(flag_new)-strlen(flag);
				memcpy(start_addr+(strlen(flag)+length_diff), start_addr+(strlen(flag)), length_to_copy);
				memcpy(start_addr+(strlen(flag)), padding, length_diff);
			}
			memcpy(start_addr, flag_new, strlen(flag_new));
		}
		else
			*(start_addr - 1) = '\0';
	}
}

static void replace_safetynet_flags(char *cmd)
{
	// WARNING: be aware that you can't replace shorter string with longer ones in the function called here...
	replace_flag(cmd, "androidboot.vbmeta.device_state=unlocked",
			  "androidboot.vbmeta.device_state=locked  ");
	replace_flag(cmd, "androidboot.enable_dm_verity=0",
			  "androidboot.enable_dm_verity=1");
	replace_flag(cmd, "androidboot.secboot=disabled",
			  "androidboot.secboot=enabled ");
	replace_flag(cmd, "androidboot.verifiedbootstate=orange",
			  "androidboot.verifiedbootstate=green ");
	replace_flag(cmd, "androidboot.veritymode=logging",
			  "androidboot.veritymode=enforcing");
	replace_flag(cmd, "androidboot.veritymode=eio",
			  "androidboot.veritymode=enforcing");

}

static int __init proc_cmdline_init(void)
{
	strcpy(new_command_line, saved_command_line);

	/*
	 * Replace various flags from command line seen by userspace in order to
	 * pass SafetyNet CTS check.
	 */
	replace_safetynet_flags(new_command_line);

	proc_create("cmdline", 0, NULL, &cmdline_proc_fops);
	return 0;
}
fs_initcall(proc_cmdline_init);