make generic code to modify kernel command line (a4486c7b) · Commits · e / devices / android_kernel_xiaomi_markw

fs/proc/cmdline.c

+158 −21

Original line number	Original line	Diff line number	Diff line
	@@ -2,6 +2,7 @@
	#include <linux/init.h>		#include <linux/init.h>
	#include <linux/proc_fs.h>		#include <linux/proc_fs.h>
	#include <linux/seq_file.h>		#include <linux/seq_file.h>
			#include <linux/ctype.h>
	#include <asm/setup.h>		#include <asm/setup.h>

	static char new_command_line[COMMAND_LINE_SIZE];		static char new_command_line[COMMAND_LINE_SIZE];
	@@ -24,38 +25,174 @@ static const struct file_operations cmdline_proc_fops = {
	.release = single_release,		.release = single_release,
	};		};

	static void remove_flag(char cmd, const char flag)		static unsigned int arg_len(const char *arg)
	{		{
	char start_addr, end_addr;		unsigned int i, quoted = 0;

	/* Ensure all instances of a flag are removed */		for(i = 0; arg[i] != '\0'; i++) {
	while ((start_addr = strstr(cmd, flag))) {		if (isspace(arg[i]) && !quoted)
	end_addr = strchr(start_addr, ' ');		break;
	if (end_addr)		if (arg[i] == '"') quoted = !quoted;
	memmove(start_addr, end_addr + 1, strlen(end_addr));
	else
	*(start_addr - 1) = '\0';
	}		}
			return i;
	}		}

	static void remove_safetynet_flags(char *cmd)		static char * unquote(char *str)
	{		{
	remove_flag(cmd, "androidboot.enable_dm_verity=");		unsigned int len;
	remove_flag(cmd, "androidboot.secboot=");
	remove_flag(cmd, "androidboot.verifiedbootstate=");		if (*str == '"') str++;
	remove_flag(cmd, "androidboot.veritymode=");		len = strlen(str);
			if ((len > 0) && (str[len - 1] == '"')) str[len - 1] = '\0';
			return str;
	}		}

	static int __init proc_cmdline_init(void)		static int append(const char *str, unsigned int len)
	{		{
	strcpy(new_command_line, saved_command_line);		unsigned int cmd_len;

			cmd_len = strlen(new_command_line);
			if (cmd_len == 0) {
			if (len >= sizeof(new_command_line))
			return -1;
			} else {
			if (cmd_len + len + 1 >= sizeof(new_command_line))
			return -1;
			new_command_line[cmd_len++] = ' ';
			}
			strncat(new_command_line + cmd_len, str, len);
			new_command_line[cmd_len + len] = '\0';
			return 0;
			}

			static int modify_cmd_line(const char *cmd_line,
			int (callback)(const char name, const char val, const char **list))
			{
			static char buf[COMMAND_LINE_SIZE];
			const char in, name, val, *list;
			char *q;
			unsigned int len;
			int i, accept;

			in = cmd_line;
			*new_command_line = '\0';
			while(*in != '\0'){
			in = skip_spaces(in);
			len = arg_len(in);
			if (len >= sizeof(buf)) {
			pr_err("modify_cmd_line: parameter is too long, len=%d\n", len);
			goto error;
			}

			strncpy(buf, in, len);
			buf[len] = '\0';
			q = strchr(buf, '=');
			if (q != NULL) {
			*q = '\0';
			name = unquote(buf);
			val = unquote(q + 1);
			} else {
			name = NULL;
			val = unquote(buf);
			}

			list = NULL;
			accept = (callback == NULL) ? 1 : callback(name, val, &list);
			if (accept && (append(in, len) != 0)) {
			pr_err("modify_cmd_line: out string overflow\n");
			goto error;
			}
			for(i = 0; (list != NULL) && (list[i] != NULL); i++) {
			if (append(list[i], strlen(list[i])) != 0) {
			pr_err("modify_cmd_line: out string overflow\n");
			goto error;
			}
			}

			in += len;
			}

			if (callback != NULL) {
			list = NULL;
			callback(NULL, NULL, &list);
			for(i = 0; (list != NULL) && (list[i] != NULL); i++) {
			if (append(list[i], strlen(list[i])) != 0) {
			pr_err("modify_cmd_line: out string overflow\n");
			goto error;
			}
			}
			}
			return 0;

			error:
			strcpy(new_command_line, cmd_line);
			return -1;
			}

	/*		/*
	* Remove various flags from command line seen by userspace in order to		* This function will be called for each of command line parameters and at the
	* pass SafetyNet CTS check.		* end of patameter list as well.
	*/		*/
	remove_safetynet_flags(new_command_line);		static int modify_cmd_line_callback(const char name, const char val, const char ***list)
			{
			/* check for end of parameter list */
			if ((name == NULL) && (val == NULL)){
			// NULL terminated list of strings to append at the end of command line
			static const char *return_list[] = { NULL };
			*list = return_list;
			return 1;
			}

			/* check for unnamed papameters */
			if ((name == NULL) && (val != NULL)) {
			return 1; /* accept */
			}

			/* drop parameters */
			if ((strcmp(name, "androidboot.enable_dm_verity") == 0) \|\|
			(strcmp(name, "androidboot.secboot") == 0) \|\|
			(strcmp(name, "androidboot.verifiedbootstate") == 0) \|\|
			(strcmp(name, "androidboot.veritymode") == 0)) {
			return 0; /* drop */
			}

			#if 0
			/* replace parameters */
			if (strcmp(name, "some_param") == 0) {
			// NULL terminated list of strings to replace "some_param"
			static const char *return_list[] = { "other_param1=some_value1", "other_param2=some_value2", NULL };
			// protection against double replacent
			static int replaced = 0;

			if (!replaced){
			replaced = 1;
			*list = return_list;
			}
			return 0; /* drop */
			}

			/* accept parameters and add some values after it */
			if ((strcmp(name, "some_param_qqq") == 0) &&
			(strcmp(val, "some_value_qqq") == 0)) {
			// NULL terminated list of strings to add after "some_param_qqq=some_value_qqq"
			static const char *return_list[] = {"other_param_qqq1=some_value1", "other_param_qqq2=some_value2", NULL};
			// protection against double addition
			static int added = 0;

			if (!added){
			added = 1;
			*list = return_list;
			}
			return 1; /* accept */
			}
			#endif

			return 1; /* accept by default */
			}

			static int __init proc_cmdline_init(void)
			{
			modify_cmd_line(saved_command_line, modify_cmd_line_callback);
	proc_create("cmdline", 0, NULL, &cmdline_proc_fops);		proc_create("cmdline", 0, NULL, &cmdline_proc_fops);
	return 0;		return 0;
	}		}