s390-tools/zipl/src/envblk.c

/*
 * zipl - zSeries Initial Program Loader tool
 *
 * Functions to manipulate with environment block
 *
 * Copyright IBM Corp. 2020
 *
 * s390-tools is free software; you can redistribute it and/or modify
 * it under the terms of the MIT license. See LICENSE for details.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "bootmap.h"
#include "envblk.h"
#include "error.h"
#include "misc.h"

/* from linux/fs.h */
#define FIGETBSZ	_IO(0x00, 2)

void envblk_create_blank(char *envblk, int envblk_len)
{
	memcpy(envblk, ZIPL_ENVBLK_SIGNATURE,
	       sizeof(ZIPL_ENVBLK_SIGNATURE) - 1);
	memset(envblk + sizeof(ZIPL_ENVBLK_SIGNATURE) - 1, '\0',
	       envblk_len - sizeof(ZIPL_ENVBLK_SIGNATURE) + 1);
}

/**
 * Find out environment block location.
 * FD: bootmap file descriptor.
 * On success the searched location is saved in variable pointed out by OFF
 */
int envblk_offset_get(int fd, off_t *off)
{
	struct bootmap_header bh;

	if (bootmap_header_read(fd, &bh)) {
		error_reason("Could not read bootmap_header");
		return -1;
	}
	*off = bh.envblk_offset;
	return 0;
}

/**
 * Save environment block location specified by OFF
 * FD: bootmap file descriptor.
 * On success the location is saved in the bootmap header.
 */
int envblk_offset_set(int fd, off_t off)
{
	struct bootmap_header bh;

	if (bootmap_header_read(fd, &bh)) {
		error_reason("Could not read bootmap header");
		return -1;
	}
	bh.envblk_offset = off;

	if (bootmap_header_write(fd, &bh)) {
		error_reason("Could not write bootmap header");
		return -1;
	}
	return 0;
}

/**
 * Find out environment block size.
 * FD: bootmap file descriptor.
 * On success the searched size is stored in RESULT
 */
int envblk_size_get(int fd, int *result)
{
	if (ioctl(fd, FIGETBSZ, result) == -1) {
		error_reason(strerror(errno));
		return -1;
	}
	return 0;
}

#define LINE_HASH_SIZE (16)

/**
 * Calculate hash function of "environment line"
 *
 * LINE: pointer to a string, containing NANE=VALUE
 * LEN: length of the NAME with trailing delimiter "="
 */
static unsigned int linehash(char *line, int len, unsigned int hash_size)
{
	unsigned int sum = 0;

	while (len) {
		sum += 5 * *(line++);
		len--;
	}
	return sum % hash_size;
}

struct line_hash_entry {
	struct line_hash_entry *next;
	char *line; /* pointer to an "environment line",
		     * a string containing NAME=VALUE with
		     * optional trailing end-of-line symbol
		     */
};

/**
 * Check if @name meets the requirements for shell environment variables
 * (IEEE Std 1003.1-2001), mitigated with lowercase letter allowance
 *
 * Return 0, if it meets, and 1 otherwise
 */
int envblk_check_name(char *name, int len)
{
	int i;

	if (len == 0)
		return 1;
	if (!isalpha(name[0]) && name[0] != '_')
		return 1;
	for (i = 1; i < len; i++)
		if (!isalpha(name[i]) && !isdigit(name[i]) && name[i] != '_')
			return 1;
	return 0;
}

/**
 * Add environment line to hash table
 *
 * LINE: pointer to a string containing NAME=VALUE
 * LEN: length of NAME with trailing delimiter "="
 */
static int hash_table_add(struct line_hash_entry **table, char *line, int len)
{
	unsigned int hash;
	struct line_hash_entry *new;

	new = malloc(sizeof(*new));
	if (!new)
		return -ENOMEM;
	memset(new, 0, sizeof(*new));
	new->line = misc_strdup(line);
	if (!new->line) {
		free(new);
		return -ENOMEM;
	}
	hash = linehash(new->line, len, LINE_HASH_SIZE);
	new->next = table[hash];
	table[hash] = new;
	return 0;
}

/**
 * Find environment line in the hash table by name
 *
 * LINE: string contailing NAME=VALUE
 * LEN: length of the NAME with trailing delimiter "="
 */
static struct line_hash_entry *hash_table_find(struct line_hash_entry **table,
					       char *name, size_t len)
{
	struct line_hash_entry *item;

	item = table[linehash(name, len, LINE_HASH_SIZE)];
	while (item) {
		if (!strncmp(item->line, name, len))
			return item;
		item = item->next;
	}
	return NULL;
}

static int hash_entry_replace(struct line_hash_entry *item, char *name,
			      int *offset)
{
	char *dup;

	dup = misc_strdup(name);
	if (!dup)
		return -ENOMEM;
	*offset -= strlen(item->line);
	free(item->line);
	item->line = dup;
	*offset += strlen(item->line);
	return 1;
}

/**
 * Scan hash table TABLE, and call ACTOR for each its entry.
 * The ACTOR is allowed even to release the entry.
 */
static void hash_table_scan(struct line_hash_entry **table,
			    void (*actor)(struct line_hash_entry *entry))
{
	int i;

	for (i = 0; i < LINE_HASH_SIZE; i++) {
		struct line_hash_entry *item = table[i];

		while (item) {
			struct line_hash_entry *next = item->next;

			actor(item);
			item = next;
		}
	}
}

static void hash_entry_free(struct line_hash_entry *this)
{
	free(this->line);
	free(this);
}

static void hash_table_free(struct line_hash_entry **table)
{
	hash_table_scan(table, hash_entry_free);
}

/**
 * Scan hash table TABLE, and for each its entry copy its line to the
 * in-memory environment block specified by DST at the offset OFF.
 * Insert end-of-line symbol, if needed. The caller should guarantee
 * enough space in the buffer DST
 */
static void hash_table_flush(struct line_hash_entry **table, char *dst,
			     int off)
{
	int i;

	for (i = 0; i < LINE_HASH_SIZE; i++) {
		struct line_hash_entry *item = table[i];

		while (item) {
			int str_len;

			str_len = strlen(item->line);
			memcpy(dst + off, item->line, str_len);
			off += str_len;
			if (dst[off - 1] != '\n') {
				dst[off] = '\n';
				off += 1;
			}
			item = item->next;
		}
	}
}

/**
 * Put a zIPL environment line into hash table.
 *
 * Identify a name in the line THIS which contains a pair NAME=VALUE, and
 * look for an entry in the hash table TABLE with a similar name. If such
 * entry exists, then replace the line in that entry with the new one
 * specified by THIS. Othewise, insert a new entry to the hash table.
 *
 * THIS: pointer to a NULL-terminated string, which contains the line to
 * be imported. If the line was successfully imported, and no line with the
 * same NAME was added before, then return 0.
 * If the line should be ignored, or it replaced previously added line with
 * the same NAME, then return > 0. On errors return < 0.
 */
static int import_one_line(char *this, struct line_hash_entry **table,
			   int *offset)
{
	struct line_hash_entry *item;
	char *p;

	if (*this == '#')
		/* Ignore "commented" line */
		return 1;

	p = strchr(this, '=');
	if (p == NULL || p == this)
		/* Could not identify NAME in the line. Ignore */
		return 1;
	if (envblk_check_name(this, p - this)) {
		error_reason("Unacceptable name '%.*s'", p - this, this);
		return -EINVAL;
	}
	/*
	 * Try to find an entry with similar NAME.
	 */
	item = hash_table_find(table, this, p - this + 1);

	return item != NULL ? hash_entry_replace(item, this, offset) :
		hash_table_add(table, this, p - this + 1);
}

/**
 * Import environment line-by-line from a regular file specified
 * by its name FROM_FILE to a pre-allocated buffer TO_BUF. Ignore
 * malformed, or "commented" lines. If the file doesn't end with
 * end-of-line symbol, then append that symbol in the destination
 * buffer. Return 0 on success.
 *
 * ENVBLK_SIZE: size of the destination buffer TO_BUF.
 */
int envblk_import(char *from_file, char *to_buf, int envblk_size)
{
	const char *err_prefix = "Failed to import environment file";
	struct line_hash_entry *table[LINE_HASH_SIZE];
	unsigned int lines_imported = 0;
	char *line = NULL;
	size_t len = 0;
	FILE *stream;
	ssize_t read;
	int ret = 0;
	int offset;

	stream = fopen(from_file, "r");
	if (stream == NULL)
		return 0;

	memset(table, 0, LINE_HASH_SIZE*sizeof(void *));
	offset = sizeof(ZIPL_ENVBLK_SIGNATURE) - 1;

	while ((read = getline(&line, &len, stream)) != -1) {
		if (read > envblk_size - offset) {
			error_reason("%s %s: maximal size (%d) exceeded",
				     err_prefix, from_file,
				     ENVBLK_MAX_IMPORT_SIZE(envblk_size));
			ret = -EINVAL;
			break;
		}
		if (read < 2)
			/* malformed line. Ignored */
			continue;
		if (line[read - 1] != '\n' && read == envblk_size - offset) {
			/*
			 * file's tail doesn't contain end-of-line symbol at
			 * the end, whereas there is no enough space in the
			 * destination buffer to insert that symbol, which is
			 * mandatory according to the environment block format
			 */
			error_reason("%s %s: maximal size (%d) exceeded",
				     err_prefix, from_file,
				     ENVBLK_MAX_IMPORT_SIZE(envblk_size));
			ret = -EINVAL;
			break;
		}
		ret = import_one_line(line, table, &offset);
		if (ret < 0) {
			/* error */
			error_text("%s %s", err_prefix, from_file);
			break;
		} else if (ret > 0) {
			/*
			 * either this line was ignored, or previously
			 * imported line was overwritten by it
			 */
			ret = 0;
			continue;
		}
		if (lines_imported >= ENVBLK_MAX_LINES) {
			error_reason("%s %s: maximum number of lines (%d) exceeded",
				     err_prefix, from_file, ENVBLK_MAX_LINES);
			ret = -EINVAL;
			break;
		}
		offset += read;
		lines_imported++;
	}
	hash_table_flush(table, to_buf, sizeof(ZIPL_ENVBLK_SIGNATURE) - 1);
	hash_table_free(table);
	free(line);
	fclose(stream);
	return ret;
}

char *envblk_next_line(char *s, const char *end)
{
	while (s < end) {
		if (*s == '\n')
			break;
		s++;
	}
	return s + 1;
}

/**
 * Scan installed environment block and call ACTOR for each found NAME.
 * Return -1 on corrupted environment blocks. Otherwise, return 0
 */
int envblk_scan(char *envblk, unsigned int envblk_size,
		void (*actor)(char *name))
{
	unsigned int lines_scanned = 0;
	const char *reason;
	char *s, *end;
	char *name;

	s = envblk + sizeof(ZIPL_ENVBLK_SIGNATURE) - 1;
	end = envblk + envblk_size;

	while (s < end && *s != 0) {
		if (lines_scanned > ENVBLK_MAX_LINES) {
			reason = "maximum number of lines exceeded";
			goto corrupted;
		}
		name = s;
		while (s < end && *s != '=')
			s++;
		if (s == end) {
			/* delimiter "=" not found */
			reason = "missed delimiter";
			goto corrupted;
		}
		/* here @s points to "=" */
		s++;

		while (s < end && *s != '\n')
			s++;
		if (s == end) {
			/* end of line not found */
			reason = "missed EOL";
			goto corrupted;
		}
		*s = '\0';
		actor(name);
		*s = '\n';
		lines_scanned++;
		s = envblk_next_line(s, end);
	}
	return 0;
corrupted:
	error_reason("Found corrupted environment block (%s) - please run zipl",
		     reason);
	return -1;
}

static void print_name_value(char *this)
{
	printf("  %s\n", this);
}

void envblk_print(char *envblk, unsigned int envblk_size)
{
	printf("Environment block content:\n");
	envblk_scan(envblk, envblk_size, print_name_value);
}