1// SPDX-License-Identifier: GPL-2.0-or-later
2// Copyright (c) 2010 Mohamed Naufal Basheer
3// Author: Mohamed Naufal Basheer
4
5#include <sys/types.h>
6#include <sys/mman.h>
7#include <sys/stat.h>
8#include <err.h>
9#include <errno.h>
10#include <fcntl.h>
11#include <stdio.h>
12#include <stdlib.h>
13#include <unistd.h>
14
15/*
16 * Named pipe to act as a communication channel between
17 * shell script & this process
18 */
19#define STATUS_PIPE "status_pipe"
20
21int flag_exit;
22int flag_allocated;
23unsigned long memsize;
24
25/*
26 * process_options: process user specified options
27 */
28void process_options(int argc, char **argv)
29{
30	int c;
31	char *end;
32
33	opterr = 0;
34	while ((c = getopt(argc, argv, "pm:")) != -1) {
35		switch (c) {
36		case 'm':
37			memsize = strtoul(optarg, &end, 10);
38			if (*end != '\0')
39				errx(2, "invalid -m usage");
40			break;
41		default:
42			errx(2, "invalid option specified");
43		}
44	}
45
46	if (memsize <= 0)
47		errx(3, "invalid usage");
48}
49
50/*
51 * touch_memory: force physical memory allocation
52 */
53void touch_memory(char *p)
54{
55	int i;
56	int pagesize = getpagesize();
57
58	for (i = 0; i < (int)memsize; i += pagesize)
59		p[i] = 0xef;
60}
61
62void mem_map(void)
63{
64	static char *p;
65
66	if (flag_allocated) {
67		if (munmap(p, memsize) == -1)
68			err(5, "munmap failed");
69	} else {
70		p = mmap(NULL, memsize, PROT_READ | PROT_WRITE,
71			 MAP_SHARED | MAP_ANONYMOUS, 0, 0);
72		if (p == MAP_FAILED)
73			err(4, "mmap failed");
74		touch_memory(p);
75	}
76	flag_allocated = !flag_allocated;
77}
78
79/*
80 * done: retrieve instructions from the named pipe
81 */
82char action(int fd)
83{
84	char ch;
85
86	if (read(fd, &ch, 1) == -1)
87		err(7, "Error reading named pipe");
88
89	return ch;
90}
91
92int main(int argc, char **argv)
93{
94	int ret;
95	int fd;
96	char ch;
97
98	process_options(argc, argv);
99
100	ret = mkfifo(STATUS_PIPE, 0666);
101
102	if (ret == -1 && errno != EEXIST)
103		errx(1, "Error creating named pipe");
104
105	if ((fd = open(STATUS_PIPE, O_RDONLY)) == -1)
106		err(6, "Error opening named pipe");
107
108	do {
109		ch = action(fd);
110
111		if (ch == 'm')
112			mem_map();
113	} while (ch != 'x');
114
115	close(fd);
116
117	remove(STATUS_PIPE);
118
119	return 0;
120}
121