summaryrefslogtreecommitdiff
path: root/miscutils/devmem.c
blob: aeb32b13afbcc1a1c865bab5d51587cf835b3452 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *  Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
 *  Copyright (C) 2008, BusyBox Team. -solar 4/26/08
 */
//config:config DEVMEM
//config:	bool "devmem"
//config:	default y
//config:	help
//config:	  devmem is a small program that reads and writes from physical
//config:	  memory using /dev/mem.

//applet:IF_DEVMEM(APPLET(devmem, BB_DIR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_DEVMEM) += devmem.o

//usage:#define devmem_trivial_usage
//usage:	"ADDRESS [WIDTH [VALUE]]"
//usage:#define devmem_full_usage "\n\n"
//usage:       "Read/write from physical address\n"
//usage:     "\n	ADDRESS	Address to act upon"
//usage:     "\n	WIDTH	Width (8/16/...)"
//usage:     "\n	VALUE	Data to be written"

#include "libbb.h"

int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int devmem_main(int argc UNUSED_PARAM, char **argv)
{
	void *map_base, *virt_addr;
	uint64_t read_result;
	uint64_t writeval = writeval; /* for compiler */
	off_t target;
	unsigned page_size, mapped_size, offset_in_page;
	int fd;
	unsigned width = 8 * sizeof(int);

	/* devmem ADDRESS [WIDTH [VALUE]] */
// TODO: options?
// -r: read and output only the value in hex, with 0x prefix
// -w: write only, no reads before or after, and no output
// or make this behavior default?
// Let's try this and see how users react.

	/* ADDRESS */
	if (!argv[1])
		bb_show_usage();
	errno = 0;
	target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */

	/* WIDTH */
	if (argv[2]) {
		if (isdigit(argv[2][0]) || argv[2][1])
			width = xatou(argv[2]);
		else {
			static const char bhwl[] ALIGN1 = "bhwl";
			static const uint8_t sizes[] ALIGN1 = {
				8 * sizeof(char),
				8 * sizeof(short),
				8 * sizeof(int),
				8 * sizeof(long),
				0 /* bad */
			};
			width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
			width = sizes[width];
		}
		/* VALUE */
		if (argv[3])
			writeval = bb_strtoull(argv[3], NULL, 0);
	} else { /* argv[2] == NULL */
		/* make argv[3] to be a valid thing to fetch */
		argv--;
	}
	if (errno)
		bb_show_usage(); /* one of bb_strtouXX failed */

	fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
	mapped_size = page_size = getpagesize();
	offset_in_page = (unsigned)target & (page_size - 1);
	if (offset_in_page + width > page_size) {
		/* This access spans pages.
		 * Must map two pages to make it possible: */
		mapped_size *= 2;
	}
	map_base = mmap(NULL,
			mapped_size,
			argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
			MAP_SHARED,
			fd,
			target & ~(off_t)(page_size - 1));
	if (map_base == MAP_FAILED)
		bb_perror_msg_and_die("mmap");

//	printf("Memory mapped at address %p.\n", map_base);

	virt_addr = (char*)map_base + offset_in_page;

	if (!argv[3]) {
		switch (width) {
		case 8:
			read_result = *(volatile uint8_t*)virt_addr;
			break;
		case 16:
			read_result = *(volatile uint16_t*)virt_addr;
			break;
		case 32:
			read_result = *(volatile uint32_t*)virt_addr;
			break;
		case 64:
			read_result = *(volatile uint64_t*)virt_addr;
			break;
		default:
			bb_error_msg_and_die("bad width");
		}
//		printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
//			target, virt_addr,
//			(unsigned long long)read_result);
		/* Zero-padded output shows the width of access just done */
		printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
	} else {
		switch (width) {
		case 8:
			*(volatile uint8_t*)virt_addr = writeval;
//			read_result = *(volatile uint8_t*)virt_addr;
			break;
		case 16:
			*(volatile uint16_t*)virt_addr = writeval;
//			read_result = *(volatile uint16_t*)virt_addr;
			break;
		case 32:
			*(volatile uint32_t*)virt_addr = writeval;
//			read_result = *(volatile uint32_t*)virt_addr;
			break;
		case 64:
			*(volatile uint64_t*)virt_addr = writeval;
//			read_result = *(volatile uint64_t*)virt_addr;
			break;
		default:
			bb_error_msg_and_die("bad width");
		}
//		printf("Written 0x%llX; readback 0x%llX\n",
//				(unsigned long long)writeval,
//				(unsigned long long)read_result);
	}

	if (ENABLE_FEATURE_CLEAN_UP) {
		if (munmap(map_base, mapped_size) == -1)
			bb_perror_msg_and_die("munmap");
		close(fd);
	}

	return EXIT_SUCCESS;
}