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/* devmem.c - Access physical addresses
*
* Copyright 2019 The Android Open Source Project
USE_DEVMEM(NEWTOY(devmem, "<1>3", TOYFLAG_USR|TOYFLAG_BIN))
config DEVMEM
bool "devmem"
default n
help
usage: devmem ADDR [WIDTH [DATA]]
Read/write physical address via /dev/mem.
WIDTH is 1, 2, 4, or 8 bytes (default 4).
*/
#define FOR_devmem
#include "toys.h"
void devmem_main(void)
{
int writing = toys.optc == 3, page_size = getpagesize(), bytes = 4, fd;
unsigned long long addr = atolx(toys.optargs[0]), data = 0, map_off, map_len;
void *map, *p;
// WIDTH?
if (toys.optc>1) {
int i;
if (strlen(toys.optargs[1])!=1 || (i=stridx("1248", *toys.optargs[1]))==-1)
error_exit("bad width: %s", toys.optargs[1]);
bytes = 1<<i;
}
// DATA? Report out of range values as errors rather than truncating.
if (writing) data = atolx_range(toys.optargs[2], 0, (1ULL<<(8*bytes))-1);
// Map in just enough.
fd = xopen("/dev/mem", (writing ? O_RDWR : O_RDONLY) | O_SYNC);
map_off = addr & ~(page_size - 1);
map_len = (addr+bytes-map_off);
map = xmmap(NULL, map_len, writing ? PROT_WRITE : PROT_READ, MAP_SHARED, fd,
map_off);
p = map + (addr & (page_size - 1));
close(fd);
if (writing) {
if (bytes == 1) *(char *)p = data;
else if (bytes == 2) *(short *)p = data;
else if (bytes == 4) *(int *)p = data;
else if (bytes == 8) *(long long *)p = data;
} else {
if (bytes == 1) data = *(char *)p;
else if (bytes == 2) data = *(short *)p;
else if (bytes == 4) data = *(int *)p;
else if (bytes == 8) data = *(long long *)p;
printf("%#0*llx\n", bytes*2, data);
}
munmap(map, map_len);
}
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