diff options
| -rw-r--r-- | miscutils/devmem.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/miscutils/devmem.c b/miscutils/devmem.c index e13dedc..39b5808 100644 --- a/miscutils/devmem.c +++ b/miscutils/devmem.c @@ -13,9 +13,9 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) uint64_t read_result; uint64_t writeval = writeval; /* for compiler */ off_t target; - unsigned page_size = getpagesize(); + unsigned page_size, mapped_size, offset_in_page; int fd; - int width = 8 * sizeof(int); + unsigned width = 8 * sizeof(int); /* devmem ADDRESS [WIDTH [VALUE]] */ // TODO: options? @@ -50,15 +50,22 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) if (argv[3]) writeval = bb_strtoull(argv[3], NULL, 0); } else { /* argv[2] == NULL */ - /* make argv[3] to be a valid thing to use */ + /* make argv[3] to be a valid thing to fetch */ argv--; } if (errno) - bb_show_usage(); /* bb_strtouXX failed */ + 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, - page_size * 2 /* in case value spans page */, + mapped_size, argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ, MAP_SHARED, fd, @@ -68,7 +75,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) // printf("Memory mapped at address %p.\n", map_base); - virt_addr = (char*)map_base + (target & (page_size - 1)); + virt_addr = (char*)map_base + offset_in_page; if (!argv[3]) { switch (width) { @@ -119,7 +126,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) } if (ENABLE_FEATURE_CLEAN_UP) { - if (munmap(map_base, page_size * 2) == -1) + if (munmap(map_base, mapped_size) == -1) bb_perror_msg_and_die("munmap"); close(fd); } |