hust testsuite: fix a false positive

[oweals/busybox.git] / miscutils / devmem.c

diff --git a/miscutils/devmem.c b/miscutils/devmem.c
index 4903b5dcba0495dde67836118514a3fc8f22ea3b..786a21bee02b567804e729805d6280d5a8cabc15 100644 (file)
--- a/miscutils/devmem.c
+++ b/miscutils/devmem.c
@@ -1,9 +1,17 @@
 /*
- * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ * 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
  */
 
+//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;
@@ -13,9 +21,9 @@ 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 +58,22 @@ 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 +83,7 @@ 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 +134,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
        }
 
        if (ENABLE_FEATURE_CLEAN_UP) {
-               if (munmap(map_base, page_size) == -1)
+               if (munmap(map_base, mapped_size) == -1)
                        bb_perror_msg_and_die("munmap");
                close(fd);
        }