Hi!
I noticed that the devmem applet maps two consecutive pages of memory in order
to allow access to a (non-aligned) object that spans two pages. This is a
problem if we are working with the last page of memory because the next page
would wrap around to the first page of memory.
This patch makes devmem map only a single page if it is at the end of the
memory address space.
--
[email protected] (040-5240412)
--- busybox-1.16.0/miscutils/devmem.c 2010-01-25 02:59:38.000000000 +0200
+++ busybox-1.16.0-devmem/miscutils/devmem.c 2010-03-26 11:57:18.000000000 +0200
@@ -58,7 +58,8 @@ int devmem_main(int argc UNUSED_PARAM, c
fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
map_base = mmap(NULL,
- page_size * 2 /* in case value spans page */,
+ (target >= (~0 & ~(off_t)(page_size - 1))) ? /* Last page? */
+ page_size : page_size * 2, /* in case value spans page */
argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
MAP_SHARED,
fd,
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