although the mmap(2) manual states in section MAP_ANON:
"The offset argument is ignored."
this doesn't seem to be true. running
printf("%p\n", mmap((void*)0x1000, 0x1000, PROT_NONE, MAP_ANON, -1,
0x12345678));
and
printf("%p\n", mmap((void*)0x1000, 0x1000, PROT_NONE, MAP_ANON, -1, 0));
produces different outputs. i've attached a patch to solve the problem. the
patch is similar to the one proposed in this PR, but should apply cleanly to
CURRENT: http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/71258
cheers.
alex
--- src/sys/vm/vm_mmap.c 2009-10-21 04:13:24.000000000 +0200
+++ src/sys/vm/vm_mmap.c 2009-10-21 04:13:43.000000000 +0200
@@ -245,15 +245,18 @@
}
/*
- * Align the file position to a page boundary,
- * and save its page offset component.
+ * Unless the MAP_ANON flag is set, align the file position
+ * to a page boundary and save its page offset component.
*/
- pageoff = (pos & PAGE_MASK);
- pos -= pageoff;
-
- /* Adjust size for rounding (on both ends). */
- size += pageoff; /* low end... */
- size = (vm_size_t) round_page(size); /* hi end */
+ if (flags & MAP_ANON) {
+ pageoff = pos = 0;
+ } else {
+ pageoff = (pos & PAGE_MASK);
+ pos -= pageoff;
+ /* Adjust size for rounding (on both ends). */
+ size += pageoff; /* low end... */
+ size = (vm_size_t) round_page(size); /* hi end */
+ }
/*
* Check for illegal addresses. Watch out for address wrap... Note
@@ -300,7 +303,6 @@
handle = NULL;
handle_type = OBJT_DEFAULT;
maxprot = VM_PROT_ALL;
- pos = 0;
} else {
/*
* Mapping file, get fp for validation and
_______________________________________________
freebsd-hackers@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
