Pintos: pintos/src/tests/userprog/boundary.c Source File

00001 /* Utility function for tests that try to break system calls by
00002    passing them data that crosses from one virtual page to
00003    another. */
00004 
00005 #include <inttypes.h>
00006 #include <round.h>
00007 #include <string.h>
00008 #include "tests/userprog/boundary.h"
00009 
00010 static char dst[8192];
00011 
00012 /* Returns the beginning of a page.  There are at least 2048
00013    modifiable bytes on either side of the pointer returned. */
00014 void *
00015 get_boundary_area (void) 
00016 {
00017   char *p = (char *) ROUND_UP ((uintptr_t) dst, 4096);
00018   if (p - dst < 2048)
00019     p += 4096;
00020   return p;
00021 }
00022 
00023 /* Returns a copy of SRC split across the boundary between two
00024    pages. */
00025 char *
00026 copy_string_across_boundary (const char *src) 
00027 {
00028   char *p = get_boundary_area ();
00029   p -= strlen (src) < 4096 ? strlen (src) / 2 : 4096;
00030   strlcpy (p, src, 4096);
00031   return p;
00032 }
00033