linux mmap

From: Ted Unangst <tedu(at)stanford.edu>
Date: Wed Jun 25 2003 - 22:36:11 EDT

linux mmap has slightly different behavior than ours with a hint. actually, this behavior may be peculiar to just uvm. uvm will avoid mapping in what it thinks is the heap, even if passed a hint. at least one linux app doesn't like this behavior.

reference:
http://marc.theaimsgroup.com/?l=netbsd-tech-kern&m=105612525808607&w=1

this goes on top of the mmap2 patch.

• compat/linux/linux_misc.c.orig Wed Jun 25 19:23:11 2003 +++ compat/linux/linux_misc.c Wed Jun 25 19:23:17 2003 @@ -664,7 +664,6 @@ return sys_mmap(p, &cma, retval); }

-#define MAP_TRYFIXED 0 /* XXX -tedu just for now */  static void
 linux_to_bsd_mmap_args(cma, uap)

         struct sys_mmap_args *cma;
Index: sys/mman.h

---

RCS file: /cvs/src/sys/sys/mman.h,v
retrieving revision 1.16
diff -u -r1.16 mman.h

--- sys/mman.h	2003/06/02 23:28:21	1.16
+++ sys/mman.h	2003/06/26 02:30:14
@@ -57,6 +57,7 @@

 #define	MAP_INHERIT	 0x0080	/* region is retained after exec */

 #define	MAP_NOEXTEND	 0x0100	/* for MAP_FILE, don't change file size */


 #define	MAP_HASSEMAPHORE 0x0200	/* region may contain semaphores */


+#define	MAP_TRYFIXED	 0x0400 /* attempt hint address, even within heap */

 /*

• Error return from mmap() Index: uvm/uvm_mmap.c

  ---

  RCS file: /cvs/src/sys/uvm/uvm_mmap.c,v retrieving revision 1.46 diff -u -r1.46 uvm_mmap.c --- uvm/uvm_mmap.c 2003/05/17 14:02:06 1.46 +++ uvm/uvm_mmap.c 2003/06/26 02:30:14 @@ -513,8 +513,10 @@
  • not fixed: make sure we skip over the largest possible heap.
  • we will refine our guess later (e.g. to account for VAC, etc) */ - - if (addr < uvm_map_hint(p, prot)) + if (addr == 0) + addr = uvm_map_hint(p, prot); + else if (!(flags & MAP_TRYFIXED) && + addr < uvm_map_hint(p, prot)) addr = uvm_map_hint(p, prot); }

-- 
"First, it was not a strip bar, it was an erotic club.  And second,
what can I say?  I'm a night owl."
      - M. Barry, Mayor of Washington, DC

Received on Wed Jun 25 22:50:44 2003