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Re: PATCH: Make libmmalloc work properly with /dev/zero
- From: Scott Pakin <pakin at uiuc dot edu>
- To: Andrew Cagney <ac131313 at cygnus dot com>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Mon, 25 Mar 2002 10:57:13 -0700
- Subject: Re: PATCH: Make libmmalloc work properly with /dev/zero
- Organization: University of Illinois at Urbana-Champaign
- References: <3C854268.2080508@uiuc.edu> <3C9CDD7A.1080302@cygnus.com>
On 23MAR2002, Andrew Cagney wrote:
> Fred's ok with this patch. However, I can't get it to apply - something
> ate something while it was in transit? Perhaphs post it as a mime
> attachment?
Attached. Let me know if that still doesn't work.
> I'll also need a ChangeLog entry.
2002-03-05 Scott Pakin <pakin@uiuc.edu>
* Modified calls to mmap() to make mmap() use MAP_PRIVATE when
MDP represents /dev/zero. In all other cases, mmap() continues
to use MAP_SHARED.
-- Scott
--- mmap-sup.c.ORIG Tue Mar 5 13:53:57 2002
+++ mmap-sup.c Tue Mar 5 14:12:16 2002
@@ -48,6 +48,15 @@
#define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + pagesize - 1) & \
~(pagesize - 1))
+
+/* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
+ MAP_SHARED. */
+
+#define MAP_PRIVATE_OR_SHARED(MDP) ((MDP -> flags & MMALLOC_DEVZERO) ? \
+ MAP_PRIVATE : \
+ MAP_SHARED)
+
+
/* Get core for the memory region specified by MDP, using SIZE as the
amount to either add to or subtract from the existing region. Works
like sbrk(), but using mmap(). */
@@ -113,7 +122,7 @@
{
/* Let mmap pick the map start address */
mapto = mmap (0, mapbytes, PROT_READ | PROT_WRITE,
- MAP_SHARED, mdp -> fd, foffset);
+ MAP_PRIVATE_OR_SHARED(mdp), mdp -> fd, foffset);
if (mapto != (caddr_t) -1)
{
mdp -> base = mdp -> breakval = mapto;
@@ -125,7 +134,8 @@
else
{
mapto = mmap (mdp -> top, mapbytes, PROT_READ | PROT_WRITE,
- MAP_SHARED | MAP_FIXED, mdp -> fd, foffset);
+ MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp -> fd,
+ foffset);
if (mapto == mdp -> top)
{
mdp -> top = moveto;
@@ -152,7 +162,7 @@
/* FIXME: Quick hack, needs error checking and other attention. */
base = mmap (mdp -> base, mdp -> top - mdp -> base,
- PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED,
+ PROT_READ | PROT_WRITE, MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED,
mdp -> fd, 0);
return ((PTR) base);
}
@@ -166,13 +176,13 @@
caddr_t base = NULL;
#ifdef MAP_ANONYMOUS
- flags = MAP_SHARED | MAP_ANONYMOUS;
+ flags = MAP_PRIVATE | MAP_ANONYMOUS;
fd = -1;
#else
#ifdef MAP_FILE
- flags = MAP_SHARED | MAP_FILE;
+ flags = MAP_PRIVATE | MAP_FILE;
#else
- flags = MAP_SHARED;
+ flags = MAP_PRIVATE;
#endif
fd = open ("/dev/zero", O_RDWR);
if (fd != -1)