[Qemu-devel] [4637] Mark host brk() area as reserved.

[Paul Brook]

Revision: 4637
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=4637
Author:   pbrook
Date:     2008-05-31 16:33:53 +0000 (Sat, 31 May 2008)

Log Message:
-----------
Mark host brk() area as reserved.

Modified Paths:
--------------
    trunk/exec.c
    trunk/linux-user/mmap.c
    trunk/linux-user/qemu.h

Modified: trunk/exec.c
===================================================================
--- trunk/exec.c        2008-05-31 16:21:33 UTC (rev 4636)
+++ trunk/exec.c        2008-05-31 16:33:53 UTC (rev 4637)
@@ -234,6 +234,7 @@
         FILE *f;
         int n;
 
+        last_brk = (unsigned long)sbrk(0);
         f = fopen("/proc/self/maps", "r");
         if (f) {
             do {

Modified: trunk/linux-user/mmap.c
===================================================================
--- trunk/linux-user/mmap.c     2008-05-31 16:21:33 UTC (rev 4636)
+++ trunk/linux-user/mmap.c     2008-05-31 16:33:53 UTC (rev 4637)
@@ -157,6 +157,8 @@
 static abi_ulong mmap_next_start = 0x40000000;
 #endif
 
+unsigned long last_brk;
+
 /* find a free memory area of size 'size'. The search starts at
    'start'. If 'start' == 0, then a default start address is used.
    Return -1 if error.
@@ -167,7 +169,21 @@
 {
     abi_ulong addr, addr1, addr_start;
     int prot;
+    unsigned long new_brk;
 
+    new_brk = (unsigned long)sbrk(0);
+    if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {
+        /* This is a hack to catch the host allocating memory with brk().
+           If it uses mmap then we loose.
+           FIXME: We really want to avoid the host allocating memory in
+           the first place, and maybe leave some slack to avoid switching
+           to mmap.  */
+        page_set_flags(last_brk & TARGET_PAGE_MASK,
+                       TARGET_PAGE_ALIGN(new_brk),
+                       PAGE_RESERVED); 
+    }
+    last_brk = new_brk;
+
     size = HOST_PAGE_ALIGN(size);
     start = start & qemu_host_page_mask;
     addr = start;

Modified: trunk/linux-user/qemu.h
===================================================================
--- trunk/linux-user/qemu.h     2008-05-31 16:21:33 UTC (rev 4636)
+++ trunk/linux-user/qemu.h     2008-05-31 16:33:53 UTC (rev 4637)
@@ -232,6 +232,7 @@
                        abi_ulong new_size, unsigned long flags,
                        abi_ulong new_addr);
 int target_msync(abi_ulong start, abi_ulong len, int flags);
+extern unsigned long last_brk;
 
 /* user access */