[Qemu-devel] [PATCH] linux-user/mmap.c: Support shared memory mapping in mmap_frag()

[chengang@emindsoft.com.cn]

From: Chen Gang <chengang@emindsoft.com.cn>

It is a temporary fix for i386 target system running Windows.

Also remove useless variable 'p'.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
---
 linux-user/mmap.c |   22 +++++++++++++++++++---
 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 445e8c6..07758d4 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -156,12 +156,28 @@ static int mmap_frag(abi_ulong real_start,
             prot1 |= page_get_flags(addr);
     }
 
+    /*
+     * It is a temporary fix. Normally, target system will let shared memory
+     * aligned with 64KB, and allocate them near with each other, no any other
+     * kinds of mapping regions nearby. e.g. Windows on i386.
+     */
+    if ((start == real_start) && (flags & MAP_SHARED)) {
+        if (prot1) {
+            munmap(host_start, qemu_host_page_size);
+        }
+        if (mmap(host_start, qemu_host_page_size, prot, flags, fd, offset)
+            == MAP_FAILED) {
+            return -1;
+        }
+        return 0;
+    }
+
     if (prot1 == 0) {
         /* no page was there, so we allocate one */
-        void *p = mmap(host_start, qemu_host_page_size, prot,
-                       flags | MAP_ANONYMOUS, -1, 0);
-        if (p == MAP_FAILED)
+        if (mmap(host_start, qemu_host_page_size, prot, flags | MAP_ANONYMOUS,
+                 -1, 0) == MAP_FAILED) {
             return -1;
+        }
         prot1 = prot;
     }
     prot1 &= PAGE_BITS;
-- 
1.7.3.4