Re: [Qemu-devel] Re: [PATCH] fix interaction with noexecstack

[Filip Navara]

Ronald wrote:

> Tested, need to include <winbase.h> (and <windows.h>).
> gcc juste produce a warning with VirtualProtect:
> /home/ronald/Prog/Win32/combo/qemu/exec.c: Dans la fonction « page_init »:
> /home/ronald/Prog/Win32/combo/qemu/exec.c:155: AVERTISSEMENT: passage de
> arg 1 de « VirtualProtect » transforme en pointeur un entier sans
> transtypage
>
> aproximative translation: in function page_init passing arg1 of
> VirtualProtect is making pointer from integer without a cast.
>  
Thanks much for testing it, now I got a minute to test it on my box. The 
attach patch adds the #include, fixes the warning and also dynamicly 
detects the page size. These changes are actually needed when running 
QEMU on WinXP SP2 on AMD64. I'm quite not happy with the (original) 
patch yet, because it uses "unsigned long" for storing pointer and this 
will *break any 64-bit build* on non-Windows platforms. It would be nice 
if someone can solve it.

(My only hope is that the MinGW build of QEMU will not be broken...)

Regards,
Filip

> Note: with **VirtualProtect or *VirtualProtect make is aborting, I have
> used VirtualProtect.
>  
Sorry, my mail client messed that up.

--- qemu/exec.c Sat Sep  4 15:51:23 2004
+++ qemu/exec.c Sat Sep  4 16:12:05 2004
@@ -18,6 +18,9 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 #include "config.h"
+#ifdef _WIN32
+#include <windows.h>
+#endif
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
@@ -127,13 +130,35 @@
 
 static void page_init(void)
 {
+#ifdef _WIN32
+    SYSTEM_INFO system_info;
+    DWORD old_protect;
+#else
+    unsigned long address;
+    unsigned long length;
+#endif
+
     /* NOTE: we can always suppose that qemu_host_page_size >=
        TARGET_PAGE_SIZE */
 #ifdef _WIN32
-    qemu_real_host_page_size = 4096;
+    GetSystemInfo(&system_info);
+    qemu_real_host_page_size = system_info.dwPageSize;
+
+    VirtualProtect(code_gen_buffer, sizeof(code_gen_buffer),
+                   PAGE_EXECUTE_READWRITE, &old_protect);
 #else
     qemu_real_host_page_size = getpagesize();
+
+    address = (unsigned long)code_gen_buffer;
+    address &= ~(qemu_real_host_page_size - 1);
+
+    length = sizeof(code_gen_buffer);
+    length += qemu_real_host_page_size - 1;
+    length &= ~(qemu_real_host_page_size - 1);
+
+    mprotect(address, length, PROT_READ | PROT_WRITE | PROT_EXEC);
 #endif
+
     if (qemu_host_page_size == 0)
         qemu_host_page_size = qemu_real_host_page_size;
     if (qemu_host_page_size < TARGET_PAGE_SIZE)