Hello dear Cygwin developpers !
This is my first post here, so I would like to begin by sending you a big thank
for Cygwin ! This is a great tool to port programs to Windows.
I think I found a bug in mprotect() implementation. This call is unable to set
some protections (PROT_READ|PROT_WRITE for example) on a given memory area,
while it can set some others (PROT_NONE or PROT_READ for example) on the same
memory area. From my tests, it seems to happen only on WNT5+ (ie. Windows 2000
and Windows XP - detailed results below).
I upgraded my whole Cygwin setup to confirm the problem is still alive. I also
searched the web, FAQ, and ML archive without success before posting here.
I wrote a simple testcase to allow you to reproduce the bug. You'll find the
source code as an attachement to this mail (to compile with "gcc -o
testcase.exe testcase.c" and to run with "./testcase.exe"). This testcase
allocate a block of memory with mmap(), fill it with memset(), plays with its
protection with mprotect() and fill it again with memset().
I ran this test on various Windows flavour available around. Here are the
results :
Windows OS Lang Result
------------------------- ------ ----------------------------------------
W98 French OK
WNT4 SP6 (Workstation) French OK
WNT4 SP6 (Server) French OK
W2K SP4 (Professional) French mprotect() (3) failed : Invalid argument
W2K SP4 (Advanced server) French mprotect() (3) failed : Invalid argument
WXP SP1 (Professional) French mprotect() (3) failed : Invalid argument
Of course I'm ready to dig more if needed. But I really need some help since
I'm not familiar with Cygwin source code, nor with Windows developpement.
For the curious, I discovered this bug while trying to support ARAnyM's m68k
JIT compiler on Cygwin. ARAnyM (http://aranym.atari.org) is a free (GPLed)
virtual Atari-compatible system.
Best Regards, and thanks in advance for any help,
Xavier
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include <errno.h>
int main(void)
{
void *addr;
size_t size, page_size;
page_size = getpagesize();
printf("Page size : %i\n", (int)page_size);
size = 6 * (int)page_size;
addr = mmap((caddr_t)0,
size,
(PROT_READ | PROT_WRITE),
(MAP_PRIVATE | MAP_ANONYMOUS),
0,
0);
if (addr == MAP_FAILED)
{
printf("mmap() failed !\n");
return 1;
}
printf("Address : %X\n", (int)addr);
if (memset(addr, 0, size) != addr)
{
printf("memset() failed !\n");
return 2;
}
if (mprotect((caddr_t)addr, size, (PROT_NONE)) != 0)
{
printf("mprotect() (1) failed : %s\n", strerror(errno));
return 3;
}
if (mprotect((caddr_t)addr, size, (PROT_READ)) != 0)
{
printf("mprotect() (2) failed : %s\n", strerror(errno));
return 3;
}
if (mprotect((caddr_t)addr, size, (PROT_READ | PROT_WRITE)) != 0)
{
printf("mprotect() (3) failed : %s\n", strerror(errno));
return 3;
}
if (memset(addr, 1, size) != addr)
{
printf("memset() failed !\n");
return 4;
}
return 0;
}
--
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Problem reports: http://cygwin.com/problems.html
Documentation: http://cygwin.com/docs.html
FAQ: http://cygwin.com/faq/
