On Sun, Jun 21, 2009 at 1:03 PM, Erich Hoover ehoover@mines.edu wrote:
On Sun, Jun 21, 2009 at 10:23 AM, Erich Hoover ehoover@mines.edu wrote:
On Sun, Jun 21, 2009 at 1:36 AM, Damjan Jovanovic damjan.jov@gmail.comwrote:
...
Maybe the memory is writable but not readable, and
WSARecvFrom()/recv() is reading it while memcpy() is not?
Maybe the memory is from a DIB section which Wine lazily mprotects and the kernel isn't raising SIGSEGV for the protection to be reapplied? Does simply zero-filling buf before calling WSARecvFrom() help?
The memory should be a buffer from the calling application that it is using temporarily to store update data before saving it to the hard-disk. Yes, oddly enough zero-filling the buffer before calling WSARecvFrom() also fixes the problem.
So, where exactly should I be looking to find the real problem? As far as I can tell the memory for the buffer is being allocated immediate prior to the call and the request is for read/write access: 0009:Call KERNEL32.VirtualAlloc(01b85000,00040000,00001000,00000004) ret=79e74a2b 0009:Ret KERNEL32.VirtualAlloc() retval=01b85000 ret=79e74a2b 0009:Call ws2_32.recv(00000380,01ba4fc1,000178d0,00000000) ret=0036a287 ...
After looking over the documentation for VirtualAlloc, it appears that Wine should be zeroing the returned memory if MEM_COMMIT is specified. Making this change (rather than playing around in the socket code) also fixes the problem (see attached patch). Do you think this step occurs if write access isn't specified?
Erich Hoover ehoover@mines.edu
Any thoughts on this? Is there anything a "+relay" wouldn't catch that could occur between the call to KERNEL32.VirtualAlloc and the call to ws2_32.recv? This behavior (the memory area having to be cleared before the recv call) seems a tad on the odd side.
Erich Hoover ehoover@mines.edu