[Bug 33275] Far Cry: Segmentation Fault on start

[wine-bugs at winehq.org]

https://bugs.winehq.org/show_bug.cgi?id=33275

Anastasius Focht <focht at gmx.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |download
             Status|UNCONFIRMED                 |NEW
                URL|                            |http://www.gamershell.com/d
                   |                            |ownload_4929.shtml
     Ever confirmed|0                           |1

--- Comment #15 from Anastasius Focht <focht at gmx.net> ---
Hello folks,

thanks for "inviting" me here :)
I took a brief look at this as I'm currently busy with other projects.

Looks like a Linux kernel bug to me -> upstream.

The game tries to determine the exact CPU type by executing various (legacy)
checks.
During the check for 80286 and 80386 CPU type, the nested task (NT) flag gets
set along with I/O Privilege Level (IOPL, 2 bits) and some reserved bit
(through 'popfw').

Upon syscall entry, the IOPL bits get cleared as configured through
MSR_SYSCALL_MASK but the NT flag is not touched at all, getting propagated to
task switching code.

Reduced test case:

--- snip ---
/* Compile:      gcc -m32 -o ntflag ntflag.c
   Run:          while true ; do ./ntflag ; done
 */
#include <stdio.h>

int main ()
{
  asm volatile("pushfl           \n\t" \
               "pop %eax         \n\t" \
               "or $0x4000,%eax  \n\t" \
               "push %eax        \n\t" \
               "popfl            \n\t");
  printf("exit or segfault\n");
  return 0;
}
--- snip ---

x86 syscall_init() MSR_SYSCALL_MASK should also include 'X86_EFLAGS_NT' to be
safe from userspace injection.

$ sha1sum DemoFarCry.zip 
65200be08d5deab0f25eed9bba915e8da374933e  DemoFarCry.zip

$ du -sh DemoFarCry.zip 
497M    DemoFarCry.zip

$ wine --version
wine-1.7.26-97-g2398124

Regards

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