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[Bug 1738434] Re: CALL FWORD PTR [ESP] handled incorrectly

From: Launchpad Bug Tracker
Subject: [Bug 1738434] Re: CALL FWORD PTR [ESP] handled incorrectly
Date: Sun, 10 Jan 2021 04:17:45 -0000

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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  CALL FWORD PTR [ESP] handled incorrectly

Status in QEMU:

Bug description:
  To keep the story short, this 32-bit code crashes on 64-bit Windows
  whereas it works fine on real system and VMware:

      push 33h
      push offset _far_call
      call fword ptr[esp]
      jmp _ret

  32-bit code running under WoW64 on 64-bit Windows has the ability to
  switch to the 64-bit mode via so called "Heaven's gate". In order to
  do that you have to make a far call/jmp by 0x33 selector how the code
  snippet above shows. QEMU throws an access violation exception whereas
  the code snippet runs with no problems on real CPU and VMware. By the
  way, this code works fine under QEMU, I hope it gives you a hint where
  to look:

      push 23h
      push offset _far_call
      call fword ptr[esp]
      jmp _ret

  0x23 is a default 32-bit selector for 32-bit processes running under

  QEMU: 2.10.93, command line: qemu-system-x86_64.exe -m 2G -snapshot -cdrom 
full_path_to_iso fullP_path_to_img
  Guest OS: Windows 7 x64 SP1 build 7601 or Windows 10 version 1709 build 
  Host OS: Windows 10 x64 version 1703 build 15063.786

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