VirtualBox

Ticket #7285 (closed defect: fixed)

Opened 4 years ago

Last modified 3 years ago

stosw fails with std in real mode => Fixed in SVN

Reported by: jtrindade Owned by:
Priority: minor Component: VMM
Version: VirtualBox 3.2.6 Keywords: stosw, std
Cc: Guest type: other
Host type: Windows

Description

At least in real mode, the string instruction "stosw" presents an incorrect behaviour when the direction flag is set.

I have observed this behaviour while testing boot code of a personal OS. The same code works fine in Bochs 2.3.7 for Linux, QEMU 0.12.2 for Windows and VMware Player 3.1.0 for Windows.

Attached: 1) Binary image of an 1.44M floppy with said behaviour in its boot sector 2) Source code for the boot sector

Attachments

boot16ex.img.gz Download (1.5 KB) - added by jtrindade 4 years ago.
1) Image of 1.44M floppy with the failing behaviour
boot16ex.s Download (654 bytes) - added by jtrindade 4 years ago.
2) Source code for the boot sector

Change History

Changed 4 years ago by jtrindade

1) Image of 1.44M floppy with the failing behaviour

Changed 4 years ago by jtrindade

2) Source code for the boot sector

comment:1 Changed 4 years ago by jtrindade

I forgot to say that the floppy should show the following string in the bottom of the screen:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

However, in VirtualBox (3.2.6) it shows only:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This happens with or without the use of the prefix "rep". Similar tests with "movsw" don't seem to present this problem.

comment:2 Changed 4 years ago by frank

  • Summary changed from stosw fails with std in real mode to stosw fails with std in real mode => Fixed in SVN

Thanks for this report and the testcase! Fixed in SVN, the fix will be part of the next maintenance release.

comment:3 Changed 3 years ago by frank

  • Status changed from new to closed
  • Resolution set to fixed

Fixed as of VBox 3.2.8.

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