[Qemu-devel] [Bug 922076] Re: doesn't clear screen on boot

[Askar Safin]

** Description changed:

- When I start Linux in Qemu via "qemu -kernel /vmlinuz ...", opens Qemu
- window, it shows message "Starting Seabios (version 0.5.1-2010...)", and
- then Linux writes messages like "Loading, please wait..." on top of
+ When I start Linux in Qemu via "qemu -kernel /vmlinuz ...", Qemu window
+ appears and it shows message "Starting Seabios (version 0.5.1-2010...)",
+ and then Linux writes messages like "Loading, please wait..." on top of
  previous message!
  
  For example, I can see "Loading, please wait...on 0.5.1-2010...)"
  
  So, Qemu doesn't clean screan before booting OS.
  
  Moreover, when I start Linux via "qemu /disk-image", Qemu shows
  "Starting Seabios (version 0.5.1-2010...)", then switches to graphical
  mode, shows GRUB, then switches back to text mode and shows "Starting
  Seabios" again! And again Linux prints messages on top of Seabios
  messages, and we see a mix of symbols on screen.
  
  Also, I found another bug! I am learning now to write kernels. And I see
  that operator "*(char *)0xb8000 = 0" in C code of kernel doesn't clean
  first charaster of screen in Qemu in "-curses" mode! If I want to real
  clean this charaster, I must type "*(char *)0xb8000 = ' '".
  
  I attach a kernel (x86, multiboot) with this bug. Just type "make" (you
  need gcc) and "qemu -curses -kernel kernel". You will see that screen is
  not cleared, but kernel tries to clean it. If you change 0 to ' ', all
  will work!

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https://bugs.launchpad.net/bugs/922076

Title:
  doesn't clear screen on boot

Status in QEMU:
  New

Bug description:
  When I start Linux in Qemu via "qemu -kernel /vmlinuz ...", Qemu
  window appears and it shows message "Starting Seabios (version
  0.5.1-2010...)", and then Linux writes messages like "Loading, please
  wait..." on top of previous message!

  For example, I can see "Loading, please wait...on 0.5.1-2010...)"

  So, Qemu doesn't clean screan before booting OS.

  Moreover, when I start Linux via "qemu /disk-image", Qemu shows
  "Starting Seabios (version 0.5.1-2010...)", then switches to graphical
  mode, shows GRUB, then switches back to text mode and shows "Starting
  Seabios" again! And again Linux prints messages on top of Seabios
  messages, and we see a mix of symbols on screen.

  Also, I found another bug! I am learning now to write kernels. And I
  see that operator "*(char *)0xb8000 = 0" in C code of kernel doesn't
  clean first charaster of screen in Qemu in "-curses" mode! If I want
  to real clean this charaster, I must type "*(char *)0xb8000 = ' '".

  I attach a kernel (x86, multiboot) with this bug. Just type "make"
  (you need gcc) and "qemu -curses -kernel kernel". You will see that
  screen is not cleared, but kernel tries to clean it. If you change 0
  to ' ', all will work!

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