[haiku-bugs] Re: [Haiku] #7787: VESA regression: 640x480 no longer works at boot (but works in Screen prefs!)

#7787: VESA regression: 640x480 no longer works at boot (but works in Screen
prefs!)
----------------------------------+-----------------------
   Reporter:  ttcoder             |      Owner:  axeld
       Type:  bug                 |     Status:  new
   Priority:  normal              |  Milestone:  R1
  Component:  System/Boot Loader  |    Version:  R1/alpha3
 Resolution:                      |   Keywords:
 Blocked By:                      |   Blocking:
Has a Patch:  0                   |   Platform:  x86
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Comment (by ttcoder):

 @devs:[[BR]]
 It still looks like a memory corruption. Been reviewing video.cpp side-by-
 side with the syslog, and I understand better the code flow: it turns out
 that the bootloader ''does'' select 800x600 when initializing, it is smart
 enough to pick that one over the smaller resolutions. But that choice gets
 lost along the way to kernel-land, AND the other choices get corrupted;
 explanation:

 - platform_switch_to_text_mode() is ok
 - platform_init_video() is ok (it does select '''800x600''' in
 vesa_init())
 - platform_switch_to_logo() oddly dprintf()s that
 gKernelArgs.frame_buffer.height='''640''' (x480) instead of 800x600 !

 You can check the 'syslog-failure' file I have posted, it does log what I
 describe: the loader [http://dev.haiku-
 os.org/browser/haiku/trunk/src/system/boot/platform/bios_ia32/video.cpp#L529
 TRACE()ing] 0x115 (that is, '''800x600'''), and then asking the kernel to
 use '''640x480x32''' ([http://dev.haiku-
 os.org/browser/haiku/trunk/src/system/boot/platform/bios_ia32/video.cpp#L859
 dprintf()])..

 So it seems that 'gKernelArgs' gets corrupted (part of it gets clobbered)
 inbetween the user menu and kernel loading. And thus when the kernel kicks
 in, it is passed the wrong arguments; additionally, the parameters for
 640x480 maybe get corrupted too (since there is also the bug that this
 resolution does not work since alpha3).. Additionally, it also corrupts
 the nVidia driver depending on the situation?

 The last few days I was thinking about building the loader from source..
 Maybe I will still do that: as experimented before, reverting to an older
 revision of 'haiku_loader' fixes the corruption, so this hints at the
 memory corruption occuring insider the loader, not in the kernel.

 NOTE on video.cpp:50 :
 {{{
 static video_mode *sMode, *sDefaultMode;
 }}}

 'sMode' is not initialized to NULL on construction, and only gets affected
 at the end of platform_init_video() though that's probably not the source
 of my problems.

-- 
Ticket URL: <http://dev.haiku-os.org/ticket/7787#comment:8>
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