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Re: [Qemu-ppc] Apple's BootX


From: Programmingkid
Subject: Re: [Qemu-ppc] Apple's BootX
Date: Fri, 26 Jan 2018 10:37:29 -0500

> On Jan 26, 2018, at 3:32 AM, Jd Lyons <address@hidden> wrote:
> 
> 
> 
>> On Jan 25, 2018, at 10:18 AM, Programmingkid <address@hidden> wrote:
>> 
>> 
>>> On Jan 25, 2018, at 10:01 AM, Jd Lyons <address@hidden> wrote:
>>> 
>>> In an effort to figure out why qemu-system-ppc hangs at BootX when using 
>>> some emulated and KVM CPU’s, I suppose it would be good to enter some 
>>> breakpoints in the code.
>>> 
>>> I found some BootX sources at:
>>> 
>>> https://opensource.apple.com/tarballs/BootX/
>>> 
>>> Tho I’m not sure what versions correspond to which release of OS X?
>>> 
>>> And it’s not clear how to build them, tho I haven’t tried yet.
>>> 
>>> I found some info on BootX as well as some idea how to do what I’m looking 
>>> to do:
>>> 
>>> https://people.ffii.org/~zoobab/bh.udev.org/filez/apple/mac6100/BootX.pdf
>>> 
>>> There are few other useful debugging tech- niques. Setting "auto-boot?" to 
>>> false will cause the system to enter the OpenFirmware User In- terface by 
>>> default. Changing kFailToBoot to 0 in include.tproj/sl.h will alter BootX’s 
>>> default be- havior on error, so that it will return to Open- Firmware. 
>>> Finally, calling Enter(), will cause BootX to drop back into the 
>>> OpenFirmware User Interface. This can be used as a break point. The "dumpl" 
>>> word will dump some memory, by en- tering the address, then the length, 
>>> then "dumpl". By calling printf in BootX immediately before En- ter(), the 
>>> address can be easily determined, and the variable can then be examined and 
>>> altered from OpenFirmware. Finally typing the "go" command will resume 
>>> BootX’s execution. 
>>> 
>>> 
>>> I noted when I boot from boot usb0/disk:3,\\:tbxi while holding command+v 
>>> BootX sends some info to the screen, seemingly via open firware, while 
>>> displaying the “Apple Logo” boot graphic. The info show some of the boot 
>>> process and what stage it’s loading” loading mach_kernel’ “ loading the 
>>> .mkext”
>>> 
>>> It would be nice to get this output going via Open Bios, if anyone has any 
>>> idea how I might be able to do that?
>> 
>> Have you tried adding "-prom-env boot-args=-v" to QEMU's arguments yet?
> 
> Yes, I usually use -prom-env 'boot-args=-v  debug=0xffe kdp=2’.
> 
> On a real PPC Mac BootX seems to give some extra debug in fo with command+V, 
> tho most of the time it goes by so fast that it’s unreadable. Booting from a 
> slower drive like USB yield the kind of info I’m looking for, to be able to 
> tell at what stage BootX is hanging.
> 
> Unfortunately, this debug info is no sent to the screen, or stdio in 
> OpenBios, or I just haven’t figured out how to do that yet.

There is another way to see what boots sends to the screen. That is to record 
the output of the screen. I use to do this when I had to read the output from 
Mac OS X when it was booting. I used Quicktime X to record the screen. Since 
you are on Linux there may be other options. You could take the output of your 
computer and send it to a a DVD recorder, VCR, DVR, Camcorder, etc... You might 
even want to try aiming your camera phone at the screen and record what Bootx 
is displaying. 

https://itsfoss.com/best-linux-screen-recorders/
This page list several programs that can record your screen on Linux. I just 
don't think it would help on a PowerPC Mac. 


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