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Old 06-05-2018, 01:04 PM   #1
Registered: Apr 2016
Posts: 382

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how to compile 32bit kernel on 64bit processor

i have a 64bit new-ish pc i'm trying to get linux on from my older pc. there's one purchased app i need, the rest i don't care about: it requires any VALID X11R6 server to display on (32 or 64 bit i dunno, i'm unsure if 64bit X11R6 is possible or talks with 32bit apps).

PROBLEM: VESA BIOS not present unless running older 32bit kernels ...

PROBLEM: x11r6 does not detect vesa bios unless kernel was built for 32bit processor (smp not allowed) on 32bit machine. otherwise x11 either fails to load** (tell me if that's wrong? if i compile x11r6 as 64bit, will it compile and 32bit apps not complain of it ????)

How do i compile a 32bit kernel using a 64bit processor?

ARCH = x86
CROSS_COMPILE = i386-pc-linux-gnu-

when i compiled i was running on a 64bit machine booted from a 32bit kernel that was built for pentium m built on a 32bit machine, for target pentium m. BUT IT DIDN'T WORK. i have to throw away the 32bit machine eventually and it takes a long time to make each tried kernel.

i'm presently compiling kernel with "gcc -march=i486" without much hope. it may even cause bad issues: because processor is selected PENTIUM M, some pentium commands might not get compiled in?

how do i know it didn't work? well i don't completely.

** int10 (reads vesa bios, fails icore5 in all casess), or fails to get right vesa bios adress and fails (pentium m smp). 0xC000 in that case, but if it boots right, it's 0xC0FF - which is probably "right". this tells me either that for smp x11 needs to be recompiled for the right offset (unlikely?) or that unless it's true 32bit on true 32bit processor that kernel or kernel I/O use the wrong addressing scheme and thus steer x11 to take the wrong bios base address

QUESTION AGAIN: is there a way, what is the right way, to compile a 32bit kernel on a 64bit machine? Or would it be more "correct" to recompile X11R6-4.8.0 code with a fix for bios offset/address adjustment? (i'm unsure that'd work, unsure if vesa is 32bit or 64bit how machine boots in what mode: i'd have to really _allot_ of mfg docs to get down to the nitty gritty and really fix x11r6: but no one but (me) uses x11R6!)

I'm really unsure if this is an X11 bug, or a Kernel bug, a Vesa bug (in MSI pcmate z170a mb), or I'm "doing it wrong".
Old 06-05-2018, 01:16 PM   #2
Registered: Apr 2016
Posts: 382

Original Poster
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Does VESA work on X11R6 when running on new-sh icore5 PC?

kernel compile by 32bit machine:
YES kernel compiled by 32bit machine for 32bit running on SINGLE 64 cpu
NO kernel compiled by 32bit machine for 32bit SMP running on 64bit
NO kernel compiled by 32bit machine for 64bit cpu running on 64bit machine
(64bit NOT selected on that, as i said 32bit is goal)

kernel compiled by 64bit machine:
NO kernel compiled by 64bit machine (64bit NOT selected)
NO kernel compiled by 64bit machine (64bit NOT selected) with ARCH CC
NO "" ARCH CROSS_COMPILE -march=i486

(and i'm afraid -march=i486 might damage kernel code that uses penium instructions and cause havoc?)

i'm unsure if VESA BIOS has both 32 and 64 bit interface on new PC's. obviously IDE has both or the PC wouldn't boot a 32bit kernel but addressing isssues should not be a problem (it should not be X11's job to fix up addresses: that would be VESA is non-standard and, per purchase, not as advertised, not really VESA. but it could be addressing issues the kernel caused. i just don't know.)

Last edited by X-LFS-2010; 06-05-2018 at 01:25 PM.


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