Anybody got 2.4.0 running on a 386 ?

Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

Hi list,

I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
The kernel was built for a 386 Processor, Math emulation has been enabled.
I tried three different 386 boards. Execution seems to get as far as
pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
if someone had pressed the reset button. The same kernel boots fine on
486 and Pentium Systems.

Any ideas/suggestions ?

Rob

----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Brian Gerst]

Robert Kaiser wrote:
> 
> Hi list,
> 
> I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> The kernel was built for a 386 Processor, Math emulation has been enabled.
> I tried three different 386 boards. Execution seems to get as far as
> pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> if someone had pressed the reset button. The same kernel boots fine on
> 486 and Pentium Systems.
> 
> Any ideas/suggestions ?


is "Checking if this processor honours the WP bit even in supervisor
mode... " the last thing you see before the reset?

--

				Brian Gerst
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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Die, 09 Jan 2001 you wrote:
> Robert Kaiser wrote:
> > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > I tried three different 386 boards. Execution seems to get as far as
> > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > if someone had pressed the reset button. The same kernel boots fine on
> > 486 and Pentium Systems.
> > 
> > Any ideas/suggestions ?
> 
> 
> is "Checking if this processor honours the WP bit even in supervisor
> mode... " the last thing you see before the reset?
> 

No, I don't see _any_ messages from the kernel. The last thing I see is
"Uncompressing Linux... Ok, booting the kernel." I have added some
quick and dirty debug code that writes messages directly to the VGA
screen buffer. According to that, execution seems to get as far as the
statement

        *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);




----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Brian Gerst]

Robert Kaiser wrote:
> 
> On Die, 09 Jan 2001 you wrote:
> > Robert Kaiser wrote:
> > > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > > I tried three different 386 boards. Execution seems to get as far as
> > > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > > if someone had pressed the reset button. The same kernel boots fine on
> > > 486 and Pentium Systems.
> > >
> > > Any ideas/suggestions ?
> >
> >
> > is "Checking if this processor honours the WP bit even in supervisor
> > mode... " the last thing you see before the reset?
> >
> 
> No, I don't see _any_ messages from the kernel. The last thing I see is
> "Uncompressing Linux... Ok, booting the kernel." I have added some
> quick and dirty debug code that writes messages directly to the VGA
> screen buffer. According to that, execution seems to get as far as the
> statement
> 
>         *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> 

Could it be possible that memory size is being misdetected?  Try mem=8M
(or less) on the command line.  Try to catch the value of pte when it
crashes.

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				Brian Gerst
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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Die, 09 Jan 2001 you wrote:
> Robert Kaiser wrote:
> > 
> > On Die, 09 Jan 2001 you wrote:
> > > Robert Kaiser wrote:
> > > > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > > > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > > > I tried three different 386 boards. Execution seems to get as far as
> > > > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > > > if someone had pressed the reset button. The same kernel boots fine on
> > > > 486 and Pentium Systems.
> >  ..... The last thing I see is
> > "Uncompressing Linux... Ok, booting the kernel." I have added some
> > quick and dirty debug code that writes messages directly to the VGA
> > screen buffer. According to that, execution seems to get as far as the
> > statement
> > 
> >         *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> > 
> 
> Could it be possible that memory size is being misdetected?  Try mem=8M
> (or less) on the command line.  Try to catch the value of pte when it
> crashes.

I tried "mem=4M" -- no effect. The value of pte is 0xc0001000, so it seems
to be the first invocation of that statement in the for() loop.

Now comes the amazing (to me) part: I split the above statement up into:

	temp = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
	*pte = temp;

where temp is declared "volatile pte_t". I inserted test-prints between the
above two lines. Accoding to that, the _first_ line , i.e. the evaluation of the
mk_pte_phys() macro is causing the crash!

I am still trying to figure out what mk_pte_phys() does. Apparently it involves
an access to the kernel's data section. My current guess is that the data
section is not correctly mapped at this point. Would that be possible ?



----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Ingo Molnar]

On Tue, 9 Jan 2001, Robert Kaiser wrote:

> Now comes the amazing (to me) part: I split the above statement up into:
>
> 	temp = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> 	*pte = temp;

this is almost impossible (except some really weird compiler bug) - unless
the mem_map address is invalid. This could happen if your kernel image is
*just* too large. Do things improve if you disable eg. ext2fs support (i
know, but should be enough to boot). Or if that part is not mapped
correctly (which does happen sometimes as well).

and are you sure it crashes there? [are you putting delays between your
printouts?]

> where temp is declared "volatile pte_t". I inserted test-prints between the
> above two lines. Accoding to that, the _first_ line , i.e. the evaluation of the
> mk_pte_phys() macro is causing the crash!

it accesses mem_map variable, which is near to the end of the kernel
image, so it could indeed something of that sort. An uncompressed kernel
image (including the data area) must not be bigger than 4MB (IIRC).

	Ingo

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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Die, 09 Jan 2001 you wrote:
> On Tue, 9 Jan 2001, Robert Kaiser wrote:
> 
> > Now comes the amazing (to me) part: I split the above statement up into:
> >
> > 	temp = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> > 	*pte = temp;
> 
> this is almost impossible (except some really weird compiler bug) - unless
> the mem_map address is invalid. This could happen if your kernel image is
> *just* too large. Do things improve if you disable eg. ext2fs support (i
> know, but should be enough to boot).

Sorry, no ext2fs in this kernel (it is for a diskless embedded system). I seem
to recall though that the problem at one point magically went away when I
disabled the FPU emulation, but I have not been able to reproduce this
recently, so I'm not sure. Making minor changes to the kernel code (such as
adding/removing some test-prints) certainly does not affect the behavior.

> Or if that part is not mapped
> correctly (which does happen sometimes as well).

What could I do to check/fix this ? 

> 
> and are you sure it crashes there? [are you putting delays between your
> printouts?]

I have put a "halting statement" (i.e. "while(1);") after my printouts to make
sure execution does not go any further than that point. I moved this halting
statement ahead in the code line by line until the crash would occur again.
So, yes, I am pretty sure.

> 
> > where temp is declared "volatile pte_t". I inserted test-prints between the
> > above two lines. Accoding to that, the _first_ line , i.e. the evaluation of the
> > mk_pte_phys() macro is causing the crash!
> 
> it accesses mem_map variable, which is near to the end of the kernel
> image, so it could indeed something of that sort. An uncompressed kernel
> image (including the data area) must not be bigger than 4MB (IIRC).

According to my System.map file, mem_map is at 0xc0244f78. Does that help ?



----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Alex Buell]

On Wed, 10 Jan 2001, Robert Kaiser wrote:

> I have put a "halting statement" (i.e. "while(1);") after my printouts
> to make sure execution does not go any further than that point. I
> moved this halting statement ahead in the code line by line until the
> crash would occur again. So, yes, I am pretty sure.

Here's a tip for anyone who has to track down bugs of this nature. To
greatly speed up work, just use a binary search technique. That is, go to
the section of code that's causing problem, put a breakpoint or similiar
half-way. If it dies before that point, move it back half way, after that
point, move it forwards half way. Iterate until you find the place.

Cheers,
Alex
-- 
If PacMan had affected us as kids we'd be running around in
dark rooms, munching pills and listening to electronic music.

http://www.tahallah.clara.co.uk

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Re: Anybody got 2.4.0 running on a 386 ?

[Ingo Molnar]

On Wed, 10 Jan 2001, Robert Kaiser wrote:

> Sorry, no ext2fs in this kernel (it is for a diskless embedded
> system). I seem to recall though that the problem at one point
> magically went away when I disabled the FPU emulation, but I have not
> been able to reproduce this recently, so I'm not sure. Making minor
> changes to the kernel code (such as adding/removing some test-prints)
> certainly does not affect the behavior.

math-FPU emulation takes up quite some space in the kernel image, so this
could indeed be the case. Could you disable any non-boot-essential
subsystem (networking, or the serial driver, or anything else), to
significantly reduce the image size?

> > Or if that part is not mapped
> > correctly (which does happen sometimes as well).
>
> What could I do to check/fix this ?

i had this a couple of times while doing the 3-level pagetables and
related highmem stuff (and i might even have added this bug ...), and
typically i just printed out the pagetables to a serial console and
analyzed them manually :-|

> > and are you sure it crashes there? [are you putting delays between your
> > printouts?]
>
> I have put a "halting statement" (i.e. "while(1);") after my printouts to make
> sure execution does not go any further than that point. I moved this halting
> statement ahead in the code line by line until the crash would occur again.
> So, yes, I am pretty sure.

(okay, that certainly is a proof. I had to ask.)

> > it accesses mem_map variable, which is near to the end of the kernel
> > image, so it could indeed something of that sort. An uncompressed kernel
> > image (including the data area) must not be bigger than 4MB (IIRC).
>
> According to my System.map file, mem_map is at 0xc0244f78. Does that help ?

not really. Could you write a small function that just reads the kernel
image from the first symbol to the last one, and see whether it crashes?
(read it into a volatile variable to make sure GCC reads it.) Kernel image
goes from _stext to _end - you can access it with something like this:

void test_image (void)
{
	extern char _stext;
	extern char _end;

	volatile char data;
	char *ptr = &_stext;

	while (ptr < _end)
		data = *ptr++;
}

another problem could be if the kernel image is in a place that is somehow
invalid physical RAM. We uncompress it into address 1MB physical (and
assume there is enough space from that point on to uncompress
successfully, without actually checking it), which should work on all 'PC
architecture compatible' systems. (other bootloaders use this method
frequently as well.)

	Ingo

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Re: Anybody got 2.4.0 running on a 386 ?

[Ingo Molnar]

you should also try to access the mem_map variable directly, in some
simple way. Could you print out the value of mem_map btw.? [This should
rule out any compiler interaction.]

	Ingo

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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Wed, 10 Jan 2001, Ingo Molnar wrote:

> math-FPU emulation takes up quite some space in the kernel image, so this
> could indeed be the case. Could you disable any non-boot-essential
> subsystem (networking, or the serial driver, or anything else), to
> significantly reduce the image size?
> 

I tried this: apparently no effect. However, there may be hardware
issues involved (see below).

> not really. Could you write a small function that just reads the kernel
> image from the first symbol to the last one, and see whether it crashes?
> (read it into a volatile variable to make sure GCC reads it.)

I tried this: Reading the entire image never caused any crashes.

However, I did have some (rare) instances of the kernel booting
successfully. Then it would fail again, booting the very same image
that had worked before.

I am beginning to suspect that I may be dealing with flaky hardware.
(I'm working from home today and I only have access to one of my 386
specimen here).

I guess I'll better shut up until I can double check on
some other 386 boards tomorrow....

In the meantime, it would be helpful if anyone who has successfully
booted a 2.4.0 kernel on a 386 could report this to the list.

----------------------------------------------------------------
Robert Kaiser                          email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14
D-55270 Klein-Winternheim / Germany    fax:   (49) 6136 9948-10

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Re: Anybody got 2.4.0 running on a 386 ?

[Tom G. Christensen]

On Wed, 10 Jan 2001, Robert Kaiser wrote:

> In the meantime, it would be helpful if anyone who has successfully
> booted a 2.4.0 kernel on a 386 could report this to the list.
>
I had no problems booting an AMD 386DX/40 with 32 megs of RAM.
I just dumped a bzImage (703K) to a floppy and it booted on that just
fine.
Kernel was built using egcs-1.1.2 from RH 6.2

If I build the same kernel on a RH7 system using gcc 2.96 (gcc-2.96-69)
the machine reboots after "Uncompressing Linux... Ok, boot the kernel" no
more text is printed.

.config is available on request.

-tgc

-- 
Tom G. Christensen, Denmark <tom.christensen@get2net.dk>
Homepage: http://hjem.get2net.dk/tgc
Linux 2.2.16-3 on an i586



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X performance on 2.4.0 v.s. 2.4.0-test12

[Alan Olsen]

I have seen a number of reports claiming something broken in 2.4.0 for
DRI.

I have tested under 2.4.0 and 2.4.0 test 12 with the exact same setup.

I see a slight variation in frame rates under the release version, but so
small as to be within statistical varience.

Everything else seems to work in reguards to DRI and AGPGART so far.  (Of
course, the X server on my desk will now explode since I said that...)

I have noticed that the framerate takes a hard nosedive if xinerama is
turned on, but that is explained in the docs.

I have not seen any "flashing" behaviour or any other reported
weirdnesses.

Maybe it is the sacrifices made to dark penguin gods during that last full
moon. 

alan@ctrl-alt-del.com | Note to AOL users: for a quick shortcut to reply
Alan Olsen            | to my mail, just hit the ctrl, alt and del keys.
    "In the future, everything will have its 15 minutes of blame."

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Re: Anybody got 2.4.0 running on a 386 ?

[Brian Gerst]

Robert Kaiser wrote:
> 
> On Die, 09 Jan 2001 you wrote:
> > Robert Kaiser wrote:
> > >
> > > On Die, 09 Jan 2001 you wrote:
> > > > Robert Kaiser wrote:
> > > > > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > > > > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > > > > I tried three different 386 boards. Execution seems to get as far as
> > > > > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > > > > if someone had pressed the reset button. The same kernel boots fine on
> > > > > 486 and Pentium Systems.
> > >  ..... The last thing I see is
> > > "Uncompressing Linux... Ok, booting the kernel." I have added some
> > > quick and dirty debug code that writes messages directly to the VGA
> > > screen buffer. According to that, execution seems to get as far as the
> > > statement
> > >
> > >         *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> > >
> >
> > Could it be possible that memory size is being misdetected?  Try mem=8M
> > (or less) on the command line.  Try to catch the value of pte when it
> > crashes.
> 
> I tried "mem=4M" -- no effect. The value of pte is 0xc0001000, so it seems
> to be the first invocation of that statement in the for() loop.
> 
> Now comes the amazing (to me) part: I split the above statement up into:
> 
>         temp = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
>         *pte = temp;
> 
> where temp is declared "volatile pte_t". I inserted test-prints between the
> above two lines. Accoding to that, the _first_ line , i.e. the evaluation of the
> mk_pte_phys() macro is causing the crash!
> 
> I am still trying to figure out what mk_pte_phys() does. Apparently it involves
> an access to the kernel's data section. My current guess is that the data
> section is not correctly mapped at this point. Would that be possible ?

How much physical memory does this box really have?

--

				Brian Gerst
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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Mit, 10 Jan 2001 you wrote:
> 
> How much physical memory does this box really have?
> 

The one I'm currently using is an old Olivetti 386SX with 5 MB, I also tried two
more boards, one 386SX, one 386DX, both with 8MB. All showed the same behavior.

----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Anuradha Ratnaweera]

How big is the kernel image? Are you making a zImage or bzImage?

Anuradha

On Wed, 10 Jan 2001, Robert Kaiser wrote:

> On Mit, 10 Jan 2001 you wrote:
> > 
> > How much physical memory does this box really have?
> > 
> 
> The one I'm currently using is an old Olivetti 386SX with 5 MB, I also tried two
> more boards, one 386SX, one 386DX, both with 8MB. All showed the same behavior.
> 
> ----------------------------------------------------------------
> Robert Kaiser                         email: rkaiser@sysgo.de
> SYSGO RTS GmbH
> Am Pfaffenstein 14                    phone: (49) 6136 9948-762
> D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
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> 

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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

On Mit, 10 Jan 2001 you wrote:
> How big is the kernel image? Are you making a zImage or bzImage?
> 

I'm using bzImage. It's size is 566964 bytes.

According to System.map, Symbol _end is 0xc0252cf0. That would mean
the uncompressed kernel size would be 1387760 bytes (0xc0252cf0-0xc0100000),
right ?

----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: Anybody got 2.4.0 running on a 386 ?

[Miles Lane]

Hi Rob,

Just out of curiosity, did you use a 2.2 series
.config file and then run make oldconfig or did
you build a new .config file from scratch?

I have periodically built kernels that crashed
immediately at the point you mention.  Usually this
was due to me choose configuration options that
were incompatible with my machine's hardware.

Another time, the machine wouldn't boot because
I needed a new version of LILO.  I also have seen
at least one machine where I needed to specify
"linear" as one of the options in lilo.conf.
If you aren't specifying "linear" now, give it
a try.

IIRC, here's my litany of goofed configurations:

	Building support for multiple framebuffer
	devices.  Apparently, the kernel would
	hang in the chip detection process.

	Wrong CPU architecture.

	Wrong IDE chipset specified.

	Built EXT2 as a module, but / was on
	an EXT2 partition.

I may have hit some other bogus configurations
over the last two years, but these are ones that
come to mind.

	Miles

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Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

Hi Miles,

Thanks very much for your suggestions!

On Tue, 9 Jan 2001, Miles Lane wrote:

> Just out of curiosity, did you use a 2.2 series
> .config file and then run make oldconfig or did
> you build a new .config file from scratch?

No, I built it from scratch with make xconfig.

> 
> I have periodically built kernels that crashed
> immediately at the point you mention.  Usually this
> was due to me choose configuration options that
> were incompatible with my machine's hardware.

You mean they crashed at the exact same statement ?
That would be an interesting hint, can you confirm it ?

> 
> Another time, the machine wouldn't boot because
> I needed a new version of LILO.  I also have seen
> at least one machine where I needed to specify
> "linear" as one of the options in lilo.conf.
> If you aren't specifying "linear" now, give it
> a try.

I am not using LILO (yet). I tried booting with SYSLINUX
or by dumping the kernel binary to floppy and booting from
it. Both showed the same result.

----------------------------------------------------------------
Robert Kaiser                          email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14
D-55270 Klein-Winternheim / Germany    fax:   (49) 6136 9948-10


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Re: Anybody got 2.4.0 running on a 386 ?

[Miles Lane]

Robert Kaiser wrote:

<snip>

>> I have periodically built kernels that crashed
>> immediately at the point you mention.  Usually this
>> was due to me choose configuration options that
>> were incompatible with my machine's hardware.
> 
> 
> You mean they crashed at the exact same statement ?
> That would be an interesting hint, can you confirm it ?

I sent the "possible config problem" list mostly
as a warning about what can cause kernels to lock up
early in the boot cycle.  Some of the problems I ]
mentioned will cause a lock up immediately after
the "Uncompressing kernel... OK Booting Linux" message.

I doubt that these problems are causing your problem
and so I really doubt that these crashes are occuring
in the same function that yours is.

Mostly, I thought you might want to double-check your
configuration options and make sure that you are using
none of these broken configuration combinations.

Good luck!  I wish I could be of more help.

	Miles


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Re: Anybody got 2.4.0 running on a 386 ?

[Paul Gortmaker]

Robert Kaiser wrote:
> 
> The one I'm currently using is an old Olivetti 386SX with 5 MB, I also
> tried two more boards, one 386SX, one 386DX, both with 8MB. All showed 
> the same behavior.

I tested 2.4.0 on probably the exact same box - an Olivetti M300-05 
386sx with 5MB and it came up ok, except that memory detection is off
by a MB. (to be fixed in 2.4.1 or boot with mem= argument in 2.4.0)

What might be important here is your gcc & binutils (as/gas) version,
combined with a miscompile in something like __verify_write that
doesn't get used on anything but 386 (and hence went undetected).

Only thing strange on my box is that the kernel is compiled with 
gcc-2.7.2 which is officially unsupported but can be managed if you 
know what the gcc bugs are.  

Paul.



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[SOLVED + PATCH] Re: Anybody got 2.4.0 running on a 386 ?

[Robert Kaiser]

Hi everybody,

I finally found the reason why 386es have trouble booting the 2.4.0 kernel:

In routine pagetable_init() in arch/i386/mm/init.c, a pte gets installed before
it actually has been filled with valid entries. This causes the kernel text
segment to be temporarily unmapped. Pentiums are only lucky to not crash
because they have a bigger TLB than 386s.

Here is a patch to fix this:

--- init.c.orig	Wed Nov 29 07:43:39 2000
+++ init.c	Mon Jan 15 18:36:08 2001
@@ -317,7 +317,7 @@
 	pgd_t *pgd, *pgd_base;
 	int i, j, k;
 	pmd_t *pmd;
-	pte_t *pte;
+	pte_t *pte, *pte_base;
 
 	/*
 	 * This can be zero as well - no problem, in that case we exit
@@ -366,11 +366,7 @@
 				continue;
 			}
 
-			pte = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
-			set_pmd(pmd, __pmd(_KERNPG_TABLE + __pa(pte)));
-
-			if (pte != pte_offset(pmd, 0))
-				BUG();
+			pte_base = pte = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
 
 			for (k = 0; k < PTRS_PER_PTE; pte++, k++) {
 				vaddr = i*PGDIR_SIZE + j*PMD_SIZE + k*PAGE_SIZE;
@@ -378,6 +374,10 @@
 					break;
 				*pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
 			}
+			set_pmd(pmd, __pmd(_KERNPG_TABLE + __pa(pte_base)));
+			if (pte_base != pte_offset(pmd, 0))
+				BUG();
+
 		}
 	}
 
Thanks to everybody who helped with ideas and suggestions, especially Ingo
Molnar!


Cheers

Rob

----------------------------------------------------------------
Robert Kaiser                         email: rkaiser@sysgo.de
SYSGO RTS GmbH
Am Pfaffenstein 14                    phone: (49) 6136 9948-762
D-55270 Klein-Winternheim / Germany   fax:   (49) 6136 9948-10
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Re: [SOLVED + PATCH] Re: Anybody got 2.4.0 running on a 386 ?

[Linus Torvalds]

On Mon, 15 Jan 2001, Robert Kaiser wrote:
> 
> I finally found the reason why 386es have trouble booting the 2.4.0 kernel:

Good job.

> Pentiums are only lucky to not crash because they have a bigger TLB than 386s.

Actually, with the 4M pages, it's not a question of luck any more - they
just don't _have_ this bug, because on a machine with 4M pages the
"cpu_has_pse" case handles this all and the buggy code is never actually
entered.

Which explains why you'd only see this on a 386 (and I suspect your TLB
size explanation is what saved some i486-class machines, although later
i486 machines will have PSE as well).

	Thanks,

		Linus

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Re: Anybody got 2.4.0 running on a 386 ?

[Timur Tabi]

** Reply to message from Robert Kaiser <rob@sysgo.de> on Tue, 9 Jan 2001
23:17:11 +0100


> temp = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> 	*pte = temp;
> 
> where temp is declared "volatile pte_t". I inserted test-prints between the
> above two lines. Accoding to that, the _first_ line , i.e. the evaluation of the
> mk_pte_phys() macro is causing the crash!

In that case, it's either a compiler bug or a race condition.

Compiling this source file with the -S option will generate an assembly output.
The output should be the same regardless of whether you use the temp variable or
not.  That will answer the question as to what the cause is.  If you're lucky,
it's a compiler bug, because they're easier to fix.


-- 
Timur Tabi - ttabi@interactivesi.com
Interactive Silicon - http://www.interactivesi.com

When replying to a mailing-list message, please direct the reply to the mailing list only.  Don't send another copy to me.
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Re: Anybody got 2.4.0 running on a 386 ?

[Brian Gerst]

Robert Kaiser wrote:
> 
> On Die, 09 Jan 2001 you wrote:
> > Robert Kaiser wrote:
> > > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > > I tried three different 386 boards. Execution seems to get as far as
> > > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > > if someone had pressed the reset button. The same kernel boots fine on
> > > 486 and Pentium Systems.
> > >
> > > Any ideas/suggestions ?
> >
> >
> > is "Checking if this processor honours the WP bit even in supervisor
> > mode... " the last thing you see before the reset?
> >
> 
> No, I don't see _any_ messages from the kernel. The last thing I see is
> "Uncompressing Linux... Ok, booting the kernel." I have added some
> quick and dirty debug code that writes messages directly to the VGA
> screen buffer. According to that, execution seems to get as far as the
> statement
> 
>         *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);

How about this patch (untested)?  max_low_pfn should be a global var...

diff -urN linux-2.4.0/arch/i386/kernel/setup.c
linux/arch/i386/kernel/setup.c
--- linux-2.4.0/arch/i386/kernel/setup.c        Sun Dec 31 13:26:18 2000
+++ linux/arch/i386/kernel/setup.c      Tue Jan  9 17:59:00 2001
@@ -598,7 +598,7 @@
 void __init setup_arch(char **cmdline_p)
 {
        unsigned long bootmap_size;
-       unsigned long start_pfn, max_pfn, max_low_pfn;
+       unsigned long start_pfn, max_pfn;
        int i;

 #ifdef CONFIG_VISWS

--

				Brian Gerst
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Re: Anybody got 2.4.0 running on a 386 ?

[mo6]

On Tue, Jan 09, 2001 at 10:17:47PM +0100, Robert Kaiser wrote:
> On Die, 09 Jan 2001 you wrote:
> > Robert Kaiser wrote:
> > > I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> > > The kernel was built for a 386 Processor, Math emulation has been enabled.
> > > I tried three different 386 boards. Execution seems to get as far as
> > > pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> > > if someone had pressed the reset button. The same kernel boots fine on
> > > 486 and Pentium Systems.
> > > 
> > > Any ideas/suggestions ?
> > 
> > 
> > is "Checking if this processor honours the WP bit even in supervisor
> > mode... " the last thing you see before the reset?
> > 
> 
> No, I don't see _any_ messages from the kernel. The last thing I see is
> "Uncompressing Linux... Ok, booting the kernel." 

I dug up an old amd 386 and started compiling kernels for it with gcc 2.95.2:

2.4.0 : doesn't boot, same symptoms as you, Robert, so you're not imagining 
	things :-)
2.2.19pre6 : compiles, boots and runs poifectly
2.3.51 : doesn't compile
2.3.99-pre1 : hrm, *cough*
2.3.99-pre2 : *tsjoum*
2.3.39: compiles and boots okay

here is where I got bored :-)

okay, anyone, which 2.3.x kernels should compile okay ?

With kind regards,
Sven
-- 
If the odds are a million to one against something occurring, chances
are 50-50 it will.
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Re: Anybody got 2.4.0 running on a 386 ?

[Brian Gerst]

mo6 wrote:
> I dug up an old amd 386 and started compiling kernels for it with gcc 2.95.2:
> 
> 2.4.0 : doesn't boot, same symptoms as you, Robert, so you're not imagining
>         things :-)
> 2.2.19pre6 : compiles, boots and runs poifectly
> 2.3.51 : doesn't compile
> 2.3.99-pre1 : hrm, *cough*
> 2.3.99-pre2 : *tsjoum*
> 2.3.39: compiles and boots okay
> 
> here is where I got bored :-)
> 
> okay, anyone, which 2.3.x kernels should compile okay ?

move up to 2.4.0-testX kernels

--

				Brian Gerst
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Re: Anybody got 2.4.0 running on a 386 ?

[mo6]

On Wed, Jan 10, 2001 at 03:18:41PM -0500, Brian Gerst wrote:
> 
> move up to 2.4.0-testX kernels

I just tested 2.4.0-test1, it doesn't boot on the 386 with the same symptoms 
as 2.4.0.

2.3.99-pre9 same.

2.3.99-pre8 is the last one that boots correctly.

There is one weird thing I notice, the vga-bios-screen at boot-up is
monochrome every other automatic reboot.

with kind regards,

Sven
-- 
If the odds are a million to one against something occurring, chances
are 50-50 it will.
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Re: Anybody got 2.4.0 running on a 386 ?

[mo6]

On Tue, Jan 09, 2001 at 10:17:47PM +0100, Robert Kaiser wrote:
> On Die, 09 Jan 2001 you wrote:
> > Robert Kaiser wrote:
> > > if someone had pressed the reset button. The same kernel boots fine on
> > > 486 and Pentium Systems.
> > > 
> > > Any ideas/suggestions ?
> > 
> > 
> > is "Checking if this processor honours the WP bit even in supervisor
> > mode... " the last thing you see before the reset?
> > 
> 
> No, I don't see _any_ messages from the kernel. The last thing I see is
> "Uncompressing Linux... Ok, booting the kernel." I have added some
> quick and dirty debug code that writes messages directly to the VGA
> screen buffer. According to that, execution seems to get as far as the
> statement
> 
>         *pte = mk_pte_phys(__pa(vaddr), PAGE_KERNEL);
> 

Changing the 
	if( end && (vaddr >= end))
		break;
just before that snippet of yours (I believe it's on lines 379-380) into
	if (vaddr >= end)
		break;
or alternatively adding
	if (!end)
		break;
between if(end &&...) break; and *pte = mk_...; produces a kernel bootable 
on 386.

With kind regards,

Sven Joos			    
-- 
If the odds are a million to one against something occurring, chances
are 50-50 it will.
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Re: Anybody got 2.4.0 running on a 386 ?

[Tom Leete]

Robert Kaiser wrote:
> 
> Hi list,
> 
> I can't seem to get the new 2.4.0 kernel running on a 386 CPU.
> The kernel was built for a 386 Processor, Math emulation has been enabled.
> I tried three different 386 boards. Execution seems to get as far as
> pagetable_init() in arch/i386/mm/init.c, then it falls back into the BIOS as
> if someone had pressed the reset button. The same kernel boots fine on
> 486 and Pentium Systems.
  ^^^
> 
> Any ideas/suggestions ?
> 
> Rob
> 

This may be off the wall, but since the 386 is diskless the kernel was
obviously built elsewhere. Had that tree previously been used for a 486
build? You might decompile vmlinux and look for non-386 instructions at or
prior to the crash point.

It might be faster to recompile from 'make mrproper' and see if it works
then.

Tom
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