Re: [Syllable-kernel] Special handling for >1GB RAM and loading apps at 0x04000000 not 0x80000000?

[Jake H. <jh...@an...>]

Kristian Van Der Vliet wrote:

> I think Jake is on the right track, provided we get the issues correctly 
> solved.  We have to be realistic and foreign binary support will be an issue 
> once we hit a certain point.  There is no sense in limiting ourselves.
> 
> Getting create_area() shouldn't be too tough, nor should fixing the device 
> drivers.  It might be a good idea to add a MEMF_DMA flag to kmalloc() that in 
> turn uses AREA_CONTIGOUS, so at least we don't need to make big changes to 
> the existing code base.  Also note that nothing should be calling 
> get_free_pages() directly; the emu10k1 driver hacks it up but shouldn't be 
> doing it.  Henrik used it to get a page aligned area but it should really be 
> using the PAGE_ALIGN() macro..
> 
> We already knew that Syllable wouldn't boot with systems of 2Gb or more, 
> exactly because of that 1:1 kernel memory mapping.  For that reason alone 
> it's good enough to move everything around and load the kernel at 0xc0000000 
> (Could there possibly be a good reason for using more than 1Gb of virtual 
> address space in a desktop OS kernel?  None I can think of).  At todays 
> growth rate 2Gb+ machines as standard are not far off.  There is also some 
> good news; current applications are compiled with -fPIC by default.  
> Theoretically we don't even need any special case handling for old binaries; 
> just load them at 0x08000000.

Cool, now I know what has to be done.  Unfortunately, something else has 
broken since I upgraded my RAM: the vm86 code to call BIOS routines.  At 
least three BIOS calls are now failing for me:


1) the e820 memory map retrieved in init_e820_memory_map() is giving an 
"ERROR : unknown v86 16 bit instruction 7c"

2) the ps2mouse probing gives an "unknown v86 16 bit instruction 2"

3) the APM power-off code has also stopped working.


If anyone is experiencing similar problems after building a recent 
kernel, please let me know.  I hope this isn't something that I broke 
somehow with one of my changes.  I've added some printk() statements so 
you should now see a dump of the BIOS memory map if you search 
/var/log/kernel for "BIOS-e820", and each BIOS call will be traced with 
a line like "sys_realint(21) -> f000:6ac8".

-Jake