Syslinux - Aug 2002 - memdisk and grub

Hi,

I am trying to use MEMDISK from the GRUB boot loader, and gets stuck on the 
memory detection. MEMDISK reports

  dos_mem = 0
  low_mem = 0
  high_mem = 0

Henrik Nordstrom wrote:
> Hi,
> 
> I am trying to use MEMDISK from the GRUB boot loader, and gets stuck on the
> memory detection. MEMDISK reports
> 
>   dos_mem = 0
>   low_mem = 0
>   high_mem = 0
> 
>>From reading the sources this would be if the e820 query does not return
any
> valid data. Confirmed by adding a printf in insertrange(). insertrange()
does
> not seem to be called at all during the memory detection (only to reserve
the
> ramdisk memory before MEMDISK bails out)
> 
> However, when booting a Linux kernel the Linux kernel does detect a e820
BIOS
> memory map that looks pretty OK to me:
> 
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000000 - 00000000000a0000 (usable)
>  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 000000000fe00000 (usable)
>  BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved)
> user-defined physical RAM map:
>  user: 0000000000000000 - 00000000000a0000 (usable)
>  user: 00000000000f0000 - 0000000000100000 (reserved)
>  user: 0000000000100000 - 000000000fe00000 (usable)
>  user: 00000000ffff0000 - 0000000100000000 (reserved)
> 
This is probably because GRUB likes to mess with the memory map instead
of letting the kernel do the right thing (hence the "user-defined
physical RAM map".)  This is a total braindamage in GRUB.

	-hpa

Hmm.. added lots of debug printf in get_e820(), and all of a sudden it works. 
Looks like a problem with the assembly code or my build environment (RedHat 
7.3 with official upgrades/fixes).

I see that there is a prebuild memdisk in the tar ball (didn't notice this
at
first), and I can confirm that this works just fine. Why didn't I try this 
first of all things?

Regards
Henrik



enrik Nordstrom wrote:
> Hi,
>
> I am trying to use MEMDISK from the GRUB boot loader, and gets stuck on the
> memory detection. MEMDISK reports
>
>   dos_mem = 0
>   low_mem = 0
>   high_mem = 0
>
> From reading the sources this would be if the e820 query does not return
> any valid data. Confirmed by adding a printf in insertrange().
> insertrange() does not seem to be called at all during the memory detection
> (only to reserve the ramdisk memory before MEMDISK bails out)
>
> However, when booting a Linux kernel the Linux kernel does detect a e820
> BIOS memory map that looks pretty OK to me:
>
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000000 - 00000000000a0000 (usable)
>  BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 000000000fe00000 (usable)
>  BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved)
> user-defined physical RAM map:
>  user: 0000000000000000 - 00000000000a0000 (usable)
>  user: 00000000000f0000 - 0000000000100000 (reserved)
>  user: 0000000000100000 - 000000000fe00000 (usable)
>  user: 00000000ffff0000 - 0000000100000000 (reserved)
>
>
> Any clues on where to look next?
>
> Regards
> Henrik
>
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