pxeboot broken by commit "x86 setup: handle boot loaders which set up the stack incorrectly"

pxeboot broken by commit "x86 setup: handle boot loaders which set up the stack incorrectly"

[Yinghai Lu]

commit 6b6815c6d5d1dc209701d1661a7a0e09a295db2f
Author: H. Peter Anvin <hpa@zytor.com>
Date:   Thu Oct 25 16:11:33 2007 -0700

    x86 setup: handle boot loaders which set up the stack incorrectly

    Apparently some specific versions of LILO enter the kernel with a
    stack pointer that doesn't match the rest of the segments.  Make our
    best attempt at untangling the resulting mess.

    Signed-off-by: H. Peter Anvin <hpa@zytor.com>


with that commit:

Linux version 2.6.24-rc1-smp-g2655e2ce-dirty
(yhlu@mpk12-office-77-204) (gcc version 4.2.1 (SUSE Linux)) #15 SMP
Tue Nov 6 15:42:01 PST 2007
Command line: console=uart8250,io,0x3f8,9600n8
initrd=kernel.org/mydisk10.3_x86_64.gz rw root=/dev/ram0 debug
apic=debug acpi.debug_level=0x0000000f p

without the commit:
Linux version 2.6.24-rc1-smp-g2655e2ce-dirty
(yhlu@mpk12-office-77-204) (gcc version 4.2.1 (SUSE Linux)) #15 SMP
Tue Nov 6 15:42:01 PST 2007
Command line: console=uart8250,io,0x3f8,9600n8
initrd=kernel.org/mydisk10.3_x86_64.gz rw root=/dev/ram0 debug
apic=debug acpi.debug_level=0x0000000f pci=routeirq ip=dhcp
load_ramdisk=1 ramdisk_size=131072
BOOT_IMAGE=kernel.org/bzImage_2.6.24_k8.7

pxeboot entry:
label k
kernel kernel.org/bzImage_2.6.24_k8.7
append console=uart8250,io,0x3f8,9600n8
initrd=kernel.org/mydisk10.3_x86_64.gz rw root=/dev/ram0 debug
apic=debug acpi.debug_level=0x0000000f pci=routeirq ip=dhcp
load_ramdisk=1 ramdisk_size=131072

YH

Re: pxeboot broken by commit "x86 setup: handle boot loaders which set up the stack incorrectly"

[Yinghai Lu]

On Nov 6, 2007 11:08 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> Ah, right - this was a longstanding bug in syslinux which was fixed in 3.50-pre7.  The workaround for abug in old LILO exposed a bug in old syslinux.  Joy.
>
> --
> Sent from my cellphone (pardon any lack of formatting)
>
>
> -----Original Message-----
> From: Yinghai Lu <yhlu.kernel@gmail.com>
> Sent: Tuesday, November 06, 2007 20:12
> To: H. Peter Anvin <hpa@zytor.com>
> Subject: Re: pxeboot broken by commit "x86 setup: handle boot loaders which set up the stack incorrectly"
>
>
> On Nov 6, 2007 6:49 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> > Could you check if 3.52 is affected as well?
> >
> > --
> 3.52 works
>
> YH
>
>

good to know. everyone need to update to 3.52 now...
but i still can not understand why that mcp55 system works but the
ck804 based doesn't on 3.10

YH

Re: pxeboot broken by commit "x86 setup: handle boot loaders which set up the stack incorrectly"

[H. Peter Anvin]

Yinghai Lu wrote:
> 
> good to know. everyone need to update to 3.52 now...
> but i still can not understand why that mcp55 system works but the
> ck804 based doesn't on 3.10
> 

The bug is that syslinux incorrectly positions the stack above the 
command line (but not the stack pointer register; hence the kernel patch 
exposing this bug.)  So the stack plus command line end up being limited 
  to 512 bytes; how much stack gets used depends on the BIOS, so one 
BIOS may use a lot more than another.

	-hpa