elfboot

[Eric W. Biederman]

Xavier Pegenaute <xpegenaute at telepolis.es> writes:

> Hi,
> 
> 
> On Tue, 2003-07-08 at 02:03, Eric W. Biederman wrote:
> > > 1) We want start an ELF binary (not payload) that is in DoC (p.e.) after
> > > LinuxBios. Then we execute elfboot() that look inside the ROM for the
> > > next code starting with a valid ELF header, build the segments, copy the
> > > segments and give the control to the program.
> > > 
> > > No problem in this case, i think.
> > 
> > Sounds like standard use.
> > 
> > > 2) We want start a Linux Kernel that is recorded (neither payload) after
> > > LinuxBios binary in DoC (p.e.), then we execute linuxbiosmain() and in
> > > the end of this function we make a long jump to 0x90000.
> > 
> > Linuxbiosmain() is deprecated code and it always jumps to 0x100000 1MB.
> > Anything is not done.  And everyone is encouraged not to use linuxbiosmain
> > for new deployments.
> > 
> > > Here, i don't see what function in linuxbiosmain() copy the code of
> > > Kernel to DRAM.Any one know it ?
> > 
> > It is the gunzip part.  But please don't use that.
> 
> The problem, is that, if i follow the instructions of
> freebios/HOWTO/SiS630, the linux kernel binary generated doesn't has
> elfheader.
>
> Then if i want to use the standard use, i have apply some external
> utility to generate an elf file (mkelfImage) and put in config file
> "fileoption USE_ELF_BOOT=1". Is it right ?

Essentially correct.  MkelfImage takes a standard x86 linux kernel and
wraps so it is a bootable ELF executable.

The latest mkelfImage can be found at:

ftp://ftp.lnxi.com/pub/mkelfImage/

> Another think, i thought that the Linux Kernel alone has the code to
> decompress himself (in the same way that we can put Kernel in a floppy
> disk and it decompress alone. (dd if=kernel of=/dev/fd0))

The strange choices in linuxbios main where it decompresses the kernel
instead of using the kernels own decompressor, are among the many
reasons it is deprecated.

Eric