[PROPOSAL] extended payload handling

Greg Watson gwatson at lanl.gov
Tue Jun 8 07:58:00 CEST 2004


I think this is a reasonable idea, particularly your suggestion of 
making linuxbios more modular. One of my main beefs with the payload 
strategy is that each payload has to provide it's own set of, 
potentially buggy, driver code. If we have 5 payloads then we have 5 
sets of drivers that all do the same thing slightly differently. If the 
drivers were modular enough so that a payload could call them directly, 
then this would go a long way to addressing these concerns.



On Jun 8, 2004, at 4:49 AM, Stefan Reinauer wrote:

> There has been a similar proposal on this list a while ago, but nothing
> happened so far, so I want to put this pack to discussion.
> Objectives
> ----------
> 1.)
> LinuxBIOS is kind of hard to set up for project newbies, since it
> does not only require manually tweaking the configuration files for
> basically every situation, but also necessarily needs an external
> payload to do anything useful.
> LinuxBIOS currently sets a high barrier due to the modular concepts it
> uses.
>  - LinuxBIOS itself is sometimes very sensitive to the build
>    environment. See requirement for setting LANG for example.
>  - For a project outsider it is hard to determine the best payload
>    solution for a specific purpose. There is basically no information
>    except the mailing list archives.
>  - Config files have to be tweaked to explicitly suit the user's
>    directory structure. There is no proposal, nothing that works out of
>    the box. One just _has to_ edit the config files.
>  - LinuxBIOS requires the user to specify a size for the payload 
> instead
>    of determining the required size and doing the needed calculations
>    itself. This is very hand-crufted and can be pretty mind wasting.
> 2.)
> LinuxBIOS can currently execute one payload. For greater flexibility 
> and
> isolated development cycles of the firmware related code parts/projects
> LinuxBIOS should allow payload chains, ie. executing multiple payloads
> one after the other.
> LinuxBIOS wants to keep up it's modularity, letting each module do it's
> job. This possibility of not doing more than one task should be passed
> on to the payloads.
> Solution
> --------
> Feature plugins like "testbios" should not be merged into LinuxBIOS'
> core code. Instead they should be implemented as a payload. Since we
> want to load an operating system later on, we also need to be able to
> load more than one payload. Implementing ELFLOAD in each such plugin is
> inadequate. Instead LinuxBIOS should execute multiple payloads the same
> way it executes multiple "drivers" now.
>  * LinuxBIOS therefore needs a way to automatically determine payload
>    sizes when building the image and later when executing payloads.
>    Hardcoding the size values in the config files is inadequate and 
> will
>    lead to unnecessary overhead
>  * LinuxBIOS at runtime needs to go through the list of available
>    payloads, either by having a linked list of payload start points
>    or by scanning the flash rom.
>  * LinuxBIOS should, to be consequent, remove all streaming code except
>  * Payloads should have the possibility to add their own enhancements 
> to
>    the LinuxBIOS table.
>  * A least one payload should be "default payload" with the possibility
>    to build this automatically and link it into the image.
>    This is why I checked the "util/extensions" directory into v2 during
>    the last discussion. It should hold possible choices to payloads 
> that
>    can automatically be built and included. Potentially one could add
>    more payloads by symlinking their source tree to this directory to 
> make
>    it available to LinuxBIOS without major reconfiguration.
>    People feel a lot safer with creating a symlink than with changing
>    config files they do not fully understand.
>    Since these can later be executed in row by elfboot, the minimum
>    overhead design of LinuxBIOS itself will not be hurt.
>    At this point I want to put an idea to discussion: If we are going
>    more and more modular and some of us think the current tree is too
>    bloated: Why do we not modularize code like pci resource allocation
>    into a payload as well. My favorite bootloader may already do this
>    and I can't stand this bloat everywhere, you know ;) Even though 
> this
>    may sound funny, I am serious about this issue. I do not see why
>    allocating PCI resources should really be part of the lowlevel code,
>    except for the fact that the NEXT payload in row, potentially Linux
>    itself is too stupid to do that. Bummer.
>  * LinuxBIOS configuration should have an easier mechanism for choosing
>    payloads from the "default" directory, allowing them to be built
>    automatically. Right now I am doing:
>      cd filo-0.4.2
>      linux32 make CC="gcc -m32" LD="ld -melf_i386"
>      cd ..
>      freebios2/targets/buildtarget amd/solo $PWD/freebios2
>      cd build-solo
>      make
>      cd ..
>      cp build-solo/solo.rom .
>    My target Config.lb comes with these constructs:
>      target  ../../../../build-solo
>      payload ../../filo-0.4.2/filo.elf
>    So I build everything completely out of the freebios2 tree, because
>    building in-tree sucks. The only thing left is to get filo and the
>    other payloads to build out-of-tree as well.
> Comments?
> Discussion?
> Assassination attempts?
>      Stefan
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