[PATCH -mm -v4 0/3] i386/x86_64 boot: 32-bit boot protocol

[PATCH -mm -v4 0/3] i386/x86_64 boot: 32-bit boot protocol

[Huang, Ying]

This patchset defines a 32-bit boot protocol for i386/x86_64 platform,
adds an extensible boot parameter passing mechanism, export the boot
parameters via sysfs.

The patchset has been tested against 2.6.23-rc8-mm2 kernel on x86_64
and i386.

This patchset is based on the proposal of Peter Anvin.


Known Issues:

- Where is safe to place the linked list of setup_data?  Because the
  length of the linked list of setup_data is variable, it can not be
  copied into BSS segment of kernel as that of "zero page". We must
  find a safe place for it, where it will not be overwritten by kernel
  during booting up. The i386 kernel will overwrite some pages after
  _end. The x86_64 kernel will overwrite some pages from 0x1000 on.

- The fields in zero page are fairly complex (such as struct
  edd_info). Is it necessary to document every field inside the first
  level fields, until the primary data type? Or is it sufficient to
  provide the C struct name only?

- Which fields of boot parameters should be exported directly in
  sysfs? Export all fields of boot parameters in sysfs is too complex
  and unnecessary. Which fields should be?


-v4

* Reserve setup_data and boot parameters for accessing during
  runtime.
* Export boot parameters via sysfs.

-v3

* Move hd0_info and hd1_info back to zero page for compatibility.

-v2

* Increase the boot protocol version number
* Check version number before parsing setup data.
* Revise zero page description according to the source code and move
  them to zero-page.txt.


Best Regards,
Huang Ying

Re: [PATCH -mm -v4 0/3] i386/x86_64 boot: 32-bit boot protocol

[H. Peter Anvin]

Huang, Ying wrote:
> 
> - Which fields of boot parameters should be exported directly in
>   sysfs? Export all fields of boot parameters in sysfs is too complex
>   and unnecessary. Which fields should be?
> 

The main this is that since this is a fixed-format, ABI-defined 
structure, regardless of individual fields it should be exported as a 
binary object.  That is also the only way to deal with a kernel which 
may not itself know about specific items making the data available to 
other users, like kexec.

It's not clear to me from reading the code what model you're using for 
exporting this data in sysfs.  Could you describe it in some detail?

What I had envisioned would be an object for the boot_params structure 
and a systematic object for each linked-list object, at a very minimum.

	-hpa

Re: [PATCH -mm -v4 0/3] i386/x86_64 boot: 32-bit boot protocol

[Huang, Ying]

On Tue, 2007-10-09 at 12:23 -0700, H. Peter Anvin wrote:
> Huang, Ying wrote:
> > 
> > - Which fields of boot parameters should be exported directly in
> >   sysfs? Export all fields of boot parameters in sysfs is too complex
> >   and unnecessary. Which fields should be?
> > 
> 
> The main this is that since this is a fixed-format, ABI-defined 
> structure, regardless of individual fields it should be exported as a 
> binary object.  That is also the only way to deal with a kernel which 
> may not itself know about specific items making the data available to 
> other users, like kexec.
> 
> It's not clear to me from reading the code what model you're using for 
> exporting this data in sysfs.  Could you describe it in some detail?
> 
> What I had envisioned would be an object for the boot_params structure 
> and a systematic object for each linked-list object, at a very minimum.
> 

OK. The directory structure is as follow:

+ sys + kernel + boot_params - version			/* version of boot protocol */
                             - data			/* binary file of boot_params */
                             + setup_data + 0 - type	/* type id of setup_data 0 */
                                              - data	/* binary file of setup_data 0 */
                                          + 1 - type	/* type id of setup_data 1 */
                                              - data	/* binary file of setup_data 1 */
                                          + 2 - type
                                              - data
                                          ...

Best Regards,
Huang Ying

Re: [PATCH -mm -v4 0/3] i386/x86_64 boot: 32-bit boot protocol

[H. Peter Anvin]

Huang, Ying wrote:
> On Tue, 2007-10-09 at 12:23 -0700, H. Peter Anvin wrote:
>> Huang, Ying wrote:
>>> - Which fields of boot parameters should be exported directly in
>>>   sysfs? Export all fields of boot parameters in sysfs is too complex
>>>   and unnecessary. Which fields should be?
>>>
>> The main this is that since this is a fixed-format, ABI-defined 
>> structure, regardless of individual fields it should be exported as a 
>> binary object.  That is also the only way to deal with a kernel which 
>> may not itself know about specific items making the data available to 
>> other users, like kexec.
>>
>> It's not clear to me from reading the code what model you're using for 
>> exporting this data in sysfs.  Could you describe it in some detail?
>>
>> What I had envisioned would be an object for the boot_params structure 
>> and a systematic object for each linked-list object, at a very minimum.
>>
> 
> OK. The directory structure is as follow:
> 
> + sys + kernel + boot_params - version			/* version of boot protocol */
>                              - data			/* binary file of boot_params */
>                              + setup_data + 0 - type	/* type id of setup_data 0 */
>                                               - data	/* binary file of setup_data 0 */
>                                           + 1 - type	/* type id of setup_data 1 */
>                                               - data	/* binary file of setup_data 1 */
>                                           + 2 - type
>                                               - data
>                                           ...
> 

Looks good to me.

	-hpa