[syslinux] KRNLINUX? CPIOLINUX?
Shao Miller
Shao.Miller at yrdsb.edu.on.ca
Mon Sep 5 13:19:29 PDT 2011
On 9/5/2011 15:56, H. Peter Anvin wrote:
> On 09/05/2011 08:19 AM, Shao Miller wrote:
>>
>> Also: Do we make this a "cpio FS" driver that uses the block-caching
>> abstraction (and hook the disk I/O to actually do memory access,
>> instead) or do we make this an "initramfs" driver that will never allow
>> for supporting initramfs on a disk, but only in memory? I could see a
>> use for the former, if we every wish to allow "mounting" initramfs files
>> that are not in memory, but it seems a tad more complicated.
>>
>
> The big problem here is of course that the cpio images are extremely
> unlikely to be aligned.
True. I'm thinking that the hash table you suggested could index nodes
with a starting block and an offset. In pcacjr's NTFS work, there's
lots of computations between blocks, clusters, sectors, MFT records,
etc. I guess we just lose out on any meaningful mapping between "files"
and "blocks" (or even sectors).
...Or maybe a 4-byte block size could work. Ha! Imagine an INT 0x13
hook that reported _that_ to consumers!
The [eventual] Linux x86 kernel format Syslinux payload could hard-wire
the root FS block device to memory, as we agree.
Now do we walk the whole initramfs with a one-time pass and build the
hash table, or do we build it as-needed? With the former, we're slow to
start. With the latter, we're slow if we process multiple files.
- Shao Miller
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