Re: [PATCH v4 02/19] kho: block: Record the entry size in the block header

[David Matlack]

On Tue Nov 10, 2026 at 5:01 AM UTC, Tarun Sahu wrote:
> Add an entry_size field to struct kho_block_header_ser. On the outgoing
> side, record bs->entry_size into every block header during allocation.
> During restoration, derive the entry stride directly from the block
> header instead of relying on caller-supplied dimensions. The
> kho_block_set_init() interface remains unchanged. A zero entry size,

Since the entry size now comes from the block headers, incoming block
sets should not take an entry size at all. I pointed this out on the
PCI patch (16/19) as well. As is, every incoming path still calls
kho_block_set_init() with this kernel's (outgoing) entry size, which
kho_block_set_restore() then silently overwrites. That makes the
callers (e.g. pci_flb_retrieve() and the LUO session/file restore
paths) read as if they iterate incoming entries with the outgoing entry
size. kho_block_set_restore() should initialize the block set itself
from the incoming block headers, and the incoming paths should drop the
kho_block_set_init() call.

Please also add an accessor for the entry size, e.g.
kho_block_set_entry_size(). Users of the block set need it to check that
incoming entries are large enough for the fields they read, and that
the fields of a feature are within the entry.

[...]

> + * Each block header also records the size of its entries. A newer kernel may
> + * append fields to an entry, so the kernel that writes a block and the kernel
> + * that reads it can use different entry sizes. The reader steps through the
> + * entries with the recorded size, so every entry is found, and it does not read
> + * beyond the recorded size of an entry.

KHO blocks can't guarantee the last part. The iterator returns a void *
that the caller casts to its own struct, so it is up to the caller to
not read fields beyond the entry size. Please document that callers must
check the entry size before accessing fields that may not be present.