[PATCH v5 3/3] luo: Update serialized data to use KHOSER_PTR
tarunsahu at google.com
tarunsahu at google.com
Tue Jun 23 13:17:09 PDT 2026
Thanks for reviewing!
Pratyush Yadav <pratyush at kernel.org> writes:
> On Tue, Jun 23 2026, Tarun Sahu wrote:
>
>> Convert raw serialized_data to KHO serializeable pointer (KHOSER_PTR).
>> This series also takes care of resolving the bug with memfd of using
>> phys_to_virt before checking the args->serialized_data value.
>>
>> Signed-off-by: Tarun Sahu <tarunsahu at google.com>
>> Acked-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
>> ---
>> include/linux/kho/abi/luo.h | 5 +++--
>> include/linux/liveupdate.h | 4 ++--
>> kernel/liveupdate/luo_file.c | 24 ++++++++++++------------
>> mm/memfd_luo.c | 20 +++++++++++---------
>> 4 files changed, 28 insertions(+), 25 deletions(-)
>>
>> diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
>> index 288076de6d4a..d5b3b1c0fec1 100644
>> --- a/include/linux/kho/abi/luo.h
>> +++ b/include/linux/kho/abi/luo.h
>> @@ -59,6 +59,7 @@
>>
>> #include <linux/align.h>
>> #include <linux/kho/abi/block.h>
>> +#include <linux/kho/abi/kexec_handover.h>
>> #include <uapi/linux/liveupdate.h>
>>
>> /*
>> @@ -89,14 +90,14 @@ struct luo_ser {
>> /**
>> * struct luo_file_ser - Represents the serialized preserves files.
>> * @compatible: File handler compatible string.
>> - * @data: Private data
>> + * @serialized_data: The serialized pointer union for this file
>
> Nit: "serialized pointer union" makes very little sense once you lose
> the context of this patch. The union is an implementation detail. I
> think "serialized KHO pointer" makes more sense from documentation
> perspective.
Ack.
>
>> * @token: User provided token for this file
>> *
>> * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
>> */
>> struct luo_file_ser {
>> char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
>> - u64 data;
>> + DECLARE_KHOSER_PTR(serialized_data, void *);
>> u64 token;
>> } __packed;
>>
>> diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
>> index 88722e5caf02..480d638b7d18 100644
>> --- a/include/linux/liveupdate.h
>> +++ b/include/linux/liveupdate.h
>> @@ -33,7 +33,7 @@ struct file;
>> * @file: The file object. For retrieve: [OUT] The callback sets
>> * this to the new file. For other ops: [IN] The caller sets
>> * this to the file being operated on.
>> - * @serialized_data: The opaque u64 handle, preserve/prepare/freeze may update
>> + * @serialized_data: The serialized pointer union, preserve/prepare/freeze may update
>
> Nit: Same here.
>
>> * this field.
>> * @private_data: Private data for the file used to hold runtime state that
>> * is not preserved. Set by the handler's .preserve()
>> @@ -47,7 +47,7 @@ struct liveupdate_file_op_args {
>> struct liveupdate_file_handler *handler;
>> int retrieve_status;
>> struct file *file;
>> - u64 serialized_data;
>> + DECLARE_KHOSER_PTR(serialized_data, void *);
>> void *private_data;
>> };
>>
>> diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
>> index c39f96961a85..aecf19033f95 100644
>> --- a/kernel/liveupdate/luo_file.c
>> +++ b/kernel/liveupdate/luo_file.c
>> @@ -125,7 +125,7 @@ static DEFINE_XARRAY(luo_preserved_files);
>> * @file: Pointer to the kernel's &struct file that is being preserved.
>> * This is NULL in the new kernel until the file is successfully
>> * retrieved.
>> - * @serialized_data: The opaque u64 handle to the serialized state of the file.
>> + * @serialized_data: The serialized pointer union to the serialized state of the file.
>> * This handle is passed back to the handler's .freeze(),
>> * .retrieve(), and .finish() callbacks, allowing it to track
>> * and update its serialized state across phases.
>> @@ -161,7 +161,7 @@ static DEFINE_XARRAY(luo_preserved_files);
>> struct luo_file {
>> struct liveupdate_file_handler *fh;
>> struct file *file;
>> - u64 serialized_data;
>> + DECLARE_KHOSER_PTR(serialized_data, void *);
>> void *private_data;
>> int retrieve_status;
>> struct mutex mutex;
>> @@ -289,7 +289,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
>> if (err)
>> goto err_kfree;
>>
>> - luo_file->serialized_data = args.serialized_data;
>> + KHOSER_COPY_PTR(luo_file->serialized_data, args.serialized_data);
>> luo_file->private_data = args.private_data;
>> list_add_tail(&luo_file->list, &file_set->files_list);
>> file_set->count++;
>> @@ -342,7 +342,7 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
>>
>> args.handler = luo_file->fh;
>> args.file = luo_file->file;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> args.private_data = luo_file->private_data;
>> luo_file->fh->ops->unpreserve(&args);
>> luo_flb_file_unpreserve(luo_file->fh);
>> @@ -375,12 +375,12 @@ static int luo_file_freeze_one(struct luo_file_set *file_set,
>>
>> args.handler = luo_file->fh;
>> args.file = luo_file->file;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> args.private_data = luo_file->private_data;
>>
>> err = luo_file->fh->ops->freeze(&args);
>> if (!err)
>> - luo_file->serialized_data = args.serialized_data;
>> + KHOSER_COPY_PTR(luo_file->serialized_data, args.serialized_data);
>> }
>>
>> return err;
>> @@ -396,7 +396,7 @@ static void luo_file_unfreeze_one(struct luo_file_set *file_set,
>>
>> args.handler = luo_file->fh;
>> args.file = luo_file->file;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> args.private_data = luo_file->private_data;
>>
>> luo_file->fh->ops->unfreeze(&args);
>> @@ -483,7 +483,7 @@ int luo_file_freeze(struct luo_file_set *file_set,
>>
>> strscpy(file_ser->compatible, luo_file->fh->compatible,
>> sizeof(file_ser->compatible));
>> - file_ser->data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(file_ser->serialized_data, luo_file->serialized_data);
>> file_ser->token = luo_file->token;
>> }
>>
>> @@ -587,7 +587,7 @@ int luo_retrieve_file(struct luo_file_set *file_set, u64 token,
>> }
>>
>> args.handler = luo_file->fh;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> err = luo_file->fh->ops->retrieve(&args);
>> if (err) {
>> /* Keep the error code for later use. */
>> @@ -621,7 +621,7 @@ static int luo_file_can_finish_one(struct luo_file_set *file_set,
>>
>> args.handler = luo_file->fh;
>> args.file = luo_file->file;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> args.retrieve_status = luo_file->retrieve_status;
>> can_finish = luo_file->fh->ops->can_finish(&args);
>> }
>> @@ -638,7 +638,7 @@ static void luo_file_finish_one(struct luo_file_set *file_set,
>>
>> args.handler = luo_file->fh;
>> args.file = luo_file->file;
>> - args.serialized_data = luo_file->serialized_data;
>> + KHOSER_COPY_PTR(args.serialized_data, luo_file->serialized_data);
>> args.retrieve_status = luo_file->retrieve_status;
>>
>> luo_file->fh->ops->finish(&args);
>> @@ -748,7 +748,7 @@ static int luo_file_deserialize_one(struct luo_file_set *file_set,
>>
>> luo_file->fh = fh;
>> luo_file->file = NULL;
>> - luo_file->serialized_data = ser->data;
>> + KHOSER_COPY_PTR(luo_file->serialized_data, ser->serialized_data);
>> luo_file->token = ser->token;
>> mutex_init(&luo_file->mutex);
>> list_add_tail(&luo_file->list, &file_set->files_list);
>> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
>> index 10f3983b0060..852b61678229 100644
>> --- a/mm/memfd_luo.c
>> +++ b/mm/memfd_luo.c
>> @@ -257,6 +257,7 @@ static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,
>>
>> static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
>> {
>> + DECLARE_KHOSER_PTR(sd, struct memfd_luo_ser *);
>> struct inode *inode = file_inode(args->file);
>> struct memfd_luo_folio_ser *folios_ser;
>> struct memfd_luo_ser *ser;
>> @@ -309,7 +310,8 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
>> inode_unlock(inode);
>>
>> args->private_data = folios_ser;
>> - args->serialized_data = virt_to_phys(ser);
>> + KHOSER_STORE_PTR(sd, ser);
>> + KHOSER_COPY_PTR(args->serialized_data, sd);
>
> This is awkward. Why do you even need sd? Why not just do
> KHOSER_STORE_PTR(args->serialized_data, ser)? KHOSER_COPY_PTR() doesn't
> give you any type safety for args->serialized_data anyway, so why the
> extra steps?
Right, I will remove that, It was needed when I was using TYPE(UN)SAFE calls.
>
>>
>> return 0;
>>
>> @@ -325,11 +327,10 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args *args)
>> {
>> struct memfd_luo_ser *ser;
>>
>> - if (WARN_ON_ONCE(!args->serialized_data))
>> + ser = KHOSER_LOAD_PTR(args->serialized_data);
>> + if (WARN_ON_ONCE(!ser))
>> return -EINVAL;
>>
>> - ser = phys_to_virt(args->serialized_data);
>> -
>> /*
>> * The pos might have changed since prepare. Everything else stays the
>> * same.
>> @@ -344,14 +345,13 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
>> struct inode *inode = file_inode(args->file);
>> struct memfd_luo_ser *ser;
>>
>> - if (WARN_ON_ONCE(!args->serialized_data))
>> + ser = KHOSER_LOAD_PTR(args->serialized_data);
>> + if (WARN_ON_ONCE(!ser))
>> return;
>>
>> inode_lock(inode);
>> shmem_freeze(inode, false);
>>
>> - ser = phys_to_virt(args->serialized_data);
>> -
>> memfd_luo_unpreserve_folios(&ser->folios, args->private_data,
>> ser->nr_folios);
>>
>> @@ -397,7 +397,8 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
>> if (args->retrieve_status)
>> return;
>>
>> - if (!args->serialized_data)
>> + ser = KHOSER_LOAD_PTR(args->serialized_data);
>> + if (!ser)
>> return;
>>
>> ser = phys_to_virt(args->serialized_data);
>
> This doesn't compile :-(
>
> You should always _test_ the changes you make. Compiling them is the
> first step. _Running_ them is the second. Both are important. Please do
> so in the next version. And for every code changes, no matter how
> trivial it seems. You never know if a simple looking change can trigger
> bugs.
>
> You should at least run the LUO selftests and make sure they pass.
>
Right, My bad.
>> @@ -523,7 +524,8 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
>> struct file *file;
>> int err;
>>
>> - if (!args->serialized_data)
>> + ser = KHOSER_LOAD_PTR(args->serialized_data);
>> + if (!ser)
>> return -EINVAL;
>>
>> ser = phys_to_virt(args->serialized_data);
>
> Here too, this doesn't compile.
>
> --
> Regards,
> Pratyush Yadav
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