From: Tarun Sahu <tarunsahu@google.com>
To: Pasha Tatashin <pasha.tatashin@soleen.com>,
Mike Rapoport <rppt@kernel.org>,
robin.murphy@arm.com, maz@kernel.org, will@kernel.org,
David Matlack <dmatlack@google.com>,
Alexander Graf <graf@amazon.com>,
seanjc@google.com, jgg@nvidia.com, loganodell@google.com,
arnd@arndb.de, dwmw2@infradead.org, baolu.lu@linux.intel.com,
Bjorn Helgaas <bhelgaas@google.com>,
oupton@kernel.org, alex@shazbot.org, gle.com@google.com,
pbonzini@redhat.com, Andrew Morton <akpm@linux-foundation.org>,
kevin.tian@intel.com, joro@8bytes.org
Cc: kvmarm@lists.linux.dev, linux-pci@vger.kernel.org,
Pratyush Yadav <pratyush@kernel.org>,
kexec@lists.infradead.org, kvm@vger.kernel.org,
iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
skhawaja@google.com, sagis@google.com,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Tarun Sahu <tarunsahu@google.com>
Subject: [PATCH v4 17/19] mm: memfd_luo: Add feature header to struct memfd_luo_ser
Date: Tue, 10 Nov 2026 05:02:00 +0000 [thread overview]
Message-ID: <20261110050202.529473-18-tarunsahu@google.com> (raw)
In-Reply-To: <20261110050202.529473-1-tarunsahu@google.com>
Precede struct memfd_luo_ser with struct kho_ser_hdr using
DECLARE_KHO_SER. Later memfd features can be appended under new
feature indices without breaking compatibility between adjacent kernels.
Allocate both the memfd_luo_ser feature header and the kho_vmalloc
feature header in the same preserved folio. On restore and retrieve,
validate incoming required features before accessing payload fields.
Signed-off-by: Tarun Sahu <tarunsahu@google.com>
---
include/linux/kho/abi/memfd.h | 7 ++--
mm/memfd_luo.c | 67 ++++++++++++++++++++++++-----------
2 files changed, 51 insertions(+), 23 deletions(-)
diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h
index b0597c438973..27f8880ee593 100644
--- a/include/linux/kho/abi/memfd.h
+++ b/include/linux/kho/abi/memfd.h
@@ -83,6 +83,8 @@ static_assert(!IS_ENABLED(CONFIG_64BIT) ||
* @nr_folios: Number of folios in the folios array.
* @folios_fhdr: Pointer to KHO vmalloc descriptor for the array of
* struct memfd_luo_folio_ser.
+ *
+ * Preceded by &struct kho_ser_hdr.
*/
struct memfd_luo_ser {
u64 pos;
@@ -93,9 +95,8 @@ struct memfd_luo_ser {
DECLARE_KHOSER_PTR(folios_fhdr, DECLARE_KHO_SER_HDR(kho_vmalloc, *));
};
-static_assert(sizeof(struct memfd_luo_ser) == 40);
-static_assert(!IS_ENABLED(CONFIG_64BIT) ||
- __alignof__(struct memfd_luo_ser) == 8);
+/* Register memfd_luo_ser with KHO serialization accessors */
+DECLARE_KHO_SER(memfd_luo_ser, 40, 0, 0);
/* The compatibility string for memfd file handler */
#define MEMFD_LUO_FH_COMPATIBLE "memfd-v3"
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 74c1ff5877c3..94510f73a606 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -256,16 +256,21 @@ static void memfd_luo_unpreserve_folios(DECLARE_KHO_SER_HDR(kho_vmalloc, *folios
static size_t memfd_luo_ser_size(void)
{
- return sizeof(struct memfd_luo_ser) + kho_ser_size(kho_vmalloc);
+ return kho_ser_size(memfd_luo_ser) + kho_ser_size(kho_vmalloc);
}
-static struct memfd_luo_ser *memfd_luo_ser_init(void *mem)
+static struct memfd_luo_ser *
+memfd_luo_ser_init(DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr))
{
DECLARE_KHO_SER_HDR(kho_vmalloc, *folios_fhdr);
- struct memfd_luo_ser *ser = mem;
+ struct memfd_luo_ser *ser;
+
+ kho_ser_init(fhdr, memfd_luo_ser);
+ folios_fhdr = (void *)fhdr + kho_ser_size(memfd_luo_ser);
- folios_fhdr = mem + sizeof(struct memfd_luo_ser);
+ ser = kho_ser_payload(fhdr, memfd_luo_ser);
KHOSER_STORE_PTR(ser->folios_fhdr, folios_fhdr);
+
return ser;
}
@@ -273,6 +278,7 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
{
struct inode *inode = file_inode(args->file);
struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
int err = 0, seals;
u64 inode_size;
@@ -304,12 +310,12 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
}
/* Allocate the main serialization structure in preserved memory */
- ser = kho_alloc_preserve(memfd_luo_ser_size());
- if (IS_ERR(ser)) {
- err = PTR_ERR(ser);
+ fhdr = kho_alloc_preserve(memfd_luo_ser_size());
+ if (IS_ERR(fhdr)) {
+ err = PTR_ERR(fhdr);
goto err_unlock;
}
- ser = memfd_luo_ser_init(ser);
+ ser = memfd_luo_ser_init(fhdr);
ser->pos = args->file->f_pos;
ser->size = inode_size;
@@ -323,12 +329,12 @@ 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);
+ args->serialized_data = virt_to_phys(fhdr);
return 0;
err_free_ser:
- kho_unpreserve_free(ser);
+ kho_unpreserve_free(fhdr);
err_unlock:
shmem_freeze(inode, false);
inode_unlock(inode);
@@ -337,12 +343,14 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
static int memfd_luo_freeze(struct liveupdate_file_op_args *args)
{
+ DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
if (WARN_ON_ONCE(!args->serialized_data))
return -EINVAL;
- ser = phys_to_virt(args->serialized_data);
+ fhdr = phys_to_virt(args->serialized_data);
+ ser = kho_ser_payload(fhdr, memfd_luo_ser);
/*
* The pos might have changed since prepare. Everything else stays the
@@ -356,6 +364,7 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args *args)
static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
{
struct inode *inode = file_inode(args->file);
+ DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
if (WARN_ON_ONCE(!args->serialized_data))
@@ -364,13 +373,14 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
inode_lock(inode);
shmem_freeze(inode, false);
- ser = phys_to_virt(args->serialized_data);
+ fhdr = phys_to_virt(args->serialized_data);
+ ser = kho_ser_payload(fhdr, memfd_luo_ser);
memfd_luo_unpreserve_folios(KHOSER_LOAD_PTR(ser->folios_fhdr),
args->private_data,
ser->nr_folios);
- kho_unpreserve_free(ser);
+ kho_unpreserve_free(fhdr);
inode_unlock(inode);
}
@@ -402,6 +412,7 @@ static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_se
static void memfd_luo_finish(struct liveupdate_file_op_args *args)
{
struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
/*
@@ -412,10 +423,16 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
if (args->retrieve_status)
return;
- ser = phys_to_virt(args->serialized_data);
- if (!ser)
+ if (WARN_ON_ONCE(!args->serialized_data))
return;
+ fhdr = phys_to_virt(args->serialized_data);
+ if (kho_ser_validate(fhdr, memfd_luo_ser)) {
+ pr_warn("invalid feature header, folios not discarded\n");
+ goto out;
+ }
+
+ ser = kho_ser_payload(fhdr, memfd_luo_ser);
if (ser->nr_folios) {
folios_ser = kho_restore_vmalloc(KHOSER_LOAD_PTR(ser->folios_fhdr));
if (!folios_ser)
@@ -426,7 +443,7 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args)
}
out:
- kho_restore_free(ser);
+ kho_restore_free(fhdr);
}
static int memfd_luo_retrieve_folios(struct file *file,
@@ -533,14 +550,24 @@ static int memfd_luo_retrieve_folios(struct file *file,
static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
{
struct memfd_luo_folio_ser *folios_ser;
+ DECLARE_KHO_SER_HDR(memfd_luo_ser, *fhdr);
struct memfd_luo_ser *ser;
struct file *file;
int err;
- ser = phys_to_virt(args->serialized_data);
- if (!ser)
+ if (WARN_ON_ONCE(!args->serialized_data))
return -EINVAL;
+ fhdr = phys_to_virt(args->serialized_data);
+ err = kho_ser_validate(fhdr, memfd_luo_ser);
+ if (err) {
+ pr_err("memfd_luo_ser feature validation failed: %pe\n",
+ ERR_PTR(err));
+ goto free_ser;
+ }
+
+ ser = kho_ser_payload(fhdr, memfd_luo_ser);
+
/* Make sure the file only has seals supported by this version. */
if (ser->seals & ~MEMFD_LUO_ALL_SEALS) {
err = -EOPNOTSUPP;
@@ -581,14 +608,14 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
}
args->file = file;
- kho_restore_free(ser);
+ kho_restore_free(fhdr);
return 0;
put_file:
fput(file);
free_ser:
- kho_restore_free(ser);
+ kho_restore_free(fhdr);
return err;
}
--
2.56.0.506.g506a7eabc5-goog
next prev parent reply other threads:[~2026-11-10 5:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 5:01 [PATCH v4 00/19] kho, liveupdate: Add feature header for fine-grained ABI compatibility Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 01/19] liveupdate, kho: Remove __packed from KHO, LUO and memfd ABI structures Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 02/19] kho: block: Record the entry size in the block header Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 03/19] kho, memfd_luo: Reference struct kho_vmalloc via serialized pointer Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 04/19] liveupdate: Reference struct luo_file_set_ser " Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 05/19] kho: Add feature header for fine-grained ABI compatibility Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 06/19] kho: kexec_metadata: Add the feature header Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 07/19] kho: vmalloc: " Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 08/19] kho: block: Add the feature header to blocks Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 09/19] liveupdate: Add feature header to struct luo_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 10/19] liveupdate: Add feature header to struct luo_session_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 11/19] liveupdate: Add feature header to struct luo_file_set_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 12/19] liveupdate: Add feature header to struct luo_file_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 13/19] liveupdate: Add feature header to struct luo_flb_header_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 14/19] liveupdate: Add feature header to struct luo_flb_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 15/19] PCI: liveupdate: Add feature header to struct pci_ser Tarun Sahu
2026-11-10 5:01 ` [PATCH v4 16/19] PCI: liveupdate: Add feature header to struct pci_dev_ser Tarun Sahu
2026-11-10 5:02 ` Tarun Sahu [this message]
2026-11-10 5:02 ` [PATCH v4 18/19] mm: memfd_luo: Add feature header to struct memfd_luo_folio_ser Tarun Sahu
2026-11-10 5:02 ` [PATCH v4 19/19] kho: Add KUnit test for the feature header helpers Tarun Sahu
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