[PATCH v3 0/8] module: Move 'struct module_signature' to UAPI

[PATCH v3 0/8] module: Move 'struct module_signature' to UAPI

[Thomas Weißschuh]

This structure definition is used outside the kernel proper.
For example in kmod and the kernel build environment.

To allow reuse, move it to a new UAPI header.

While it is not a true UAPI, it is a common practice to have
non-UAPI interface definitions in the kernel's UAPI headers.

This came up as part of my CONFIG_MODULE_HASHES series [0].
But it is useful on its own and so we get it out of the way.

[0] https://lore.kernel.org/lkml/aZ3OfJJSJgfOb0rJ@levanger/

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
Changes in v3:
- Also adapt the include path for the custom sign-file rule in the bpf selftests.
  (My manual run of BPF CI still fails, due to an BUG() on s390,
  I don't see how this is due to this patch)
- Link to v2: https://lore.kernel.org/r/20260305-module-signature-uapi-v2-0-dc4d81129dee@linutronix.de

Changes in v2:
- Drop spurious definition of MODULE_SIGNATURE_TYPE_MERKLE.
- s/modules/module/ in two patch subjects.
- Pick up review tags.
- Link to v1: https://lore.kernel.org/r/20260302-module-signature-uapi-v1-0-207d955e0d69@linutronix.de

---
Thomas Weißschuh (8):
      extract-cert: drop unused definition of PKEY_ID_PKCS7
      module: Drop unused signature types
      module: Give 'enum pkey_id_type' a more specific name
      module: Give MODULE_SIG_STRING a more descriptive name
      module: Move 'struct module_signature' to UAPI
      tools uapi headers: add linux/module_signature.h
      sign-file: use 'struct module_signature' from the UAPI headers
      selftests/bpf: verify_pkcs7_sig: Use 'struct module_signature' from the UAPI headers

 arch/s390/kernel/machine_kexec_file.c              |  6 ++--
 certs/extract-cert.c                               |  2 --
 include/linux/module_signature.h                   | 30 +---------------
 include/uapi/linux/module_signature.h              | 41 ++++++++++++++++++++++
 kernel/module/signing.c                            |  4 +--
 kernel/module_signature.c                          |  2 +-
 scripts/Makefile                                   |  1 +
 scripts/sign-file.c                                | 19 +++-------
 security/integrity/ima/ima_modsig.c                |  6 ++--
 tools/include/uapi/linux/module_signature.h        | 41 ++++++++++++++++++++++
 tools/testing/selftests/bpf/Makefile               |  1 +
 .../selftests/bpf/prog_tests/verify_pkcs7_sig.c    | 28 ++-------------
 12 files changed, 101 insertions(+), 80 deletions(-)
---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260302-module-signature-uapi-61fa80b1e2bb

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>

[PATCH v3 1/8] extract-cert: drop unused definition of PKEY_ID_PKCS7

[Thomas Weißschuh]

This definition duplicates a definition from an internal kernel header
which is going to be renamed.

To get rid of an instance of the old name, drop the definition.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 certs/extract-cert.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/certs/extract-cert.c b/certs/extract-cert.c
index 7d6d468ed612..8c762f908443 100644
--- a/certs/extract-cert.c
+++ b/certs/extract-cert.c
@@ -33,8 +33,6 @@
 #endif
 #include "ssl-common.h"
 
-#define PKEY_ID_PKCS7 2
-
 static __attribute__((noreturn))
 void format(void)
 {

-- 
2.53.0

[PATCH v3 2/8] module: Drop unused signature types

[Thomas Weißschuh]

Only PKCS#7 signatures are used today.

Remove the unused enum values. As this enum is used in on-disk data,
preserve the numeric value.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 include/linux/module_signature.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 7eb4b00381ac..820cc1473383 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -15,9 +15,7 @@
 #define MODULE_SIG_STRING "~Module signature appended~\n"
 
 enum pkey_id_type {
-	PKEY_ID_PGP,		/* OpenPGP generated key ID */
-	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
-	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
+	PKEY_ID_PKCS7 = 2,	/* Signature in PKCS#7 message */
 };
 
 /*

-- 
2.53.0

[PATCH v3 3/8] module: Give 'enum pkey_id_type' a more specific name

[Thomas Weißschuh]

This enum originates in generic cryptographic code and has a very
generic name. Nowadays it is only used for module signatures.

As this enum is going to be exposed in a UAPI header, give it a more
specific name for clarity and consistency.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 arch/s390/kernel/machine_kexec_file.c | 2 +-
 include/linux/module_signature.h      | 6 +++---
 kernel/module_signature.c             | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index 1bf59c3f0e2b..667ee9279e23 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -53,7 +53,7 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 		return -EKEYREJECTED;
 	kernel_len -= sig_len;
 
-	if (ms->id_type != PKEY_ID_PKCS7)
+	if (ms->id_type != MODULE_SIGNATURE_TYPE_PKCS7)
 		return -EKEYREJECTED;
 
 	if (ms->algo != 0 ||
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 820cc1473383..c3a05d4cfe67 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -14,8 +14,8 @@
 /* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
 #define MODULE_SIG_STRING "~Module signature appended~\n"
 
-enum pkey_id_type {
-	PKEY_ID_PKCS7 = 2,	/* Signature in PKCS#7 message */
+enum module_signature_type {
+	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
 };
 
 /*
@@ -31,7 +31,7 @@ enum pkey_id_type {
 struct module_signature {
 	u8	algo;		/* Public-key crypto algorithm [0] */
 	u8	hash;		/* Digest algorithm [0] */
-	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
+	u8	id_type;	/* Key identifier type [enum module_signature_type] */
 	u8	signer_len;	/* Length of signer's name [0] */
 	u8	key_id_len;	/* Length of key identifier [0] */
 	u8	__pad[3];
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
index 00132d12487c..a0eee2fe4368 100644
--- a/kernel/module_signature.c
+++ b/kernel/module_signature.c
@@ -24,7 +24,7 @@ int mod_check_sig(const struct module_signature *ms, size_t file_len,
 	if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
 		return -EBADMSG;
 
-	if (ms->id_type != PKEY_ID_PKCS7) {
+	if (ms->id_type != MODULE_SIGNATURE_TYPE_PKCS7) {
 		pr_err("%s: not signed with expected PKCS#7 message\n",
 		       name);
 		return -ENOPKG;

-- 
2.53.0

Re: [PATCH v3 3/8] module: Give 'enum pkey_id_type' a more specific name

[David Howells]

Thomas Weißschuh <thomas.weissschuh@linutronix.de> wrote:

> -enum pkey_id_type {
> -	PKEY_ID_PKCS7 = 2,	/* Signature in PKCS#7 message */
> +enum module_signature_type {
> +	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
>  };

It might be best to just kill the enum and replace it with a single #define.

David

Re: [PATCH v3 3/8] module: Give 'enum pkey_id_type' a more specific name

[=?utf-8?q?Thomas_Wei=C3=9Fschuh?=]

On Thu, Mar 05, 2026 at 10:52:47AM +0000, David Howells wrote:
> 
> Thomas Weißschuh <thomas.weissschuh@linutronix.de> wrote:
> 
> > -enum pkey_id_type {
> > -	PKEY_ID_PKCS7 = 2,	/* Signature in PKCS#7 message */
> > +enum module_signature_type {
> > +	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
> >  };
> 
> It might be best to just kill the enum and replace it with a single #define.

I am about to introduce another value in [0].
But personally I don't really care one way or another.

[0] https://lore.kernel.org/lkml/20260113-module-hashes-v4-0-0b932db9b56b@weissschuh.net/

[PATCH v3 4/8] module: Give MODULE_SIG_STRING a more descriptive name

[Thomas Weißschuh]

The purpose of the constant it is not entirely clear from its name.

As this constant is going to be exposed in a UAPI header, give it a more
specific name for clarity. As all its users call it 'marker', use that
wording in the constant itself.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 arch/s390/kernel/machine_kexec_file.c | 4 ++--
 include/linux/module_signature.h      | 2 +-
 kernel/module/signing.c               | 4 ++--
 security/integrity/ima/ima_modsig.c   | 6 +++---
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index 667ee9279e23..6f0852d5a3a9 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -28,7 +28,7 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 #ifdef CONFIG_KEXEC_SIG
 int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 {
-	const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
+	const unsigned long marker_len = sizeof(MODULE_SIGNATURE_MARKER) - 1;
 	struct module_signature *ms;
 	unsigned long sig_len;
 	int ret;
@@ -40,7 +40,7 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 	if (marker_len > kernel_len)
 		return -EKEYREJECTED;
 
-	if (memcmp(kernel + kernel_len - marker_len, MODULE_SIG_STRING,
+	if (memcmp(kernel + kernel_len - marker_len, MODULE_SIGNATURE_MARKER,
 		   marker_len))
 		return -EKEYREJECTED;
 	kernel_len -= marker_len;
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index c3a05d4cfe67..915549c779dc 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -12,7 +12,7 @@
 #include <linux/types.h>
 
 /* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
-#define MODULE_SIG_STRING "~Module signature appended~\n"
+#define MODULE_SIGNATURE_MARKER "~Module signature appended~\n"
 
 enum module_signature_type {
 	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
diff --git a/kernel/module/signing.c b/kernel/module/signing.c
index a2ff4242e623..590ba29c85ab 100644
--- a/kernel/module/signing.c
+++ b/kernel/module/signing.c
@@ -70,7 +70,7 @@ int mod_verify_sig(const void *mod, struct load_info *info)
 int module_sig_check(struct load_info *info, int flags)
 {
 	int err = -ENODATA;
-	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+	const unsigned long markerlen = sizeof(MODULE_SIGNATURE_MARKER) - 1;
 	const char *reason;
 	const void *mod = info->hdr;
 	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
@@ -81,7 +81,7 @@ int module_sig_check(struct load_info *info, int flags)
 	 */
 	if (!mangled_module &&
 	    info->len > markerlen &&
-	    memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
+	    memcmp(mod + info->len - markerlen, MODULE_SIGNATURE_MARKER, markerlen) == 0) {
 		/* We truncate the module to discard the signature */
 		info->len -= markerlen;
 		err = mod_verify_sig(mod, info);
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index 9aa92fd35a03..632c746fd81e 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -40,7 +40,7 @@ struct modsig {
 int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		    struct modsig **modsig)
 {
-	const size_t marker_len = strlen(MODULE_SIG_STRING);
+	const size_t marker_len = strlen(MODULE_SIGNATURE_MARKER);
 	const struct module_signature *sig;
 	struct modsig *hdr;
 	size_t sig_len;
@@ -51,7 +51,7 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		return -ENOENT;
 
 	p = buf + buf_len - marker_len;
-	if (memcmp(p, MODULE_SIG_STRING, marker_len))
+	if (memcmp(p, MODULE_SIGNATURE_MARKER, marker_len))
 		return -ENOENT;
 
 	buf_len -= marker_len;
@@ -105,7 +105,7 @@ void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size)
 	 * Provide the file contents (minus the appended sig) so that the PKCS7
 	 * code can calculate the file hash.
 	 */
-	size -= modsig->raw_pkcs7_len + strlen(MODULE_SIG_STRING) +
+	size -= modsig->raw_pkcs7_len + strlen(MODULE_SIGNATURE_MARKER) +
 		sizeof(struct module_signature);
 	rc = pkcs7_supply_detached_data(modsig->pkcs7_msg, buf, size);
 	if (rc)

-- 
2.53.0

[PATCH v3 5/8] module: Move 'struct module_signature' to UAPI

[Thomas Weißschuh]

This structure definition is used outside the kernel proper.
For example in kmod and the kernel build environment.

To allow reuse, move it to a new UAPI header.

While it is not a true UAPI, it is a common practice to have
non-UAPI interface definitions in the kernel's UAPI headers.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 include/linux/module_signature.h      | 28 +-----------------------
 include/uapi/linux/module_signature.h | 41 +++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 27 deletions(-)

diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 915549c779dc..db335d46787f 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -10,33 +10,7 @@
 #define _LINUX_MODULE_SIGNATURE_H
 
 #include <linux/types.h>
-
-/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
-#define MODULE_SIGNATURE_MARKER "~Module signature appended~\n"
-
-enum module_signature_type {
-	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
-};
-
-/*
- * Module signature information block.
- *
- * The constituents of the signature section are, in order:
- *
- *	- Signer's name
- *	- Key identifier
- *	- Signature data
- *	- Information block
- */
-struct module_signature {
-	u8	algo;		/* Public-key crypto algorithm [0] */
-	u8	hash;		/* Digest algorithm [0] */
-	u8	id_type;	/* Key identifier type [enum module_signature_type] */
-	u8	signer_len;	/* Length of signer's name [0] */
-	u8	key_id_len;	/* Length of key identifier [0] */
-	u8	__pad[3];
-	__be32	sig_len;	/* Length of signature data */
-};
+#include <uapi/linux/module_signature.h>
 
 int mod_check_sig(const struct module_signature *ms, size_t file_len,
 		  const char *name);
diff --git a/include/uapi/linux/module_signature.h b/include/uapi/linux/module_signature.h
new file mode 100644
index 000000000000..634c9f1c8fc2
--- /dev/null
+++ b/include/uapi/linux/module_signature.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Module signature handling.
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _UAPI_LINUX_MODULE_SIGNATURE_H
+#define _UAPI_LINUX_MODULE_SIGNATURE_H
+
+#include <linux/types.h>
+
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIGNATURE_MARKER "~Module signature appended~\n"
+
+enum module_signature_type {
+	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
+};
+
+/*
+ * Module signature information block.
+ *
+ * The constituents of the signature section are, in order:
+ *
+ *	- Signer's name
+ *	- Key identifier
+ *	- Signature data
+ *	- Information block
+ */
+struct module_signature {
+	__u8	algo;		/* Public-key crypto algorithm [0] */
+	__u8	hash;		/* Digest algorithm [0] */
+	__u8	id_type;	/* Key identifier type [enum module_signature_type] */
+	__u8	signer_len;	/* Length of signer's name [0] */
+	__u8	key_id_len;	/* Length of key identifier [0] */
+	__u8	__pad[3];
+	__be32	sig_len;	/* Length of signature data */
+};
+
+#endif /* _UAPI_LINUX_MODULE_SIGNATURE_H */

-- 
2.53.0

[PATCH v3 6/8] tools uapi headers: add linux/module_signature.h

[Thomas Weißschuh]

This header is going to be used from scripts/sign-file.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 tools/include/uapi/linux/module_signature.h | 41 +++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/tools/include/uapi/linux/module_signature.h b/tools/include/uapi/linux/module_signature.h
new file mode 100644
index 000000000000..634c9f1c8fc2
--- /dev/null
+++ b/tools/include/uapi/linux/module_signature.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Module signature handling.
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _UAPI_LINUX_MODULE_SIGNATURE_H
+#define _UAPI_LINUX_MODULE_SIGNATURE_H
+
+#include <linux/types.h>
+
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIGNATURE_MARKER "~Module signature appended~\n"
+
+enum module_signature_type {
+	MODULE_SIGNATURE_TYPE_PKCS7 = 2,	/* Signature in PKCS#7 message */
+};
+
+/*
+ * Module signature information block.
+ *
+ * The constituents of the signature section are, in order:
+ *
+ *	- Signer's name
+ *	- Key identifier
+ *	- Signature data
+ *	- Information block
+ */
+struct module_signature {
+	__u8	algo;		/* Public-key crypto algorithm [0] */
+	__u8	hash;		/* Digest algorithm [0] */
+	__u8	id_type;	/* Key identifier type [enum module_signature_type] */
+	__u8	signer_len;	/* Length of signer's name [0] */
+	__u8	key_id_len;	/* Length of key identifier [0] */
+	__u8	__pad[3];
+	__be32	sig_len;	/* Length of signature data */
+};
+
+#endif /* _UAPI_LINUX_MODULE_SIGNATURE_H */

-- 
2.53.0

[PATCH v3 7/8] sign-file: use 'struct module_signature' from the UAPI headers

[Thomas Weißschuh]

Now that the UAPI headers provide the required definitions, use those.
Some symbols have been renamed, adapt to those.

Also adapt the include path for the custom sign-file rule in the
bpf selftests.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/Makefile                     |  1 +
 scripts/sign-file.c                  | 19 ++++---------------
 tools/testing/selftests/bpf/Makefile |  1 +
 3 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/scripts/Makefile b/scripts/Makefile
index 0941e5ce7b57..3434a82a119f 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -35,6 +35,7 @@ HOSTCFLAGS_sorttable.o = -I$(srctree)/tools/include
 HOSTLDLIBS_sorttable = -lpthread
 HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
 HOSTCFLAGS_sign-file.o = $(shell $(HOSTPKG_CONFIG) --cflags libcrypto 2> /dev/null)
+HOSTCFLAGS_sign-file.o += -I$(srctree)/tools/include/uapi/
 HOSTLDLIBS_sign-file = $(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)
 
 ifdef CONFIG_UNWINDER_ORC
diff --git a/scripts/sign-file.c b/scripts/sign-file.c
index 73fbefd2e540..86b010ac1514 100644
--- a/scripts/sign-file.c
+++ b/scripts/sign-file.c
@@ -40,19 +40,7 @@
 #endif
 #include "ssl-common.h"
 
-struct module_signature {
-	uint8_t		algo;		/* Public-key crypto algorithm [0] */
-	uint8_t		hash;		/* Digest algorithm [0] */
-	uint8_t		id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
-	uint8_t		signer_len;	/* Length of signer's name [0] */
-	uint8_t		key_id_len;	/* Length of key identifier [0] */
-	uint8_t		__pad[3];
-	uint32_t	sig_len;	/* Length of signature data */
-};
-
-#define PKEY_ID_PKCS7 2
-
-static char magic_number[] = "~Module signature appended~\n";
+#include <linux/module_signature.h>
 
 static __attribute__((noreturn))
 void format(void)
@@ -197,7 +185,7 @@ static X509 *read_x509(const char *x509_name)
 
 int main(int argc, char **argv)
 {
-	struct module_signature sig_info = { .id_type = PKEY_ID_PKCS7 };
+	struct module_signature sig_info = { .id_type = MODULE_SIGNATURE_TYPE_PKCS7 };
 	char *hash_algo = NULL;
 	char *private_key_name = NULL, *raw_sig_name = NULL;
 	char *x509_name, *module_name, *dest_name;
@@ -357,7 +345,8 @@ int main(int argc, char **argv)
 	sig_size = BIO_number_written(bd) - module_size;
 	sig_info.sig_len = htonl(sig_size);
 	ERR(BIO_write(bd, &sig_info, sizeof(sig_info)) < 0, "%s", dest_name);
-	ERR(BIO_write(bd, magic_number, sizeof(magic_number) - 1) < 0, "%s", dest_name);
+	ERR(BIO_write(bd, MODULE_SIGNATURE_MARKER, sizeof(MODULE_SIGNATURE_MARKER) - 1) < 0,
+	    "%s", dest_name);
 
 	ERR(BIO_free(bd) != 1, "%s", dest_name);
 
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 6776158f1f3e..2b1080892208 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -270,6 +270,7 @@ $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_r
 $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c
 	$(call msg,SIGN-FILE,,$@)
 	$(Q)$(CC) $(shell $(PKG_CONFIG) --cflags libcrypto 2> /dev/null) \
+		  -I$(srctree)/tools/include/uapi/ \
 		  $< -o $@ \
 		  $(shell $(PKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)
 

-- 
2.53.0

[PATCH v3 8/8] selftests/bpf: verify_pkcs7_sig: Use 'struct module_signature' from the UAPI headers

[Thomas Weißschuh]

Now that the UAPI headers provide the required definitions, use those.
Some symbols have been renamed, adapt to those.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 .../selftests/bpf/prog_tests/verify_pkcs7_sig.c    | 28 +++-------------------
 1 file changed, 3 insertions(+), 25 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/verify_pkcs7_sig.c b/tools/testing/selftests/bpf/prog_tests/verify_pkcs7_sig.c
index 4d69d9d55e17..f327feb8e38c 100644
--- a/tools/testing/selftests/bpf/prog_tests/verify_pkcs7_sig.c
+++ b/tools/testing/selftests/bpf/prog_tests/verify_pkcs7_sig.c
@@ -18,6 +18,7 @@
 #include <linux/keyctl.h>
 #include <sys/xattr.h>
 #include <linux/fsverity.h>
+#include <linux/module_signature.h>
 #include <test_progs.h>
 
 #include "test_verify_pkcs7_sig.skel.h"
@@ -33,29 +34,6 @@
 #define SHA256_DIGEST_SIZE      32
 #endif
 
-/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
-#define MODULE_SIG_STRING "~Module signature appended~\n"
-
-/*
- * Module signature information block.
- *
- * The constituents of the signature section are, in order:
- *
- *	- Signer's name
- *	- Key identifier
- *	- Signature data
- *	- Information block
- */
-struct module_signature {
-	__u8	algo;		/* Public-key crypto algorithm [0] */
-	__u8	hash;		/* Digest algorithm [0] */
-	__u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
-	__u8	signer_len;	/* Length of signer's name [0] */
-	__u8	key_id_len;	/* Length of key identifier [0] */
-	__u8	__pad[3];
-	__be32	sig_len;	/* Length of signature data */
-};
-
 struct data {
 	__u8 data[MAX_DATA_SIZE];
 	__u32 data_len;
@@ -215,7 +193,7 @@ static int populate_data_item_mod(struct data *data_item)
 		return 0;
 
 	modlen = st.st_size;
-	marker_len = sizeof(MODULE_SIG_STRING) - 1;
+	marker_len = sizeof(MODULE_SIGNATURE_MARKER) - 1;
 
 	fd = open(mod_path, O_RDONLY);
 	if (fd == -1)
@@ -228,7 +206,7 @@ static int populate_data_item_mod(struct data *data_item)
 	if (mod == MAP_FAILED)
 		return -errno;
 
-	if (strncmp(mod + modlen - marker_len, MODULE_SIG_STRING, marker_len)) {
+	if (strncmp(mod + modlen - marker_len, MODULE_SIGNATURE_MARKER, marker_len)) {
 		ret = -EINVAL;
 		goto out;
 	}

-- 
2.53.0

Re: [PATCH v3 0/8] module: Move 'struct module_signature' to UAPI

[Nicolas Schier]

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On Thu, Mar 05, 2026 at 10:31:36AM +0100, Thomas Weißschuh wrote:
> This structure definition is used outside the kernel proper.
> For example in kmod and the kernel build environment.
> 
> To allow reuse, move it to a new UAPI header.
> 
> While it is not a true UAPI, it is a common practice to have
> non-UAPI interface definitions in the kernel's UAPI headers.
> 
> This came up as part of my CONFIG_MODULE_HASHES series [0].
> But it is useful on its own and so we get it out of the way.
> 
> [0] https://lore.kernel.org/lkml/aZ3OfJJSJgfOb0rJ@levanger/
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
> Changes in v3:
> - Also adapt the include path for the custom sign-file rule in the bpf selftests.
>   (My manual run of BPF CI still fails, due to an BUG() on s390,
>   I don't see how this is due to this patch)
> - Link to v2: https://lore.kernel.org/r/20260305-module-signature-uapi-v2-0-dc4d81129dee@linutronix.de
> 
> Changes in v2:
> - Drop spurious definition of MODULE_SIGNATURE_TYPE_MERKLE.
> - s/modules/module/ in two patch subjects.
> - Pick up review tags.
> - Link to v1: https://lore.kernel.org/r/20260302-module-signature-uapi-v1-0-207d955e0d69@linutronix.de
> 
> ---
> Thomas Weißschuh (8):
>       extract-cert: drop unused definition of PKEY_ID_PKCS7
>       module: Drop unused signature types
>       module: Give 'enum pkey_id_type' a more specific name
>       module: Give MODULE_SIG_STRING a more descriptive name
>       module: Move 'struct module_signature' to UAPI
>       tools uapi headers: add linux/module_signature.h
>       sign-file: use 'struct module_signature' from the UAPI headers
>       selftests/bpf: verify_pkcs7_sig: Use 'struct module_signature' from the UAPI headers
> 
>  arch/s390/kernel/machine_kexec_file.c              |  6 ++--
>  certs/extract-cert.c                               |  2 --
>  include/linux/module_signature.h                   | 30 +---------------
>  include/uapi/linux/module_signature.h              | 41 ++++++++++++++++++++++
>  kernel/module/signing.c                            |  4 +--
>  kernel/module_signature.c                          |  2 +-
>  scripts/Makefile                                   |  1 +
>  scripts/sign-file.c                                | 19 +++-------
>  security/integrity/ima/ima_modsig.c                |  6 ++--
>  tools/include/uapi/linux/module_signature.h        | 41 ++++++++++++++++++++++
>  tools/testing/selftests/bpf/Makefile               |  1 +
>  .../selftests/bpf/prog_tests/verify_pkcs7_sig.c    | 28 ++-------------
>  12 files changed, 101 insertions(+), 80 deletions(-)
> ---
> base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
> change-id: 20260302-module-signature-uapi-61fa80b1e2bb
> 

Thanks for these patches!

For the whole series:

Reviewed-by: Nicolas Schier <nsc@kernel.org>

-- 
Nicolas

[-- Attachment #2: signature.asc --]
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Re: [PATCH v3 0/8] module: Move 'struct module_signature' to UAPI

[Sami Tolvanen]

On Thu, 05 Mar 2026 10:31:36 +0100, Thomas Weißschuh wrote:
> This structure definition is used outside the kernel proper.
> For example in kmod and the kernel build environment.
> 
> To allow reuse, move it to a new UAPI header.
> 
> While it is not a true UAPI, it is a common practice to have
> non-UAPI interface definitions in the kernel's UAPI headers.
> 
> [...]

Applied to modules-next, thanks!

[1/8] extract-cert: drop unused definition of PKEY_ID_PKCS7
      commit: 137676d4482d8b8d755890b4ed29fe8223661d20
[2/8] module: Drop unused signature types
      commit: 8988913aacee82e5401bf3b96839731982dcbde7
[3/8] module: Give 'enum pkey_id_type' a more specific name
      commit: acd87264af525dba6e9355310e8acdf066a5f6b5
[4/8] module: Give MODULE_SIG_STRING a more descriptive name
      commit: 2ae4ea2d9aaf25cb74fbc23450b1b8f0a5b7aa89
[5/8] module: Move 'struct module_signature' to UAPI
      commit: f9909cf0a2dcc9e99377f3fcc965ccd93e518e34
[6/8] tools uapi headers: add linux/module_signature.h
      commit: d2d7561dc656748f592cc34d34bf5db8d5c67f7b
[7/8] sign-file: use 'struct module_signature' from the UAPI headers
      commit: e340db306c3bb85877490f33a78eb80549ac43a7
[8/8] selftests/bpf: verify_pkcs7_sig: Use 'struct module_signature' from the UAPI headers
      commit: 55722b3f80377103bac6ac748554129108c75651

Best regards,

	Sami