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[PATCH v14 4/5] pkcs7, x509: Add ML-DSA support

David Howells posted 5 patches 2 weeks, 3 days ago
[PATCH v14 4/5] pkcs7, x509: Add ML-DSA support
Posted by David Howells 2 weeks, 3 days ago 
Add support for ML-DSA keys and signatures to the CMS/PKCS#7 and X.509
implementations.  ML-DSA-44, -65 and -87 are all supported.  For X.509
certificates, the TBSCertificate is required to be signed directly; for CMS,
direct signing of the data is preferred, though use of SHA512 (and only that)
as an intermediate hash of the content is permitted with signedAttrs.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Lukas Wunner <lukas@wunner.de>
cc: Ignat Korchagin <ignat@cloudflare.com>
cc: Stephan Mueller <smueller@chronox.de>
cc: Eric Biggers <ebiggers@kernel.org>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: keyrings@vger.kernel.org
cc: linux-crypto@vger.kernel.org
---
 crypto/asymmetric_keys/pkcs7_parser.c     | 24 +++++++++++++++++++-
 crypto/asymmetric_keys/public_key.c       | 10 +++++++++
 crypto/asymmetric_keys/x509_cert_parser.c | 27 ++++++++++++++++++++++-
 include/linux/oid_registry.h              |  5 +++++
 4 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
index 3cdbab3b9f50..594a8f1d9dfb 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.c
+++ b/crypto/asymmetric_keys/pkcs7_parser.c
@@ -95,11 +95,18 @@ static int pkcs7_check_authattrs(struct pkcs7_message *msg)
 	if (sinfo->authattrs) {
 		want = true;
 		msg->have_authattrs = true;
+	} else if (sinfo->sig->algo_takes_data) {
+		sinfo->sig->hash_algo = "none";
 	}
 
-	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
+	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next) {
 		if (!!sinfo->authattrs != want)
 			goto inconsistent;
+
+		if (!sinfo->authattrs &&
+		    sinfo->sig->algo_takes_data)
+			sinfo->sig->hash_algo = "none";
+	}
 	return 0;
 
 inconsistent:
@@ -297,6 +304,21 @@ int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
 		ctx->sinfo->sig->pkey_algo = "ecrdsa";
 		ctx->sinfo->sig->encoding = "raw";
 		break;
+	case OID_id_ml_dsa_44:
+		ctx->sinfo->sig->pkey_algo = "mldsa44";
+		ctx->sinfo->sig->encoding = "raw";
+		ctx->sinfo->sig->algo_takes_data = true;
+		break;
+	case OID_id_ml_dsa_65:
+		ctx->sinfo->sig->pkey_algo = "mldsa65";
+		ctx->sinfo->sig->encoding = "raw";
+		ctx->sinfo->sig->algo_takes_data = true;
+		break;
+	case OID_id_ml_dsa_87:
+		ctx->sinfo->sig->pkey_algo = "mldsa87";
+		ctx->sinfo->sig->encoding = "raw";
+		ctx->sinfo->sig->algo_takes_data = true;
+		break;
 	default:
 		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
 		return -ENOPKG;
diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index a46356e0c08b..09a0b83d5d77 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -142,6 +142,16 @@ software_key_determine_akcipher(const struct public_key *pkey,
 		if (strcmp(hash_algo, "streebog256") != 0 &&
 		    strcmp(hash_algo, "streebog512") != 0)
 			return -EINVAL;
+	} else if (strcmp(pkey->pkey_algo, "mldsa44") == 0 ||
+		   strcmp(pkey->pkey_algo, "mldsa65") == 0 ||
+		   strcmp(pkey->pkey_algo, "mldsa87") == 0) {
+		if (strcmp(encoding, "raw") != 0)
+			return -EINVAL;
+		if (!hash_algo)
+			return -EINVAL;
+		if (strcmp(hash_algo, "none") != 0 &&
+		    strcmp(hash_algo, "sha512") != 0)
+			return -EINVAL;
 	} else {
 		/* Unknown public key algorithm */
 		return -ENOPKG;
diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index b37cae914987..2fe094f5caf3 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -257,6 +257,15 @@ int x509_note_sig_algo(void *context, size_t hdrlen, unsigned char tag,
 	case OID_gost2012Signature512:
 		ctx->cert->sig->hash_algo = "streebog512";
 		goto ecrdsa;
+	case OID_id_ml_dsa_44:
+		ctx->cert->sig->pkey_algo = "mldsa44";
+		goto ml_dsa;
+	case OID_id_ml_dsa_65:
+		ctx->cert->sig->pkey_algo = "mldsa65";
+		goto ml_dsa;
+	case OID_id_ml_dsa_87:
+		ctx->cert->sig->pkey_algo = "mldsa87";
+		goto ml_dsa;
 	}
 
 rsa_pkcs1:
@@ -274,6 +283,12 @@ int x509_note_sig_algo(void *context, size_t hdrlen, unsigned char tag,
 	ctx->cert->sig->encoding = "x962";
 	ctx->sig_algo = ctx->last_oid;
 	return 0;
+ml_dsa:
+	ctx->cert->sig->algo_takes_data = true;
+	ctx->cert->sig->hash_algo = "none";
+	ctx->cert->sig->encoding = "raw";
+	ctx->sig_algo = ctx->last_oid;
+	return 0;
 }
 
 /*
@@ -300,7 +315,8 @@ int x509_note_signature(void *context, size_t hdrlen,
 
 	if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0 ||
 	    strcmp(ctx->cert->sig->pkey_algo, "ecrdsa") == 0 ||
-	    strcmp(ctx->cert->sig->pkey_algo, "ecdsa") == 0) {
+	    strcmp(ctx->cert->sig->pkey_algo, "ecdsa") == 0 ||
+	    strncmp(ctx->cert->sig->pkey_algo, "mldsa", 5) == 0) {
 		/* Discard the BIT STRING metadata */
 		if (vlen < 1 || *(const u8 *)value != 0)
 			return -EBADMSG;
@@ -524,6 +540,15 @@ int x509_extract_key_data(void *context, size_t hdrlen,
 			return -ENOPKG;
 		}
 		break;
+	case OID_id_ml_dsa_44:
+		ctx->cert->pub->pkey_algo = "mldsa44";
+		break;
+	case OID_id_ml_dsa_65:
+		ctx->cert->pub->pkey_algo = "mldsa65";
+		break;
+	case OID_id_ml_dsa_87:
+		ctx->cert->pub->pkey_algo = "mldsa87";
+		break;
 	default:
 		return -ENOPKG;
 	}
diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index 6de479ebbe5d..ebce402854de 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -145,6 +145,11 @@ enum OID {
 	OID_id_rsassa_pkcs1_v1_5_with_sha3_384, /* 2.16.840.1.101.3.4.3.15 */
 	OID_id_rsassa_pkcs1_v1_5_with_sha3_512, /* 2.16.840.1.101.3.4.3.16 */
 
+	/* NIST FIPS-204 ML-DSA */
+	OID_id_ml_dsa_44,			/* 2.16.840.1.101.3.4.3.17 */
+	OID_id_ml_dsa_65,			/* 2.16.840.1.101.3.4.3.18 */
+	OID_id_ml_dsa_87,			/* 2.16.840.1.101.3.4.3.19 */
+
 	OID__NR
 };
Re: [PATCH v14 4/5] pkcs7, x509: Add ML-DSA support
Posted by Jarkko Sakkinen 1 week, 6 days ago 
On Wed, Jan 21, 2026 at 10:36:06PM +0000, David Howells wrote:
> Add support for ML-DSA keys and signatures to the CMS/PKCS#7 and X.509
> implementations.  ML-DSA-44, -65 and -87 are all supported.  For X.509
> certificates, the TBSCertificate is required to be signed directly; for CMS,
> direct signing of the data is preferred, though use of SHA512 (and only that)
> as an intermediate hash of the content is permitted with signedAttrs.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Lukas Wunner <lukas@wunner.de>
> cc: Ignat Korchagin <ignat@cloudflare.com>
> cc: Stephan Mueller <smueller@chronox.de>
> cc: Eric Biggers <ebiggers@kernel.org>
> cc: Herbert Xu <herbert@gondor.apana.org.au>
> cc: keyrings@vger.kernel.org
> cc: linux-crypto@vger.kernel.org
> ---
>  crypto/asymmetric_keys/pkcs7_parser.c     | 24 +++++++++++++++++++-
>  crypto/asymmetric_keys/public_key.c       | 10 +++++++++
>  crypto/asymmetric_keys/x509_cert_parser.c | 27 ++++++++++++++++++++++-
>  include/linux/oid_registry.h              |  5 +++++
>  4 files changed, 64 insertions(+), 2 deletions(-)
> 
> diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
> index 3cdbab3b9f50..594a8f1d9dfb 100644
> --- a/crypto/asymmetric_keys/pkcs7_parser.c
> +++ b/crypto/asymmetric_keys/pkcs7_parser.c
> @@ -95,11 +95,18 @@ static int pkcs7_check_authattrs(struct pkcs7_message *msg)
>  	if (sinfo->authattrs) {
>  		want = true;
>  		msg->have_authattrs = true;
> +	} else if (sinfo->sig->algo_takes_data) {
> +		sinfo->sig->hash_algo = "none";
>  	}
>  
> -	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
> +	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next) {
>  		if (!!sinfo->authattrs != want)
>  			goto inconsistent;
> +
> +		if (!sinfo->authattrs &&
> +		    sinfo->sig->algo_takes_data)
> +			sinfo->sig->hash_algo = "none";

Why don't we have a constant for "none"?

$ git grep "\"none\"" security/
security/apparmor/audit.c:      "none",
security/apparmor/lib.c:        { "none", DEBUG_NONE },
security/security.c:    [LOCKDOWN_NONE] = "none",

$ git grep "\"none\"" crypto
crypto/asymmetric_keys/public_key.c:                                    hash_algo = "none";
crypto/asymmetric_keys/public_key.c:                            hash_algo = "none";
crypto/testmgr.h: * PKCS#1 RSA test vectors for hash algorithm "none"

IMHO, this a bad practice.


> +	}
>  	return 0;
>  
>  inconsistent:
> @@ -297,6 +304,21 @@ int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
>  		ctx->sinfo->sig->pkey_algo = "ecrdsa";
>  		ctx->sinfo->sig->encoding = "raw";
>  		break;
> +	case OID_id_ml_dsa_44:
> +		ctx->sinfo->sig->pkey_algo = "mldsa44";
> +		ctx->sinfo->sig->encoding = "raw";
> +		ctx->sinfo->sig->algo_takes_data = true;
> +		break;
> +	case OID_id_ml_dsa_65:
> +		ctx->sinfo->sig->pkey_algo = "mldsa65";
> +		ctx->sinfo->sig->encoding = "raw";
> +		ctx->sinfo->sig->algo_takes_data = true;
> +		break;
> +	case OID_id_ml_dsa_87:
> +		ctx->sinfo->sig->pkey_algo = "mldsa87";
> +		ctx->sinfo->sig->encoding = "raw";
> +		ctx->sinfo->sig->algo_takes_data = true;
> +		break;
>  	default:
>  		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
>  		return -ENOPKG;
> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
> index a46356e0c08b..09a0b83d5d77 100644
> --- a/crypto/asymmetric_keys/public_key.c
> +++ b/crypto/asymmetric_keys/public_key.c
> @@ -142,6 +142,16 @@ software_key_determine_akcipher(const struct public_key *pkey,
>  		if (strcmp(hash_algo, "streebog256") != 0 &&
>  		    strcmp(hash_algo, "streebog512") != 0)
>  			return -EINVAL;
> +	} else if (strcmp(pkey->pkey_algo, "mldsa44") == 0 ||
> +		   strcmp(pkey->pkey_algo, "mldsa65") == 0 ||
> +		   strcmp(pkey->pkey_algo, "mldsa87") == 0) {
> +		if (strcmp(encoding, "raw") != 0)
> +			return -EINVAL;
> +		if (!hash_algo)
> +			return -EINVAL;
> +		if (strcmp(hash_algo, "none") != 0 &&
> +		    strcmp(hash_algo, "sha512") != 0)
> +			return -EINVAL;
>  	} else {
>  		/* Unknown public key algorithm */
>  		return -ENOPKG;
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index b37cae914987..2fe094f5caf3 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -257,6 +257,15 @@ int x509_note_sig_algo(void *context, size_t hdrlen, unsigned char tag,
>  	case OID_gost2012Signature512:
>  		ctx->cert->sig->hash_algo = "streebog512";
>  		goto ecrdsa;
> +	case OID_id_ml_dsa_44:
> +		ctx->cert->sig->pkey_algo = "mldsa44";
> +		goto ml_dsa;
> +	case OID_id_ml_dsa_65:
> +		ctx->cert->sig->pkey_algo = "mldsa65";
> +		goto ml_dsa;
> +	case OID_id_ml_dsa_87:
> +		ctx->cert->sig->pkey_algo = "mldsa87";
> +		goto ml_dsa;
>  	}
>  
>  rsa_pkcs1:
> @@ -274,6 +283,12 @@ int x509_note_sig_algo(void *context, size_t hdrlen, unsigned char tag,
>  	ctx->cert->sig->encoding = "x962";
>  	ctx->sig_algo = ctx->last_oid;
>  	return 0;
> +ml_dsa:
> +	ctx->cert->sig->algo_takes_data = true;
> +	ctx->cert->sig->hash_algo = "none";
> +	ctx->cert->sig->encoding = "raw";
> +	ctx->sig_algo = ctx->last_oid;
> +	return 0;
>  }
>  
>  /*
> @@ -300,7 +315,8 @@ int x509_note_signature(void *context, size_t hdrlen,
>  
>  	if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0 ||
>  	    strcmp(ctx->cert->sig->pkey_algo, "ecrdsa") == 0 ||
> -	    strcmp(ctx->cert->sig->pkey_algo, "ecdsa") == 0) {
> +	    strcmp(ctx->cert->sig->pkey_algo, "ecdsa") == 0 ||
> +	    strncmp(ctx->cert->sig->pkey_algo, "mldsa", 5) == 0) {
>  		/* Discard the BIT STRING metadata */
>  		if (vlen < 1 || *(const u8 *)value != 0)
>  			return -EBADMSG;
> @@ -524,6 +540,15 @@ int x509_extract_key_data(void *context, size_t hdrlen,
>  			return -ENOPKG;
>  		}
>  		break;
> +	case OID_id_ml_dsa_44:
> +		ctx->cert->pub->pkey_algo = "mldsa44";
> +		break;
> +	case OID_id_ml_dsa_65:
> +		ctx->cert->pub->pkey_algo = "mldsa65";
> +		break;
> +	case OID_id_ml_dsa_87:
> +		ctx->cert->pub->pkey_algo = "mldsa87";
> +		break;
>  	default:
>  		return -ENOPKG;
>  	}
> diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
> index 6de479ebbe5d..ebce402854de 100644
> --- a/include/linux/oid_registry.h
> +++ b/include/linux/oid_registry.h
> @@ -145,6 +145,11 @@ enum OID {
>  	OID_id_rsassa_pkcs1_v1_5_with_sha3_384, /* 2.16.840.1.101.3.4.3.15 */
>  	OID_id_rsassa_pkcs1_v1_5_with_sha3_512, /* 2.16.840.1.101.3.4.3.16 */
>  
> +	/* NIST FIPS-204 ML-DSA */
> +	OID_id_ml_dsa_44,			/* 2.16.840.1.101.3.4.3.17 */
> +	OID_id_ml_dsa_65,			/* 2.16.840.1.101.3.4.3.18 */
> +	OID_id_ml_dsa_87,			/* 2.16.840.1.101.3.4.3.19 */
> +
>  	OID__NR
>  };
>  
> 

BR, Jarkko
Re: [PATCH v14 4/5] pkcs7, x509: Add ML-DSA support
Posted by Christophe Leroy (CS GROUP) 1 week, 5 days ago 

Le 25/01/2026 à 15:42, Jarkko Sakkinen a écrit :
> On Wed, Jan 21, 2026 at 10:36:06PM +0000, David Howells wrote:
>> Add support for ML-DSA keys and signatures to the CMS/PKCS#7 and X.509
>> implementations.  ML-DSA-44, -65 and -87 are all supported.  For X.509
>> certificates, the TBSCertificate is required to be signed directly; for CMS,
>> direct signing of the data is preferred, though use of SHA512 (and only that)
>> as an intermediate hash of the content is permitted with signedAttrs.
>>
>> Signed-off-by: David Howells <dhowells@redhat.com>
>> cc: Lukas Wunner <lukas@wunner.de>
>> cc: Ignat Korchagin <ignat@cloudflare.com>
>> cc: Stephan Mueller <smueller@chronox.de>
>> cc: Eric Biggers <ebiggers@kernel.org>
>> cc: Herbert Xu <herbert@gondor.apana.org.au>
>> cc: keyrings@vger.kernel.org
>> cc: linux-crypto@vger.kernel.org
>> ---
>>   crypto/asymmetric_keys/pkcs7_parser.c     | 24 +++++++++++++++++++-
>>   crypto/asymmetric_keys/public_key.c       | 10 +++++++++
>>   crypto/asymmetric_keys/x509_cert_parser.c | 27 ++++++++++++++++++++++-
>>   include/linux/oid_registry.h              |  5 +++++
>>   4 files changed, 64 insertions(+), 2 deletions(-)
>>
>> diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
>> index 3cdbab3b9f50..594a8f1d9dfb 100644
>> --- a/crypto/asymmetric_keys/pkcs7_parser.c
>> +++ b/crypto/asymmetric_keys/pkcs7_parser.c
>> @@ -95,11 +95,18 @@ static int pkcs7_check_authattrs(struct pkcs7_message *msg)
>>   	if (sinfo->authattrs) {
>>   		want = true;
>>   		msg->have_authattrs = true;
>> +	} else if (sinfo->sig->algo_takes_data) {
>> +		sinfo->sig->hash_algo = "none";
>>   	}
>>   
>> -	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next)
>> +	for (sinfo = sinfo->next; sinfo; sinfo = sinfo->next) {
>>   		if (!!sinfo->authattrs != want)
>>   			goto inconsistent;
>> +
>> +		if (!sinfo->authattrs &&
>> +		    sinfo->sig->algo_takes_data)
>> +			sinfo->sig->hash_algo = "none";
> 
> Why don't we have a constant for "none"?
> 
> $ git grep "\"none\"" security/
> security/apparmor/audit.c:      "none",
> security/apparmor/lib.c:        { "none", DEBUG_NONE },
> security/security.c:    [LOCKDOWN_NONE] = "none",
> 
> $ git grep "\"none\"" crypto
> crypto/asymmetric_keys/public_key.c:                                    hash_algo = "none";
> crypto/asymmetric_keys/public_key.c:                            hash_algo = "none";
> crypto/testmgr.h: * PKCS#1 RSA test vectors for hash algorithm "none"
> 
> IMHO, this a bad practice.

What is a bad practice ?

$ git grep "\"sha256\"" security
security/apparmor/apparmorfs.c:         dent = 
aafs_create_file("sha256", S_IFREG | 0444, dir,
security/apparmor/apparmorfs.c: return rawdata_get_link_base(dentry, 
inode, done, "sha256");
security/apparmor/apparmorfs.c:         dent = create_profile_file(dir, 
"sha256", profile,
security/integrity/ima/Kconfig: default "sha256" if IMA_DEFAULT_HASH_SHA256
security/ipe/audit.c:#define IPE_AUDIT_HASH_ALG "sha256" /* keep in sync 
with audit_policy() */

$ git grep "\"sha256\"" crypto
crypto/asymmetric_keys/mscode_parser.c:         ctx->digest_algo = "sha256";
crypto/asymmetric_keys/pkcs7_parser.c: 
ctx->sinfo->sig->hash_algo = "sha256";
crypto/asymmetric_keys/public_key.c:                strcmp(hash_algo, 
"sha256") != 0 &&
crypto/asymmetric_keys/x509_cert_parser.c: 
ctx->cert->sig->hash_algo = "sha256";
crypto/asymmetric_keys/x509_cert_parser.c: 
ctx->cert->sig->hash_algo = "sha256";
crypto/drbg.c:          .cra_name = "sha256",
crypto/drbg.c:          .backend_cra_name = "sha256",
crypto/essiv.c: /* Synchronous hash, e.g., "sha256" */
crypto/krb5/rfc8009_aes2.c:     .hash_name      = "sha256",
crypto/sha256.c:                .base.cra_name          = "sha256",
crypto/sha256.c:MODULE_ALIAS_CRYPTO("sha256");
crypto/tcrypt.c:                ret = min(ret, tcrypt_test("sha256"));
crypto/tcrypt.c:                test_hash_speed("sha256", sec, 
generic_hash_speed_template);
crypto/tcrypt.c:                test_ahash_speed("sha256", sec, 
generic_hash_speed_template);
crypto/testmgr.c:               .alg = "sha256",

How is the handling of "none" different from other hash algorithms ?

Christophe
Re: [PATCH v14 4/5] pkcs7, x509: Add ML-DSA support
Posted by David Howells 1 week, 5 days ago 
Jarkko Sakkinen <jarkko@kernel.org> wrote:

> Why don't we have a constant for "none"?
> 
> $ git grep "\"none\"" security/
> security/apparmor/audit.c:      "none",
> security/apparmor/lib.c:        { "none", DEBUG_NONE },
> security/security.c:    [LOCKDOWN_NONE] = "none",
> 
> $ git grep "\"none\"" crypto
> crypto/asymmetric_keys/public_key.c:                                    hash_algo = "none";
> crypto/asymmetric_keys/public_key.c:                            hash_algo = "none";
> crypto/testmgr.h: * PKCS#1 RSA test vectors for hash algorithm "none"
> 
> IMHO, this a bad practice.

You'd think that the compiler and linker ought to be able to deal with
read-only string sharing within compilation units.  I don't particularly want
to deal with combining every "none" string within the kernel into one within
this patchset.

I could move back to using an enum of algorithms, I suppose - though again,
I'd rather not do that in this patchset.

David
Re: [PATCH v14 4/5] pkcs7, x509: Add ML-DSA support
Posted by James Bottomley 1 week, 5 days ago 
On Mon, 2026-01-26 at 11:25 +0000, David Howells wrote:
> Jarkko Sakkinen <jarkko@kernel.org> wrote:
> 
> > Why don't we have a constant for "none"?
> > 
> > $ git grep "\"none\"" security/
> > security/apparmor/audit.c:      "none",
> > security/apparmor/lib.c:        { "none", DEBUG_NONE },
> > security/security.c:    [LOCKDOWN_NONE] = "none",
> > 
> > $ git grep "\"none\"" crypto
> > crypto/asymmetric_keys/public_key.c:                               
> >      hash_algo = "none";
> > crypto/asymmetric_keys/public_key.c:                           
> > hash_algo = "none";
> > crypto/testmgr.h: * PKCS#1 RSA test vectors for hash algorithm
> > "none"
> > 
> > IMHO, this a bad practice.
> 
> You'd think that the compiler and linker ought to be able to deal
> with read-only string sharing within compilation units.

They do ... it's -fmerge-string-constants, which has been enabled in
gcc for any optimization level above 0 for ages.  The way its supposed
to work is that each string gets its own rodata section and the linker
eliminates duplicates.

>   I don't particularly want to deal with combining every "none"
> string within the kernel into one within this patchset.

Agree: let's just rely on the tools and if they're not getting it right
someone can fix the tools.

Regards,

James

Patchew 2.1-devel-b67e4c2

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