x86/sgx: Use SHA-256 library API instead of crypto_shash API

This user of SHA-256 does not support any other algorithm, so the
crypto_shash abstraction provides no value.  Just use the SHA-256
library API instead, which is much simpler and easier to use.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250428183838.799333-1-ebiggers%40kernel.org

Author: ebiggers

arch/x86/Kconfig

@@ -1881,8 +1881,7 @@ endchoice
 config X86_SGX
 	bool "Software Guard eXtensions (SGX)"
 	depends on X86_64 && CPU_SUP_INTEL && X86_X2APIC
-	depends on CRYPTO=y
-	depends on CRYPTO_SHA256=y
+	select CRYPTO_LIB_SHA256
 	select MMU_NOTIFIER
 	select NUMA_KEEP_MEMINFO if NUMA
 	select XARRAY_MULTI

arch/x86/kernel/cpu/sgx/driver.h

@@ -2,7 +2,6 @@
 #ifndef __ARCH_SGX_DRIVER_H__
 #define __ARCH_SGX_DRIVER_H__
 
-#include <crypto/hash.h>
 #include <linux/kref.h>
 #include <linux/mmu_notifier.h>
 #include <linux/radix-tree.h>

arch/x86/kernel/cpu/sgx/ioctl.c

@@ -3,6 +3,7 @@
 
 #include <asm/mman.h>
 #include <asm/sgx.h>
+#include <crypto/sha2.h>
 #include <linux/mman.h>
 #include <linux/delay.h>
 #include <linux/file.h>
@@ -463,31 +464,6 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
 	return ret;
 }
 
-static int __sgx_get_key_hash(struct crypto_shash *tfm, const void *modulus,
-			      void *hash)
-{
-	SHASH_DESC_ON_STACK(shash, tfm);
-
-	shash->tfm = tfm;
-
-	return crypto_shash_digest(shash, modulus, SGX_MODULUS_SIZE, hash);
-}
-
-static int sgx_get_key_hash(const void *modulus, void *hash)
-{
-	struct crypto_shash *tfm;
-	int ret;
-
-	tfm = crypto_alloc_shash("sha256", 0, CRYPTO_ALG_ASYNC);
-	if (IS_ERR(tfm))
-		return PTR_ERR(tfm);
-
-	ret = __sgx_get_key_hash(tfm, modulus, hash);
-
-	crypto_free_shash(tfm);
-	return ret;
-}
-
 static int sgx_encl_init(struct sgx_encl *encl, struct sgx_sigstruct *sigstruct,
 			 void *token)
 {
@@ -523,9 +499,7 @@ static int sgx_encl_init(struct sgx_encl *encl, struct sgx_sigstruct *sigstruct,
 	    sgx_xfrm_reserved_mask)
 		return -EINVAL;
 
-	ret = sgx_get_key_hash(sigstruct->modulus, mrsigner);
-	if (ret)
-		return ret;
+	sha256(sigstruct->modulus, SGX_MODULUS_SIZE, (u8 *)mrsigner);
 
 	mutex_lock(&encl->lock);