kexec: clean up arch_kexec_kernel_verify_sig

Before commit 105e10e2cf1c ("kexec_file: drop weak attribute from
functions"), there was already no arch-specific implementation
of arch_kexec_kernel_verify_sig. With weak attribute dropped by that
commit, arch_kexec_kernel_verify_sig is completely useless. So clean it
up.

Note later patches are dependent on this patch so it should be backported
to the stable tree as well.

Cc: stable@vger.kernel.org
Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Reviewed-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
[zohar@linux.ibm.com: reworded patch description "Note"]
Link: https://lore.kernel.org/linux-integrity/20220714134027.394370-1-coxu@redhat.com/Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

include/linux/kexec.h

@@ -212,11 +212,6 @@ static inline void *arch_kexec_kernel_image_load(struct kimage *image)
 }
 #endif
 
-#ifdef CONFIG_KEXEC_SIG
-int arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
-				 unsigned long buf_len);
-#endif
-
 extern int kexec_add_buffer(struct kexec_buf *kbuf);
 int kexec_locate_mem_hole(struct kexec_buf *kbuf);
 

kernel/kexec_file.c

@@ -81,24 +81,6 @@ int kexec_image_post_load_cleanup_default(struct kimage *image)
 	return image->fops->cleanup(image->image_loader_data);
 }
 
-#ifdef CONFIG_KEXEC_SIG
-static int kexec_image_verify_sig_default(struct kimage *image, void *buf,
-					  unsigned long buf_len)
-{
-	if (!image->fops || !image->fops->verify_sig) {
-		pr_debug("kernel loader does not support signature verification.\n");
-		return -EKEYREJECTED;
-	}
-
-	return image->fops->verify_sig(buf, buf_len);
-}
-
-int arch_kexec_kernel_verify_sig(struct kimage *image, void *buf, unsigned long buf_len)
-{
-	return kexec_image_verify_sig_default(image, buf, buf_len);
-}
-#endif
-
 /*
  * Free up memory used by kernel, initrd, and command line. This is temporary
  * memory allocation which is not needed any more after these buffers have
@@ -141,13 +123,24 @@ void kimage_file_post_load_cleanup(struct kimage *image)
 }
 
 #ifdef CONFIG_KEXEC_SIG
+static int kexec_image_verify_sig(struct kimage *image, void *buf,
+				  unsigned long buf_len)
+{
+	if (!image->fops || !image->fops->verify_sig) {
+		pr_debug("kernel loader does not support signature verification.\n");
+		return -EKEYREJECTED;
+	}
+
+	return image->fops->verify_sig(buf, buf_len);
+}
+
 static int
 kimage_validate_signature(struct kimage *image)
 {
 	int ret;
 
-	ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
-					   image->kernel_buf_len);
+	ret = kexec_image_verify_sig(image, image->kernel_buf,
+				     image->kernel_buf_len);
 	if (ret) {
 
 		if (sig_enforce) {