kexec, KEYS: make the code in bzImage64_verify_sig generic

commit 278311e417 ("kexec, KEYS: Make use of platform keyring for
signature verify") adds platform keyring support on x86 kexec but not
arm64.

The code in bzImage64_verify_sig uses the keys on the
.builtin_trusted_keys, .machine, if configured and enabled,
.secondary_trusted_keys, also if configured, and .platform keyrings
to verify the signed kernel image as PE file.

Cc: kexec@lists.infradead.org
Cc: keyrings@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Reviewed-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Coiby Xu <coxu@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

include/linux/kexec.h

@@ -19,6 +19,7 @@
 #include <asm/io.h>
 
 #include <uapi/linux/kexec.h>
+#include <linux/verification.h>
 
 /* Location of a reserved region to hold the crash kernel.
  */
@@ -212,6 +213,12 @@ static inline void *arch_kexec_kernel_image_load(struct kimage *image)
 }
 #endif
 
+#ifdef CONFIG_KEXEC_SIG
+#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
+int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len);
+#endif
+#endif
+
 extern int kexec_add_buffer(struct kexec_buf *kbuf);
 int kexec_locate_mem_hole(struct kexec_buf *kbuf);