kexec/uefi: copy secure_boot flag in boot params across kexec reboot

Kexec reboot in case secure boot being enabled does not keep the secure
boot mode in new kernel, so later one can load unsigned kernel via legacy
kexec_load.  In this state, the system is missing the protections provided
by secure boot. Adding a patch to fix this by retain the secure_boot flag
in original kernel.

secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
stub. Fixing this issue by copying secure_boot flag across kexec reboot.

Signed-off-by: Dave Young <dyoung@redhat.com>
static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
{
	bool trusted;
	int ret;

	ret = verify_pefile_signature(kernel, kernel_len,
				      system_trusted_keyring,
				      VERIFYING_KEXEC_PE_SIGNATURE,
				      &trusted);
	if (ret < 0)
		return ret;
	if (!trusted)
		return -EKEYREJECTED;
	return 0;
}

static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
{
	bool trusted;
	int ret;

	ret = verify_pefile_signature(kernel, kernel_len,
				      system_trusted_keyring,
				      VERIFYING_KEXEC_PE_SIGNATURE,
				      &trusted);
	if (ret < 0)
		return ret;
	if (!trusted)
		return -EKEYREJECTED;
	return 0;
}
