s390/kexec_file: Add purgatory

The common code expects the architecture to have a purgatory that runs
between the two kernels. Add it now. For simplicity first skip crash
support.

Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/arch/s390/purgatory/purgatory.c b/arch/s390/purgatory/purgatory.c
new file mode 100644
index 000000000000..52b92f2bf0b9
--- /dev/null
+++ b/arch/s390/purgatory/purgatory.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Purgatory code running between two kernels.
+ *
+ * Copyright IBM Corp. 2018
+ *
+ * Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
+ */
+
+#include <linux/kexec.h>
+#include <linux/sha256.h>
+#include <linux/string.h>
+#include <asm/purgatory.h>
+
+struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX];
+u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE];
+
+u64 kernel_entry;
+
+int verify_sha256_digest(void)
+{
+	struct kexec_sha_region *ptr, *end;
+	u8 digest[SHA256_DIGEST_SIZE];
+	struct sha256_state sctx;
+
+	sha256_init(&sctx);
+	end = purgatory_sha_regions + ARRAY_SIZE(purgatory_sha_regions);
+
+	for (ptr = purgatory_sha_regions; ptr < end; ptr++)
+		sha256_update(&sctx, (uint8_t *)(ptr->start), ptr->len);
+
+	sha256_final(&sctx, digest);
+
+	if (memcmp(digest, purgatory_sha256_digest, sizeof(digest)))
+		return 1;
+
+	return 0;
+}