arm64: Store IMA log information in kimage used for kexec

Address and size of the buffer containing the IMA measurement log need
to be passed from the current kernel to the next kernel on kexec.

Add address and size fields to "struct kimage_arch" for ARM64 platform
to hold the address and size of the IMA measurement log buffer.
Define an architecture specific function for ARM64 namely
arch_ima_add_kexec_buffer() that will set the address and size of
the current kernel's IMA buffer to be passed to the next kernel on kexec.

Co-developed-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

arch/arm64/include/asm/ima.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARCH_IMA_H
+#define _ASM_ARCH_IMA_H
+
+struct kimage;
+
+#ifdef CONFIG_IMA_KEXEC
+int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
+			      size_t size);
+#else
+static inline int arch_ima_add_kexec_buffer(struct kimage *image,
+			unsigned long load_addr, size_t size)
+{
+	return 0;
+}
+#endif /* CONFIG_IMA_KEXEC */
+#endif /* _ASM_ARCH_IMA_H */

arch/arm64/include/asm/kexec.h

@@ -100,6 +100,9 @@ struct kimage_arch {
 	void *elf_headers;
 	unsigned long elf_headers_mem;
 	unsigned long elf_headers_sz;
+
+	phys_addr_t ima_buffer_addr;
+	size_t ima_buffer_size;
 };
 
 extern const struct kexec_file_ops kexec_image_ops;

arch/arm64/kernel/machine_kexec_file.c

@@ -38,6 +38,23 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 	NULL
 };
 
+/**
+ * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
+ *
+ * Architectures should use this function to pass on the IMA buffer
+ * information to the next kernel.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
+			      size_t size)
+{
+	image->arch.ima_buffer_addr = load_addr;
+	image->arch.ima_buffer_size = size;
+	return 0;
+}
+
+
 int arch_kimage_file_post_load_cleanup(struct kimage *image)
 {
 	vfree(image->arch.dtb);