HV: Add elf loader sketch

This patch adds a function elf_loader() to load elf image.
It checks the elf header, get its 32/64 bit type, then calls
the corresponding loading routines, which are empty, and
will be realized later.

Tracked-On: #6323

Signed-off-by: Zhou, Wu <wu.zhou@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/Makefile

@@ -289,6 +289,9 @@ endif
 ifeq ($(CONFIG_GUEST_KERNEL_RAWIMAGE),y)
 VP_BASE_C_SRCS += boot/guest/rawimage_loader.c
 endif
+ifeq ($(CONFIG_GUEST_KERNEL_ELF),y)
+VP_BASE_C_SRCS += boot/guest/elf_loader.c
+endif
 VP_BASE_C_SRCS += common/hv_main.c
 VP_BASE_C_SRCS += common/vm_load.c
 VP_BASE_C_SRCS += arch/x86/configs/pci_dev.c

hypervisor/boot/guest/elf_loader.c

@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2021 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm/guest/vm.h>
+#include <vboot.h>
+#include <elf.h>
+#include <logmsg.h>
+
+/**
+ * @pre vm != NULL
+ * must run in stac/clac context
+ */
+static void *do_load_elf64(struct acrn_vm *vm)
+{
+	struct sw_kernel_info *sw_kernel = &(vm->sw.kernel_info);
+	void *p_elf_img = (void *)sw_kernel->kernel_src_addr;
+
+	return p_elf_img;
+}
+
+/**
+ * @pre vm != NULL
+ * must run in stac/clac context
+ */
+static void *do_load_elf32(struct acrn_vm *vm)
+{
+	struct sw_kernel_info *sw_kernel = &(vm->sw.kernel_info);
+	void *p_elf_img = (void *)sw_kernel->kernel_src_addr;
+
+	return p_elf_img;
+}
+
+/**
+ * @pre vm != NULL
+ */
+static int32_t load_elf(struct acrn_vm *vm)
+{
+	void *elf_entry = NULL;
+	struct sw_kernel_info *sw_kernel = &(vm->sw.kernel_info);
+	void *p_elf_img = (void *)sw_kernel->kernel_src_addr;
+	int32_t ret = 0;
+
+	stac();
+
+	if (*(uint32_t *)p_elf_img == ELFMAGIC) {
+		if (*(uint8_t *)(p_elf_img + EI_CLASS) == ELFCLASS64) {
+			elf_entry = do_load_elf64(vm);
+		} else if (*(uint8_t *)(p_elf_img + EI_CLASS) == ELFCLASS32) {
+			elf_entry = do_load_elf32(vm);
+		} else {
+			pr_err("%s, unsupported elf class(%d)", __func__, *(uint8_t *)(p_elf_img + EI_CLASS));
+		}
+	} else {
+		pr_err("%s, booting elf but no elf header found!", __func__);
+	}
+
+	clac();
+
+	sw_kernel->kernel_entry_addr = elf_entry;
+
+	if (elf_entry == NULL) {
+		ret = -EFAULT;
+	}
+
+	return ret;
+}
+
+int32_t elf_loader(struct acrn_vm *vm)
+{
+	uint64_t vgdt_gpa = 0x800;
+
+	/*
+	 * TODO:
+	 *    - We need to initialize the guest BSP(boot strap processor) registers according to
+	 *	guest boot mode (real mode vs protect mode)
+	 *    - The memory layout usage is unclear, only GDT might be needed as its boot param.
+	 *	currently we only support Zephyr which has no needs on cmdline/e820/efimmap/etc.
+	 *	hardcode the vGDT GPA to 0x800 where is not used by Zephyr so far;
+	 */
+	init_vcpu_protect_mode_regs(vcpu_from_vid(vm, BSP_CPU_ID), vgdt_gpa);
+
+	return load_elf(vm);
+}

hypervisor/boot/include/guest/vboot.h

@@ -17,6 +17,8 @@ int32_t bzimage_loader(struct acrn_vm *vm);
 #ifdef CONFIG_GUEST_KERNEL_RAWIMAGE
 int32_t rawimage_loader(struct acrn_vm *vm);
 #endif
-
+#ifdef CONFIG_GUEST_KERNEL_ELF
+int32_t elf_loader(struct acrn_vm *vm);
+#endif
 
 #endif /* end of include guard: VBOOT_H */

hypervisor/common/vm_load.c

@@ -39,6 +39,11 @@ int32_t prepare_os_image(struct acrn_vm *vm)
 	case KERNEL_RAWIMAGE:
 		ret = rawimage_loader(vm);
 		break;
+#endif
+#ifdef CONFIG_GUEST_KERNEL_ELF
+	case KERNEL_ELF:
+		ret = elf_loader(vm);
+		break;
 #endif
 	default:
 		ret = -EINVAL;