From 472ec944d2ed81d0304cc6cac80946a6a44776be Mon Sep 17 00:00:00 2001
From: Freya Murphy <freya@freyacat.org>
Date: Sat, 19 Apr 2025 16:36:51 -0400
Subject: UEFI and republicans

---
 kernel/efi/mmap.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 kernel/efi/mmap.c

(limited to 'kernel/efi/mmap.c')

diff --git a/kernel/efi/mmap.c b/kernel/efi/mmap.c
new file mode 100644
index 0000000..26aba6a
--- /dev/null
+++ b/kernel/efi/mmap.c
@@ -0,0 +1,87 @@
+#include <lib.h>
+#include <efi.h>
+#include <comus/efi.h>
+#include <comus/memory.h>
+
+struct memory_map efi_mmap = { 0 };
+
+EFI_STATUS efi_load_mmap(EFI_SYSTEM_TABLE *ST)
+{
+	EFI_STATUS status = EFI_SUCCESS;
+
+	EFI_MEMORY_DESCRIPTOR *memory_map = NULL;
+	UINT32 version = 0;
+	UINTN map_key = 0;
+	UINTN descriptor_size = 0;
+	UINTN memory_map_size = 0;
+
+	status = ST->BootServices->GetMemoryMap(
+		&memory_map_size, memory_map, &map_key, &descriptor_size, &version);
+
+	assert(status != EFI_SUCCESS,
+		   "GetMemoryMap should NEVER succeed the first time");
+	if (status != EFI_BUFFER_TOO_SMALL)
+		return status;
+
+	UINTN encompassing_size = memory_map_size + (2 * descriptor_size);
+	void *buffer = NULL;
+	status = ST->BootServices->AllocatePool(EfiLoaderData, encompassing_size,
+											&buffer);
+
+	if (EFI_ERROR(status))
+		return status;
+
+	memory_map = (EFI_MEMORY_DESCRIPTOR *)buffer;
+	memory_map_size = encompassing_size;
+	status = ST->BootServices->GetMemoryMap(
+		&memory_map_size, memory_map, &map_key, &descriptor_size, &version);
+
+	if (EFI_ERROR(status))
+		return status;
+
+	uint32_t idx = 0;
+	for (size_t i = 0; i < (memory_map_size / descriptor_size); i++) {
+		EFI_MEMORY_DESCRIPTOR *seg =
+			(EFI_MEMORY_DESCRIPTOR *)((char *)memory_map +
+									  (descriptor_size * i));
+		if (idx >= N_MMAP_ENTRY)
+			panic("Too many mmap entries: limit is %d", N_MMAP_ENTRY);
+		efi_mmap.entries[idx].addr = seg->PhysicalStart;
+		efi_mmap.entries[idx].len = seg->NumberOfPages * PAGE_SIZE;
+		switch (seg->Type) {
+		case EfiReservedMemoryType:
+		case EfiMemoryMappedIO:
+		case EfiMemoryMappedIOPortSpace:
+			efi_mmap.entries[idx].type = SEG_TYPE_RESERVED;
+			break;
+		case EfiConventionalMemory:
+			efi_mmap.entries[idx].type = SEG_TYPE_FREE;
+			break;
+		case EfiACPIReclaimMemory:
+		case EfiACPIMemoryNVS:
+			efi_mmap.entries[idx].type = SEG_TYPE_ACPI;
+			break;
+		case EfiUnusableMemory:
+			efi_mmap.entries[idx].type = SEG_TYPE_DEFECTIVE;
+			break;
+		default:
+			efi_mmap.entries[idx].type = SEG_TYPE_EFI;
+			break;
+		}
+		idx++;
+	}
+	efi_mmap.entry_count = idx;
+
+	ST->BootServices->FreePool(buffer);
+
+	return status;
+}
+
+int efi_get_mmap(struct memory_map *map)
+{
+	if (efi_mmap.entry_count) {
+		*map = efi_mmap;
+		return 0;
+	}
+	return 1;
+}
-- 
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