1 files changed, 131 insertions, 0 deletions
diff --git a/src/kernel/arch/amd64/32/paging.c b/src/kernel/arch/amd64/32/paging.c
new file mode 100644
index 0000000..975dd98
--- /dev/null
+++ b/src/kernel/arch/amd64/32/paging.c
@@ -0,0 +1,131 @@
+#include <stddef.h>
+#include <stdint.h>
+
+struct pml4e {
+	uint64_t present   : 1;
+	uint64_t writeable : 1;
+	uint64_t user      : 1;
+	uint64_t writethru : 1;
+
+	uint64_t uncached  : 1;
+	uint64_t accessed  : 1;
+	uint64_t _unused1  : 1;
+	uint64_t reserved  : 1; // always 0
+
+	uint64_t _unused2  : 3;
+	uint64_t _unused3  : 1; // HLAT thing
+
+	uint64_t address   : 40;
+
+	uint64_t _unused4  : 11;
+	uint64_t noexec    : 1;
+} __attribute__((packed));
+
+struct pdpte { // page directory pointer table entry, 1gb page | 512 * pde
+	uint64_t present   : 1;
+	uint64_t writeable : 1;
+	uint64_t user      : 1;
+	uint64_t writethru : 1;
+
+	uint64_t uncached  : 1;
+	uint64_t accessed  : 1;
+	uint64_t _unused1  : 1;
+	uint64_t large     : 1; // 1gb page
+
+	uint64_t _unused2  : 3;
+	uint64_t _unused3  : 1; // HLAT
+
+	uint64_t address   : 40;
+
+	uint64_t _unused4  : 11;
+	uint64_t noexec    : 1;
+} __attribute__((packed));
+
+struct pde { // page directory entry, 2mb page | 512 * pte
+	uint64_t present   : 1;
+	uint64_t writeable : 1;
+	uint64_t user      : 1;
+	uint64_t writethru : 1;
+
+	uint64_t uncached  : 1;
+	uint64_t accessed  : 1;
+	uint64_t dirty     : 1; // only if large
+	uint64_t large     : 1; // 2mb
+
+	uint64_t global    : 1; // only if large ; TODO enable CR4.PGE
+	uint64_t _unused2  : 2;
+	uint64_t _unused3  : 1; // HLAT
+
+	uint64_t address   : 40; // highest bit - PAT
+
+	uint64_t _unused4  : 7;
+	uint64_t pke       : 4;
+	uint64_t noexec    : 1;
+} __attribute__((packed));
+
+struct pte { // page table entry, 4kb page
+	uint64_t present   : 1;
+	uint64_t writeable : 1;
+	uint64_t user      : 1;
+	uint64_t writethru : 1;
+
+	uint64_t uncached  : 1;
+	uint64_t accessed  : 1;
+	uint64_t dirty     : 1;
+	uint64_t pat       : 1;
+
+	uint64_t global    : 1; // TODO enable CR4.PGE
+	uint64_t _unused2  : 2;
+	uint64_t _unused3  : 1; // HLAT
+
+	uint64_t address   : 40;
+
+	uint64_t _unused4  : 7;
+	uint64_t pke       : 4;
+	uint64_t noexec    : 1;
+} __attribute__((packed));
+
+__attribute__((aligned(4096)))
+struct pml4e pml4_identity[512];
+
+__attribute__((aligned(4096)))
+struct pdpte pdpte_low[512]; // 0-512gb
+
+__attribute__((aligned(4096)))
+struct pde pde_low[512]; // 0-1gb
+
+
+static void *memset32(void *s, int c, size_t n) {
+	uint8_t *s2 = s;
+	for (size_t i = 0; i < n; i++)
+		s2[i] = c;
+	return s;
+}
+
+
+void pml4_identity_init(void) {
+	memset32(pml4_identity, 0, sizeof pml4_identity);
+	memset32(pdpte_low, 0, sizeof pdpte_low);
+	memset32(pde_low, 0, sizeof pde_low);
+
+	pml4_identity[0] = (struct pml4e) {
+		.present = 1,
+		.writeable = 1,
+		.address = ((uintptr_t)pdpte_low) >> 12,
+	};
+
+	pdpte_low[0] = (struct pdpte) {
+		.present = 1,
+		.writeable = 1,
+		.address = ((uintptr_t)pde_low) >> 12,
+	};
+
+	for (int i = 0; i < 512; i++) {
+		pde_low[i] = (struct pde) {
+			.present = 1,
+			.writeable = 1,
+			.large = 1,
+			.address = (i * 2 * 1024 * 1024) >> 12,
+		};
+	}
+}