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#include <stddef.h>
#include <stdint.h>
struct page_generic {
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 large : 1; // also PAT
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 page_generic pml4_identity[512];
__attribute__((aligned(4096)))
struct page_generic pdpte_low[512]; // 0-512gb
__attribute__((aligned(4096)))
struct page_generic 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 page_generic) {
.present = 1,
.writeable = 1,
.address = ((uintptr_t)pdpte_low) >> 12,
};
pdpte_low[0] = (struct page_generic) {
.present = 1,
.writeable = 1,
.address = ((uintptr_t)pde_low) >> 12,
};
for (int i = 0; i < 512; i++) {
pde_low[i] = (struct page_generic) {
.present = 1,
.writeable = 1,
.large = 1,
.address = (i * 2 * 1024 * 1024) >> 12,
};
}
}
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