dreamcast-vmem.c

#include <errno.h>
#include <stdlib.h>
#include <stdint.h>
#include <kos.h>

static volatile uint32_t * const pteh = (uint32 *)(0xff000000);
static volatile uint32_t * const ptel = (uint32 *)(0xff000004);
static volatile uint32_t * const mmucr = (uint32 *)(0xff000010);

#define BUILD_PTEH(VA, ASID) \
    ( ((VA) & 0xfffffc00) | ((ASID) & 0xff) )

#define SET_PTEH(VA, ASID) \
    do { *pteh = BUILD_PTEH(VA, ASID); } while(0)

#define BUILD_PTEL(PA, V, SZ, PR, C, D, SH, WT) \
    ( ((PA) & 0x1ffffc00) | ((V) << 8) \
      | ( ((SZ) & 2) << 6 ) | ( ((SZ) & 1) << 4 ) \
      | ( (PR) << 5 ) \
      | ( (C) << 3 ) \
      | ( (D) << 2 ) \
      | ( (SH) << 1 ) \
      | ( (WT) << 0 ) )

#define SET_PTEL(PA, V, SZ, PR, C, D, SH, WT) \
    do { *ptel = BUILD_PTEL(PA, V, SZ, PR, C, D, SH, WT); } while (0)

#define SET_MMUCR(URB, URC, SQMD, SV, TI, AT) \
    do { *mmucr = ((URB) << 18) \
                      | ((URC) << 10) \
                      | ((SQMD) << 9) \
                      | ((SV) << 8) \
                      | ((TI) << 2) \
                      | ((AT) << 0); } while(0)

#define SET_URC(URC) \
    do { *mmucr = (*mmucr & ~(63 << 10)) \
                      | (((URC) & 63) << 10); } while(0)

#define GET_URC() ((*mmucr >> 10) & 63)

#define INCR_URC() \
    do { SET_URC(GET_URC() + 1); } while(0)

KOS_INIT_FLAGS(INIT_DEFAULT);

enum page_size {
	PAGE_SIZE_1K,
	PAGE_SIZE_4K,
	PAGE_SIZE_64K,
	PAGE_SIZE_1M,
};

enum page_prot {
	PAGE_PROT_RO,
	PAGE_PROT_RW,
	PAGE_PROT_RO_U,
	PAGE_PROT_RW_U,
};

static int map_page(void *ptr, uint32_t virt_addr, enum page_size size)
{
	unsigned int page_mask[] = { 0x3ff, 0xfff, 0xffff, 0xfffff };
	uint32_t phys_addr = (uint32_t)ptr;

	if (phys_addr & virt_addr & page_mask[size])
		return -EINVAL;

	SET_PTEH(virt_addr, 0);
	SET_PTEL(phys_addr, 1, size, PAGE_PROT_RW, 1, 0, 0, 0);
	__asm__("ldtlb");

	INCR_URC();

	return 0;
}

void mmu_reset_itlb();

int main(void)
{
	unsigned int i;
	char *addr;
	int err;

	fclose(stdout);
	stdout = stderr;

	printf("Hello world.\n");

	/* Turn ON MMU */
	SET_MMUCR(0x3f, 0, 0, 1, 1, 1);

	mmu_reset_itlb();

	printf("MMU enabled.\n");

	addr = aligned_alloc(1024 * 1024, 2 * 1024 * 1024);
	if (!addr) {
		printf("Could not allocate memory\n");
		return 1;
	}

	printf("Memory allocated to 0x%x\n", (unsigned int)addr);

	err = map_page(addr, 0x0, PAGE_SIZE_1M);
	if (err)
		goto handle_err;

	printf("Mapped correctly!\n");

	*(unsigned int *)addr = 0xdeadbeef;

	printf("Reading from virtual memory: 0x%x\n", *(unsigned int *)0x0);

handle_err:
	if (err)
		printf("Could not map page: %d\n", err);

	printf("Free address\n");
	free(addr);

#if 1
	/* Turn OFF MMU */
	*mmucr = 0x00000204;
#endif

	return err != 0;
}