mango/arch/x86_64/pmap.c

#include <mango/compiler.h>
#include <mango/memblock.h>
#include <mango/pmap.h>
#include <mango/printk.h>
#include <mango/status.h>
#include <mango/types.h>
#include <mango/vm.h>

/* some helpful datasize constants */
#define C_1GiB          0x40000000ULL
#define C_2GiB          (2 * C_1GiB)

#define BAD_INDEX       ((unsigned int)-1)
#define PTR_TO_ENTRY(x) (((x) & ~VM_PAGE_MASK) | PTE_PRESENT | PTE_RW)
#define ENTRY_TO_PTR(x) ((x) & ~VM_PAGE_MASK)

#define PFN(x)          ((x) >> VM_PAGE_SHIFT)

static int can_use_gbpages = 0;
static pmap_t kernel_pmap;

static size_t ps_size(enum page_size ps)
{
	switch (ps) {
	case PS_4K:
		return 0x1000;
	case PS_2M:
		return 0x200000;
	case PS_1G:
		return 0x40000000;
	default:
		return 0;
	}
}

static pmap_t alloc_pmap(void)
{
	struct pml4t *p = kzalloc(sizeof *p, 0);
	return vm_virt_to_phys(p);
}

static pte_t make_pte(pfn_t pfn, enum vm_prot prot, enum page_size size)
{
	pte_t v = pfn;

	switch (size) {
	case PS_1G:
		/* pfn_t is in terms of 4KiB pages, convert to 1GiB page frame
		 * number */
		pfn >>= 18;
		v = (pfn & 0x3FFFFF) << 30;
		break;
	case PS_2M:
		/* pfn_t is in terms of 4KiB pages, convert to 2MiB page frame
		 * number */
		pfn >>= 9;
		v = (pfn & 0x7FFFFFFF) << 21;
		break;
	case PS_4K:
		v = (pfn & 0xFFFFFFFFFF) << 12;
		break;
	default:
		return 0;
	}

	v |= PTE_PRESENT;

	if (size != PS_4K) {
		v |= PTE_PAGESIZE;
	}

	if (prot & VM_PROT_WRITE) {
		v |= PTE_RW;
	}

	if (prot & VM_PROT_NOCACHE) {
		v |= PTE_NOCACHE;
	}

	if (!(prot & VM_PROT_EXEC)) {
		v |= PTE_NX;
	}

	if ((prot & VM_PROT_USER) && !(prot & VM_PROT_SVR)) {
		v |= PTE_USR;
	}

	return v;
}

static void delete_ptab(phys_addr_t pt)
{
	if (pt & PTE_PAGESIZE) {
		/* this entry points to a hugepage, nothing to delete */
		return;
	}

	pt &= ~VM_PAGE_MASK;
	if (!pt) {
		/* physical address of 0x0, nothing to delete */
		return;
	}

	struct ptab *ptab = vm_phys_to_virt(pt);
	kfree(ptab);
}

static void delete_pdir(phys_addr_t pd)
{
	if (pd & PTE_PAGESIZE) {
		/* this entry points to a hugepage, nothing to delete */
		return;
	}

	pd &= ~0x1FFFFFULL;
	if (!pd) {
		/* physical address of 0x0, nothing to delete */
		return;
	}

	struct pdir *pdir = vm_phys_to_virt(pd);
	for (int i = 0; i < 512; i++) {
		if (pdir->p_pages[i] & PTE_PAGESIZE) {
			/* this is a hugepage, there is nothing to delete */
			continue;
		}

		delete_ptab(pdir->p_entries[i]);
	}

	kfree(pdir);
}

static kern_status_t do_pmap_add(
	pmap_t pmap,
	void *p,
	pfn_t pfn,
	enum vm_prot prot,
	enum page_size size)
{
	uintptr_t pv = (uintptr_t)p;
	unsigned int pml4t_index = BAD_INDEX, pdpt_index = BAD_INDEX,
		     pd_index = BAD_INDEX, pt_index = BAD_INDEX;

	switch (size) {
	case PS_4K:
		pml4t_index = (pv >> 39) & 0x1FF;
		pdpt_index = (pv >> 30) & 0x1FF;
		pd_index = (pv >> 21) & 0x1FF;
		pt_index = (pv >> 12) & 0x1FF;
		break;
	case PS_2M:
		pml4t_index = (pv >> 39) & 0x1FF;
		pdpt_index = (pv >> 30) & 0x1FF;
		pd_index = (pv >> 21) & 0x1FF;
		break;
	case PS_1G:
		if (!can_use_gbpages) {
			return KERN_UNSUPPORTED;
		}
		pml4t_index = (pv >> 39) & 0x1FF;
		pdpt_index = (pv >> 30) & 0x1FF;
		break;
	default:
		return KERN_INVALID_ARGUMENT;
	}

	/* 1. get PML4T (mandatory) */
	struct pml4t *pml4t = vm_phys_to_virt(ENTRY_TO_PTR(pmap));
	if (!pml4t) {
		return KERN_INVALID_ARGUMENT;
	}

	/* 2. traverse PML4T, get PDPT (mandatory) */
	struct pdpt *pdpt = NULL;
	if (!pml4t->p_entries[pml4t_index]) {
		pdpt = kzalloc(sizeof *pdpt, 0);
		pml4t->p_entries[pml4t_index]
			= PTR_TO_ENTRY(vm_virt_to_phys(pdpt));
	} else {
		pdpt = vm_phys_to_virt(
			ENTRY_TO_PTR(pml4t->p_entries[pml4t_index]));
	}

	/* if we're mapping a 1GiB page, we stop here */
	if (size == PS_1G) {
		if (pdpt->p_entries[pdpt_index] != 0) {
			/* this slot points to a pdir, delete it.
			   if this slot points to a hugepage, this does nothing
			 */
			delete_pdir(pdpt->p_entries[pdpt_index]);
		}

		pdpt->p_pages[pdpt_index] = make_pte(pfn, prot, size);

		return KERN_OK;
	}

	/* 3. traverse PDPT, get PDIR (optional, 4K and 2M only) */
	struct pdir *pdir = NULL;
	if (!pdpt->p_entries[pdpt_index]
	    || pdpt->p_pages[pdpt_index] & PTE_PAGESIZE) {
		/* entry is null, or points to a hugepage */
		pdir = kzalloc(sizeof *pdir, 0);
		pdpt->p_entries[pdpt_index]
			= PTR_TO_ENTRY(vm_virt_to_phys(pdir));
	} else {
		pdir = vm_phys_to_virt(
			ENTRY_TO_PTR(pdpt->p_entries[pdpt_index]));
	}

	/* if we're mapping a 2MiB page, we stop here */
	if (size == PS_2M) {
		if (pdir->p_entries[pd_index] != 0) {
			/* this slot points to a ptab, delete it.
			   if this slot points to a hugepage, this does nothing
			 */
			delete_ptab(pdir->p_entries[pd_index]);
		}

		pdir->p_pages[pd_index] = make_pte(pfn, prot, size);
		return KERN_OK;
	}

	/* 4. traverse PDIR, get PTAB (optional, 4K only) */
	struct ptab *ptab = NULL;
	if (!pdir->p_entries[pd_index]
	    || pdir->p_pages[pd_index] & PTE_PAGESIZE) {
		/* entry is null, or points to a hugepage */
		ptab = kzalloc(sizeof *ptab, 0);
		pdir->p_entries[pd_index] = PTR_TO_ENTRY(vm_virt_to_phys(ptab));
	} else {
		ptab = vm_phys_to_virt(ENTRY_TO_PTR(pdir->p_entries[pd_index]));
	}

	ptab->p_pages[pt_index] = make_pte(pfn, prot, size);
	return KERN_OK;
}

pmap_t get_kernel_pmap(void)
{
	return kernel_pmap;
}

void pmap_bootstrap(void)
{
	can_use_gbpages = gigabyte_pages();
	printk("pmap: gigabyte pages %sabled",
	       can_use_gbpages == 1 ? "en" : "dis");
	enable_nx();
	printk("pmap: NX protection enabled");

	enum page_size hugepage = PS_2M;
	if (can_use_gbpages) {
		hugepage = PS_1G;
	}
	size_t hugepage_sz = ps_size(hugepage);

	kernel_pmap = alloc_pmap();

	/* map 2GiB at the end of the address space to
	   replace the mapping created by start_32 and allow access to
	   the kernel and memblock-allocated data. */
	uintptr_t vbase = VM_KERNEL_VOFFSET;
	for (size_t i = 0; i < C_2GiB; i += hugepage_sz) {
		do_pmap_add(
			kernel_pmap,
			(void *)(vbase + i),
			PFN(i),
			VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXEC
				| VM_PROT_SVR,
			hugepage);
	}

	phys_addr_t pmem_limit = 0x0;
	struct memblock_iter it;
	for_each_mem_range(&it, 0x00, UINTPTR_MAX)
	{
		if (it.it_limit > pmem_limit) {
			pmem_limit = it.it_limit;
		}
	}

	vbase = VM_PAGEMAP_BASE;
	for (size_t i = 0; i < pmem_limit; i += hugepage_sz) {
		do_pmap_add(
			kernel_pmap,
			(void *)(vbase + i),
			PFN(i),
			VM_PROT_READ | VM_PROT_WRITE | VM_PROT_SVR
				| VM_PROT_NOCACHE,
			hugepage);
	}

	pmap_switch(kernel_pmap);
}

pmap_t pmap_create(void)
{
	return 0;
}

void pmap_destroy(pmap_t pmap)
{
}

kern_status_t pmap_add(
	pmap_t pmap,
	void *p,
	pfn_t pfn,
	enum vm_prot prot,
	enum pmap_flags flags)
{
	enum page_size ps = PS_4K;
	if (flags & PMAP_HUGEPAGE) {
		ps = PS_2M;
	}

	return do_pmap_add(pmap, p, pfn, prot, ps);
}

kern_status_t pmap_add_block(
	pmap_t pmap,
	void *p,
	pfn_t pfn,
	size_t len,
	enum vm_prot prot,
	enum pmap_flags flags)
{
	return KERN_OK;
}

kern_status_t pmap_remove(pmap_t pmap, void *p)
{
	return KERN_OK;
}

kern_status_t pmap_remove_range(pmap_t pmap, void *p, size_t len)
{
	return KERN_OK;
}