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#include "kernel/mm.h"
#include "kernel/pmm.h"
#include "kernel/riscv.h"
#include "common/types.h"
#include "lib/string.h"
#include "drivers/uart.h"
// COW Flag (PTE bit 8)
#define PTE_COW (1L << 8)
extern "C"
{
extern char kernel_end[];
extern char trampoline[];
}
namespace VM
{
uint64 *kernel_pagetable;
static void page_ref_inc(uint64 pa)
{
struct Page *p = PMM::pa_to_page(pa);
if (p)
{
__atomic_add_fetch(&p->refcnt, 1, __ATOMIC_RELAXED);
}
}
static bool page_ref_dec(uint64 pa)
{
struct Page *p = PMM::pa_to_page(pa);
if (p)
{
if (__atomic_sub_fetch(&p->refcnt, 1, __ATOMIC_RELEASE) == 0)
{
return true;
}
}
return false;
}
static uint64 *walk(uint64 *pagetable, uint64 va, int alloc)
{
if (va >= MAXVA)
return nullptr;
for (int level = 2; level > 0; level--)
{
uint64 *pte = &pagetable[PX(level, va)];
if (*pte & PTE_V)
{
pagetable = (uint64 *)PTE2PA(*pte);
}
else
{
if (!alloc || (pagetable = (uint64 *)PMM::alloc_page()) == nullptr)
return nullptr;
memset(pagetable, 0, PGSIZE);
*pte = PA2PTE(pagetable) | PTE_V;
}
}
return &pagetable[PX(0, va)];
}
int mappages(uint64 *pagetable, uint64 va, uint64 size, uint64 pa, int perm)
{
uint64 a, last;
uint64 *pte;
if (size == 0)
return -1;
a = PGROUNDDOWN(va);
last = PGROUNDDOWN(va + size - 1);
for (;;)
{
if ((pte = walk(pagetable, a, 1)) == nullptr)
return -1;
if (*pte & PTE_V)
{
return -1;
}
*pte = PA2PTE(pa) | perm | PTE_V;
if (a == last)
break;
a += PGSIZE;
pa += PGSIZE;
}
return 0;
}
uint64 *uvmcreate()
{
uint64 *pagetable = (uint64 *)PMM::alloc_page();
if (pagetable)
{
memset(pagetable, 0, PGSIZE);
if (mappages(pagetable, TRAMPOLINE, PGSIZE, (uint64)trampoline, PTE_R | PTE_X) < 0)
{
PMM::free_page(pagetable);
return nullptr;
}
}
return pagetable;
}
void uvminit(uint64 *pagetable, uchar *src, uint64 sz)
{
char *mem;
if (sz >= PGSIZE)
{
Drivers::uart_puts("uvminit: initcode too big!\n");
return;
}
mem = (char *)PMM::alloc_page();
memset(mem, 0, PGSIZE);
mappages(pagetable, 0, PGSIZE, (uint64)mem, PTE_W | PTE_R | PTE_X | PTE_U);
memmove(mem, src, sz);
}
uint64 uvmalloc(uint64 *pagetable, uint64 oldsz, uint64 newsz, int xperm)
{
char *mem;
uint64 a;
if (newsz < oldsz)
return oldsz;
oldsz = PGROUNDUP(oldsz);
for (a = oldsz; a < newsz; a += PGSIZE)
{
mem = (char *)PMM::alloc_page();
if (mem == nullptr)
{
uvmdealloc(pagetable, a, oldsz);
return 0;
}
memset(mem, 0, PGSIZE);
if (mappages(pagetable, a, PGSIZE, (uint64)mem, PTE_R | PTE_U | xperm) != 0)
{
PMM::free_page(mem);
uvmdealloc(pagetable, a, oldsz);
return 0;
}
}
return newsz;
}
uint64 uvmdealloc(uint64 *pagetable, uint64 oldsz, uint64 newsz)
{
if (newsz >= oldsz)
return oldsz;
if (PGROUNDUP(newsz) < PGROUNDUP(oldsz))
{
int npages = (PGROUNDUP(oldsz) - PGROUNDUP(newsz)) / PGSIZE;
uvmunmap(pagetable, PGROUNDUP(newsz), npages, 1);
}
return newsz;
}
void uvmunmap(uint64 *pagetable, uint64 va, uint64 npages, int do_free)
{
uint64 a;
uint64 *pte;
if ((va % PGSIZE) != 0)
return;
for (a = va; a < va + npages * PGSIZE; a += PGSIZE)
{
if ((pte = walk(pagetable, a, 0)) == nullptr)
continue;
if ((*pte & PTE_V) == 0)
continue;
if ((PTE_FLAGS(*pte) & (PTE_R | PTE_W | PTE_X)) == 0)
{
continue;
}
if (do_free)
{
uint64 pa = PTE2PA(*pte);
if (page_ref_dec(pa))
{
PMM::free_page((void *)pa);
}
}
*pte = 0;
}
}
static void freewalk(uint64 *pagetable)
{
for (int i = 0; i < 512; i++)
{
uint64 pte = pagetable[i];
if ((pte & PTE_V) && (pte & (PTE_R | PTE_W | PTE_X)) == 0)
{
uint64 *child = (uint64 *)PTE2PA(pte);
freewalk(child);
pagetable[i] = 0;
}
}
PMM::free_page(pagetable);
}
void uvmfree(uint64 *pagetable, uint64 sz)
{
if (sz > 0)
uvmunmap(pagetable, 0, PGROUNDUP(sz) / PGSIZE, 1);
freewalk(pagetable);
}
int uvmcopy(uint64 *oldpt, uint64 *newpt, uint64 sz)
{
uint64 *pte;
uint64 pa, i;
uint flags;
for (i = 0; i < sz; i += PGSIZE)
{
if ((pte = walk(oldpt, i, 0)) == nullptr)
continue;
if ((*pte & PTE_V) == 0)
continue;
pa = PTE2PA(*pte);
flags = PTE_FLAGS(*pte);
if (flags & PTE_W)
{
flags &= ~PTE_W;
flags |= PTE_COW;
*pte = PA2PTE(pa) | flags;
}
if (mappages(newpt, i, PGSIZE, pa, flags) != 0)
{
return -1;
}
page_ref_inc(pa);
}
sfence_vma();
return 0;
}
int copyout(uint64 *pagetable, uint64 dstva, char *src, uint64 len)
{
uint64 n, va0, pa0;
uint64 *pte;
while (len > 0)
{
va0 = PGROUNDDOWN(dstva);
pte = walk(pagetable, va0, 0);
if (pte == nullptr || (*pte & PTE_V) == 0 || (*pte & PTE_U) == 0)
return -1;
pa0 = PTE2PA(*pte);
n = PGSIZE - (dstva - va0);
if (n > len)
n = len;
memmove((void *)(pa0 + (dstva - va0)), src, n);
len -= n;
src += n;
dstva = va0 + PGSIZE;
}
return 0;
}
int copyin(uint64 *pagetable, char *dst, uint64 srcva, uint64 len)
{
uint64 n, va0, pa0;
uint64 *pte;
while (len > 0)
{
va0 = PGROUNDDOWN(srcva);
pte = walk(pagetable, va0, 0);
if (pte == nullptr || (*pte & PTE_V) == 0 || (*pte & PTE_U) == 0)
return -1;
pa0 = PTE2PA(*pte);
n = PGSIZE - (srcva - va0);
if (n > len)
n = len;
memmove(dst, (void *)(pa0 + (srcva - va0)), n);
len -= n;
dst += n;
srcva = va0 + PGSIZE;
}
return 0;
}
int handle_cow_fault(uint64 *pagetable, uint64 va)
{
if (va >= MAXVA)
return -1;
uint64 *pte = walk(pagetable, va, 0);
if (pte == nullptr || (*pte & PTE_V) == 0 || (*pte & PTE_U) == 0)
return -1;
if ((*pte & PTE_COW) == 0)
return -1;
uint64 pa = PTE2PA(*pte);
uint64 flags = PTE_FLAGS(*pte);
char *mem = (char *)PMM::alloc_page();
if (mem == nullptr)
return -1;
memmove(mem, (char *)pa, PGSIZE);
uint64 new_flags = (flags | PTE_W) & ~PTE_COW;
*pte = PA2PTE((uint64)mem) | new_flags | PTE_V;
if (page_ref_dec(pa))
{
PMM::free_page((void *)pa);
}
sfence_vma();
return 0;
}
static void kvmmap(uint64 va, uint64 pa, uint64 sz, int perm)
{
if (mappages(kernel_pagetable, va, sz, pa, perm) != 0)
{
Drivers::uart_puts("kvmmap: failed\n");
while (1)
;
}
}
void kvminit()
{
kernel_pagetable = uvmcreate();
kvmmap(0x10000000, 0x10000000, 0x10000, PTE_R | PTE_W);
kvmmap(0x0c000000, 0x0c000000, 0x400000, PTE_R | PTE_W);
kvmmap(0x02000000, 0x02000000, 0x10000, PTE_R | PTE_W); // CLINT
kvmmap(KERNBASE, KERNBASE, PHYSTOP - KERNBASE, PTE_R | PTE_W | PTE_X);
}
void kvminithart()
{
w_satp(MAKE_SATP(kernel_pagetable));
sfence_vma();
Drivers::uart_puts("[Boot] MMU ENABLED! Using virtual addresses.\n");
}
}
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