implement paging map and unmap

core/mem.c

@@ -71,7 +71,7 @@ int unrefPhyPage(paddr_t addr)
 		list_add_tail(free_page, mem);
 	}
 
-	return 0;
+	return mem->ref;
 }
 
 int refPhyPage(paddr_t addr)

core/mem.h

@@ -12,7 +12,7 @@ extern uint32_t __ld_kernel_end;
 
 struct mem_desc{
 	paddr_t phy_addr;
-	unsigned long ref;
+	long ref;
 	struct mem_desc *next, *prev;
 };
 

core/paging.c

@@ -1,6 +1,9 @@
 #include "klibc.h"
+#include "errno.h"
 #include "mem.h"
+#include "paging.h"
 #include "stdarg.h"
+#include "vga.h"
 
 // In a Vaddr, 10 first bit (MSB) are the index in the Page Directory. A Page Directory Entry point to a Page Table.
 // The 10 next bits are then an index in this Page Table. A Page Table Entry then point to a physical address at which is added the remaining 12 bits.
@@ -58,6 +61,8 @@ struct pdbr {
 	uint32_t pd_paddr : 20;
 } __attribute__((packed));
 
+
+// invalidate the TLB entry for the page located at the given virtual address
 static inline void __native_flush_tlb_single(unsigned long addr)
 {
 	asm volatile("invlpg (%0)" ::"r"(addr) : "memory");
@@ -123,12 +128,67 @@ int pageMap(vaddr_t vaddr, paddr_t paddr, int flags)
 	uint ptEntry = (vaddr >> PT_SHIFT) & PTE_MASK;
 
 	// Thank to mirroring, we can access the PD
-	struct pde *pd = (struct pde *)(PD_MIRROR_PAGE_IDX * 4 * (1 << 20) +
-					PD_MIRROR_PAGE_IDX * 4 * (1 << 10));
+	struct pde *pd = (struct pde *)(PD_MIRROR_PAGE_IDX * (1U << 22) +
+					PD_MIRROR_PAGE_IDX * (1U << 12));
 
-	struct pte *pt = (struct pte *)(PD_MIRROR_PAGE_IDX * 4 * (1 << 20) +
-					PD_MIRROR_PAGE_IDX * 4 * (1 << 10));
+	struct pte *pt = (struct pte *)(PD_MIRROR_PAGE_IDX * (1U << 22) +
+					pdEntry * (1U << 12));
 
-	if(pd[pdEntry].present){
+	if(!pd[pdEntry].present){
+		paddr_t ptPhy = allocPhyPage();
+		memset((void *)ptPhy, 0, PAGE_SIZE);
+
+		pd[pdEntry].user = (flags & PAGING_MEM_USER) ? 0:1;
+		pd[pdEntry].present = 1;
+		pd[pdEntry].write = 1;
+		pd[pdEntry].pt_addr = (ptPhy >> PT_SHIFT);
+
+		__native_flush_tlb_single((vaddr_t)pt);
 	}
+
+	// Already mapped ? Remove old mapping
+	if (pt[ptEntry].present) {
+		unrefPhyPage(pt[ptEntry].paddr << PAGE_SHIFT);
+	} // PTE not already used ? We will use it ! So increase the PT ref count
+	else {
+		refPhyPage(pd[pdEntry].pt_addr << PAGE_SHIFT);
+	}
+
+	pt[ptEntry].user    = (flags & PAGING_MEM_USER) ? 0 : 1;
+	pt[ptEntry].present = 1;
+	pt[ptEntry].write   = (flags & PAGING_MEM_WRITE) ? 0 : 1;
+	pt[ptEntry].paddr   = paddr >> PAGE_SHIFT;
+	refPhyPage(paddr);
+
+	__native_flush_tlb_single(vaddr);
+	return 0;
+}
+
+int pageUnmap(vaddr_t vaddr)
+{
+	uint pdEntry = vaddr >> (PD_SHIFT);
+	uint ptEntry = (vaddr >> PT_SHIFT) & PTE_MASK;
+
+	// Thank to mirroring, we can access the PD
+	struct pde *pd =
+	    (struct pde *)(PD_MIRROR_PAGE_IDX * (1U << 22) + PD_MIRROR_PAGE_IDX * (1U << 12));
+
+	struct pte *pt =
+	    (struct pte *)(PD_MIRROR_PAGE_IDX * (1U << 22) + pdEntry * (1U << 12));
+	if (!pd[pdEntry].present)
+		return -EINVAL;
+	if (!pt[ptEntry].present)
+		return -EINVAL;
+
+	unrefPhyPage(pt[ptEntry].paddr << PAGE_SHIFT);
+	pt[ptEntry].present = 0;
+
+	// PTE not used. Decrease refcount on it. Is PT not used anymore ?
+	if(unrefPhyPage(pd[pdEntry].pt_addr<< PT_SHIFT) == 0){
+		pd[pdEntry].present = 0;
+		__native_flush_tlb_single((vaddr_t)pt);
+	}
+	__native_flush_tlb_single(vaddr);
+	return 0;
+
 }

core/paging.h

@@ -1,6 +1,10 @@
 #pragma once
 #include "types.h"
 
+#define PAGING_MEM_USER 1
+#define PAGING_MEM_READ (1 << 1)
+#define PAGING_MEM_WRITE (1 << 2)
+
 int pagingSetup(paddr_t upperKernelAddr);
 
 int pageMap(vaddr_t vaddr, paddr_t paddr, int flags);