FreeNos Memory类的继承关系表(x86Memory继承自Memory)
1.成员变量
Memory类的成员变量memoryAvail和memoryMapEnd的访问权限是protected的，成员变量memoryAvail和memoryMapEnd是全局变量；
分别表示的是：
memorySize 所有的可用的物理内存；
memoryAvail 可用的物理内存；
memoryMap 映射所有可用的物理内存；
2.构造方法和析构方法
Memory::Memory()
{
/* 标记Kernel使用的内存地址 */
allocatePhysical(0x00400000, 0);
/* 标记boot模块使用的内存地址 */
for (Size i = 0; i < multibootInfo.modsCount; i++)
{
MultibootModule *mod = &((MultibootModule *) multibootInfo.modsAddress)[i];
Size modSize = mod->modEnd - mod->modStart;
/* 标记使用的物理内存地址*/
allocatePhysical(modSize, mod->modStart);
}
}
Memory还提供了一个初始化memoryMap和kernel heap的方法：initialize()
void Memory::initialize()
{
Address page = 0x00300000;
Size meta = sizeof(BubbleAllocator) + sizeof(PoolAllocator);
Allocator *bubble, *pool;
/* 保存内存大小到MemoryAvail变量中*/
memorySize = (multibootInfo.memLower + multibootInfo.memUpper) * 1024;
memoryAvail = memorySize;
/* 分配memoryMap */
memoryMap = (u8 *)(&kernelEnd);
memoryMapEnd = memoryMap + (memorySize / PAGESIZE / 8);
/* 清空memoryMap*/
for (u8 *p = memoryMap; p < memoryMapEnd; p++)
{
*p = 0;
}
/* 设置动态内存堆*/
bubble = new (page) BubbleAllocator();
pool = new (page + sizeof(BubbleAllocator)) PoolAllocator();
pool->setParent(bubble);
/* 设置堆的大小*/
bubble->region(page + meta, (1024 * 1024) - meta);
/* 设置默认分配器*/
Allocator::setDefault(pool);
}
析构函数： ~Memory 是虚函数，可在其他地方实现；
3.其他对象方法
Size getTotalMemory()
{
/*对memorySize的引用*/
return memorySize;
}
Size getAvailableMemory()
{
/*对memoryAvail的引用*/
return memoryAvail;
}
从源代码可知Memory类主要是对物理内存的分配和内存映射的操作：
/*分配物理和标记使用的内存到memoryMap中*/
Address allocatePhysical(Size sz, Address addr = 4194304);
/*取消参数在memoryMap中的标记*/
void releasePhysical(Address paddr);
Address allocateVirtual(Address vaddr, ulong prot);
Address allocateVirtual(ArchProcess *p, Address vaddr, ulong prot);
/*将物理内存映射到进程的虚拟地址空间中*/
virtual Address mapVirtual(Address paddr, Address vaddr, ulong prot) = 0;
/*将物理内存映射到进程的虚拟地址空间中*/
virtual Address mapVirtual(ArchProcess *p, Address paddr, Address vaddr, ulong prot) = 0;
/*把参数进程中的所有的物理页标记为释放*/
virtual void releaseAll(ArchProcess *p) = 0;
在以上方法实现之前，先看一下对内存映射的操作：
bool Memory::isMarked(Address addr)
{
Size index = (addr >> PAGESHIFT) / 8;
Size bit = (addr >> PAGESHIFT) % 8;
return memoryMap[index] & (1 << bit);
}
void Memory::setMark(Address addr, bool marked)
{
Size index = (addr >> PAGESHIFT) / 8;
Size bit = (addr >> PAGESHIFT) % 8;
if (marked)
memoryMap[index] |= (1 << bit);
else
memoryMap[index] &= ~(1 << bit);
}
接下来的是上面方法的详细实现:
Address Memory::allocatePhysical(Size sz, Address paddr)
{
Address start = paddr & PAGEMASK, end = memorySize;
Address from = 0, count = 0;
/* Loop the memoryMap for a free block. */
for (Address i = start; i < end; i += PAGESIZE)
{
if (!isMarked(i))
{
/* Remember this page. */
if (!count)
{
from = i;
count = 1;
}
else
count++;
/* Are there enough contigious pages? */
if (count * PAGESIZE >= sz)
{
for (Address j = from; j < from + (count * PAGESIZE); j += PAGESIZE)
{
setMark(j, true);
}
memoryAvail -= count * PAGESIZE;
return from;
}
}
else
{
from = count = 0;
}
}
/* Out of memory! */
return (Address) ZERO;
}
void Memory::releasePhysical(Address addr)
{
setMark(addr & PAGEMASK, false);
memoryAvail += PAGESIZE;
}
Address Memory::allocateVirtual(Address vaddr, ulong prot)
{
Address newPage = allocatePhysical(PAGESIZE);
return mapVirtual(newPage, vaddr, prot);
}
Address Memory::allocateVirtual(ArchProcess *p, Address vaddr, ulong prot)
{
Address newPage = allocatePhysical(PAGESIZE);
return mapVirtual(p, newPage, vaddr, prot);
}
virtual Address mapVirtual(Address paddr, Address vaddr, ulong prot) = 0
virtual Address mapVirtual(ArchProcess *p, Address paddr, Address vaddr, ulong prot) = 0
这两个方法可以在/x86/x86Memory类中找到实现。
Address X86Memory::mapVirtual(Address paddr, Address vaddr, ulong prot)
{
/* Virtual address specified? */
if (vaddr == ZERO)
{
vaddr = findFree(PAGETABFROM, PAGEDIRADDR);
}
/* Point to the correct page table. */
myPageTab = PAGETABADDR(vaddr);
/* Do we have the page table in memory? */
if (!(myPageDir[DIRENTRY(vaddr)] & PAGE_PRESENT))
{
/* Then first allocate new page table. */
Address newPageTab = memory->allocatePhysical(PAGESIZE);
newPageTab |= PAGE_PRESENT | PAGE_RW | prot;
/* Map the new page table into memory. */
myPageDir[DIRENTRY(vaddr)] = newPageTab;
tlb_flush(myPageTab);
/* Zero the new page table. */
memset(myPageTab, 0, PAGESIZE);
}
/* Map physical to virtual address. */
myPageTab[TABENTRY(vaddr)] = (paddr & PAGEMASK) | prot;
tlb_flush(vaddr);
/* Success. */
return vaddr;
}
Address X86Memory::mapVirtual(X86Process *p, Address paddr,
Address vaddr, ulong prot)
{
/* Map remote pages. */
mapRemote(p, vaddr);
/* Virtual address specified? */
if (vaddr == ZERO)
{
vaddr = findFree(PAGETABFROM_REMOTE, remPageDir);
}
/* Repoint to the correct (remote) page table. */
remPageTab = PAGETABADDR_FROM(vaddr, PAGETABFROM_REMOTE);
/* Does the remote process have the page table in memory? */
if (!(remPageDir[DIRENTRY(vaddr)] & PAGE_PRESENT))
{
/* Nope, allocate a page table first. */
Address newPageTab = memory->allocatePhysical(PAGESIZE);
newPageTab |= PAGE_PRESENT | PAGE_RW | prot;
/* Map the new page table into remote memory. */
remPageDir[DIRENTRY(vaddr)] = newPageTab;
/* Update caches. */
tlb_flush(remPageTab);
/* Zero the new page. */
memset(remPageTab, 0, PAGESIZE);
}
/* Map physical address to remote virtual address. */
remPageTab[TABENTRY(vaddr)] = (paddr & PAGEMASK) | prot;
tlb_flush(vaddr);
/* Success. */
return (Address) vaddr;
}
Address X86Memory::lookupVirtual(X86Process *p, Address vaddr)
{
Address ret = ZERO;
/* Map remote page tables. */
mapRemote(p, vaddr);
/* Lookup the address, if mapped. */
if (remPageDir[DIRENTRY(vaddr)] & PAGE_PRESENT &&
remPageTab[TABENTRY(vaddr)] & PAGE_PRESENT)
{
ret = remPageTab[TABENTRY(vaddr)];
}
return ret;
}
void X86Memory::releaseAll(X86Process *p)
{
/* Map page tables. */
mapRemote(p, 0x0);
/* Mark all our physical pages free. */
for (Size i = 0; i < 1024; i++)
{
/* May we release these physical pages? */
if ((remPageDir[i] & PAGE_PRESENT) && !(remPageDir[i] & PAGE_PINNED))
{
/* Repoint page table. */
remPageTab = PAGETABADDR_FROM(i * PAGESIZE * 1024,
PAGETABFROM_REMOTE);
/* Scan page table. */
for (Size j = 0; j < 1024; j++)
{
if (remPageTab[j] & PAGE_PRESENT && !(remPageTab[j] & PAGE_PINNED))
{
memory->releasePhysical(remPageTab[j]);
}
}
}
}
}
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