los_vm_fault.c 文件参考

浏览源代码.

函数
STATIC STATUS_T	OsVmRegionPermissionCheck (LosVmMapRegion *region, UINT32 flags)
STATIC VOID	OsFaultTryFixup (ExcContext *frame, VADDR_T excVaddr, STATUS_T *status)
STATIC STATUS_T	OsDoReadFault (LosVmMapRegion *region, LosVmPgFault *vmPgFault)
STATIC LosVmPage *	OsCowUnmapOrg (LosArchMmu *archMmu, LosVmMapRegion *region, LosVmPgFault *vmf)
status_t	OsDoCowFault (LosVmMapRegion *region, LosVmPgFault *vmPgFault)
status_t	OsDoSharedFault (LosVmMapRegion *region, LosVmPgFault *vmPgFault)
	在共享线性区写文件操作发生缺页的情况处理,因为线性区是共享的 更多...
STATIC STATUS_T	OsDoFileFault (LosVmMapRegion *region, LosVmPgFault *vmPgFault, UINT32 flags)
STATUS_T	OsVmPageFaultHandler (VADDR_T vaddr, UINT32 flags, ExcContext *frame)

变量
char	__exc_table_start []
char	__exc_table_end []

函数说明

OsCowUnmapOrg()

STATIC LosVmPage * OsCowUnmapOrg	(	LosArchMmu *	archMmu,
		LosVmMapRegion *	region,
		LosVmPgFault *	vmf
	)

在文件 los_vm_fault.c 第 144 行定义.

{
    UINT32 intSave;
    LosVmPage *oldPage = NULL;
    LosMapInfo *mapInfo = NULL;
    LosFilePage *fpage = NULL;
    VADDR_T vaddr = (VADDR_T)vmf->vaddr;
 
    LOS_SpinLockSave(&region->unTypeData.rf.vnode->mapping.list_lock, &intSave);
    fpage = OsFindGetEntry(&region->unTypeData.rf.vnode->mapping, vmf->pgoff);
    if (fpage != NULL) {
        oldPage = fpage->vmPage;
        OsSetPageLocked(oldPage);
        mapInfo = OsGetMapInfo(fpage, archMmu, vaddr);
        if (mapInfo != NULL) {
            OsUnmapPageLocked(fpage, mapInfo);
        } else {
            LOS_ArchMmuUnmap(archMmu, vaddr, 1);
        }
    } else {
        LOS_ArchMmuUnmap(archMmu, vaddr, 1);
    }
    LOS_SpinUnlockRestore(&region->unTypeData.rf.vnode->mapping.list_lock, intSave);
 
    return oldPage;
}

函数调用图:

这是这个函数的调用关系图:

OsDoCowFault()

status_t OsDoCowFault	(	LosVmMapRegion *	region,
		LosVmPgFault *	vmPgFault
	)

here we get two conditions, 1.this page hasn't mapped or mapped from pagecache, we can take it as a normal file cow map. 2.this page has done file cow map, we can take it as a anonymous cow map.

在文件 los_vm_fault.c 第 172 行定义.

{
    STATUS_T ret;
    VOID *kvaddr = NULL;
    PADDR_T oldPaddr = 0;
    PADDR_T newPaddr;
    LosVmPage *oldPage = NULL;
    LosVmPage *newPage = NULL;
    LosVmSpace *space = NULL;
 
    if ((vmPgFault == NULL) || (region == NULL) ||
        (region->unTypeData.rf.vmFOps == NULL) || (region->unTypeData.rf.vmFOps->fault == NULL)) {
        VM_ERR("region args invalid");
        return LOS_ERRNO_VM_INVALID_ARGS;
    }
 
    space = region->space;
    ret = LOS_ArchMmuQuery(&space->archMmu, (VADDR_T)vmPgFault->vaddr, &oldPaddr, NULL);//查询出老物理地址
    if (ret == LOS_OK) {
        oldPage = OsCowUnmapOrg(&space->archMmu, region, vmPgFault);//取消页面映射
    }
 
    newPage = LOS_PhysPageAlloc();//分配一个新页面
    if (newPage == NULL) {
        VM_ERR("LOS_PhysPageAlloc failed");
        ret = LOS_ERRNO_VM_NO_MEMORY;
        goto ERR_OUT;
    }
 
    newPaddr = VM_PAGE_TO_PHYS(newPage);//拿到新的物理地址
    kvaddr = OsVmPageToVaddr(newPage);//拿到新的虚拟地址
 
    (VOID)LOS_MuxAcquire(&region->unTypeData.rf.vnode->mapping.mux_lock);
    ret = region->unTypeData.rf.vmFOps->fault(region, vmPgFault);// 函数指针 g_commVmOps.OsVmmFileFault
    if (ret != LOS_OK) {
        VM_ERR("call region->vm_ops->fault fail");
        (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
        goto ERR_OUT;
    }
 
    /**
     * here we get two conditions, 1.this page hasn't mapped or mapped from pagecache,
     * we can take it as a normal file cow map. 2.this page has done file cow map,
     * we can take it as a anonymous cow map.
     */
    if ((oldPaddr == 0) || (LOS_PaddrToKVaddr(oldPaddr) == vmPgFault->pageKVaddr)) {//没有映射或者 已在pagecache有映射
        (VOID)memcpy_s(kvaddr, PAGE_SIZE, vmPgFault->pageKVaddr, PAGE_SIZE);//直接copy到新页
        LOS_AtomicInc(&newPage->refCounts);//引用ref++
        OsCleanPageLocked(LOS_VmPageGet(LOS_PaddrQuery(vmPgFault->pageKVaddr)));//解锁
    } else {
        OsPhysSharePageCopy(oldPaddr, &newPaddr, newPage);//调用之前 oldPaddr肯定不等于newPaddr
        /* use old page free the new one */
        if (newPaddr == oldPaddr) {//注意这里newPaddr可能已经被改变了,参数传入的是 &newPaddr 
            LOS_PhysPageFree(newPage);//释放新页,别浪费的内存,内核使用内存是一分钱当十块用.
            newPage = NULL;
        }
    }
 
    ret = LOS_ArchMmuMap(&space->archMmu, (VADDR_T)vmPgFault->vaddr, newPaddr, 1, region->regionFlags);//把新物理地址映射给缺页的虚拟地址,这样就不会缺页啦
    if (ret < 0) {
        VM_ERR("LOS_ArchMmuMap failed");
        ret =  LOS_ERRNO_VM_NO_MEMORY;
        (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
        goto ERR_OUT;
    }
    (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
 
    if (oldPage != NULL) {
        OsCleanPageLocked(oldPage);
    }
 
    return LOS_OK;
 
ERR_OUT:
    if (newPage != NULL) {
        LOS_PhysPageFree(newPage);
    }
    if (oldPage != NULL) {
        OsCleanPageLocked(oldPage);
    }
 
    return ret;
}

函数调用图:

这是这个函数的调用关系图:

OsDoFileFault()

STATIC STATUS_T OsDoFileFault	(	LosVmMapRegion *	region,
		LosVmPgFault *	vmPgFault,
		UINT32	flags
	)

Page read operation is a simple case, just share the pagecache(save memory) and make a read permission mmapping (region->arch_mmu_flags & (~ARCH_MMU_FLAG_PERM_WRITE)). However for write operation, vmflag (VM_PRIVATE|VM_SHREAD) decides COW or SHARED fault. For COW fault, pagecache is copied to private anonyous pages and the changes on this page won't write through to the underlying file. For SHARED fault, pagecache is mapping with region->arch_mmu_flags and the changes on this page will write through to the underlying file

在文件 los_vm_fault.c 第 323 行定义.

{
    STATUS_T ret;
 
    if (flags & VM_MAP_PF_FLAG_WRITE) {//写页的时候产生缺页
        if (region->regionFlags & VM_MAP_REGION_FLAG_SHARED) {//共享线性区
            ret = OsDoSharedFault(region, vmPgFault);//写操作时的共享缺页,最复杂,此页上的更改将写入磁盘文件
        } else {//非共享线性区
            ret = OsDoCowFault(region, vmPgFault);//(写时拷贝技术)写操作时的私有缺页,pagecache被复制到私有的任意一个页面上，并在此页面上进行更改,不会直接写入磁盘文件
        }
    } else {//读页的时候产生缺页
        ret = OsDoReadFault(region, vmPgFault);//页面读取操作很简单，只需共享页面缓存（节省内存）并进行读权限映射（region->arch_mmu_flags&（~arch_mmu_FLAG_PERM_WRITE））
    }
    return ret;
}

函数调用图:

这是这个函数的调用关系图:

OsDoReadFault()

STATIC STATUS_T OsDoReadFault	(	LosVmMapRegion *	region,
		LosVmPgFault *	vmPgFault
	)

在文件 los_vm_fault.c 第 100 行定义.

{
    status_t ret;
    PADDR_T paddr;
    LosVmPage *page = NULL;
    VADDR_T vaddr = (VADDR_T)vmPgFault->vaddr;
    LosVmSpace *space = region->space;
 
    ret = LOS_ArchMmuQuery(&space->archMmu, vaddr, NULL, NULL);//查询是否缺页
    if (ret == LOS_OK) {//注意这里时LOS_OK却返回,都OK了说明查到了物理地址,有页了。
        return LOS_OK;//查到了就说明不缺页的，缺页就是因为虚拟地址没有映射到物理地址嘛
    }
    if (region->unTypeData.rf.vmFOps == NULL || region->unTypeData.rf.vmFOps->fault == NULL) {//线性区必须有实现了缺页接口
        VM_ERR("region args invalid, file path: %s", region->unTypeData.rf.vnode->filePath);
        return LOS_ERRNO_VM_INVALID_ARGS;
    }
 
    (VOID)LOS_MuxAcquire(&region->unTypeData.rf.vnode->mapping.mux_lock);
    ret = region->unTypeData.rf.vmFOps->fault(region, vmPgFault);// 函数指针，执行的是g_commVmOps.OsVmmFileFault
    if (ret == LOS_OK) {
        paddr = LOS_PaddrQuery(vmPgFault->pageKVaddr);//查询物理地址
        page = LOS_VmPageGet(paddr);//获取page
        if (page != NULL) { /* just incase of page null */
            LOS_AtomicInc(&page->refCounts);//ref 自增
            OsCleanPageLocked(page);
        }
        ret = LOS_ArchMmuMap(&space->archMmu, vaddr, paddr, 1,
                             region->regionFlags & (~VM_MAP_REGION_FLAG_PERM_WRITE));//重新映射为非可写
        if (ret < 0) {
            VM_ERR("LOS_ArchMmuMap failed");
            OsDelMapInfo(region, vmPgFault, false);
            (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
            return LOS_ERRNO_VM_NO_MEMORY;
        }
 
        (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
        return LOS_OK;
    }
    (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
 
    return LOS_ERRNO_VM_NO_MEMORY;
}

函数调用图:

这是这个函数的调用关系图:

OsDoSharedFault()

status_t OsDoSharedFault	(	LosVmMapRegion *	region,
		LosVmPgFault *	vmPgFault
	)

在共享线性区写文件操作发生缺页的情况处理,因为线性区是共享的

在文件 los_vm_fault.c 第 256 行定义.

{
    STATUS_T ret;
    UINT32 intSave;
    PADDR_T paddr = 0;
    VADDR_T vaddr = (VADDR_T)vmPgFault->vaddr;
    LosVmSpace *space = region->space;
    LosVmPage *page = NULL;
    LosFilePage *fpage = NULL;
 
    if ((region->unTypeData.rf.vmFOps == NULL) || (region->unTypeData.rf.vmFOps->fault == NULL)) {
        VM_ERR("region args invalid");
        return LOS_ERRNO_VM_INVALID_ARGS;
    }
 
    ret = LOS_ArchMmuQuery(&space->archMmu, vmPgFault->vaddr, &paddr, NULL);//查询物理地址
    if (ret == LOS_OK) {
        LOS_ArchMmuUnmap(&space->archMmu, vmPgFault->vaddr, 1);//先取消映射
        ret = LOS_ArchMmuMap(&space->archMmu, vaddr, paddr, 1, region->regionFlags);//再重新映射,为啥这么干,是因为regionFlags变了,
        if (ret < 0) {
            VM_ERR("LOS_ArchMmuMap failed. ret=%d", ret);
            return LOS_ERRNO_VM_NO_MEMORY;
        }
 
        LOS_SpinLockSave(&region->unTypeData.rf.vnode->mapping.list_lock, &intSave);
        fpage = OsFindGetEntry(&region->unTypeData.rf.vnode->mapping, vmPgFault->pgoff);
        if (fpage) {//在页高速缓存(page cache)中找到了
            OsMarkPageDirty(fpage, region, 0, 0);//标记为脏页
        }
        LOS_SpinUnlockRestore(&region->unTypeData.rf.vnode->mapping.list_lock, intSave);
 
        return LOS_OK;
    }
    //以下是没有映射到物理地址的处理
    (VOID)LOS_MuxAcquire(&region->unTypeData.rf.vnode->mapping.mux_lock);
    ret = region->unTypeData.rf.vmFOps->fault(region, vmPgFault);//函数指针，执行的是g_commVmOps.OsVmmFileFault
    if (ret == LOS_OK) {
        paddr = LOS_PaddrQuery(vmPgFault->pageKVaddr);
        page = LOS_VmPageGet(paddr);
         /* just in case of page null */
        if (page != NULL) {
            LOS_AtomicInc(&page->refCounts);
            OsCleanPageLocked(page);
        }
        ret = LOS_ArchMmuMap(&space->archMmu, vaddr, paddr, 1, region->regionFlags);
        if (ret < 0) {
            VM_ERR("LOS_ArchMmuMap failed. ret=%d", ret);
            OsDelMapInfo(region, vmPgFault, TRUE);
            (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
            return LOS_ERRNO_VM_NO_MEMORY;
        }
 
        (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
        return LOS_OK;
    }
    (VOID)LOS_MuxRelease(&region->unTypeData.rf.vnode->mapping.mux_lock);
    return ret;
}

函数调用图:

这是这个函数的调用关系图:

OsFaultTryFixup()

STATIC VOID OsFaultTryFixup	(	ExcContext *	frame,
		VADDR_T	excVaddr,
		STATUS_T *	status
	)

在文件 los_vm_fault.c 第 81 行定义.

{
    INT32 tableNum = (__exc_table_end - __exc_table_start) / sizeof(LosExcTable);
    LosExcTable *excTable = (LosExcTable *)__exc_table_start;
 
    if ((frame->regCPSR & CPSR_MODE_MASK) != CPSR_MODE_USR) {
        for (int i = 0; i < tableNum; ++i, ++excTable) {
            if (frame->PC == (UINTPTR)excTable->excAddr) {
                frame->PC = (UINTPTR)excTable->fixAddr;
                frame->R2 = (UINTPTR)excVaddr;
                *status = LOS_OK;
                return;
            }
        }
    }
}

这是这个函数的调用关系图:

OsVmPageFaultHandler()

STATUS_T OsVmPageFaultHandler	(	VADDR_T	vaddr,
		UINT32	flags,
		ExcContext *	frame
	)

参数

vaddr
flags
frame

返回

STATUS_T

在文件 los_vm_fault.c 第 352 行定义.

{
    LosVmSpace *space = LOS_SpaceGet(vaddr);//获取虚拟地址所属空间
    LosVmMapRegion *region = NULL;
    STATUS_T status;
    PADDR_T oldPaddr;
    PADDR_T newPaddr;
    VADDR_T excVaddr = vaddr;
    LosVmPage *newPage = NULL;
    LosVmPgFault vmPgFault = { 0 };
 
    if (space == NULL) {
        VM_ERR("vm space not exists, vaddr: %#x", vaddr);
        status = LOS_ERRNO_VM_NOT_FOUND;
        OsFaultTryFixup(frame, excVaddr, &status);
        return status;
    }
 
    if (((flags & VM_MAP_PF_FLAG_USER) != 0) && (!LOS_IsUserAddress(vaddr))) {//地址保护,用户空间不允许跨界访问
        VM_ERR("user space not allowed to access invalid address: %#x", vaddr);
        return LOS_ERRNO_VM_ACCESS_DENIED;//拒绝访问
    }
 
    (VOID)LOS_MuxAcquire(&space->regionMux);
    region = LOS_RegionFind(space, vaddr);//通过虚拟地址找到所在线性区
    if (region == NULL) {
        VM_ERR("region not exists, vaddr: %#x", vaddr);
        status = LOS_ERRNO_VM_NOT_FOUND;
        goto CHECK_FAILED;
    }
 
    status = OsVmRegionPermissionCheck(region, flags);
    if (status != LOS_OK) {
        status = LOS_ERRNO_VM_ACCESS_DENIED;//拒绝访问
        goto CHECK_FAILED;
    }
 
    if (OomCheckProcess()) {//低内存检查
        /*
         * under low memory, when user process request memory allocation
         * it will fail, and result is LOS_NOK and current user process
         * will be deleted. memory usage detail will be printed.
         */
        status = LOS_ERRNO_VM_NO_MEMORY;
        goto CHECK_FAILED;
    }
 
    vaddr = ROUNDDOWN(vaddr, PAGE_SIZE);//为啥要向下圆整，因为这一页要重新使用，需找到页面基地址
#ifdef LOSCFG_FS_VFS 
    if (LOS_IsRegionFileValid(region)) {//是否为文件线性区
        if (region->unTypeData.rf.vnode == NULL) {
            goto  CHECK_FAILED;
        }
        vmPgFault.vaddr = vaddr;//虚拟地址
        vmPgFault.pgoff = ((vaddr - region->range.base) >> PAGE_SHIFT) + region->pgOff;//计算出文件读取位置
        vmPgFault.flags = flags;
        vmPgFault.pageKVaddr = NULL;//缺失页初始化没有物理地址
 
        status = OsDoFileFault(region, &vmPgFault, flags);//缺页处理
        if (status) {
            VM_ERR("vm fault error, status=%d", status);
            goto CHECK_FAILED;
        }
        goto DONE;
    }
#endif
    //请求调页:推迟到不能再推迟为止
    newPage = LOS_PhysPageAlloc();//分配一个新的物理页
    if (newPage == NULL) {
        status = LOS_ERRNO_VM_NO_MEMORY;
        goto CHECK_FAILED;
    }
 
    newPaddr = VM_PAGE_TO_PHYS(newPage);//获取物理地址
    (VOID)memset_s(OsVmPageToVaddr(newPage), PAGE_SIZE, 0, PAGE_SIZE);//获取虚拟地址 清0
    status = LOS_ArchMmuQuery(&space->archMmu, vaddr, &oldPaddr, NULL);//通过虚拟地址查询老物理地址
    if (status >= 0) {//已经映射过了,@note_thinking 不是缺页吗,怎么会有页的情况? 
        LOS_ArchMmuUnmap(&space->archMmu, vaddr, 1);//解除映射关系
        OsPhysSharePageCopy(oldPaddr, &newPaddr, newPage);//将oldPaddr的数据拷贝到newPage
        /* use old page free the new one */
        if (newPaddr == oldPaddr) {//新老物理地址一致
            LOS_PhysPageFree(newPage);//继续使用旧页释放新页
            newPage = NULL;
        }
 
        /* map all of the pages */
        status = LOS_ArchMmuMap(&space->archMmu, vaddr, newPaddr, 1, region->regionFlags);//重新映射新物理地址
        if (status < 0) {
            VM_ERR("failed to map replacement page, status:%d", status);
            status = LOS_ERRNO_VM_MAP_FAILED;
            goto VMM_MAP_FAILED;
        }
 
        status = LOS_OK;
        goto DONE;
    } else {//
        /* map all of the pages */
        LOS_AtomicInc(&newPage->refCounts);//引用数自增
        status = LOS_ArchMmuMap(&space->archMmu, vaddr, newPaddr, 1, region->regionFlags);//映射新物理地址,如此下次就不会缺页了
        if (status < 0) {
            VM_ERR("failed to map page, status:%d", status);
            status = LOS_ERRNO_VM_MAP_FAILED;
            goto VMM_MAP_FAILED;
        }
    }
 
    status = LOS_OK;
    goto DONE;
VMM_MAP_FAILED:
    if (newPage != NULL) {
        LOS_PhysPageFree(newPage);
    }
CHECK_FAILED:
    OsFaultTryFixup(frame, excVaddr, &status);
DONE:
    (VOID)LOS_MuxRelease(&space->regionMux);
    return status;
}

函数调用图:

这是这个函数的调用关系图:

OsVmRegionPermissionCheck()

STATIC STATUS_T OsVmRegionPermissionCheck	(	LosVmMapRegion *	region,
		UINT32	flags
	)

在文件 los_vm_fault.c 第 57 行定义.

{
    if ((region->regionFlags & VM_MAP_REGION_FLAG_PERM_READ) != VM_MAP_REGION_FLAG_PERM_READ) {
        VM_ERR("read permission check failed operation flags %x, region flags %x", flags, region->regionFlags);
        return LOS_NOK;
    }
 
    if ((flags & VM_MAP_PF_FLAG_WRITE) == VM_MAP_PF_FLAG_WRITE) {//写入许可
        if ((region->regionFlags & VM_MAP_REGION_FLAG_PERM_WRITE) != VM_MAP_REGION_FLAG_PERM_WRITE) {
            VM_ERR("write permission check failed operation flags %x, region flags %x", flags, region->regionFlags);
            return LOS_NOK;
        }
    }
 
    if ((flags & VM_MAP_PF_FLAG_INSTRUCTION) == VM_MAP_PF_FLAG_INSTRUCTION) {//指令
        if ((region->regionFlags & VM_MAP_REGION_FLAG_PERM_EXECUTE) != VM_MAP_REGION_FLAG_PERM_EXECUTE) {
            VM_ERR("exec permission check failed operation flags %x, region flags %x", flags, region->regionFlags);
            return LOS_NOK;
        }
    }
 
    return LOS_OK;
}

这是这个函数的调用关系图:

变量说明

__exc_table_end

char __exc_table_end[]

extern

__exc_table_start

char __exc_table_start[]

extern