Re: [Xen-devel] The address in xen

[weiming <zephyr.zhao@xxxxxxxxx>]

In the xen kernel, there's existing functions/macros to convert between these addresses.
Your calculation may be not correct. Every address stored in the page table/directory is machine address. But your pointer should use virtual address to access them.

weiming

2008/3/17 张琳 <zhanglin_nk@xxxxxxx>:

It seems that the address in xen has three layer: the virtual address , the pesurdo-physical address and the machine address.

I obtained some addresses of kernel symbols by parsing the system.map file.
I think this address is virtual address.Is it correct?
Then I want to calculate the hash value of memory area start from those addresses. So I have to access the corresponding machine address.

Then problem came.
How to translate the virtual address to machine address?

First, I want to translate the virtual address to pesurdo-physical address by traversing page table tree. But segmentation fault always occurs.

I put my code in the following~~~
Can anyone tell me that what is wrong?

unsigned long VAtoPA(unsigned long VirtualAddress)
{
/*This variable is used for storing the address of
the Page Directory.*/
unsigned long PDAddress;

/*This variable is a pointer pointing to the entry
in the page directory which contains the address
of the Page Table.*/
unsigned long* pPTAddress;

/*This variable is used for storing the address of
the Page Table.*/
unsigned long PTAddress;

/*This variable is a pointer pointing to the entry
in the page table which contains the address of
the physical page.*/
unsigned long* pPPAddress;

/*This variable is used for storing the address of
the physical page.*/
unsigned long PPAddress;

/*This is physical address for the corresponding
virtual address.*/
unsigned long PhysicalAddress;

/*Get the address of the Page Directory from CR3*/
int xc_handle = xc_interface_open();
if(xc_handle == -1)
{
printf("Sorry! Cannot open an interface on xen
hypervisor, please check that whether
the xen is running or not!\n");
exit(1);
}

vcpu_guest_context_t context;
int result = xc_vcpu_getcontext(xc_handle,
1, 0, &context);
if(result == -1)
{
printf("Sorry! Cannot get the context of the
virtual CPU-1 in domain-1, please check
that whether the domain-1 is running or
not!\n");
exit(1);
}
PDAddress = context.ctrlreg[3] & 0xFFFFF000;

int index;
/*Get the index number in Page Directory.*/
index = VirtualAddress >> 22;
/*Get the address of the entry which contains the
address of the Page Table.*/
pPTAddress = PDAddress + (index << 2);
/*Get the address of the Page Table*/
PTAddress = (*pPTAddress) & 0xFFFFF000;
/*Get the index number in Page Table.*/
index = (VirtualAddress >> 12) & 0x000003FF;
/*Get the address of the entry which contains the
address of the physical page.*/
pPPAddress = PTAddress + (index << 2);
/*Get the address of the physical page.*/
PPAddress = (*pPPAddress) & 0xFFFFF000;

PhysicalAddress = PPAddress + (VirtualAddress & 0x00000FFF);


result = xc_interface_close(xc_handle);
if(result == -1)
{
printf("Sorry! Cannot close the special
interface on xen hypervisor!\n");
exit(1);
}

return PhysicalAddress;
}

===============================================
快来和我一起享受TOM免费邮箱吧！ 看看除了1.5G，还有什么？

看看女人都在聊什么? 美图尽赏 聊天世界

明星金曲免费送(http://mm.tom.com/ivr/)：周杰伦 林俊杰 庞龙 张惠妹

劲爆歌曲尽情点(http://mm.tom.com/ivr/)：霍元甲 吉祥三宝 人质 曹操

炫酷彩铃免费送(http://mm.tom.com/cailing/)：周杰伦帮你接电话 麻烦女朋友 七里香 小城故事
===============================================

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel