[Crash-utility] [营销邮件] Re: [营销邮件] Re: [External Mail][????] Re: ramdump support for va_bits_actual

[Dave Anderson]

----- Original Message -----
> Hi
> vmemmap and VMEMMAP_START are different,vmemmap begin from physical address
> 0x0 of page,but VMEMMAP_START start with memstart_addr.
> 
> [mm/init.c]
> arm64_memblock_init
> 348         vmemmap = ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT));

Right, so VMEMMAP_START can be calculated by reading vmemmap and memstart_addr.

> 
> We can look at address_markers, this symbol indicates the entire memory map allocation
> check vmemmap and address_markers, we can see vmemmap has out of vmemmap range

It would be ideal if address_markers was guaranteed to be there, but it 
only exists if CONFIG_PTDUMP_CORE was configured.

> crash> p -x vmemmap
> vmemmap = $1 = (struct page *) 0xfffffffefde00000
> 
> address_markers = $2 =
>  {{
>       start_address = 0xffffff8000000000,
>     name = 0xffffffd44b1fed8f "Linear Mapping start"
> ...
>   }, {
>     start_address = 0xfffffffeffe00000,
>     name = 0xffffffd44b2c5beb "vmemmap start"
>   }, {
>     start_address = 0xffffffffffe00000,
>     name = 0xffffffd44b1eb00c "vmemmap end"
>   }, {
>     start_address = 0xffffffffffffffff,
>     name = 0x0
>   }}
> 
> 
> > When the readmem() of symbol_value("physvirt_offset") is made, arm64_VTOP() will
> > be called with its virtual address, right?
> Yes, arm64_VTOP to get physvirt_offset needs virtual address, and
> physvirt_offset is a kimage symbol,so just need kimage_voffset can translate
> to physical address,then get value of physvirt_offset.

Ah, you're right, it's a mapped kernel symbol and doesn't use it.  

Dave