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

[赵乾利]

In fact,vmemmap  not easy to calculated in crash-utility,if CONFIG_RANDOMIZE_BASE is configured,memstart_addr  will be changed since below codes:
[arm64_memblock_init]
348         vmemmap = ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT));
...
413         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
414                 extern u16 memstart_offset_seed;
415                 u64 range = linear_region_size -
416                             (memblock_end_of_DRAM() - memblock_start_of_DRAM());
417
418                 /*
419                  * If the size of the linear region exceeds, by a sufficient
420                  * margin, the size of the region that the available physical
421                  * memory spans, randomize the linear region as well.
422                  */
423                 if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
424                         range /= ARM64_MEMSTART_ALIGN;
425                         memstart_addr -= ARM64_MEMSTART_ALIGN *
426                                          ((range * memstart_offset_seed) >> 16);
427                 }
428         }

the reason i  showed the "address_markers " is just to prove vmemmap and ms->vmemmap_start is wrong.we'd better to do below change.
-               vmemmap_start = (-vmemmap_size);
+               vmemmap_start = (-vmemmap_size - MEGABYTES(2));

________________________________________
From: crash-utility-bounces at redhat.com <crash-utility-bounces at redhat.com> on behalf of Dave Anderson <anderson at redhat.com>
Sent: Monday, April 20, 2020 21:13
To: Discussion list for crash utility usage,    maintenance and development
Subject: [营销邮件] Re: [Crash-utility] [营销邮件] Re:  [营销邮件] Re:  [External Mail][????] Re: ramdump support for   va_bits_actual

----- 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

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