Re: [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
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(a)redhat.com <crash-utility-bounces(a)redhat.com> on behalf
of Dave Anderson <anderson(a)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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