On 11/2/2018 5:00 PM, Kazuhito Hagio wrote:
> Originally, info->page_offset (PAGE_OFFSET) is used in the following
> parts on arm64.
>
> arch/arm64.c:
> __pa(unsigned long vaddr)
> {
> if (kimage_voffset == NOT_FOUND_NUMBER ||
> (vaddr >= PAGE_OFFSET))
> return (vaddr - PAGE_OFFSET + info->phys_base);
> else
> return (vaddr - kimage_voffset);
> }
>
> elf_info.c:
> kvstart = (ulong)start + PAGE_OFFSET;
> kvend = (ulong)end + PAGE_OFFSET;
> --
> kvaddr = (ulong)vmcoreinfo_addr + PAGE_OFFSET;
>
> I'm wondering about its consistency. Is it OK to set
> (virt_start - phys_start) to info->page_offset on arm64?
> In other words, on arm64 system with info->phys_base != 0, does it
> work correctly for both /proc/vmcore and --mem-usage /proc/kcore?
I found an arm64 system available and (virt_start - phys_start)
tested OK for both /proc/vmcore and --mem-usage /proc/kcore,
because the __pa() function is used just only for swapper_pg_dir
and the "(vaddr - PAGE_OFFSET + info->phys_base)" line is not used.
The definition of PAGE_OFFSET in kernel is:
#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
(UL(1) << (VA_BITS - 1)) + 1)
The one in crash is:
#define ARM64_PAGE_OFFSET ((0xffffffffffffffffUL) \
<< (machdep->machspec->VA_BITS - 1))
So I think it would be better to use the same definition also in
makedumpfile to avoid confusion. In other words, I think the following
does not support arm64 now, and ideally should be fixed by introducing
something like phys_to_virt()..
elf_info.c:
kvstart = (ulong)start + PAGE_OFFSET;
kvend = (ulong)end + PAGE_OFFSET;
--
kvaddr = (ulong)vmcoreinfo_addr + PAGE_OFFSET;
and then,
if (NUMBER(VA_BITS) != NOT_FOUND_NUMBER)
va_bits = NUMBER(VA_BITS);
else
... va_vits calculation ...
info->page_offset = 0xffffffffffffffffUL << (va_bits - 1);
And also we will need to add get_phys_base() to show_mem_usage()
with some additional code for arm64 with old kernels.
I'm considering this approach.
Thanks,
Kazu
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