Good catch!
Ack
???? iPhone
> ? 2017?5?8????8:41?Pratyush Anand <panand at redhat.com> ???
>
> I received following on a specific x86_64 hp virtual machine while
> executing `makedumpfile --mem-usage /proc/kcore`.
>
> vtop4_x86_64: Can't get a valid pte.
> readmem: Can't convert a virtual address(ffffffff88115860) to physical address.
> readmem: type_addr: 0, addr:ffffffff88115860, size:128
> get_nodes_online: Can't get the node online map.
>
> With some debug print in vtop4_x86_64() I noticed that pte value is read
> as 0, while crash reads the value correctly:
>
> from makedumpfile:
> vaddr=ffffffff88115860
> page_dir=59eaff8
> pml4=59ed067
> pgd_paddr=59edff0
> pgd_pte=59ee063
> pmd_paddr=59ee200
> pmd_pte=3642f063
> pte_paddr=3642f8a8
> pte=0
>
> from crash
> crash> vtop ffffffff88115860
> VIRTUAL PHYSICAL
> ffffffff88115860 5b15860
>
> PML4 DIRECTORY: ffffffff87fea000
> PAGE DIRECTORY: 59ed067
> PUD: 59edff0 => 59ee063
> PMD: 59ee200 => 3642f063
> PTE: 3642f8a8 => 5b15163
> PAGE: 5b15000
>
> With some more debug prints in elf_info.c
>
> Before calling exclude_segment()
>
> LOAD (2)
> phys_start : 100000
> phys_end : dfffd000
> virt_start : ffff8a5a40100000
> virt_end : ffff8a5b1fffd000
> file_offset: a5a40102000
> file_size : dfefd000
>
> exclude_segment() is called for Crash Kernel whose range is
> 2b000000-350fffff.
>
> We see following after exclude_segment()
>
> LOAD (2)
> phys_start : 100000
> phys_end : 2affffff
> virt_start : ffff8a5a40100000
> virt_end : ffff8a5a6affffff
> file_offset: a5a40102000
> file_size : dfefd000
> LOAD (3)
> phys_start : 35100000
> phys_end : dfffd000
> virt_start : ffff8a5a75100000
> virt_end : ffff8a5b1fffd000
> file_offset: a5a75102000
> file_size : 0
>
> Since file_size is calculated wrong therefore readpage_elf() does not
> behave correctly.
>
> This patch fixes above wrong behavior.
>
> Signed-off-by: Pratyush Anand <panand at redhat.com>
> ---
> elf_info.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/elf_info.c b/elf_info.c
> index 8e2437622141..6bf5e3373595 100644
> --- a/elf_info.c
> +++ b/elf_info.c
> @@ -826,9 +826,12 @@ static int exclude_segment(struct pt_load_segment **pt_loads,
> temp_seg.virt_end = vend;
> temp_seg.file_offset = (*pt_loads)[i].file_offset
> + temp_seg.virt_start - (*pt_loads)[i].virt_start;
> + temp_seg.file_size = temp_seg.phys_end
> + - temp_seg.phys_start;
>
> (*pt_loads)[i].virt_end = kvstart - 1;
> (*pt_loads)[i].phys_end = start - 1;
> + (*pt_loads)[i].file_size -= temp_seg.file_size;
>
> tidx = i+1;
> } else if (kvstart != vstart) {
> --
> 2.9.3
>
