[Makedumpfile PATCH V3] elf_info: fix file_size if segment is excluded

[Atsushi Kumagai]

Hello Pratyush,

Sorry for late reply.
I have no further comment for now, but the current --mem-usage
seems have some problems. I can't decide that this patch is insufficient or
that's quite a different matter now, so please let me defer acknowledgment
for a while.

Thanks,
Atsushi Kumagai

>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>
>---
>v1->v2 : subtracted (end - start) from file_size as well
>v2->v3 : subtracted (end - start) for boundary cases as well.
> elf_info.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
>diff --git a/elf_info.c b/elf_info.c
>index 8e2437622141..2c58359a438f 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) {
>@@ -838,6 +841,7 @@ static int exclude_segment(struct pt_load_segment **pt_loads,
> 				(*pt_loads)[i].phys_start = end + 1;
> 				(*pt_loads)[i].virt_start = kvend + 1;
> 			}
>+			(*pt_loads)[i].file_size -= (end -start);
> 		}
> 	}
> 	/* Insert split load segment, if any. */
>--
>2.9.3
>