Hi Lichen,
sorry for the long delay.
On 2024/06/25 10:57, Lichen Liu wrote:
> Run 'makedumpfile --mem-usage /proc/kcore' will coredump on ppc64, it is
> because show_mem_usage()->get_page_offset()->get_versiondep_info_ppc64()
> ->readmem() use cache before it is inited by initial().
>
> Currently only ppc64 has this issue because only
> get_versiondep_info_ppc64() call readmem().
>
> Signed-off-by: Lichen Liu <lichliu@xxxxxxxxxx>
> ---
> makedumpfile.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/makedumpfile.c b/makedumpfile.c
> index 5b34712..6a42264 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -12019,6 +12019,9 @@ int show_mem_usage(void)
> DEBUG_MSG("Read vmcoreinfo from NOTE segment: %d\n", vmcoreinfo);
> }
>
> + if (!initial())
> + return FALSE;
> +
> if (!get_page_offset())
> return FALSE;
>
> @@ -12034,9 +12037,6 @@ int show_mem_usage(void)
> return FALSE;
> }
>
> - if (!initial())
> - return FALSE;
> -
> if (!open_dump_bitmap())
> return FALSE;
>
initial() needs to be called after set_kcore_vmcoreinfo(), when there is
no vmcoreinfo in /proc/kcore ELF note.
So with the patch, "makedumpfile --mem-usage" fails on kernels that do
not have a vmcoreinfo in ELF note, e.g. RHEL7 kernel:
# makedumpfile-dev -f --mem-usage /proc/kcore
exclude_free_page: Can't get necessary symbols for excluding free pages.
makedumpfile Failed.
Probably readmem() should not be called before initial() in the first
place. I think it's the root cause, but I'm not sure how we can fix it.
A workaround I thought of is that moving get_page_offset() and
get_phys_base() into the !vmcoreinfo block. These are needed by
set_kcore_vmcoreinfo(), so we can avoid calling them if there is a
vmcoreinfo in ELF note:
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -12019,14 +12019,14 @@ int show_mem_usage(void)
DEBUG_MSG("Read vmcoreinfo from NOTE segment: %d\n",
vmcoreinfo);
}
- if (!get_page_offset())
- return FALSE;
+ if (!vmcoreinfo) {
+ if (!get_page_offset())
+ return FALSE;
- /* paddr_to_vaddr() on arm64 needs phys_base. */
- if (!get_phys_base())
- return FALSE;
+ /* paddr_to_vaddr() on arm64 needs phys_base. */
+ if (!get_phys_base())
+ return FALSE;
- if (!vmcoreinfo) {
if (!get_sys_kernel_vmcoreinfo(&vmcoreinfo_addr,
&vmcoreinfo_len))
return FALSE;
This will work only for 4.19 and later kernels, but might reduce users
that hit the issue. Does this work for you?
Thanks,
Kazu
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