[PATCH] makedumpfile: call initial before use cache

[HAGIO KAZUHITO(萩尾 一仁)]

On 2024/07/23 16:31, Lichen Liu wrote:
> Yes, it works!
> Thank you so much!

Thanks, applied.
https://github.com/makedumpfile/makedumpfile/commit/900190de6b67b2de410cfc8023c1b198a416ceb3

Kazu

> 
> On Mon, Jul 22, 2024 at 2:46 PM HAGIO KAZUHITO(萩尾　一仁)
> <k-hagio-ab at nec.com> wrote:
>>
>> On 2024/07/20 16:38, Lichen Liu wrote:
>>
>>>> This will work only for 4.19 and later kernels, but might reduce users
>>>> that hit the issue.  Does this work for you?
>>> That works for me because I'm testing for the 6.x kernel.
>>
>> Thanks for the check.  Is the issue a segmentation fault?
>> I've made a patch below, is this OK?
>>
>>
>>   From 084742cba5b81da563074454ab8c879e8e411cb0 Mon Sep 17 00:00:00 2001
>> From: Kazuhito Hagio <k-hagio-ab at nec.com>
>> Date: Mon, 22 Jul 2024 14:31:43 +0900
>> Subject: [PATCH] Workaround for segfault by "makedumpfile --mem-usage" on PPC64
>>
>> "makedumpfile --mem-usage /proc/kcore" can cause a segmentation fault on
>> PPC64, because the readmem() of the following code path uses cache
>> before it's initialized in initial().
>>
>>     show_mem_usage
>>       get_page_offset
>>         get_versiondep_info_ppc64
>>           readmem
>>       ...
>>       initial
>>           cache_init
>>
>> The get_page_offset() is needed to get vmcoreinfo from /proc/kcore data,
>> so we can avoid calling it when a vmcoreinfo exists in the ELF NOTE
>> segment of /proc/kcore, i.e. on Linux 4.19 and later.
>>
>> (Note: for older kernels, we will need another way to fix it.)
>>
>> Reported-by: Lichen Liu <lichliu at redhat.com>
>> Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
>> ---
>>    makedumpfile.c | 12 ++++++------
>>    1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/makedumpfile.c b/makedumpfile.c
>> index 5b347126db76..7d1dfcca50d8 100644
>> --- 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;
>>
>> --
>> 2.31.1