[Crash-utility] [PATCH 1/1] Calculate offset to field 'init_uts_ns.name'

[HAGIO KAZUHITO(萩尾 一仁)]

Hi Alex,

sorry for the delayed response.

I misunderstood at first glance and have waited for the kernel patch
adding the vmcoreinfo entry you posted, but I just found no need to
wait for it with respect to crash.

-----Original Message-----
> The offset has changed in linux-next (v5.9.0) from 4 to 0 because
> there is no more 'kref' member variable at the beginning of 'init_uts_ns'.
> The change was introduced with commit 9a56493f6942c0e2df1579986128721da96e00d8.
> To handle both cases correctly, calculate the offset at run time instead.
> 
> Signed-off-by: Alexander Egorenkov <egorenar at linux.ibm.com>
> ---
>  kernel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel.c b/kernel.c
> index 21bd1eb..13942b9 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -237,7 +237,7 @@ kernel_init()
>                  	sizeof(struct new_utsname), "system_utsname",
>  			RETURN_ON_ERROR);
>  	else if (symbol_exists("init_uts_ns"))
> -		readmem(symbol_value("init_uts_ns") + sizeof(int),
> +		readmem(symbol_value("init_uts_ns") + ANON_MEMBER_OFFSET("uts_namespace","name"),

When we get an offset from vmlinux, usually we introduce a member to
struct offset_table (at the tail of it) and populate it with MEMBER_OFFSET_INIT()
macro so that we can reuse it and dump it with dump_offset_table() function.
Can you please update so?

For reference:
https://www.redhat.com/archives/crash-utility/2020-August/msg00052.html

and fyi, crash doesn't use the vmcoreinfo entry OFFSET(uts_namespace.name)
with respect to this case.

Thanks,
Kazu

>  			KVADDR,  &kt->utsname, sizeof(struct new_utsname),
>  			"init_uts_ns", RETURN_ON_ERROR);
>  	else
> --
> 2.26.2
> 
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