Re: [Crash-utility] [PATCH v4 1/4] Improve the performance of symbol searching for kernel modules
-----Original Message-----
Hi Kazu,
Sorry for the late reply, it was a public holiday for the past few days...
No problem.
On Tue, Oct 5, 2021 at 4:51 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab(a)nec.com> wrote:
>
> Hi Tao,
>
> Found another issue.
>
> The first symbol of duplicated ones will not be shown by sym command
> after mod -s.
>
> # crash -s
> crash> sym cleanup_module | head -n 1
> ffffffffc02527ff (t) cleanup_module [fuse]
> crash> mod -s fuse
> MODULE NAME BASE SIZE OBJECT FILE
> ffffffffc025eac0 fuse ffffffffc023f000 151552
/usr/lib/debug/lib/modules/4.18.0-305.el8.x86_64/kernel/fs/fuse/fuse.ko.debug
> crash> sym cleanup_module | grep fuse
>
> It looks like symbol_search() has to return the lowest address symbol and
> symbol_search_next() returns the next lowest symbol, so removing/installing
> module symbols from/to the hash table breaks this.
>
> The patch will need sorted installation or other solution.
>
Agreed, I haven't considered this case. Yes, a sorting installation is
necessary.
> Also, I've not looked at this enough, but kallsyms_module_symbol() changes
> spx->cnt from lm->mod_ext_symtable. Is there no interference with the
> patch?
>
No, this patch didn't interfere with it. Actually I didn't notice
kallsyms_module_symbol() also changed spx->cnt, so the patch
definitely needs further improvement. I will think of a better
solution for handling sp->cnt field, please wait for a while before I
send the v5 patch.
ok..
fyi, store_load_module_symbols() also changes(clears) spx->cnt from
lm->mod_ext_symtable:
for (spx = lm->mod_ext_symtable; spx <= lm->mod_ext_symend; spx++)
spx->cnt = 0;
Thanks,
Kazu