On Mon, Nov 14, 2022 at 06:00:38PM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/11/14 17:27, Jiri Olsa wrote: > > On Mon, Nov 14, 2022 at 04:50:25PM +0800, Leizhen (ThunderTown) wrote: > >> > >> On 2022/11/14 15:47, Jiri Olsa wrote: > >>> On Wed, Nov 02, 2022 at 04:49:19PM +0800, Zhen Lei wrote: > >>>> Currently we traverse all symbols of all modules to find the specified > >>>> function for the specified module. But in reality, we just need to find > >>>> the given module and then traverse all the symbols in it. > >>> hi, > >>> sorry for delayed answer, I did not notice this until Stephen's email > >>> about merge issue with recent bpf change [1] > >>> > >>>> Let's add a new parameter 'const char *modname' to function > >>>> module_kallsyms_on_each_symbol(), then we can compare the module names > >>> we have use case for iterating all modules and their symbols when we > >>> want to resolve passed addresses for tracing > >>> > >>> we don't have 'modname' that we could pass, we need to iterate all modules > >>> > >>> so perhaps this could be made optional like with passing NULL for modname? > >> The deletion of modname was suggested by Petr Mladek. The reason is that > >> everyone passes modname as NULL, there was no actual demand at the time. > >> https://lkml.org/lkml/2022/9/20/682 > >> > >>>> directly in this function and call hook 'fn' after matching. And the > >>>> parameter 'struct module *' in the hook 'fn' can also be deleted. > >>> we need 'struct module *' argument in the callback as well because we are > >>> taking the module reference if we trace function in it, so it wont get > >>> unloaded > >>> > >>> please let me know if I should do the change or can help in any way > >> It seems that we should take the module reference before invoking callback > >> and put it after it is called, without passing modname. > > we take the module ref only if we (callback) find the traced address in > > the module, we don't have the module object before > > > > jirka > > > > Do it in function module_kallsyms_on_each_symbol()? > > But I just saw that mutex_lock(&module_mutex) protection is already > provided in this function. So reference counting protection may not > be required. we take the module ref so it won't unload even outside of the module_kallsyms_on_each_symbol function jirka
