Messages in this thread | | | Date | Thu, 28 Nov 2013 11:02:57 +0900 | From | Masami Hiramatsu <> | Subject | Re: Re: modules, add_kallsyms() && DEFINE_PER_CPU |
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(2013/11/27 22:35), Oleg Nesterov wrote: > On 11/27, Masami Hiramatsu wrote: >> >> (2013/11/27 2:50), Oleg Nesterov wrote: >>> On 11/26, Oleg Nesterov wrote: >>>> >>>> Note: this doesn't work for modules, but module's per-cpu data is >>>> not visible for kallsyms_lookup_name() anyway. >>> >>> Rusty, I am just curious if it makes sense to change this or not... >>> >>> But DEFINE_PER_CPU'ed symbols are ignored by add_kallsyms(). I guess >>> this is because is_core_symbol() requires "sh_flags & SHF_ALLOC". >>> And probably because of INIT_OFFSET_MASK. >> >> Oleg, I think you can do it by using is_module_percpu_address(). :) > > Not only is_module_percpu_address() can't help. We can solve the > is-it-percpu problem (although the check won't be cheap).
I think you can do this at registering phase (by adding a flag in symbol_cache). That is in a slow path.
> The problem is, sc->addr is always NULL if DEFINE_PER_CPU() was used > in a module. kallsyms_lookup_name() can never see it because it is > ignored by add_kallsyms(), it is nacked by is_core_symbol(). > > IOW, with or without this patch @modular_percpu_sym never reads the > memory.
Hmm, in that case, should we support it? It looks non-existed symbol is given. I think until the module.c support per-cpu in kallsyms, we can delay to support it. I mean we can do 3 steps 1. support percpu symbol in the kernel except for drivers 2. update module.c to store the percpu symbols into kallsyms. 3. support percpu symbol in module .
Thank you,
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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