linux-kernel - Re: [PATCH v2] module: keep percpu symbols in module's symtab

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Message-ID: <87bnahv5jw.fsf@rustcorp.com.au>
Date:	Thu, 26 Nov 2015 13:19:07 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Miroslav Benes <mbenes@...e.cz>
Cc:	linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2] module: keep percpu symbols in module's symtab

Miroslav Benes <mbenes@...e.cz> writes:
> Currently, percpu symbols from .data..percpu ELF section of a module are
> not copied over and stored in final symtab array of struct module.
> Consequently such symbol cannot be returned via kallsyms API (for
> example kallsyms_lookup_name). This can be especially confusing when the
> percpu symbol is exported. Only its __ksymtab et al. are present in its
> symtab.
>
> The culprit is in layout_and_allocate() function where SHF_ALLOC flag is
> dropped for .data..percpu section. There is in fact no need to copy the
> section to final struct module, because kernel module loader allocates
> extra percpu section by itself. Unfortunately only symbols from
> SHF_ALLOC sections are copied due to a check in is_core_symbol().
>
> The patch changes is_core_symbol() function to copy over also percpu
> symbols (their st_shndx points to .data..percpu ELF section). We do it
> only if CONFIG_KALLSYMS_ALL is set to be consistent with the rest of the
> function (ELF section is SHF_ALLOC but !SHF_EXECINSTR). Finally
> elf_type() returns type 'a' for a percpu symbol because its address is
> absolute.
>
> Signed-off-by: Miroslav Benes <mbenes@...e.cz>

Thanks, applied!

Cheers,
Rusty.
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