On 2017/04/27 11:21AM, Masami Hiramatsu wrote:
> On Thu, 27 Apr 2017 01:38:10 +0530
> "Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote:
>
> > Michael Ellerman wrote:
> > > "Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> writes:
> > >> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > >> index 6a3b249a2ae1..d134b060564f 100644
> > >> --- a/kernel/kallsyms.c
> > >> +++ b/kernel/kallsyms.c
> > >> @@ -205,6 +205,12 @@ unsigned long kallsyms_lookup_name(const char *name)
> > >> unsigned long i;
> > >> unsigned int off;
> > >>
> > >> + if (!name || *name == '\0')
> > >> + return false;
> > >> +
> > >> + if (strnchr(name, MODULE_NAME_LEN, ':'))
> > >> + return module_kallsyms_lookup_name(name);
> > >> +
> > >> for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
> > >> off = kallsyms_expand_symbol(off, namebuf,
> > >> ARRAY_SIZE(namebuf));
> > > ...
> > > }
> > > return module_kallsyms_lookup_name(name);
> > >
> > > Is the rest of the context.
> > >
> > > Which looks a bit odd, we already did module lookup previously?
> > >
> > > But it's correct, because you can lookup a symbol in a module without a
> > > module prefix, it just looks in every module.
> >
> > Yes.
> >
> > >
> > > You could invert the logic, ie. check that there isn't a ":" in the name
> > > and only in that case do the for loop, always falling back to module
> > > lookup.
> > >
> > > Or just add a comment explaining why we call module lookup in two places.
> >
> > Good point. Here's a v2 - I'm using a goto so as to not indent the code too
> > much.
> >
> > Thanks for the review!
> > - Naveen
> >
> > --
> > [PATCH v2] kallsyms: optimize kallsyms_lookup_name() for a few cases
> >
> > 1. Fail early for invalid/zero length symbols.
> > 2. Detect names of the form <mod:name> and skip checking for kernel
> > symbols in that case.
> >
>
> Looks good to me.
>
> Reviewed-by: Masami Hiramatsu <mhira...@kernel.org>
Thanks, Masami!
I am not quite sure who maintains kallsyms...
Ingo,
Can you please help with merging this patch?
Thanks,
Naveen
>
> Thanks,
>
>
> > Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> > ---
> > kernel/kallsyms.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > index 6a3b249a2ae1..f7558dc5c6ac 100644
> > --- a/kernel/kallsyms.c
> > +++ b/kernel/kallsyms.c
> > @@ -205,12 +205,20 @@ unsigned long kallsyms_lookup_name(const char *name)
> > unsigned long i;
> > unsigned int off;
> >
> > + if (!name || *name == '\0')
> > + return 0;
> > +
> > + /* For symbols of the form <mod>:<sym>, only check the modules */
> > + if (strnchr(name, MODULE_NAME_LEN, ':'))
> > + goto mod;
> > +
> > for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
> > off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
> >
> > if (strcmp(namebuf, name) == 0)
> > return kallsyms_sym_address(i);
> > }
> > +mod:
> > return module_kallsyms_lookup_name(name);
> > }
> > EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
> > --
> > 2.12.2
> >
>
>
> --
> Masami Hiramatsu <mhira...@kernel.org>
>
