Re: [RFC PATCH 3/7] static_call: use helper to access non-exported key

Ard Biesheuvel
2021-11-09T18:54:37Z

On Tue, 9 Nov 2021 at 19:53, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Nov 09, 2021 at 05:45:45PM +0100, Ard Biesheuvel wrote:
> > @@ -196,13 +190,21 @@ extern long __static_call_return0(void);
> > EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name)); \
> > EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
> >
> > +#define EXPORT_STATIC_CALL_GETKEY_HELPER(name) \
> > + struct static_call_key *STATIC_CALL_GETKEY(name)(void) { \
> > + BUG_ON(!core_kernel_text( \
> > + (unsigned long)__builtin_return_address(0))); \
> > + return &STATIC_CALL_KEY(name); \
> > + } \
> > + EXPORT_SYMBOL_GPL(STATIC_CALL_GETKEY(name))
>
> So if I were a nevarious module, I would look up the above symbol from
> kallsyms (it is exported and easily obtainable) and then simply
> read the text to discover the key address and we're in business.
>

Yeah I realised that. So would you prefer to have a
.static_call_tramp_key section in each module and look up the keys in
the module loader?