Messages in this thread | | | Date | Mon, 8 Nov 2021 11:08:04 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v6 1/2] static_call: use non-function types to refer to the trampolines |
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On Fri, Nov 05, 2021 at 03:59:16PM +0100, Ard Biesheuvel wrote: > In order to prevent CFI enabled code from grabbing a jump table entry > that jumps to the trampoline, rather than the trampoline itself, use an > incomplete non-function type for the trampoline, and cast it to the > right type only when invoking it. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Very grudingly:
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> --- > include/linux/static_call.h | 4 ++-- > include/linux/static_call_types.h | 11 ++++++++--- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/include/linux/static_call.h b/include/linux/static_call.h > index 3e56a9751c06..616607393273 100644 > --- a/include/linux/static_call.h > +++ b/include/linux/static_call.h > @@ -151,7 +151,7 @@ extern void arch_static_call_transform(void *site, void *tramp, void *func, bool > > #define static_call_update(name, func) \ > ({ \ > - typeof(&STATIC_CALL_TRAMP(name)) __F = (func); \ > + typeof(&STATIC_CALL_TYPE(name)) __F = (func); \ > __static_call_update(&STATIC_CALL_KEY(name), \ > STATIC_CALL_TRAMP_ADDR(name), __F); \ > }) > @@ -306,7 +306,7 @@ static inline void __static_call_nop(void) { } > void *func = READ_ONCE(STATIC_CALL_KEY(name).func); \ > if (!func) \ > func = &__static_call_nop; \ > - (typeof(STATIC_CALL_TRAMP(name))*)func; \ > + (typeof(&STATIC_CALL_TYPE(name)))func; \ > }) > > #define static_call_cond(name) (void)__static_call_cond(name) > diff --git a/include/linux/static_call_types.h b/include/linux/static_call_types.h > index 5a00b8b2cf9f..5e658ef537e4 100644 > --- a/include/linux/static_call_types.h > +++ b/include/linux/static_call_types.h > @@ -18,6 +18,9 @@ > #define STATIC_CALL_TRAMP(name) __PASTE(STATIC_CALL_TRAMP_PREFIX, name) > #define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name)) > > +#define STATIC_CALL_TYPE_PREFIX __SCtype__ > +#define STATIC_CALL_TYPE(name) __PASTE(STATIC_CALL_TYPE_PREFIX, name) > + > /* > * Flags in the low bits of static_call_site::key. > */ > @@ -36,11 +39,13 @@ struct static_call_site { > > #define DECLARE_STATIC_CALL(name, func) \ > extern struct static_call_key STATIC_CALL_KEY(name); \ > - extern typeof(func) STATIC_CALL_TRAMP(name); > + extern struct static_call_tramp STATIC_CALL_TRAMP(name); \ > + extern typeof(func) STATIC_CALL_TYPE(name) > > #ifdef CONFIG_HAVE_STATIC_CALL > > -#define __raw_static_call(name) (&STATIC_CALL_TRAMP(name)) > +#define __raw_static_call(name) \ > + ((typeof(&STATIC_CALL_TYPE(name)))&STATIC_CALL_TRAMP(name)) > > #ifdef CONFIG_HAVE_STATIC_CALL_INLINE > > @@ -96,7 +101,7 @@ struct static_call_key { > }; > > #define static_call(name) \ > - ((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func)) > + ((typeof(&STATIC_CALL_TYPE(name)))(STATIC_CALL_KEY(name).func)) > > #endif /* CONFIG_HAVE_STATIC_CALL */ > > -- > 2.30.2 >
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