Messages in this thread Patch in this message | | | From | Ard Biesheuvel <> | Subject | [PATCH v6 1/2] static_call: use non-function types to refer to the trampolines | Date | Fri, 5 Nov 2021 15:59:16 +0100 |
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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> --- 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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