Commit 92efda8e authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Kees Cook
Browse files

cfi: Drop __CFI_ADDRESSABLE 



The __CFI_ADDRESSABLE macro is used for init_module and cleanup_module
to ensure we have the address of the CFI jump table, and with
CONFIG_X86_KERNEL_IBT to ensure LTO won't optimize away the symbols.
As __CFI_ADDRESSABLE is no longer necessary with -fsanitize=kcfi, add
a more flexible version of the __ADDRESSABLE macro and always ensure
these symbols won't be dropped.

Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Tested-by: default avatarNathan Chancellor <nathan@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-5-samitolvanen@google.com
parent 9fca7115

include/linux/cfi.h

+0 −20
Original line number Diff line number Diff line
@@ -13,26 +13,6 @@ typedef void (*cfi_check_fn)(uint64_t id, void *ptr, void *diag); 
/* Compiler-generated function in each module, and the kernel */

extern void __cfi_check(uint64_t id, void *ptr, void *diag);



/*

 * Force the compiler to generate a CFI jump table entry for a function

 * and store the jump table address to __cfi_jt_<function>.

 */

#define __CFI_ADDRESSABLE(fn, __attr) \

	const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn



#else /* !CONFIG_CFI_CLANG */



#ifdef CONFIG_X86_KERNEL_IBT



#define __CFI_ADDRESSABLE(fn, __attr) \

	const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn



#endif /* CONFIG_X86_KERNEL_IBT */



#endif /* CONFIG_CFI_CLANG */



#ifndef __CFI_ADDRESSABLE

#define __CFI_ADDRESSABLE(fn, __attr)

#endif



#endif /* _LINUX_CFI_H */

include/linux/compiler.h

+4 −2
Original line number Diff line number Diff line
@@ -221,9 +221,11 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 
 * otherwise, or eliminated entirely due to lack of references that are

 * visible to the compiler.

 */

#define __ADDRESSABLE(sym) \

	static void * __section(".discard.addressable") __used \

#define ___ADDRESSABLE(sym, __attrs) \

	static void * __used __attrs \

		__UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym;

#define __ADDRESSABLE(sym) \

	___ADDRESSABLE(sym, __section(".discard.addressable"))



/**

 * offset_to_ptr - convert a relative memory offset to an absolute pointer

include/linux/module.h

+2 −2
Original line number Diff line number Diff line
@@ -132,7 +132,7 @@ extern void cleanup_module(void); 
	{ return initfn; }					\

	int init_module(void) __copy(initfn)			\

		__attribute__((alias(#initfn)));		\

	__CFI_ADDRESSABLE(init_module, __initdata);

	___ADDRESSABLE(init_module, __initdata);



/* This is only required if you want to be unloadable. */

#define module_exit(exitfn)					\
@@ -140,7 +140,7 @@ extern void cleanup_module(void); 
	{ return exitfn; }					\

	void cleanup_module(void) __copy(exitfn)		\

		__attribute__((alias(#exitfn)));		\

	__CFI_ADDRESSABLE(cleanup_module, __exitdata);

	___ADDRESSABLE(cleanup_module, __exitdata);



#endif