From 514ca14ed5444b911de59ed3381dfd195d99fe4b Mon Sep 17 00:00:00 2001 From: "ndesaulniers@google.com" Date: Mon, 17 Apr 2023 15:00:05 -0700 Subject: start_kernel: Add __no_stack_protector function attribute Back during the discussion of commit a9a3ed1eff36 ("x86: Fix early boot crash on gcc-10, third try") we discussed the need for a function attribute to control the omission of stack protectors on a per-function basis; at the time Clang had support for no_stack_protector but GCC did not. This was fixed in gcc-11. Now that the function attribute is available, let's start using it. Callers of boot_init_stack_canary need to use this function attribute unless they're compiled with -fno-stack-protector, otherwise the canary stored in the stack slot of the caller will differ upon the call to boot_init_stack_canary. This will lead to a call to __stack_chk_fail() then panic. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94722 Link: https://lore.kernel.org/all/20200316130414.GC12561@hirez.programming.kicks-ass.net/ Tested-by: Nathan Chancellor Acked-by: Michael Ellerman (powerpc) Acked-by: Miguel Ojeda Acked-by: Peter Zijlstra (Intel) Signed-off-by: Nick Desaulniers Link: https://lore.kernel.org/r/20230412-no_stackp-v2-1-116f9fe4bbe7@google.com Signed-off-by: Josh Poimboeuf Signed-off-by: ndesaulniers@google.com --- include/linux/compiler_attributes.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'include/linux/compiler_attributes.h') diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index e659cb6fded3..84864767a56a 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -255,6 +255,18 @@ */ #define __noreturn __attribute__((__noreturn__)) +/* + * Optional: only supported since GCC >= 11.1, clang >= 7.0. + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute + * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers + */ +#if __has_attribute(__no_stack_protector__) +# define __no_stack_protector __attribute__((__no_stack_protector__)) +#else +# define __no_stack_protector +#endif + /* * Optional: not supported by gcc. * -- cgit v1.2.3 From dd06e72e68bcb4070ef211be100d2896e236c8fb Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 17 May 2023 12:08:44 -0700 Subject: Compiler Attributes: Add __counted_by macro In an effort to annotate all flexible array members with their run-time size information, the "element_count" attribute is being introduced by Clang[1] and GCC[2] in future releases. This annotation will provide the CONFIG_UBSAN_BOUNDS and CONFIG_FORTIFY_SOURCE features the ability to perform run-time bounds checking on otherwise unknown-size flexible arrays. Even though the attribute is under development, we can start the annotation process in the kernel. This requires defining a macro for it, even if we have to change the name of the actual attribute later. Since it is likely that this attribute may change its name to "counted_by" in the future (to better align with a future total bytes "sized_by" attribute), name the wrapper macro "__counted_by", which also reads more clearly (and concisely) in structure definitions. [1] https://reviews.llvm.org/D148381 [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 Cc: Bill Wendling Cc: Qing Zhao Cc: Gustavo A. R. Silva Cc: Nick Desaulniers Cc: Nathan Chancellor Cc: Tom Rix Cc: llvm@lists.linux.dev Signed-off-by: Kees Cook Reviewed-by: Gustavo A. R. Silva Reviewed-by: Nathan Chancellor Acked-by: Miguel Ojeda Link: https://lore.kernel.org/r/20230517190841.gonna.796-kees@kernel.org --- include/linux/compiler_attributes.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux/compiler_attributes.h') diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index e659cb6fded3..5588bffe53b9 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -123,6 +123,19 @@ # define __designated_init #endif +/* + * Optional: only supported since gcc >= 14 + * Optional: only supported since clang >= 17 + * + * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 + * clang: https://reviews.llvm.org/D148381 + */ +#if __has_attribute(__element_count__) +# define __counted_by(member) __attribute__((__element_count__(#member))) +#else +# define __counted_by(member) +#endif + /* * Optional: only supported since clang >= 14.0 * -- cgit v1.2.3