| Message ID | 20210323203946.2159693-5-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for Clang CFI | expand |
On Tue, Mar 23, 2021 at 01:39:33PM -0700, Sami Tolvanen wrote: > CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page > aligned and at the beginning of the .text section. While Clang would > normally align the function correctly, it fails to do so for modules > with no executable code. > > This change ensures the correct __cfi_check() location and > alignment. It also discards the .eh_frame section, which Clang can > generate with certain sanitizers, such as CFI. > > Link: https://bugs.llvm.org/show_bug.cgi?id=46293 > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Yay macros! :) Reviewed-by: Kees Cook <keescook@chromium.org>
+++ Sami Tolvanen [23/03/21 13:39 -0700]: >CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page >aligned and at the beginning of the .text section. While Clang would >normally align the function correctly, it fails to do so for modules >with no executable code. > >This change ensures the correct __cfi_check() location and >alignment. It also discards the .eh_frame section, which Clang can >generate with certain sanitizers, such as CFI. > >Link: https://bugs.llvm.org/show_bug.cgi?id=46293 >Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Acked-by: Jessica Yu <jeyu@kernel.org> Thanks!
diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 168cd27e6122..2ba9e5ce71df 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -3,10 +3,21 @@ * Archs are free to supply their own linker scripts. ld will * combine them automatically. */ +#include <asm/page.h> + +#ifdef CONFIG_CFI_CLANG +# define ALIGN_CFI ALIGN(PAGE_SIZE) +# define SANITIZER_DISCARDS *(.eh_frame) +#else +# define ALIGN_CFI +# define SANITIZER_DISCARDS +#endif + SECTIONS { /DISCARD/ : { *(.discard) *(.discard.*) + SANITIZER_DISCARDS } __ksymtab 0 : { *(SORT(___ksymtab+*)) } @@ -40,7 +51,14 @@ SECTIONS { *(.rodata..L*) } - .text : { *(.text .text.[0-9a-zA-Z_]*) } + /* + * With CONFIG_CFI_CLANG, we assume __cfi_check is at the beginning + * of the .text section, and is aligned to PAGE_SIZE. + */ + .text : ALIGN_CFI { + *(.text.__cfi_check) + *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) + } } /* bring in arch-specific sections */
CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page aligned and at the beginning of the .text section. While Clang would normally align the function correctly, it fails to do so for modules with no executable code. This change ensures the correct __cfi_check() location and alignment. It also discards the .eh_frame section, which Clang can generate with certain sanitizers, such as CFI. Link: https://bugs.llvm.org/show_bug.cgi?id=46293 Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- scripts/module.lds.S | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)