With CONFIG_LTO_CLANG_FULL, LLVM drops all CFI jump table symbols
from vmlinux, which doesn't affect kernel functionality, but can
make stack traces and other kernel output that prints out jump
table addresses harder to read.
This change works around the issue for now by adding a script that
tells kallsyms about the missing jump table symbols, even though
they don't actually exist in the symbol table, and generates a
linker script to add the missing symbols to kernel modules.
Bug: 186152035
Bug: 187415564
Change-Id: Ic3c51751c756f2f5fb2a31229e16c3397eb6e666
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
On modules with no executable code, LLVM generates a __cfi_check stub,
but won't align it to page size as expected. This change ensures the
function is at the beginning of the .text section and correctly aligned
for the CFI shadow.
Also discard the .eh_frame section, which LLD may emit with CFI_CLANG.
Bug: 145210207
Change-Id: I08923febb549aa64454282cc864ac80dadd717b9
Link: https://bugs.llvm.org/show_bug.cgi?id=46293
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
There was a request to preprocess the module linker script like we
do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512)
The difference between vmlinux.lds and module.lds is that the latter
is needed for external module builds, thus must be cleaned up by
'make mrproper' instead of 'make clean'. Also, it must be created
by 'make modules_prepare'.
You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by
'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to
arch/$(SRCARCH)/include/asm/module.lds.h, which is included from
scripts/module.lds.S.
scripts/module.lds is fine because 'make clean' keeps all the
build artifacts under scripts/.
You can add arch-specific sections in <asm/module.lds.h>.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
