On Sat, 31 Jul 2021 at 04:33, Nathan Chancellor nathan@kernel.org wrote:
A recent change in LLVM causes module_{c,d}tor sections to appear when CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings because these are not handled anywhere:
ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor' ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor' ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor'
Fangrui explains: "the function asan.module_ctor has the SHF_GNU_RETAIN flag, so it is in a separate section even with -fno-function-sections (default)".
Place them in the TEXT_TEXT section so that these technologies continue to work with the newer compiler versions. All of the KASAN and KCSAN KUnit tests continue to pass after this change.
Cc: stable@vger.kernel.org Link: https://github.com/ClangBuiltLinux/linux/issues/1432 Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a... Signed-off-by: Nathan Chancellor nathan@kernel.org
Acked-by: Marco Elver elver@google.com
For KASAN module_ctors are very much required to support detecting globals out-of-bounds: https://reviews.llvm.org/D81390 For KASAN the test would have revealed that at the latest.
KCSAN does not yet have much use for the module_ctors, but it may change in future, so keeping them all was the right call.
Thanks, -- Marco
v1 -> v2:
Fix inclusion of .text.tsan.* (Nick)
Drop .text.asan as it does not exist plus it would be handled by a different line (Fangrui)
Add Fangrui's explanation about why the LLVM commit caused these sections to appear.
include/asm-generic/vmlinux.lds.h | 1 + 1 file changed, 1 insertion(+)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 17325416e2de..62669b36a772 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -586,6 +586,7 @@ NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \
*(.text.asan.* .text.tsan.*) \ TEXT_CFI_JT \ MEM_KEEP(init.text*) \ MEM_KEEP(exit.text*) \base-commit: 4669e13cd67f8532be12815ed3d37e775a9bdc16
2.32.0.264.g75ae10bc75