linux-kernel - [PATCH v2] vmlinux.lds.h: Handle clang's module.{c,d}tor sections

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Date:   Fri, 30 Jul 2021 19:31:08 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Fangrui Song <maskray@...gle.com>, Marco Elver <elver@...gle.com>,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, clang-built-linux@...glegroups.com,
        Nathan Chancellor <nathan@...nel.org>, stable@...r.kernel.org
Subject: [PATCH v2] vmlinux.lds.h: Handle clang's module.{c,d}tor sections

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@...r.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1432
Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---

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