From: Kees Cook <keescook@chromium.org>
To: kernel test robot <lkp@intel.com>
Cc: kbuild-all@lists.01.org, clang-built-linux@googlegroups.com,
linux-kernel@vger.kernel.org, Marco Elver <elver@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com
Subject: Re: [PATCH v3 4/9] x86/build: Warn on orphan section placement
Date: Sat, 27 Jun 2020 08:44:08 -0700 [thread overview]
Message-ID: <202006270840.E0BC752A72@keescook> (raw)
In-Reply-To: <202006250240.J1VuMKoC%lkp@intel.com>
On Thu, Jun 25, 2020 at 02:36:27AM +0800, kernel test robot wrote:
> I love your patch! Perhaps something to improve:
> [...]
> config: x86_64-randconfig-a012-20200624 (attached as .config)
CONFIG_KCSAN=y
> compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 1d4c87335d5236ea1f35937e1014980ba961ae34)
> [...]
> All warnings (new ones prefixed by >>):
>
> ld.lld: warning: drivers/built-in.a(mfd/mt6397-irq.o):(.init_array.0) is being placed in '.init_array.0'
As far as I can tell, this is a Clang bug. But I don't know the
internals here, so I've opened:
https://bugs.llvm.org/show_bug.cgi?id=46478
and created a work-around patch for the kernel:
commit 915f2c343e59a14f00c68f4d7afcfdc621de0674
Author: Kees Cook <keescook@chromium.org>
Date: Sat Jun 27 08:07:54 2020 -0700
vmlinux.lds.h: Avoid KCSAN's unwanted sections
KCSAN (-fsanitize=thread) produces unwanted[1] .eh_frame and .init_array.*
sections. Add them to DISCARDS, except with CONFIG_CONSTRUCTORS, which
wants to keep .init_array.* sections.
[1] https://bugs.llvm.org/show_bug.cgi?id=46478
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f8a5b2333729..41c8c73de6c4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -195,7 +195,9 @@ endif
# Workaround for a gcc prelease that unfortunately was shipped in a suse release
KBUILD_CFLAGS += -Wno-sign-compare
#
-KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
+KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+KBUILD_LDFLAGS += $(call ld-option,--no-ld-generated-unwind-info)
# Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b1dca0762fc5..a44ee16abc78 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -934,10 +934,28 @@
EXIT_DATA
#endif
+/*
+ * Clang's -fsanitize=thread produces unwanted sections (.eh_frame
+ * and .init_array.*), but CONFIG_CONSTRUCTORS wants to keep any
+ * .init_array.* sections.
+ * https://bugs.llvm.org/show_bug.cgi?id=46478
+ */
+#if defined(CONFIG_KCSAN) && !defined(CONFIG_CONSTRUCTORS)
+#define KCSAN_DISCARDS \
+ *(.init_array) *(.init_array.*) \
+ *(.eh_frame)
+#elif defined(CONFIG_KCSAN) && defined(CONFIG_CONSTRUCTORS)
+#define KCSAN_DISCARDS \
+ *(.eh_frame)
+#else
+#define KCSAN_DISCARDS
+#endif
+
#define DISCARDS \
/DISCARD/ : { \
EXIT_DISCARDS \
EXIT_CALL \
+ KCSAN_DISCARDS \
*(.discard) \
*(.discard.*) \
*(.modinfo) \
--
Kees Cook
next prev parent reply other threads:[~2020-06-27 15:45 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 1:49 [PATCH v3 0/9] Warn on orphan section placement Kees Cook
2020-06-24 1:49 ` [PATCH v3 1/9] vmlinux.lds.h: Add .gnu.version* to DISCARDS Kees Cook
2020-06-24 1:49 ` [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS_DEBUG Kees Cook
2020-06-24 15:39 ` Arvind Sankar
2020-06-24 16:16 ` Fangrui Song
2020-06-24 17:11 ` Arvind Sankar
2020-06-24 17:26 ` Fangrui Song
2020-06-24 17:35 ` Arvind Sankar
2020-06-24 1:49 ` [PATCH v3 3/9] efi/libstub: Remove .note.gnu.property Kees Cook
2020-06-24 3:31 ` Fangrui Song
2020-06-24 4:44 ` Kees Cook
2020-06-24 10:43 ` Will Deacon
2020-06-24 10:46 ` Ard Biesheuvel
2020-06-24 11:26 ` Will Deacon
2020-06-24 13:48 ` Dave Martin
2020-06-24 15:26 ` Will Deacon
2020-06-24 16:26 ` Dave Martin
2020-06-24 15:21 ` Kees Cook
2020-06-24 15:31 ` Ard Biesheuvel
2020-06-24 15:45 ` Kees Cook
2020-06-24 15:48 ` Ard Biesheuvel
2020-06-24 16:29 ` Dave Martin
2020-06-24 16:40 ` Ard Biesheuvel
2020-06-24 17:16 ` Dave Martin
2020-06-24 18:23 ` Ard Biesheuvel
2020-06-24 18:57 ` Ard Biesheuvel
2020-06-24 1:49 ` [PATCH v3 4/9] x86/build: Warn on orphan section placement Kees Cook
[not found] ` <202006250240.J1VuMKoC%lkp@intel.com>
2020-06-27 15:44 ` Kees Cook [this message]
2020-06-29 14:54 ` Marco Elver
2020-06-29 15:26 ` Kees Cook
2020-06-24 1:49 ` [PATCH v3 5/9] x86/boot: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 6/9] arm/build: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 7/9] arm/boot: " Kees Cook
2020-06-24 1:49 ` [PATCH v3 8/9] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-06-24 1:49 ` [PATCH v3 9/9] arm64/build: Warn on orphan section placement Kees Cook
2020-06-24 7:57 ` Will Deacon
2020-06-24 15:36 ` Kees Cook
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