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e2d8abf5af
[ Upstream commit 2d7ce49f58 ]
Enabling CONFIG_KCSAN leads to unconverted, default return thunks to
remain after patching.
As David Kaplan describes in his debugging of the issue, it is caused by
a couple of KCSAN-generated constructors which aren't processed by
objtool:
"When KCSAN is enabled, GCC generates lots of constructor functions
named _sub_I_00099_0 which call __tsan_init and then return. The
returns in these are generally annotated normally by objtool and fixed
up at runtime. But objtool runs on vmlinux.o and vmlinux.o does not
include a couple of object files that are in vmlinux, like
init/version-timestamp.o and .vmlinux.export.o, both of which contain
_sub_I_00099_0 functions. As a result, the returns in these functions
are not annotated, and the panic occurs when we call one of them in
do_ctors and it uses the default return thunk.
This difference can be seen by counting the number of these functions in the object files:
$ objdump -d vmlinux.o|grep -c "<_sub_I_00099_0>:"
2601
$ objdump -d vmlinux|grep -c "<_sub_I_00099_0>:"
2603
If these functions are only run during kernel boot, there is no
speculation concern."
Fix it by disabling KCSAN on version-timestamp.o and .vmlinux.export.o
so the extra functions don't get generated. KASAN and GCOV are already
disabled for those files.
[ bp: Massage commit message. ]
Closes: https://lore.kernel.org/lkml/20231016214810.GA3942238@dev-arch.thelio-3990X/
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Marco Elver <elver@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20231017165946.v4i2d4exyqwqq3bx@treble
Signed-off-by: Sasha Levin <sashal@kernel.org>
65 lines
1.9 KiB
Makefile
65 lines
1.9 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# Makefile for the linux kernel.
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#
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ccflags-y := -fno-function-sections -fno-data-sections
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obj-y := main.o version.o mounts.o
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ifneq ($(CONFIG_BLK_DEV_INITRD),y)
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obj-y += noinitramfs.o
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else
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obj-$(CONFIG_BLK_DEV_INITRD) += initramfs.o
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endif
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obj-$(CONFIG_GENERIC_CALIBRATE_DELAY) += calibrate.o
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obj-y += init_task.o
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mounts-y := do_mounts.o
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mounts-$(CONFIG_BLK_DEV_RAM) += do_mounts_rd.o
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mounts-$(CONFIG_BLK_DEV_INITRD) += do_mounts_initrd.o
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#
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# UTS_VERSION
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#
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smp-flag-$(CONFIG_SMP) := SMP
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preempt-flag-$(CONFIG_PREEMPT_BUILD) := PREEMPT
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preempt-flag-$(CONFIG_PREEMPT_DYNAMIC) := PREEMPT_DYNAMIC
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preempt-flag-$(CONFIG_PREEMPT_RT) := PREEMPT_RT
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build-version = $(or $(KBUILD_BUILD_VERSION), $(build-version-auto))
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build-timestamp = $(or $(KBUILD_BUILD_TIMESTAMP), $(build-timestamp-auto))
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# Maximum length of UTS_VERSION is 64 chars
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filechk_uts_version = \
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utsver=$$(echo '$(pound)'"$(build-version)" $(smp-flag-y) $(preempt-flag-y) "$(build-timestamp)" | cut -b -64); \
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echo '$(pound)'define UTS_VERSION \""$${utsver}"\"
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#
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# Build version.c with temporary UTS_VERSION
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#
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$(obj)/utsversion-tmp.h: FORCE
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$(call filechk,uts_version)
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clean-files += utsversion-tmp.h
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$(obj)/version.o: $(obj)/utsversion-tmp.h
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CFLAGS_version.o := -include $(obj)/utsversion-tmp.h
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#
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# Build version-timestamp.c with final UTS_VERSION
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#
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include/generated/utsversion.h: build-version-auto = $(shell $(srctree)/$(src)/build-version)
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include/generated/utsversion.h: build-timestamp-auto = $(shell LC_ALL=C date)
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include/generated/utsversion.h: FORCE
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$(call filechk,uts_version)
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$(obj)/version-timestamp.o: include/generated/utsversion.h
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CFLAGS_version-timestamp.o := -include include/generated/utsversion.h
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KASAN_SANITIZE_version-timestamp.o := n
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KCSAN_SANITIZE_version-timestamp.o := n
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GCOV_PROFILE_version-timestamp.o := n
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