[tip: locking/kcsan] x86, kcsan: Enable KCSAN for x86

From: tip-bot2 for Marco Elver
Date: Fri Nov 22 2019 - 06:18:55 EST

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The following commit has been merged into the locking/kcsan branch of tip:

Commit-ID: 40d04110f87940b6a03bf0aa19cd29e84f465f20
Gitweb: https://git.kernel.org/tip/40d04110f87940b6a03bf0aa19cd29e84f465f20
Author: Marco Elver <elver@xxxxxxxxxx>
AuthorDate: Thu, 14 Nov 2019 19:03:03 +01:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Sat, 16 Nov 2019 07:23:16 -08:00

x86, kcsan: Enable KCSAN for x86

This patch enables KCSAN for x86, with updates to build rules to not use
KCSAN for several incompatible compilation units.

Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
arch/x86/Kconfig | 1 +
arch/x86/boot/Makefile | 2 ++
arch/x86/boot/compressed/Makefile | 2 ++
arch/x86/entry/vdso/Makefile | 3 +++
arch/x86/include/asm/bitops.h | 6 +++++-
arch/x86/kernel/Makefile | 4 ++++
arch/x86/kernel/cpu/Makefile | 3 +++
arch/x86/lib/Makefile | 4 ++++
arch/x86/mm/Makefile | 4 ++++
arch/x86/purgatory/Makefile | 2 ++
arch/x86/realmode/Makefile | 3 +++
arch/x86/realmode/rm/Makefile | 3 +++
12 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa..81859be 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -226,6 +226,7 @@ config X86
select VIRT_TO_BUS
select X86_FEATURE_NAMES if PROC_FS
select PROC_PID_ARCH_STATUS if PROC_FS
+ select HAVE_ARCH_KCSAN if X86_64

config INSTRUCTION_DECODER
def_bool y
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index e2839b5..9c79427 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -9,7 +9,9 @@
# Changed by many, many contributors over the years.
#

+# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

# Kernel does not boot with kcov instrumentation here.
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 6b84afd..a1c248b 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -17,7 +17,9 @@
# (see scripts/Makefile.lib size_append)
# compressed vmlinux.bin.all + u32 size of vmlinux.bin.all

+# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 0f21541..a23deba 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -10,8 +10,11 @@ ARCH_REL_TYPE_ABS += R_386_GLOB_DAT|R_386_JMP_SLOT|R_386_RELATIVE
include $(srctree)/lib/vdso/Makefile

KBUILD_CFLAGS += $(DISABLE_LTO)
+
+# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
+KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index 7d1f6a4..542b63d 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -201,8 +201,12 @@ arch_test_and_change_bit(long nr, volatile unsigned long *addr)
return GEN_BINARY_RMWcc(LOCK_PREFIX __ASM_SIZE(btc), *addr, c, "Ir", nr);
}

-static __always_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
+static __no_kcsan_or_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
{
+ /*
+ * Because this is a plain access, we need to disable KCSAN here to
+ * avoid double instrumentation via instrumented bitops.
+ */
return ((1UL << (nr & (BITS_PER_LONG-1))) &
(addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
}
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 3578ad2..a9a1cab 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -28,6 +28,10 @@ KASAN_SANITIZE_dumpstack_$(BITS).o := n
KASAN_SANITIZE_stacktrace.o := n
KASAN_SANITIZE_paravirt.o := n

+# With some compiler versions the generated code results in boot hangs, caused
+# by several compilation units. To be safe, disable all instrumentation.
+KCSAN_SANITIZE := n
+
OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o := y
OBJECT_FILES_NON_STANDARD_test_nx.o := y
OBJECT_FILES_NON_STANDARD_paravirt_patch.o := y
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index d7a1e5a..1f1b0ed 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -13,6 +13,9 @@ endif
KCOV_INSTRUMENT_common.o := n
KCOV_INSTRUMENT_perf_event.o := n

+# As above, instrumenting secondary CPU boot code causes boot hangs.
+KCSAN_SANITIZE_common.o := n
+
# Make sure load_percpu_segment has no stackprotector
nostackp := $(call cc-option, -fno-stack-protector)
CFLAGS_common.o := $(nostackp)
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 5246db4..432a077 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -6,10 +6,14 @@
# Produces uninteresting flaky coverage.
KCOV_INSTRUMENT_delay.o := n

+# KCSAN uses udelay for introducing watchpoint delay; avoid recursion.
+KCSAN_SANITIZE_delay.o := n
+
# Early boot use of cmdline; don't instrument it
ifdef CONFIG_AMD_MEM_ENCRYPT
KCOV_INSTRUMENT_cmdline.o := n
KASAN_SANITIZE_cmdline.o := n
+KCSAN_SANITIZE_cmdline.o := n

ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_cmdline.o = -pg
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 84373dc..3559f42 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -7,6 +7,10 @@ KCOV_INSTRUMENT_mem_encrypt_identity.o := n
KASAN_SANITIZE_mem_encrypt.o := n
KASAN_SANITIZE_mem_encrypt_identity.o := n

+# Disable KCSAN entirely, because otherwise we get warnings that some functions
+# reference __initdata sections.
+KCSAN_SANITIZE := n
+
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_mem_encrypt.o = -pg
CFLAGS_REMOVE_mem_encrypt_identity.o = -pg
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index fb4ee54..69379bc 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -17,7 +17,9 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
targets += purgatory.ro

+# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
KCOV_INSTRUMENT := n

# These are adjustments to the compiler flags used for objects that
diff --git a/arch/x86/realmode/Makefile b/arch/x86/realmode/Makefile
index 682c895..6b1f3a4 100644
--- a/arch/x86/realmode/Makefile
+++ b/arch/x86/realmode/Makefile
@@ -6,7 +6,10 @@
# for more details.
#
#
+
+# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

subdir- := rm
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index f60501a..fdbbb94 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -6,7 +6,10 @@
# for more details.
#
#
+
+# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.

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