[PATCH v3 9/9] x86, kcsan: Enable KCSAN for x86

Marco Elver
2019-11-04T14:29:27Z

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@google.com>
---
v3:
* Moved EFI stub build exception hunk to generic build exception patch,
since it's not x86-specific.

v2:
* Document build exceptions where no previous above comment explained
why we cannot instrument.
---
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 | 7 +++++++
arch/x86/kernel/cpu/Makefile | 3 +++
arch/x86/lib/Makefile | 4 ++++
arch/x86/mm/Makefile | 3 +++
arch/x86/purgatory/Makefile | 2 ++
arch/x86/realmode/Makefile | 3 +++
arch/x86/realmode/rm/Makefile | 3 +++
12 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa28c58..81859be4a005 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 e2839b5c246c..9c7942794164 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 6b84afdd7538..a1c248b8439f 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 0f2154106d01..a23debaad5b9 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 7d1f6a49bfae..ee08917d3d92 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 bitops-instrumented.h.
+ */
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 3578ad248bc9..2aa122d94956 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -28,6 +28,13 @@ KASAN_SANITIZE_dumpstack_$(BITS).o := n
KASAN_SANITIZE_stacktrace.o := n
KASAN_SANITIZE_paravirt.o := n

+# Do not instrument early boot code.
+KCSAN_SANITIZE_head$(BITS).o := n
+# Do not instrument debug code to avoid corrupting bug reporting.
+KCSAN_SANITIZE_dumpstack.o := n
+KCSAN_SANITIZE_dumpstack_$(BITS).o := n
+KCSAN_SANITIZE_stacktrace.o := 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 d7a1e5a9331c..1f1b0edc0187 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 5246db42de45..432a07705677 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 84373dc9b341..ee871602f96a 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -7,6 +7,9 @@ KCOV_INSTRUMENT_mem_encrypt_identity.o := n
KASAN_SANITIZE_mem_encrypt.o := n
KASAN_SANITIZE_mem_encrypt_identity.o := n

+KCSAN_SANITIZE_mem_encrypt.o := n
+KCSAN_SANITIZE_mem_encrypt_identity.o := 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 fb4ee5444379..69379bce9574 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 682c895753d9..6b1f3a4eeb44 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 f60501a384f9..fdbbb945c216 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.
--
2.24.0.rc1.363.gb1bccd3e3d-goog