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@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d6e1faa..81859be 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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.