[PATCH v6 33/44] x86: kmsan: disable instrumentation of unsupported code

Alexander Potapenko
2022-09-05T12:32:14Z

Instrumenting some files with KMSAN will result in kernel being unable
to link, boot or crashing at runtime for various reasons (e.g. infinite
recursion caused by instrumentation hooks calling instrumented code again).

Completely omit KMSAN instrumentation in the following places:
- arch/x86/boot and arch/x86/realmode/rm, as KMSAN doesn't work for i386;
- arch/x86/entry/vdso, which isn't linked with KMSAN runtime;
- three files in arch/x86/kernel - boot problems;
- arch/x86/mm/cpu_entry_area.c - recursion.

Signed-off-by: Alexander Potapenko <glider@google.com>
---
v2:
-- moved the patch earlier in the series so that KMSAN can compile
-- split off the non-x86 part into a separate patch

v3:
-- added a comment to lib/Makefile

v5:
-- removed a comment belonging to another patch

Link: https://linux-review.googlesource.com/id/Id5e5c4a9f9d53c24a35ebb633b814c414628d81b
---
arch/x86/boot/Makefile | 1 +
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/entry/vdso/Makefile | 3 +++
arch/x86/kernel/Makefile | 2 ++
arch/x86/kernel/cpu/Makefile | 1 +
arch/x86/mm/Makefile | 2 ++
arch/x86/realmode/rm/Makefile | 1 +
7 files changed, 11 insertions(+)

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index ffec8bb01ba8c..9860ca5979f8a 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -12,6 +12,7 @@
# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
KASAN_SANITIZE := n
KCSAN_SANITIZE := n
+KMSAN_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 35ce1a64068b7..3a261abb6d158 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -20,6 +20,7 @@
# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
KASAN_SANITIZE := n
KCSAN_SANITIZE := n
+KMSAN_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 12f6c4d714cd6..ce4eb7e44e5b8 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -11,6 +11,9 @@ include $(srctree)/lib/vdso/Makefile

# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
+KMSAN_SANITIZE_vclock_gettime.o := n
+KMSAN_SANITIZE_vgetcpu.o := n
+
UBSAN_SANITIZE := n
KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a20a5ebfacd73..ac564c5d7b1f0 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -33,6 +33,8 @@ KASAN_SANITIZE_sev.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
+KMSAN_SANITIZE_head$(BITS).o := n
+KMSAN_SANITIZE_nmi.o := n

# If instrumentation of this dir is enabled, boot hangs during first second.
# Probably could be more selective here, but note that files related to irqs,
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index 9661e3e802be5..f10a921ee7565 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -12,6 +12,7 @@ endif
# If these files are instrumented, boot hangs during the first second.
KCOV_INSTRUMENT_common.o := n
KCOV_INSTRUMENT_perf_event.o := n
+KMSAN_SANITIZE_common.o := n

# As above, instrumenting secondary CPU boot code causes boot hangs.
KCSAN_SANITIZE_common.o := n
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index f8220fd2c169a..39c0700c9955c 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -12,6 +12,8 @@ KASAN_SANITIZE_mem_encrypt_identity.o := n
# Disable KCSAN entirely, because otherwise we get warnings that some functions
# reference __initdata sections.
KCSAN_SANITIZE := n
+# Avoid recursion by not calling KMSAN hooks for CEA code.
+KMSAN_SANITIZE_cpu_entry_area.o := n

ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_mem_encrypt.o = -pg
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index 83f1b6a56449f..f614009d3e4e2 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -10,6 +10,7 @@
# Sanitizer runtimes are unavailable and cannot be linked here.
KASAN_SANITIZE := n
KCSAN_SANITIZE := n
+KMSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD := y

# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
--
2.37.2.789.g6183377224-goog