From: Arvind Sankar <nivedita@alum.mit.edu>
To: x86@kernel.org, kasan-dev@googlegroups.com
Cc: Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org
Subject: [RFC PATCH 1/2] lib/string: Disable instrumentation
Date: Sat, 5 Sep 2020 18:23:22 -0400 [thread overview]
Message-ID: <20200905222323.1408968-2-nivedita@alum.mit.edu> (raw)
In-Reply-To: <20200905222323.1408968-1-nivedita@alum.mit.edu>
String functions can be useful in early boot, but using instrumented
versions can be problematic: eg on x86, some of the early boot code is
executing out of an identity mapping rather than the kernel virtual
addresses. Accessing any global variables at this point will lead to a
crash.
Tracing and KCOV are already disabled, and CONFIG_AMD_MEM_ENCRYPT will
additionally disable KASAN and stack protector.
Additionally disable GCOV, UBSAN, KCSAN, STACKLEAK_PLUGIN and branch
profiling, and make it unconditional to allow safe use of string
functions.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
lib/Makefile | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/lib/Makefile b/lib/Makefile
index a4a4c6864f51..5e421769bbc6 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,6 @@ ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
# These files are disabled because they produce lots of non-interesting and/or
# flaky coverage that is not a function of syscall inputs. For example,
# rbtree can be global and individual rotations don't correlate with inputs.
-KCOV_INSTRUMENT_string.o := n
KCOV_INSTRUMENT_rbtree.o := n
KCOV_INSTRUMENT_list_debug.o := n
KCOV_INSTRUMENT_debugobjects.o := n
@@ -20,12 +19,16 @@ KCOV_INSTRUMENT_fault-inject.o := n
# them into calls to themselves.
CFLAGS_string.o := -ffreestanding
-# Early boot use of cmdline, don't instrument it
-ifdef CONFIG_AMD_MEM_ENCRYPT
+# Early boot use of string functions, disable instrumentation
+GCOV_PROFILE_string.o := n
+KCOV_INSTRUMENT_string.o := n
KASAN_SANITIZE_string.o := n
+UBSAN_SANITIZE_string.o := n
+KCSAN_SANITIZE_string.o := n
CFLAGS_string.o += -fno-stack-protector
-endif
+CFLAGS_string.o += $(DISABLE_STACKLEAK_PLUGIN)
+CFLAGS_string.o += -DDISABLE_BRANCH_PROFILING
# Used by KCSAN while enabled, avoid recursion.
KCSAN_SANITIZE_random32.o := n
--
2.26.2
next prev parent reply other threads:[~2020-09-05 22:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-05 22:23 [RFC PATCH 0/2] Allow use of lib/string in early boot Arvind Sankar
2020-09-05 22:23 ` Arvind Sankar [this message]
2020-09-08 9:39 ` [RFC PATCH 1/2] lib/string: Disable instrumentation Marco Elver
2020-09-08 17:21 ` Kees Cook
2020-09-08 18:40 ` Arvind Sankar
2020-09-09 5:20 ` Dmitry Vyukov
2020-09-05 22:23 ` [RFC PATCH 2/2] x86/cmdline: Use strscpy to initialize boot_command_line Arvind Sankar
2020-09-05 22:59 ` Randy Dunlap
2020-09-05 23:16 ` Arvind Sankar
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