Enablement of AMD's Secure Memory Encryption feature is determined
very early after start_kernel() is entered. Part of this procedure
involves scanning the command line for the parameter 'mem_encrypt'.
To determine intended state, the function sme_enable() uses library
functions cmdline_find_option() and strncmp(). Their use occurs early
enough such that we can't assume that any instrumentation subsystem is
initialized. For example, making calls to a KASAN-instrumented
function before KASAN is set up will result in the use of uninitialized
memory and a boot failure.
When AMD's SME support is enabled, conditionally disable instrumentation
of these dependent functions in lib/string.c and arch/x86/lib/cmdline.c.
Fixes: aca20d546214 ("x86/mm: Add support to make use of Secure Memory
Encryption")
Reported-by: Li RongQing <lirongq...@baidu.com>
Signed-off-by: Gary R Hook <gary.h...@amd.com>
---
arch/x86/lib/Makefile | 16 ++++++++++++++++
lib/Makefile | 14 ++++++++++++++
2 files changed, 30 insertions(+)
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 140e61843a07..b5b932124280 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -6,6 +6,22 @@
# Produces uninteresting flaky coverage.
KCOV_INSTRUMENT_delay.o := n
+ifdef CONFIG_AMD_MEM_ENCRYPT
+#
+# Early boot use of cmdline; don't instrument it
+#
+KCOV_INSTRUMENT_cmdline.o := n
+
+KASAN_SANITIZE_cmdline.o := n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_cmdline.o = -pg
+endif
+
+nostackp := $(call cc-option, -fno-stack-protector)
+CFLAGS_cmdline.o := $(nostackp)
+endif
+
inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
inat_tables_maps = $(srctree)/arch/x86/lib/x86-opcode-map.txt
quiet_cmd_inat_tables = GEN $@
diff --git a/lib/Makefile b/lib/Makefile
index 3b08673e8881..07d71662f6b2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -17,6 +17,20 @@ KCOV_INSTRUMENT_list_debug.o := n
KCOV_INSTRUMENT_debugobjects.o := n
KCOV_INSTRUMENT_dynamic_debug.o := n
+ifdef CONFIG_AMD_MEM_ENCRYPT
+#
+# Early boot use of cmdline, don't instrument it
+#
+KASAN_SANITIZE_string.o := n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_string.o = -pg
+endif
+
+nostackp := $(call cc-option, -fno-stack-protector)
+CFLAGS_string.o := $(nostackp)
+endif
+
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o timerqueue.o xarray.o \
idr.o int_sqrt.o extable.o \
