linux-kernel - [PATCH] x86/mm: Disable various instrumentations of mem

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Date:   Tue, 10 Oct 2017 14:45:04 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     x86@...nel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86/mm: Disable various instrumentations of mem_encrypt.c

Some routines in mem_encrypt.c are called very early in the boot process,
e.g. sme_enable().  When CONFIG_KCOV is defined the resulting code added
to sme_enable() (and others) for KCOV instrumentation results in a kernel
crash.  Disable the KCOV instrumentation for mem_encrypt.c by adding
KCOV_INSTRUMENT_mem_encrypt.o := n to arch/x86/mm/Makefile.

In order to avoid other possible early boot issues, model mem_encrypt.c
after head64.c in regards to tools. In addition to disabling KCOV as
stated above and a previous patch that disables branch profiling, also
remove the "-pg" CFLAG if CONFIG_FUNCTION_TRACER is enabled and set
KASAN_SANITIZE to "n", each of which are done on a file basis.

Reported-by: kernel test robot <lkp@...org>
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/mm/Makefile |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 72bf8c0..e1f0958 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,5 +1,12 @@
-# Kernel does not boot with instrumentation of tlb.c.
-KCOV_INSTRUMENT_tlb.o	:= n
+# Kernel does not boot with instrumentation of tlb.c and mem_encrypt.c
+KCOV_INSTRUMENT_tlb.o		:= n
+KCOV_INSTRUMENT_mem_encrypt.o	:= n
+
+KASAN_SANITIZE_mem_encrypt.o	:= n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_mem_encrypt.o	= -pg
+endif

 obj-y	:=  init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
 	    pat.o pgtable.o physaddr.o setup_nx.o tlb.o