remove dependency on rdmsr

spectre-meltdown-checker.sh

@@ -1,7 +1,7 @@
 #! /bin/sh
 # Spectre & Meltdown checker
 # Stephane Lesimple
-VERSION=0.02
+VERSION=0.06
 
 pstatus()
 {
@@ -11,7 +11,7 @@ pstatus()
 		yellow) col="\033[103m\033[30m";;
 		*)      col="";;
 	esac
-	/bin/echo -ne "$col$2\033[0m"
+	/bin/echo -ne "$col $2 \033[0m"
 	[ -n "$3" ] && /bin/echo -n " ($3)"
 	/bin/echo
 }
@@ -73,13 +73,20 @@ extract_vmlinux()
 /bin/echo -e "\033[1;34mCVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'\033[0m"
 /bin/echo -n "* Kernel compiled with LFENCE opcode inserted at the proper places: "
 
-vmlinux=$(extract_vmlinux /boot/vmlinuz-4.4.110)
 status=0
-if [ -z "$vmlinux" -o ! -r "$vmlinux" ]; then
-	pstatus yellow UNKNOWN "couldn't extract your kernel"
-elif ! which objdump >/dev/null 2>&1; then
-	pstatus yellow UNKNOWN "missing 'objdump' tool, please install it, usually it's in the binutils package"
+img=''
+[ -e /boot/vmlinuz-$(uname -r) ] && img=/boot/vmlinuz-$(uname -r)
+[ -e /boot/vmlinux-$(uname -r) ] && img=/boot/vmlinux-$(uname -r)
+[ -e /boot/bzImage-$(uname -r) ] && img=/boot/bzImage-$(uname -r)
+if [ -z "$img" ]; then
+	pstatus yellow UNKNOWN "couldn't find your kernel image in /boot"
 else
+	vmlinux=$(extract_vmlinux $img)
+	if [ -z "$vmlinux" -o ! -r "$vmlinux" ]; then
+		pstatus yellow UNKNOWN "couldn't extract your kernel"
+	elif ! which objdump >/dev/null 2>&1; then
+		pstatus yellow UNKNOWN "missing 'objdump' tool, please install it, usually it's in the binutils package"
+	else
 		nb_lfence=$(objdump -D "$vmlinux" | grep -wc lfence)
 		if [ "$nb_lfence" -lt 60 ]; then
 			pstatus red NO "only $nb_lfence opcodes found, should be >= 60"
@@ -89,6 +96,7 @@ else
 			status=2
 		fi
 		rm -f $vmlinux
+	fi
 fi
 
 /bin/echo -ne "> \033[46m\033[30mSTATUS:\033[0m "
@@ -108,14 +116,13 @@ fi
 if [ ! -e /dev/cpu/0/msr ]; then
 	pstatus yellow UNKNOWN "couldn't read /dev/cpu/0/msr, is msr support enabled in your kernel?"
 else
-	dd if=/dev/cpu/0/msr of=/dev/null bs=1 count=8 skip=72 2>/dev/null
+	# same that rdmsr 0x48 but without needing the rdmsr tool
+	dd if=/dev/cpu/0/msr of=/dev/null bs=8 count=1 skip=9 2>/dev/null
 	if [ $? -eq 0 ]; then
 		pstatus green YES
 	else
 		pstatus red NO
 	fi
-	#dd if=/dev/cpu/0/msr of=/dev/null bs=1 count=8 skip=73 2>/dev/null
-	#/bin/echo $?
 fi
 
 if [ "$insmod_msr" = 1 ]; then
@@ -155,16 +162,33 @@ if [ "$mounted_debugfs" = 1 ]; then
 fi
 
 /bin/echo "* Mitigation 2"
-/bin/echo -n "*   Kernel recompiled with retpolines: "
-pstatus yellow UNKNOWN "check not yet implemented"
+/bin/echo -n "*   Kernel compiled with retpolines: "
+# XXX this doesn't mean the kernel has been compiled with a retpoline-aware gcc
+if [ -e /proc/config.gz ]; then
+	if zgrep -q '^CONFIG_RETPOLINE=y' /proc/config.gz; then
+		pstatus green YES
+		retpoline=1
+	else
+		pstatus red NO
+	fi
+elif [ -e /boot/config-$(uname -r) ]; then
+	if grep  -q '^CONFIG_RETPOLINE=y' /boot/config-$(uname -r); then
+		pstatus green YES
+		retpoline=1
+	else
+		pstatus red NO
+	fi
+fi
 
 /bin/echo -ne "> \033[46m\033[30mSTATUS:\033[0m "
 if grep -q AMD /proc/cpuinfo; then
 	pstatus green "NOT VULNERABLE" "your CPU is not vulnerable as per the vendor"
 elif [ "$ibrs_enabled" = 1 -o "$ibrs_enabled" = 2 ]; then
 	pstatus green "NOT VULNERABLE" "IBRS mitigates the vulnerability"
+elif [ "$retpoline" = 1 ]; then
+	pstatus green "NOT VULNERABLE" "retpolines mitigate the vulnerability"
 else
-	pstatus red VULNERABLE "IBRS hardware + kernel support OR retpolines-compiled kernel are needed to mitigate the vulnerability"
+	pstatus red VULNERABLE "IBRS hardware + kernel support OR kernel with retpolines are needed to mitigate the vulnerability"
 fi
 
 # MELTDOWN