fix MSR reading, need rdmsr for now

spectre-meltdown-checker.sh

@@ -1,7 +1,7 @@
 #! /bin/sh
 # Spectre & Meltdown checker
 # Stephane Lesimple
-VERSION=0.02
+VERSION=0.05
 
 pstatus()
 {
@@ -73,8 +73,15 @@ 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=$(extract_vmlinux /boot/vmlinuz-4.4.110)
 status=0
+img=''
+[ -e /boot/vmlinuz-$(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
@@ -90,6 +97,7 @@ else
 		fi
 		rm -f $vmlinux
 	fi
+fi
 
 /bin/echo -ne "> \033[46m\033[30mSTATUS:\033[0m "
 [ "$status" = 0 ] && pstatus yellow UNKNOWN
@@ -108,14 +116,23 @@ 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
+	if which rdmsr >/dev/null 2>&1; then
+		rdmsr 0x48 >/dev/null 2>&1
 		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
+	else
-	#/bin/echo $?
+		pstatus yellow UNKNOWN "missing 'rdmsr' tool, please install it, usually it's in the msr-tools package"
+		# doesn't work:
+		#dd if=/dev/cpu/0/msr of=/dev/null bs=1 count=8 skip=72 2>/dev/null
+		#if [ $? -eq 0 ]; then
+		#	pstatus green YES
+		#else
+		#	pstatus red NO
+		#fi
+	fi
 fi
 
 if [ "$insmod_msr" = 1 ]; then
@@ -156,15 +173,32 @@ fi
 
 /bin/echo "* Mitigation 2"
 /bin/echo -n "*   Kernel recompiled with retpolines: "
-pstatus yellow UNKNOWN "check not yet implemented"
+# 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