push the lfence opcodes threshold to 70

Avoid 'cat: /sys/kernel/debug/x86/pti_enabled: Permission denied'

spectre-meltdown-checker.sh

@@ -1,7 +1,7 @@
 #! /bin/sh
 # Spectre & Meltdown checker
 # Stephane Lesimple
-VERSION=0.12
+VERSION=0.13
 
 # print status function
 pstatus()
@@ -90,7 +90,7 @@ if [ "$(id -u)" -ne 0 ]; then
 	/bin/echo
 fi
 
-/bin/echo -e "Checking vulnerabilities against \033[35m"$(uname -s) $(uname -r) $(uname -m)"\033[0m"
+/bin/echo -e "Checking vulnerabilities against \033[35m"$(uname -s) $(uname -r) $(uname -v) $(uname -m)"\033[0m"
 /bin/echo
 
 ###########
@@ -117,13 +117,16 @@ else
 	else
 		# here we disassemble the kernel and count the number of occurences of the LFENCE opcode
 		# in non-patched kernels, this has been empirically determined as being around 40-50
-		# in patched kernels, this is more around 70-80
+		# in patched kernels, this is more around 70-80, sometimes way higher (100+)
+		# v0.13: 68 found in a 3.10.23-xxxx-std-ipv6-64 (with lots of modules compiled-in directly), which doesn't have the LFENCE patches,
+		# so let's push the threshold to 70.
+		# TODO LKML patch is starting to dump LFENCE in favor of the PAUSE opcode, we might need to check that (patch not stabilized yet)
 		nb_lfence=$(objdump -D "$vmlinux" | grep -wc lfence)
-		if [ "$nb_lfence" -lt 60 ]; then
-			pstatus red NO "only $nb_lfence opcodes found, should be >= 60"
+		if [ "$nb_lfence" -lt 70 ]; then
+			pstatus red NO "only $nb_lfence opcodes found, should be >= 70"
 			status=1
 		else
-			pstatus green YES "$nb_lfence opcodes found, which is >= 60"
+			pstatus green YES "$nb_lfence opcodes found, which is >= 70"
 			status=2
 		fi
 	fi
@@ -164,7 +167,7 @@ if [ "$insmod_msr" = 1 ]; then
 fi
 
 /bin/echo -n "*   Kernel support for IBRS: "
-if [ -e /sys/kernel/debug/sched_features ]; then
+if [ ! -e /sys/kernel/debug/sched_features ]; then
 	# try to mount the debugfs hierarchy ourselves and remember it to umount afterwards
 	mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null && mounted_debugfs=1
 fi
@@ -291,7 +294,7 @@ elif dmesg | grep -Eq 'Kernel/User page tables isolation: enabled|Kernel page ta
 	# if we can't find the flag, grep in dmesg
 	pstatus green YES
 	kpti_enabled=1
-elif [ -e /sys/kernel/debug/x86/pti_enabled -a "$(cat /sys/kernel/debug/x86/pti_enabled)" = 1 ]; then
+elif [ -e /sys/kernel/debug/x86/pti_enabled -a "$(cat /sys/kernel/debug/x86/pti_enabled 2>/dev/null)" = 1 ]; then
 	pstatus green YES
 	kpti_enabled=1
 else