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detect retpoline-compliant compiler from latest LKML patches

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Stéphane Lesimple 2018-01-08 17:32:19 +01:00
parent 206e4b7fbc
commit 34656827f5
1 changed files with 16 additions and 39 deletions
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55
spectre-meltdown-checker.sh
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@ -1,7 +1,7 @@
#! /bin/sh
# Spectre & Meltdown checker
# Stephane Lesimple
VERSION=0.14
VERSION=0.15
# print status function
pstatus()
@ -231,52 +231,29 @@ fi
# Now check if the compiler used to compile the kernel knows how to insert retpolines in generated asm
# For gcc, this is -mindirect-branch=thunk-extern (detected by the kernel makefiles)
# See gcc commit https://github.com/hjl-tools/gcc/commit/23b517d4a67c02d3ef80b6109218f2aadad7bd79
# We'll look for the presence of 'retpoline_call_target' in symbols
# In latest retpoline LKML patches, the noretpoline_setup symbol exists only if CONFIG_RETPOLINE is set
# *AND* if the compiler is retpoline-compliant, so look for that symbol
if [ -n "$vmlinux" ]; then
# look for the symbol
if which nm >/dev/null 2>&1; then
# the proper way: use nm and look for the symbol
if nm "$vmlinux" 2>/dev/null | grep -qw retpoline_call_target; then
if [ -e /boot/System.map-$(uname -r) ]; then
if grep -qw noretpoline_setup /boot/System.map-$(uname -r); then
retpoline_compiler=1
pstatus green YES "retpoline_call_target found"
pstatus green YES "noretpoline_setup symbol found in System.map"
fi
else
elif which nm >/dev/null 2>&1; then
# the proper way: use nm and look for the symbol
if nm "$vmlinux" 2>/dev/null | grep -qw 'noretpoline_setup'; then
retpoline_compiler=1
pstatus green YES "noretpoline_setup symbol found in vmlinux"
fi
elif grep -q noretpoline_setup "$vmlinux"; then
# if we don't have nm, nevermind, the symbol name is long enough to not have
# any false positive using good old grep directly on the binary
if grep -q retpoline_call_target "$vmlinux"; then
retpoline_compiler=1
pstatus green YES "retpoline_call_target found"
fi
retpoline_compiler=1
pstatus green YES "noretpoline_setup symbol found in vmlinux"
fi
if [ "$retpoline_compiler" != 1 ]; then
# still not ? maybe we just don't have symbols in the kernel image (stripped)
# let's objdump it and look for the asm sequence (here for 64 bits)
#
# ffffffff81000350 <__x86.indirect_thunk>:
# ffffffff81000350: e8 05 00 00 00 callq ffffffff8100035a <retpoline_call_target>
# ffffffff81000355: 0f ae e8 lfence
# ffffffff81000358: eb fb jmp ffffffff81000355 <__x86.indirect_thunk+0x5>
# ffffffff8100035a <retpoline_call_target>:
# ffffffff8100035a: 48 8d 64 24 08 lea 0x8(%rsp),%rsp
# ffffffff8100035f: c3 retq
#
if ! which perl >/dev/null 2>&1; then
pstatus yellow UNKNOWN "missing 'perl', please install it"
else
# directly look for the opcode sequence in the binary
# 64 bits version
if perl -ne '/\xe8\x05\x00\x00\x00\x0f\xae\xe8\xeb\xfb\x48\x8d\x64\x24\x08\xc3/ and $found=1; END { exit($found ? 0 : 1) }' "$vmlinux"; then
retpoline_compiler=1
pstatus green YES "retpoline 64 bits asm sequence found"
#elif perl -ne ... 32 bits version of retpoline asm seq
# TODO
# retpoline_compiler=1
# pstatus green YES "retpoline 33 bits asm sequence found"
else
pstatus red NO
fi
fi
pstatus red NO
fi
else
pstatus yellow UNKNOWN "couldn't find your kernel image"