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feat(extract_vmlinux): look for ELF magic in decompressed blob and cut at found offset

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This commit is contained in:
Stéphane Lesimple 2018-03-17 13:34:53 +01:00
parent 2d993812ab
commit 6a94c3f158
1 changed files with 15 additions and 3 deletions
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18
spectre-meltdown-checker.sh
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@ -18,6 +18,7 @@ exit_cleanup()
# cleanup the temp decompressed config & kernel image
[ -n "$dumped_config" ] && [ -f "$dumped_config" ] && rm -f "$dumped_config"
[ -n "$vmlinuxtmp" ] && [ -f "$vmlinuxtmp" ] && rm -f "$vmlinuxtmp"
[ -n "$vmlinuxtmp2" ] && [ -f "$vmlinuxtmp2" ] && rm -f "$vmlinuxtmp2"
[ "$mounted_debugfs" = 1 ] && umount /sys/kernel/debug 2>/dev/null
[ "$insmod_cpuid" = 1 ] && rmmod cpuid 2>/dev/null
[ "$insmod_msr" = 1 ] && rmmod msr 2>/dev/null
@ -572,6 +573,7 @@ try_decompress()
# "grep" that report the byte offset of the line instead of the pattern.
# Try to find the header ($1) and decompress from here
_debug "try_decompress: looking for $3 magic in $6"
for pos in $(tr "$1\n$2" "\n$2=" < "$6" | grep -abo "^$2")
do
_debug "try_decompress: magic for $3 found at offset $pos"
@ -581,13 +583,22 @@ try_decompress()
fi
pos=${pos%%:*}
# shellcheck disable=SC2086
tail -c+$pos "$6" 2>/dev/null | $3 $4 > "$vmlinuxtmp" 2>/dev/null
if check_vmlinux "$vmlinuxtmp"; then
tail -c+$pos "$6" 2>/dev/null | $3 $4 > "$vmlinuxtmp" 2>/dev/null; ret=$?
if [ ! -s "$vmlinuxtmp" ]; then
# don't rely on $ret, sometimes it's != 0 but worked
# (e.g. gunzip ret=2 just means there was trailing garbage)
_debug "try_decompress: decompression with $3 failed (err=$ret)"
elif check_vmlinux "$vmlinuxtmp"; then
vmlinux="$vmlinuxtmp"
_debug "try_decompress: decompressed with $3 successfully!"
return 0
elif [ "$3" != "cat" ]; then
_debug "try_decompress: decompression with $3 worked but result is not a kernel, trying with an offset"
[ -z "$vmlinuxtmp2" ] && vmlinuxtmp2=$(mktemp /tmp/vmlinux-XXXXXX)
cat "$vmlinuxtmp" > "$vmlinuxtmp2"
try_decompress '\177ELF' xxy 'cat' '' cat "$vmlinuxtmp2" && return 0
else
_debug "try_decompress: decompression with $3 did not work"
_debug "try_decompress: decompression with $3 worked but result is not a kernel"
fi
done
return 1
@ -614,6 +625,7 @@ extract_vmlinux()
try_decompress '\211\114\132' xy 'lzop' '-d' lzop "$1" && return 0
try_decompress '\002\041\114\030' xyy 'lz4' '-d -l' liblz4-tool "$1" && return 0
try_decompress '\177ELF' xxy 'cat' '' cat "$1" && return 0
_verbose "Couldn't extract the kernel image, accuracy might be reduced"
return 1
}