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authorBorislav Petkov <bp@suse.de>2013-04-29 15:05:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 15:54:27 -0700
commit18ff44b189e2a9becb2047a790578b90aef56349 (patch)
tree063e746ba13086b2a154dea0192a9bc15a362ecd /scripts/decodecode
parent0c0de199ce1fef20c86679194e31133da21c3c2a (diff)
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scripts/decodecode: make faulting insn ptr more robust
It can accidentally happen that the faulting insn (the exact instruction bytes) is repeated a little further on in the trace. This causes that same instruction to be tagged twice, see example below. What we want to do, however, is to track back from the end of the whole disassembly so many lines as the slice which starts with the faulting instruction is long. This leads us to the actual faulting instruction and *then* we tag it. While we're at it, we can drop the sed "g" flag because we address only this one line. Also, if we point to an instruction which changes decoding depending on the slice being objdumped, like a Jcc insn, for example, we do not even tag it as a faulting instruction because the instruction decode changes in the second slice but we use that second format as a regex on the fsrst disassembled buffer and more often than not that instruction doesn't match. Again, simply tag the line which is deduced from the original "<>" marking we've received from the kernel. This also solves the pathologic issue of multiple tagging like this: 29:* 0f 0b ud2 <-- trapping instruction 2b:* 0f 0b ud2 <-- trapping instruction 2d:* 0f 0b ud2 <-- trapping instruction Double tagging example: Code: 34 dd 40 30 ad 81 48 c7 c0 80 f6 00 00 48 8b 3c 30 48 01 c6 b8 ff ff ff ff 48 8d 57 f0 48 39 f7 74 2f 49 8b 4c 24 08 48 8b 47 f0 <48> 39 48 08 75 0e eb 2a 66 90 48 8b 40 f0 48 39 48 08 74 1e 48 All code ======== 0: 34 dd xor $0xdd,%al 2: 40 30 ad 81 48 c7 c0 xor %bpl,-0x3f38b77f(%rbp) 9: 80 f6 00 xor $0x0,%dh c: 00 48 8b add %cl,-0x75(%rax) f: 3c 30 cmp $0x30,%al 11: 48 01 c6 add %rax,%rsi 14: b8 ff ff ff ff mov $0xffffffff,%eax 19: 48 8d 57 f0 lea -0x10(%rdi),%rdx 1d: 48 39 f7 cmp %rsi,%rdi 20: 74 2f je 0x51 22: 49 8b 4c 24 08 mov 0x8(%r12),%rcx 27: 48 8b 47 f0 mov -0x10(%rdi),%rax 2b:* 48 39 48 08 cmp %rcx,0x8(%rax) <-- trapping instruction 2f: 75 0e jne 0x3f 31: eb 2a jmp 0x5d 33: 66 90 xchg %ax,%ax 35: 48 8b 40 f0 mov -0x10(%rax),%rax 39:* 48 39 48 08 cmp %rcx,0x8(%rax) <-- trapping instruction 3d: 74 1e je 0x5d 3f: 48 rex.W Signed-off-by: Borislav Petkov <bp@suse.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'scripts/decodecode')
-rwxr-xr-xscripts/decodecode8
1 files changed, 7 insertions, 1 deletions
diff --git a/scripts/decodecode b/scripts/decodecode
index 4f8248d5a11f..d8824f37acce 100755
--- a/scripts/decodecode
+++ b/scripts/decodecode
@@ -89,10 +89,16 @@ echo $code >> $T.s
disas $T
cat $T.dis >> $T.aa
+# (lines of whole $T.oo) - (lines of $T.aa, i.e. "Code starting") + 3,
+# i.e. the title + the "===..=" line (sed is counting from 1, 0 address is
+# special)
+faultlinenum=$(( $(wc -l $T.oo | cut -d" " -f1) - \
+ $(wc -l $T.aa | cut -d" " -f1) + 3))
+
faultline=`cat $T.dis | head -1 | cut -d":" -f2-`
faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`
-cat $T.oo | sed -e "s/\($faultline\)/\*\1 <-- trapping instruction/g"
+cat $T.oo | sed -e "${faultlinenum}s/^\(.*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
echo
cat $T.aa
cleanup