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[S390] kprobes: fix instruction length calculation 

Placing a kprobe on "bc" instruction (s390/s390x) can cause an oops.
The instruction length is encoded into the first two bits of the s390
instruction. Kprobe is incorrectly computing the instruction length.
The instruction length is used for determining what type of "fix-up" is
needed for conditional branch instruction. The problem can bee seen by
placing a kprobe on a "bc" instruction that will not branch. The
results is that Kprobe incorrectly computes the new instruction
pointer (psw.addr) after single stepping the instruction. The problem
is corrected with this patch.

Signed-off-by: David Wilder <dwilder@us.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
David Wilder 2007-08-22 13:51:44 +02:00 committed by Martin Schwidefsky
parent 9b5a03e198
commit 9c5f225f1a
1 changed files with 1 additions and 1 deletions
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2
arch/s390/kernel/kprobes.c
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@ -85,7 +85,7 @@ void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
ainsn->reg = (*ainsn->insn & 0xf0) >> 4; ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
/* save the instruction length (pop 5-5) in bytes */ /* save the instruction length (pop 5-5) in bytes */
switch (*(__u8 *) (ainsn->insn) >> 4) { switch (*(__u8 *) (ainsn->insn) >> 6) {
case 0: case 0:
ainsn->ilen = 2; ainsn->ilen = 2;
break; break;