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powerpc/sstep: Fix emulation fall-through 

There is a switch fallthough in instr_analyze() which can cause an
invalid instruction to be emulated as a different, valid, instruction.
The rld* (opcode 30) case extracts a sub-opcode from bits 3:1 of the
instruction word. However, the only valid values of this field are 001
and 000. These cases are correctly handled, but the others are not which
causes execution to fall through into case 31.

Breaking out of the switch causes the instruction to be marked as
unknown and allows the caller to deal with the invalid instruction in a
manner consistent with other invalid instructions.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Oliver O'Halloran 2016-02-16 17:31:53 +11:00 committed by Michael Ellerman
parent dd21731022
commit 6670783606
1 changed files with 1 additions and 0 deletions
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arch/powerpc/lib/sstep.c
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@ -925,6 +925,7 @@ int __kprobes analyse_instr(struct instruction_op *op, struct pt_regs *regs,
}
}
#endif
break; /* illegal instruction */
case 31:
switch ((instr >> 1) & 0x3ff) {