[Capstone-users] PPC 64-bit relative branch target address is truncated to 32-bit

[Per M. <pe...@si...>]

On 64-bit PPC a branch, like “bce TARGET” gets the target truncated to 32-bits.


        00003fff76030028 bge    0x760300c0 # this is really branching to the ld instruction, below.
...
        00003fff760300c0 ld     r6, -8(r20)


I think the cause is the (int) cast in the following procedure, in PPCInstPrinter.c:

static void printAbsBranchOperand(MCInst *MI, unsigned OpNo, SStream *O)
{
        int imm;

        if (!MCOperand_isImm(MCInst_getOperand(MI, OpNo))) {
                printOperand(MI, OpNo, O);
                return;
        }

        imm = ((int)MCOperand_getImm(MCInst_getOperand(MI, OpNo)) << 2);

        if (!PPC_abs_branch(MI->csh, MCInst_getOpcode(MI))) {
                imm = (int)MI->address + imm;
        }

        SStream_concat(O, "0x%x", imm);

        if (MI->csh->detail) {
                MI->flat_insn->detail->ppc.operands[MI->flat_insn->detail->ppc.op_count].type = PPC_OP_IMM;
                MI->flat_insn->detail->ppc.operands[MI->flat_insn->detail->ppc.op_count].imm = imm;
                MI->flat_insn->detail->ppc.op_count++;
        }
}

If I change that procedure, as follows, I get the correct result:

        00003fff87940028 bge    0x3fff87940060
...
        00003fff87940060 ld     r6, -8(r20)

# New version, using int64_t instead of int

static void printAbsBranchOperand(MCInst *MI, unsigned OpNo, SStream *O)
{
        int64_t imm;

        if (!MCOperand_isImm(MCInst_getOperand(MI, OpNo))) {
                printOperand(MI, OpNo, O);
		return;
	}

        imm = MCOperand_getImm(MCInst_getOperand(MI, OpNo)) << 2;

	if (!PPC_abs_branch(MI->csh, MCInst_getOpcode(MI))) {
		imm = MI->address + imm;
	}

        SStream_concat(O, "0x%"PRIx64, imm);

	if (MI->csh->detail) {
		MI->flat_insn->detail->ppc.operands[MI->flat_insn->detail->ppc.op_count].type = PPC_OP_IMM;
		MI->flat_insn->detail->ppc.operands[MI->flat_insn->detail->ppc.op_count].imm = imm;
		MI->flat_insn->detail->ppc.op_count++;
	}
}

uname -a on this machine says: Linux ... 3.10.0-229.4.2.ael7b.ppc64le #1 SMP Fri Apr 24 15:23:58 EDT 2015 ppc64le ppc64le ppc64le GNU/Linux
Capstone branch “next” at commit 16ae82e0fcd707466f27f4bf84afdbd13667e27d


Regards,

Per Mildner                                     Per...@si...
Swedish Institute of Computer Science