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Add support for PC-relative LDRi12 #1157

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Oct 4, 2017
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Add support for PC-relative LDRi12 #1157

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25 changes: 24 additions & 1 deletion gapii/interceptor-lib/cc/lib/ARM/target_arm.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,7 @@ static void *calculatePcRelativeAddressArm(void *data, size_t pc_offset,

data_addr += pc_offset; // Add the PC
data_addr += 8; // Add the 8 byte implicit offset
data_addr += offset; // Add the offset
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This looks like a nasty bug you've fixed. Was nothing passing offset before?

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Only ARM::Bcc seems to have been affected (non-Thumb).
The Thumb calculation is correct.

return reinterpret_cast<void *>(data_addr);
}

Expand Down Expand Up @@ -176,7 +177,6 @@ Error TargetARM::RewriteInstruction(const llvm::MCInst &inst,
case llvm::ARM::LDR_PRE_REG:
case llvm::ARM::LDR_POST_IMM:
case llvm::ARM::LDR_POST_REG:
case llvm::ARM::LDRi12:
case llvm::ARM::LDRH_PRE:
case llvm::ARM::LDRH_POST:
case llvm::ARM::LDRH:
Expand Down Expand Up @@ -278,6 +278,29 @@ Error TargetARM::RewriteInstruction(const llvm::MCInst &inst,
}
break;
}
case llvm::ARM::LDRi12: {
uint32_t Rt = inst.getOperand(0).getReg();
uint32_t Rn = inst.getOperand(1).getReg();
int64_t imm = inst.getOperand(2).getImm();
int64_t p = inst.getOperand(3).getImm();
possible_end_of_function = (Rt == llvm::ARM::PC);

if (Rn == llvm::ARM::PC) {
void *load_source =
calculatePcRelativeAddressArm(data, offset, imm);
uint32_t load_data = 0;
memcpy(&load_data, load_source, sizeof(uint32_t));
codegen.AddInstruction(llvm::MCInstBuilder(llvm::ARM::LDRi12)
.addReg(Rt)
.addExpr(codegen.CreateDataExpr(load_data))
.addImm(0)
.addImm(p)
.addImm(0));
} else {
codegen.AddInstruction(inst);
}
break;
}
case llvm::ARM::tLDRpci:
case llvm::ARM::t2LDRpci: {
uint32_t Rt = inst.getOperand(0).getReg();
Expand Down