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Fix for undefined behavior while updating PC value on arm-linux 

Differential revision: http://reviews.llvm.org/D15877

llvm-svn: 256847
This commit is contained in:
Omair Javaid 2016-01-05 16:56:13 +00:00
parent c7b073a23a
commit a7d7f7cf33
1 changed files with 18 additions and 1 deletions
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19
lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp
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@ -973,7 +973,24 @@ NativeRegisterContextLinux_arm::DoWriteRegisterValue(uint32_t offset,
if (error.Fail())
return error;
m_gpr_arm[offset / sizeof(uint32_t)] = value.GetAsUInt32();
uint32_t reg_value = value.GetAsUInt32();
// As precaution for an undefined behavior encountered while setting PC we
// will clear thumb bit of new PC if we are already in thumb mode; that is
// CPSR thumb mode bit is set.
if (offset / sizeof(uint32_t) == gpr_pc_arm)
{
// Check if we are already in thumb mode and
// thumb bit of current PC is read out to be zero and
// thumb bit of next PC is read out to be one.
if ((m_gpr_arm[gpr_cpsr_arm] & 0x20) &&
!(m_gpr_arm[gpr_pc_arm] & 0x01) &&
(value.GetAsUInt32() & 0x01))
{
reg_value &= (~1ull);
}
}
m_gpr_arm[offset / sizeof(uint32_t)] = reg_value;
return DoWriteGPR(m_gpr_arm, sizeof(m_gpr_arm));
}