diff options
| -rw-r--r-- | lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp | 85 |
1 files changed, 57 insertions, 28 deletions
diff --git a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp index c0daaac2882..27e3622696d 100644 --- a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp +++ b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp @@ -676,40 +676,69 @@ loopnext: } // Now look at the byte at the end of the AddressRange for a limited attempt at describing the - // epilogue. If this function is built -fomit-frame-pointer (so the CFA is defined in terms of the - // stack pointer) we'd need to profile every instruction which causes rsp to change to backtrace - // all the time. But assuming the CFA is in terms of rbp most of the time, this one additional Row - // will be sufficient. + // epilogue. We're looking for the sequence - if (m_func_bounds.GetByteSize() > 2) + // [ 0x5d ] mov %rbp, %rsp + // [ 0xc3 ] ret + // [ 0xe8 xx xx xx xx ] call __stack_chk_fail (this is sometimes the final insn in the function) + + // We want to add a Row describing how to unwind when we're stopped on the 'ret' instruction where the + // CFA is no longer defined in terms of rbp, but is now defined in terms of rsp like on function entry. + + uint64_t ret_insn_offset = LLDB_INVALID_ADDRESS; + Address end_of_fun(m_func_bounds.GetBaseAddress()); + end_of_fun.SetOffset (end_of_fun.GetOffset() + m_func_bounds.GetByteSize()); + + if (m_func_bounds.GetByteSize() > 7) { - Address last_insn (m_func_bounds.GetBaseAddress()); - last_insn.SetOffset (last_insn.GetOffset() + m_func_bounds.GetByteSize() - 1); - uint8_t bytebuf[1]; - if (target->ReadMemory (last_insn, prefer_file_cache, bytebuf, 1, error) != -1) + uint8_t bytebuf[7]; + Address last_seven_bytes(end_of_fun); + last_seven_bytes.SetOffset (last_seven_bytes.GetOffset() - 7); + if (target->ReadMemory (last_seven_bytes, prefer_file_cache, bytebuf, 7, error) != -1) { - if (bytebuf[0] == 0xc3) // ret aka retq + if (bytebuf[5] == 0x5d && bytebuf[6] == 0xc3) // mov, ret { - // Create a fresh, empty Row and RegisterLocation - don't mention any other registers - UnwindPlan::Row epi_row; - UnwindPlan::Row::RegisterLocation epi_regloc; - - // When the ret instruction is about to be executed, here's our state - epi_row.SetOffset (m_func_bounds.GetByteSize() - 1); - epi_row.SetCFARegister (m_lldb_sp_regnum); - epi_row.SetCFAOffset (m_wordsize); - - // caller's stack pointer value before the call insn is the CFA address - epi_regloc.SetIsCFAPlusOffset (0); - epi_row.SetRegisterInfo (m_lldb_sp_regnum, epi_regloc); - - // saved instruction pointer can be found at CFA - wordsize - epi_regloc.SetAtCFAPlusOffset (-m_wordsize); - epi_row.SetRegisterInfo (m_lldb_ip_regnum, epi_regloc); - - unwind_plan.AppendRow (epi_row); + ret_insn_offset = m_func_bounds.GetByteSize() - 1; + } + else if (bytebuf[0] == 0x5d && bytebuf[1] == 0xc3 && bytebuf[2] == 0xe8) // mov, ret, call + { + ret_insn_offset = m_func_bounds.GetByteSize() - 6; } } + } else if (m_func_bounds.GetByteSize() > 2) + { + uint8_t bytebuf[2]; + Address last_two_bytes(end_of_fun); + last_two_bytes.SetOffset (last_two_bytes.GetOffset() - 2); + if (target->ReadMemory (last_two_bytes, prefer_file_cache, bytebuf, 2, error) != -1) + { + if (bytebuf[0] == 0x5d && bytebuf[1] == 0xc3) // mov, ret + { + ret_insn_offset = m_func_bounds.GetByteSize() - 1; + } + } + } + + if (ret_insn_offset != LLDB_INVALID_ADDRESS) + { + // Create a fresh, empty Row and RegisterLocation - don't mention any other registers + UnwindPlan::Row epi_row; + UnwindPlan::Row::RegisterLocation epi_regloc; + + // When the ret instruction is about to be executed, here's our state + epi_row.SetOffset (ret_insn_offset); + epi_row.SetCFARegister (m_lldb_sp_regnum); + epi_row.SetCFAOffset (m_wordsize); + + // caller's stack pointer value before the call insn is the CFA address + epi_regloc.SetIsCFAPlusOffset (0); + epi_row.SetRegisterInfo (m_lldb_sp_regnum, epi_regloc); + + // saved instruction pointer can be found at CFA - wordsize + epi_regloc.SetAtCFAPlusOffset (-m_wordsize); + epi_row.SetRegisterInfo (m_lldb_ip_regnum, epi_regloc); + + unwind_plan.AppendRow (epi_row); } unwind_plan.SetSourceName ("assembly insn profiling"); |
