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      1 //===------------------------- UnwindCursor.hpp ---------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is dual licensed under the MIT and the University of Illinois Open
      6 // Source Licenses. See LICENSE.TXT for details.
      7 //
      8 //
      9 // C++ interface to lower levels of libuwind
     10 //===----------------------------------------------------------------------===//
     11 
     12 #ifndef __UNWINDCURSOR_HPP__
     13 #define __UNWINDCURSOR_HPP__
     14 
     15 #include <stdint.h>
     16 #include <stdlib.h>
     17 #include <pthread.h>
     18 
     19 #include "AddressSpace.hpp"
     20 #include "DwarfInstructions.hpp"
     21 #include "Registers.hpp"
     22 
     23 namespace _Unwind {
     24 
     25 template <typename A, typename R> class UnwindCursor {
     26 public:
     27   UnwindCursor(R &regs, A &as)
     28       : fRegisters(regs), fAddressSpace(as), fUnwindInfoMissing(false),
     29         fIsSignalFrame(false) {
     30     memset(&fInfo, 0, sizeof(fInfo));
     31   }
     32 
     33   uint64_t getIP() const { return fRegisters.getIP(); }
     34 
     35   void setIP(uint64_t value) { return fRegisters.setIP(value); }
     36 
     37   uint64_t getSP() const { return fRegisters.getSP(); }
     38 
     39   void setSP(uint64_t value) { return fRegisters.setSP(value); }
     40 
     41   bool validReg(int regNum) { return fRegisters.validRegister(regNum); }
     42 
     43   uint64_t getReg(int regNum) { return fRegisters.getRegister(regNum); }
     44 
     45   void setReg(int regNum, uint64_t value) {
     46     fRegisters.setRegister(regNum, value);
     47   }
     48 
     49   step_result step() {
     50     // Bottom of stack is defined as having no more unwind info.
     51     if (fUnwindInfoMissing)
     52       return UNW_STEP_END;
     53 
     54     // Apply unwinding to register set.
     55     switch (this->stepWithDwarfFDE()) {
     56     case UNW_STEP_FAILED:
     57       return UNW_STEP_FAILED;
     58     case UNW_STEP_END:
     59       return UNW_STEP_END;
     60     case UNW_STEP_SUCCESS:
     61       this->setInfoBasedOnIPRegister(true);
     62       if (fUnwindInfoMissing)
     63         return UNW_STEP_END;
     64       return UNW_STEP_SUCCESS;
     65     }
     66     __builtin_unreachable();
     67   }
     68 
     69   void getInfo(unw_proc_info_t *info) { *info = fInfo; }
     70 
     71   bool isSignalFrame() { return fIsSignalFrame; }
     72   void setInfoBasedOnIPRegister(bool isReturnAddress = false);
     73 
     74   void jumpto() { fRegisters.jumpto(); }
     75 
     76 private:
     77   typedef typename A::pint_t pint_t;
     78   typedef uint32_t EncodedUnwindInfo;
     79 
     80   bool getInfoFromDwarfSection(pint_t, pint_t, uint32_t, uint32_t);
     81 
     82   step_result stepWithDwarfFDE() {
     83     return DwarfInstructions<A, R>::stepWithDwarf(
     84         fAddressSpace, this->getIP(), fInfo.unwind_info, fRegisters, &fInfo);
     85   }
     86 
     87   unw_proc_info_t fInfo;
     88   R fRegisters;
     89   A &fAddressSpace;
     90   bool fUnwindInfoMissing;
     91   bool fIsSignalFrame;
     92 };
     93 
     94 template <typename A, typename R>
     95 void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
     96   pint_t pc = this->getIP();
     97 
     98   // If the last line of a function is a "throw", the compiler sometimes
     99   // emits no instructions after the call to __cxa_throw.  This means
    100   // the return address is actually the start of the next function.
    101   // To disambiguate this, back up the PC when we know it is a return
    102   // address.
    103   if (isReturnAddress)
    104     --pc;
    105 
    106   pint_t fdeStart, data_base;
    107   if (!fAddressSpace.findFDE(pc, fdeStart, data_base)) {
    108     fUnwindInfoMissing = true;
    109     return;
    110   }
    111   fInfo.data_base = data_base;
    112 
    113   typename CFI_Parser<A, R>::FDE_Info fdeInfo;
    114   typename CFI_Parser<A, R>::CIE_Info cieInfo;
    115   CFI_Parser<A, R>::decodeFDE(fAddressSpace, fdeStart, &fdeInfo, &cieInfo,
    116                               &fInfo);
    117   if (pc < fdeInfo.pcStart || pc > fdeInfo.pcEnd) {
    118     fUnwindInfoMissing = true;
    119     return;
    120   }
    121   fInfo.start_ip = fdeInfo.pcStart;
    122 
    123   typename CFI_Parser<A, R>::PrologInfo prolog;
    124   if (!CFI_Parser<A, R>::parseFDEInstructions(fAddressSpace, fdeInfo, cieInfo,
    125                                               pc, &prolog, &fInfo)) {
    126     fUnwindInfoMissing = true;
    127     return;
    128   }
    129   // Save off parsed FDE info
    130   fInfo.end_ip = fdeInfo.pcEnd;
    131   fInfo.lsda = fdeInfo.lsda;
    132   fInfo.handler = cieInfo.personality;
    133   fInfo.extra_args = prolog.spExtraArgSize;
    134   fInfo.unwind_info = fdeInfo.fdeStart;
    135 }
    136 
    137 }; // namespace _Unwind
    138 
    139 #endif // __UNWINDCURSOR_HPP__
    140