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      1 // Copyright (c) 2010, Google Inc.
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions are
      6 // met:
      7 //
      8 //     * Redistributions of source code must retain the above copyright
      9 // notice, this list of conditions and the following disclaimer.
     10 //     * Redistributions in binary form must reproduce the above
     11 // copyright notice, this list of conditions and the following disclaimer
     12 // in the documentation and/or other materials provided with the
     13 // distribution.
     14 //     * Neither the name of Google Inc. nor the names of its
     15 // contributors may be used to endorse or promote products derived from
     16 // this software without specific prior written permission.
     17 //
     18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29 
     30 // Original author: Jim Blandy <jimb (at) mozilla.com> <jimb (at) red-bean.com>
     31 
     32 // cfi_assembler.cc: Implementation of google_breakpad::CFISection class.
     33 // See cfi_assembler.h for details.
     34 
     35 #include "common/dwarf/cfi_assembler.h"
     36 
     37 #include <assert.h>
     38 #include <stdlib.h>
     39 
     40 namespace google_breakpad {
     41 
     42 using dwarf2reader::DwarfPointerEncoding;
     43 
     44 CFISection &CFISection::CIEHeader(uint64_t code_alignment_factor,
     45                                   int data_alignment_factor,
     46                                   unsigned return_address_register,
     47                                   uint8_t version,
     48                                   const string &augmentation,
     49                                   bool dwarf64) {
     50   assert(!entry_length_);
     51   entry_length_ = new PendingLength();
     52   in_fde_ = false;
     53 
     54   if (dwarf64) {
     55     D32(kDwarf64InitialLengthMarker);
     56     D64(entry_length_->length);
     57     entry_length_->start = Here();
     58     D64(eh_frame_ ? kEHFrame64CIEIdentifier : kDwarf64CIEIdentifier);
     59   } else {
     60     D32(entry_length_->length);
     61     entry_length_->start = Here();
     62     D32(eh_frame_ ? kEHFrame32CIEIdentifier : kDwarf32CIEIdentifier);
     63   }
     64   D8(version);
     65   AppendCString(augmentation);
     66   ULEB128(code_alignment_factor);
     67   LEB128(data_alignment_factor);
     68   if (version == 1)
     69     D8(return_address_register);
     70   else
     71     ULEB128(return_address_register);
     72   return *this;
     73 }
     74 
     75 CFISection &CFISection::FDEHeader(Label cie_pointer,
     76                                   uint64_t initial_location,
     77                                   uint64_t address_range,
     78                                   bool dwarf64) {
     79   assert(!entry_length_);
     80   entry_length_ = new PendingLength();
     81   in_fde_ = true;
     82   fde_start_address_ = initial_location;
     83 
     84   if (dwarf64) {
     85     D32(0xffffffff);
     86     D64(entry_length_->length);
     87     entry_length_->start = Here();
     88     if (eh_frame_)
     89       D64(Here() - cie_pointer);
     90     else
     91       D64(cie_pointer);
     92   } else {
     93     D32(entry_length_->length);
     94     entry_length_->start = Here();
     95     if (eh_frame_)
     96       D32(Here() - cie_pointer);
     97     else
     98       D32(cie_pointer);
     99   }
    100   EncodedPointer(initial_location);
    101   // The FDE length in an .eh_frame section uses the same encoding as the
    102   // initial location, but ignores the base address (selected by the upper
    103   // nybble of the encoding), as it's a length, not an address that can be
    104   // made relative.
    105   EncodedPointer(address_range,
    106                  DwarfPointerEncoding(pointer_encoding_ & 0x0f));
    107   return *this;
    108 }
    109 
    110 CFISection &CFISection::FinishEntry() {
    111   assert(entry_length_);
    112   Align(address_size_, dwarf2reader::DW_CFA_nop);
    113   entry_length_->length = Here() - entry_length_->start;
    114   delete entry_length_;
    115   entry_length_ = NULL;
    116   in_fde_ = false;
    117   return *this;
    118 }
    119 
    120 CFISection &CFISection::EncodedPointer(uint64_t address,
    121                                        DwarfPointerEncoding encoding,
    122                                        const EncodedPointerBases &bases) {
    123   // Omitted data is extremely easy to emit.
    124   if (encoding == dwarf2reader::DW_EH_PE_omit)
    125     return *this;
    126 
    127   // If (encoding & dwarf2reader::DW_EH_PE_indirect) != 0, then we assume
    128   // that ADDRESS is the address at which the pointer is stored --- in
    129   // other words, that bit has no effect on how we write the pointer.
    130   encoding = DwarfPointerEncoding(encoding & ~dwarf2reader::DW_EH_PE_indirect);
    131 
    132   // Find the base address to which this pointer is relative. The upper
    133   // nybble of the encoding specifies this.
    134   uint64_t base;
    135   switch (encoding & 0xf0) {
    136     case dwarf2reader::DW_EH_PE_absptr:  base = 0;                  break;
    137     case dwarf2reader::DW_EH_PE_pcrel:   base = bases.cfi + Size(); break;
    138     case dwarf2reader::DW_EH_PE_textrel: base = bases.text;         break;
    139     case dwarf2reader::DW_EH_PE_datarel: base = bases.data;         break;
    140     case dwarf2reader::DW_EH_PE_funcrel: base = fde_start_address_; break;
    141     case dwarf2reader::DW_EH_PE_aligned: base = 0;                  break;
    142     default: abort();
    143   };
    144 
    145   // Make ADDRESS relative. Yes, this is appropriate even for "absptr"
    146   // values; see gcc/unwind-pe.h.
    147   address -= base;
    148 
    149   // Align the pointer, if required.
    150   if ((encoding & 0xf0) == dwarf2reader::DW_EH_PE_aligned)
    151     Align(AddressSize());
    152 
    153   // Append ADDRESS to this section in the appropriate form. For the
    154   // fixed-width forms, we don't need to differentiate between signed and
    155   // unsigned encodings, because ADDRESS has already been extended to 64
    156   // bits before it was passed to us.
    157   switch (encoding & 0x0f) {
    158     case dwarf2reader::DW_EH_PE_absptr:
    159       Address(address);
    160       break;
    161 
    162     case dwarf2reader::DW_EH_PE_uleb128:
    163       ULEB128(address);
    164       break;
    165 
    166     case dwarf2reader::DW_EH_PE_sleb128:
    167       LEB128(address);
    168       break;
    169 
    170     case dwarf2reader::DW_EH_PE_udata2:
    171     case dwarf2reader::DW_EH_PE_sdata2:
    172       D16(address);
    173       break;
    174 
    175     case dwarf2reader::DW_EH_PE_udata4:
    176     case dwarf2reader::DW_EH_PE_sdata4:
    177       D32(address);
    178       break;
    179 
    180     case dwarf2reader::DW_EH_PE_udata8:
    181     case dwarf2reader::DW_EH_PE_sdata8:
    182       D64(address);
    183       break;
    184 
    185     default:
    186       abort();
    187   }
    188 
    189   return *this;
    190 };
    191 
    192 const uint32_t CFISection::kDwarf64InitialLengthMarker;
    193 const uint32_t CFISection::kDwarf32CIEIdentifier;
    194 const uint64_t CFISection::kDwarf64CIEIdentifier;
    195 const uint32_t CFISection::kEHFrame32CIEIdentifier;
    196 const uint64_t CFISection::kEHFrame64CIEIdentifier;
    197 
    198 } // namespace google_breakpad
    199