xref: /freebsd-11.0-release/contrib/llvm/tools/lldb/include/lldb/Symbol/CompactUnwindInfo.h

//===-- CompactUnwindInfo.h -------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef liblldb_CompactUnwindInfo_h_
#define liblldb_CompactUnwindInfo_h_

#include <vector>

#include "lldb/Core/DataExtractor.h"
#include "lldb/Core/RangeMap.h"
#include "lldb/Host/Mutex.h"
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Symbol/UnwindPlan.h"
#include "lldb/lldb-private.h"

namespace lldb_private {

// Compact Unwind info is an unwind format used on Darwin.  The unwind instructions
// for typical compiler-generated functions can be expressed in a 32-bit encoding.
// The format includes a two-level index so the unwind information for a function
// can be found by two binary searches in the section.  It can represent both
// stack frames that use a frame-pointer register and frameless functions, on
// i386/x86_64 for instance.  When a function is too complex to be represented in
// the compact unwind format, it calls out to eh_frame unwind instructions.

// On Mac OS X / iOS, a function will have either a compact unwind representation
// or an eh_frame representation.  If lldb is going to benefit  from the compiler's
// description about saved register locations, it must be able to read both
// sources of information.

class CompactUnwindInfo
{
public:

    CompactUnwindInfo (ObjectFile& objfile,
                       lldb::SectionSP& section);

    ~CompactUnwindInfo();

    bool
    GetUnwindPlan (Target &target, Address addr, UnwindPlan& unwind_plan);

    bool
    IsValid (const lldb::ProcessSP &process_sp);

private:


    // The top level index entries of the compact unwind info
    //   (internal representation of struct unwind_info_section_header_index_entry)
    // There are relatively few of these (one per 500/1000 functions, depending on format) so
    // creating them on first scan will not be too costly.
    struct UnwindIndex
    {
        uint32_t        function_offset; // The offset of the first function covered by this index
        uint32_t        second_level;    // The offset (inside unwind_info sect) to the second level page for this index
        // (either UNWIND_SECOND_LEVEL_REGULAR or UNWIND_SECOND_LEVEL_COMPRESSED)
        uint32_t        lsda_array_start;// The offset (inside unwind_info sect) LSDA array for this index
        uint32_t        lsda_array_end;  // The offset to the LSDA array for the NEXT index
        bool            sentinal_entry;  // There is an empty index at the end which provides the upper bound of
        // function addresses that are described

        UnwindIndex() :
        function_offset (0),
        second_level (0),
        lsda_array_start(0),
        lsda_array_end(0),
        sentinal_entry (false)
        { }

        bool
        operator< (const CompactUnwindInfo::UnwindIndex& rhs) const
        {
            return function_offset < rhs.function_offset;
        }

        bool
        operator== (const CompactUnwindInfo::UnwindIndex& rhs) const
        {
            return function_offset == rhs.function_offset;
        }

    };

    // An internal object used to store the information we retrieve about a function --
    // the encoding bits and possibly the LSDA/personality function.
    struct FunctionInfo
    {
        uint32_t  encoding;                   // compact encoding 32-bit value for this function
        Address   lsda_address;               // the address of the LSDA data for this function
        Address   personality_ptr_address;    // the address where the personality routine addr can be found

        uint32_t  valid_range_offset_start;   // first offset that this encoding is valid for (start of the function)
        uint32_t  valid_range_offset_end;     // the offset of the start of the next function
        FunctionInfo () : encoding(0), lsda_address(), personality_ptr_address(), valid_range_offset_start(0), valid_range_offset_end(0) { }
    };

    struct UnwindHeader
    {
        uint32_t    version;
        uint32_t    common_encodings_array_offset;
        uint32_t    common_encodings_array_count;
        uint32_t    personality_array_offset;
        uint32_t    personality_array_count;

        UnwindHeader () : common_encodings_array_offset (0), common_encodings_array_count (0), personality_array_offset (0), personality_array_count (0) { }
    };

    void
    ScanIndex(const lldb::ProcessSP &process_sp);

    bool
    GetCompactUnwindInfoForFunction (Target &target, Address address, FunctionInfo &unwind_info);

    lldb::offset_t
    BinarySearchRegularSecondPage (uint32_t entry_page_offset, uint32_t entry_count, uint32_t function_offset, uint32_t *entry_func_start_offset, uint32_t *entry_func_end_offset);

    uint32_t
    BinarySearchCompressedSecondPage (uint32_t entry_page_offset, uint32_t entry_count, uint32_t function_offset_to_find, uint32_t function_offset_base, uint32_t *entry_func_start_offset, uint32_t *entry_func_end_offset);

    uint32_t
    GetLSDAForFunctionOffset (uint32_t lsda_offset, uint32_t lsda_count, uint32_t function_offset);

    bool
    CreateUnwindPlan_x86_64 (Target &target, FunctionInfo &function_info, UnwindPlan &unwind_plan, Address pc_or_function_start);

    bool
    CreateUnwindPlan_i386 (Target &target, FunctionInfo &function_info, UnwindPlan &unwind_plan, Address pc_or_function_start);

    ObjectFile                  &m_objfile;
    lldb::SectionSP             m_section_sp;
    lldb::DataBufferSP          m_section_contents_if_encrypted; // if the binary is encrypted, read the sect contents
                                                                 // out of live memory and cache them here
    Mutex                       m_mutex;
    std::vector<UnwindIndex>    m_indexes;

    LazyBool                    m_indexes_computed;         // eLazyBoolYes once we've tried to parse the unwind info
                                                            // eLazyBoolNo means we cannot parse the unwind info & should not retry
                                                            // eLazyBoolCalculate means we haven't tried to parse it yet

    DataExtractor               m_unwindinfo_data;
    bool                        m_unwindinfo_data_computed; // true once we've mapped in the unwindinfo data

    UnwindHeader                m_unwind_header;
};

} // namespace lldb_private

#endif  // liblldb_CompactUnwindInfo_h_