SymbolFile/DWARF/DWARFDebugArangeSet.cpp

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

#include "DWARFDebugArangeSet.h"

#include <assert.h>
#include "lldb/Core/Stream.h"
#include "SymbolFileDWARF.h"

using namespace lldb_private;

DWARFDebugArangeSet::DWARFDebugArangeSet() :
    m_offset(DW_INVALID_OFFSET),
    m_header(),
    m_arange_descriptors()
{
    m_header.length     = 0;
    m_header.version    = 0;
    m_header.cu_offset  = 0;
    m_header.addr_size  = 0;
    m_header.seg_size   = 0;
}

void
DWARFDebugArangeSet::Clear()
{
    m_offset = DW_INVALID_OFFSET;
    m_header.length     = 0;
    m_header.version    = 0;
    m_header.cu_offset  = 0;
    m_header.addr_size  = 0;
    m_header.seg_size   = 0;
    m_arange_descriptors.clear();
}

void
DWARFDebugArangeSet::SetHeader
(
    uint16_t version,
    uint32_t cu_offset,
    uint8_t addr_size,
    uint8_t seg_size
)
{
    m_header.version    = version;
    m_header.cu_offset  = cu_offset;
    m_header.addr_size  = addr_size;
    m_header.seg_size   = seg_size;
}

void
DWARFDebugArangeSet::Compact()
{
    if (m_arange_descriptors.empty())
        return;

    // Iterate through all arange descriptors and combine any ranges that
    // overlap or have matching boundaries. The m_arange_descriptors are assumed
    // to be in ascending order after being built by adding descriptors
    // using the AddDescriptor method.
    uint32_t i = 0;
    while (i + 1 < m_arange_descriptors.size())
    {
        if (m_arange_descriptors[i].end_address() >= m_arange_descriptors[i+1].address)
        {
            // The current range ends at or exceeds the start of the next address range.
            // Compute the max end address between the two and use that to make the new
            // length.
            const dw_addr_t max_end_addr = std::max(m_arange_descriptors[i].end_address(), m_arange_descriptors[i+1].end_address());
            m_arange_descriptors[i].length = max_end_addr - m_arange_descriptors[i].address;
            // Now remove the next entry as it was just combined with the previous one.
            m_arange_descriptors.erase(m_arange_descriptors.begin()+i+1);
        }
        else
        {
            // Discontiguous address range, just proceed to the next one.
            ++i;
        }
    }
}
//----------------------------------------------------------------------
// Compare function DWARFDebugArangeSet::Descriptor structures
//----------------------------------------------------------------------
static bool DescriptorLessThan (const DWARFDebugArangeSet::Descriptor& range1, const DWARFDebugArangeSet::Descriptor& range2)
{
    return range1.address < range2.address;
}

//----------------------------------------------------------------------
// Add a range descriptor and keep things sorted so we can easily
// compact the ranges before being saved or used.
//----------------------------------------------------------------------
void
DWARFDebugArangeSet::AddDescriptor(const DWARFDebugArangeSet::Descriptor& range)
{
    if (m_arange_descriptors.empty())
    {
        m_arange_descriptors.push_back(range);
        return;
    }

    DescriptorIter end = m_arange_descriptors.end();
    DescriptorIter pos = lower_bound(m_arange_descriptors.begin(), end, range, DescriptorLessThan);
    const dw_addr_t range_end_addr = range.end_address();
    if (pos != end)
    {
        const dw_addr_t found_end_addr = pos->end_address();
        if (range.address < pos->address)
        {
            if (range_end_addr < pos->address)
            {
                // Non-contiguous entries, add this one before the found entry
                m_arange_descriptors.insert(pos, range);
            }
            else if (range_end_addr == pos->address)
            {
                // The top end of 'range' is the lower end of the entry
                // pointed to by 'pos'. We can combine range with the
                // entry we found by setting the starting address and
                // increasing the length since they don't overlap.
                pos->address = range.address;
                pos->length += range.length;
            }
            else
            {
                // We can combine these two and make sure the largest end
                // address is used to make end address.
                pos->address = range.address;
                pos->length = std::max(found_end_addr, range_end_addr) - pos->address;
            }
        }
        else if (range.address == pos->address)
        {
            pos->length = std::max(pos->length, range.length);
        }
    }
    else
    {
        // NOTE: 'pos' points to entry past the end which is ok for insert,
        // don't use otherwise!!!
        const dw_addr_t max_addr = m_arange_descriptors.back().end_address();
        if (max_addr < range.address)
        {
            // Non-contiguous entries, add this one before the found entry
            m_arange_descriptors.insert(pos, range);
        }
        else if (max_addr == range.address)
        {
            m_arange_descriptors.back().length += range.length;
        }
        else
        {
            m_arange_descriptors.back().length = std::max(max_addr, range_end_addr) - m_arange_descriptors.back().address;
        }
    }
}

bool
DWARFDebugArangeSet::Extract(const DataExtractor &data, lldb::offset_t *offset_ptr)
{
    if (data.ValidOffset(*offset_ptr))
    {
        m_arange_descriptors.clear();
        m_offset = *offset_ptr;

        // 7.20 Address Range Table
        //
        // Each set of entries in the table of address ranges contained in
        // the .debug_aranges section begins with a header consisting of: a
        // 4-byte length containing the length of the set of entries for this
        // compilation unit, not including the length field itself; a 2-byte
        // version identifier containing the value 2 for DWARF Version 2; a
        // 4-byte offset into the.debug_infosection; a 1-byte unsigned integer
        // containing the size in bytes of an address (or the offset portion of
        // an address for segmented addressing) on the target system; and a
        // 1-byte unsigned integer containing the size in bytes of a segment
        // descriptor on the target system. This header is followed by a series
        // of tuples. Each tuple consists of an address and a length, each in
        // the size appropriate for an address on the target architecture.
        m_header.length     = data.GetU32(offset_ptr);
        m_header.version    = data.GetU16(offset_ptr);
        m_header.cu_offset  = data.GetU32(offset_ptr);
        m_header.addr_size  = data.GetU8(offset_ptr);
        m_header.seg_size   = data.GetU8(offset_ptr);


        // The first tuple following the header in each set begins at an offset
        // that is a multiple of the size of a single tuple (that is, twice the
        // size of an address). The header is padded, if necessary, to the
        // appropriate boundary.
        const uint32_t header_size = *offset_ptr - m_offset;
        const uint32_t tuple_size = m_header.addr_size << 1;
        uint32_t first_tuple_offset = 0;
        while (first_tuple_offset < header_size)
            first_tuple_offset += tuple_size;

        *offset_ptr = m_offset + first_tuple_offset;

        Descriptor arangeDescriptor;

        assert(sizeof(arangeDescriptor.address) == sizeof(arangeDescriptor.length));
        assert(sizeof(arangeDescriptor.address) >= m_header.addr_size);

        while (data.ValidOffset(*offset_ptr))
        {
            arangeDescriptor.address    = data.GetMaxU64(offset_ptr, m_header.addr_size);
            arangeDescriptor.length     = data.GetMaxU64(offset_ptr, m_header.addr_size);

            // Each set of tuples is terminated by a 0 for the address and 0
            // for the length.
            if (arangeDescriptor.address || arangeDescriptor.length)
                m_arange_descriptors.push_back(arangeDescriptor);
            else
                break;  // We are done if we get a zero address and length
        }

        return !m_arange_descriptors.empty();
    }
    return false;
}


dw_offset_t
DWARFDebugArangeSet::GetOffsetOfNextEntry() const
{
    return m_offset + m_header.length + 4;
}


void
DWARFDebugArangeSet::Dump(Stream *s) const
{
    s->Printf("Address Range Header: length = 0x%8.8x, version = 0x%4.4x, cu_offset = 0x%8.8x, addr_size = 0x%2.2x, seg_size = 0x%2.2x\n",
        m_header.length ,m_header.version, m_header.cu_offset, m_header.addr_size, m_header.seg_size);

    const uint32_t hex_width = m_header.addr_size * 2;
    DescriptorConstIter pos;
    DescriptorConstIter end = m_arange_descriptors.end();
    for (pos = m_arange_descriptors.begin(); pos != end; ++pos)
        s->Printf("[0x%*.*" PRIx64 " - 0x%*.*" PRIx64 ")\n",
            hex_width, hex_width, pos->address,
            hex_width, hex_width, pos->end_address());
}


class DescriptorContainsAddress
{
public:
    DescriptorContainsAddress (dw_addr_t address) : m_address(address) {}
    bool operator() (const DWARFDebugArangeSet::Descriptor& desc) const
    {
        return (m_address >= desc.address) && (m_address < (desc.address + desc.length));
    }
 private:
   const dw_addr_t m_address;
};

dw_offset_t
DWARFDebugArangeSet::FindAddress(dw_addr_t address) const
{
    DescriptorConstIter end = m_arange_descriptors.end();
    DescriptorConstIter pos = std::find_if( m_arange_descriptors.begin(), end,  // Range
                                            DescriptorContainsAddress(address));// Predicate
    if (pos != end)
        return m_header.cu_offset;

    return DW_INVALID_OFFSET;
}