/src/system/boot/mips/Elf32.cc

/*
 * Copyright (c) 2008 James Molloy, Jörg Pfähler, Matthew Iselin
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "Elf32.h"
//include <utilities/utility.h>
extern void writeStr(const char *str);
int strncpy(char *dest, const char *src, int len)
{
  while (*src && len)
  {
    *dest++ = *src++;
    len--;
  }
  *dest = '\0';
}
int memset(void *buf, int c, size_t len)
{
  unsigned char *tmp = (unsigned char *)buf;
  while(len--)
  {
    *tmp++ = c;
  }
}

void memcpy(void *dest, const void *src, size_t len)
{
  const unsigned char *sp = (const unsigned char *)src;
  unsigned char *dp = (unsigned char *)dest;
  for (; len != 0; len--) *dp++ = *sp++;
}

int strcmp(const char *p1, const char *p2)
{
  int i = 0;
  int failed = 0;
  while(p1[i] != '\0' && p2[i] != '\0')
  {
    if(p1[i] != p2[i])
    {
      failed = 1;
      break;
    }
    i++;
  }
  // why did the loop exit?
  if( (p1[i] == '\0' && p2[i] != '\0') || (p1[i] != '\0' && p2[i] == '\0') )
    failed = 1;

  return failed;
}

Elf32::Elf32(const char *name) :
  m_pHeader(0),
  m_pSymbolTable(0),
  m_pStringTable(0),
  m_pShstrtab(0),
  m_pGotTable(0),
  m_pRelTable(0),
  m_pSectionHeaders(0),
  m_pBuffer(0)
{
  strncpy(m_pId, name, 127);
}

Elf32::~Elf32()
{
}

bool Elf32::load(uint8_t *pBuffer, unsigned int nBufferLength)
{
  // The main header will be at pBuffer[0].
  m_pHeader = reinterpret_cast<Elf32Header_t *>(pBuffer);
  
  // Check the ident.
  if ( (m_pHeader->ident[1] != 'E') ||
       (m_pHeader->ident[2] != 'L') ||
       (m_pHeader->ident[3] != 'F') ||
       (m_pHeader->ident[0] != 127) )
  {
    m_pHeader = (Elf32Header_t*)0;
    return false;
  }
  
  // Load in the section headers.
  m_pSectionHeaders = reinterpret_cast<Elf32SectionHeader_t *>(&pBuffer[m_pHeader->shoff]);
  
  // Find the string tab&pBuffer[m_pStringTable->offset];le.
  m_pStringTable = &m_pSectionHeaders[m_pHeader->shstrndx];
  
  // Temporarily load the string table.
  const char *pStrtab = reinterpret_cast<const char *>(&pBuffer[m_pStringTable->offset]);
  
  // Go through each section header, trying to find .symtab.
  for (int i = 0; i < m_pHeader->shnum; i++)
  {
    const char *pStr = pStrtab + m_pSectionHeaders[i].name;
    if (!strcmp(pStr, ".symtab"))
    {
      m_pSymbolTable = &m_pSectionHeaders[i];
    }
    if (!strcmp(pStr, ".strtab"))
      m_pStringTable = &m_pSectionHeaders[i];
  }
  
  
  m_pBuffer = pBuffer;
  
  // Success.
  return true;
}

// bool Elf32::load(BootstrapInfo *pBootstrap)
// {
//   // Firstly get the section header string table.
//   m_pShstrtab = reinterpret_cast<Elf32SectionHeader_t *>( pBootstrap->getSectionHeader(
//                                                           pBootstrap->getStringTable() ));
//   
//   // Normally we will try to use the sectionHeader->offset member to access data, so an
//   // Elf section's data can be accessed without being mapped into virtual memory. However,
//   // when GRUB loads us, it doesn't tell us where exactly ->offset is with respect to, so here
//   // we fix offset = addr, then we work w.r.t 0x00.
//   
//   // Temporarily load the string table.
//   const char *pStrtab = reinterpret_cast<const char *>(m_pShstrtab->addr);
// 
//   // Now search for the symbol table.
//   for (int i = 0; i < pBootstrap->getSectionHeaderCount(); i++)
//   {
//     Elf32SectionHeader_t *pSh = reinterpret_cast<Elf32SectionHeader_t *>(pBootstrap->getSectionHeader(i));
//     const char *pStr = pStrtab + pSh->name;
// 
//     if (pSh->type == SHT_SYMTAB)
//     {
//       m_pSymbolTable = pSh;
//       m_pSymbolTable->offset = m_pSymbolTable->addr;
//     }
//     else if (!strcmp(pStr, ".strtab"))
//     {
//       m_pStringTable = pSh;
//       m_pStringTable->offset = m_pStringTable->addr;
//     }
//   }
// 
//   return true;
// }

bool Elf32::writeSections()
{
  for (int i = 0; i < m_pHeader->shnum; i++)
  {
    if (m_pSectionHeaders[i].flags & SHF_ALLOC)
    {
      if (m_pSectionHeaders[i].type != SHT_NOBITS)
      {
        // Copy section data from the file.
        memcpy((uint8_t*)m_pSectionHeaders[i].addr,
                        &m_pBuffer[m_pSectionHeaders[i].offset],
                        m_pSectionHeaders[i].size);
      }
      else
      {
        memset((uint8_t*)m_pSectionHeaders[i].addr,
                        0,
                        m_pSectionHeaders[i].size);
      }
    }
  } 
}

unsigned int Elf32::getLastAddress()
{
}

const char *Elf32::lookupSymbol(unsigned int addr, unsigned int *startAddr)
{
  if (!m_pSymbolTable || !m_pStringTable)
    return (const char*)2; // Just return null if we haven't got a symbol table.
  
  Elf32Symbol_t *pSymbol = reinterpret_cast<Elf32Symbol_t *>(&m_pBuffer[m_pSymbolTable->offset]);
  const char *pStrtab = reinterpret_cast<const char *>(&m_pBuffer[m_pStringTable->offset]);

  for (size_t i = 0; i < m_pSymbolTable->size / sizeof(Elf32Symbol_t); i++)
  {
    // Make sure we're looking at an object or function.
    if (ELF32_ST_TYPE(pSymbol->info) != 0x2 /* function */ &&
        ELF32_ST_TYPE(pSymbol->info) != 0x0 /* notype (asm functions) */)
    {
      pSymbol++;
      continue;
    }
    
    // If we're checking for a symbol that is apparently zero-sized, add one so we can actually
    // count it!
    uint32_t size = pSymbol->size;
    if (size == 0)
      size = 1;
    if ( (addr >= pSymbol->value) &&
         (addr < (pSymbol->value + size)) )
    {
      const char *pStr = pStrtab + pSymbol->name;
      if (startAddr)
        *startAddr = pSymbol->value;
      return pStr;
    }
    pSymbol ++;
  }
  return (const char*)3;
  
}

uint32_t Elf32::lookupDynamicSymbolAddress(uint32_t off)
{
}

char *Elf32::lookupDynamicSymbolName(uint32_t off)
{
}

uint32_t Elf32::getGlobalOffsetTable()
{
}

uint32_t Elf32::getEntryPoint()
{
  return m_pHeader->entry;
}