gcc/libiberty/simple-object.c

/* simple-object.c -- simple routines to read and write object files.
   Copyright (C) 2010-2017 Free Software Foundation, Inc.
   Written by Ian Lance Taylor, Google.

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, 51 Franklin Street - Fifth Floor,
Boston, MA 02110-1301, USA.  */

#include "config.h"
#include "libiberty.h"
#include "simple-object.h"

#include <errno.h>
#include <fcntl.h>

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif

#ifdef HAVE_STRING_H
#include <string.h>
#endif

#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif

#ifndef SEEK_SET
#define SEEK_SET 0
#endif

#include "simple-object-common.h"

/* The known object file formats.  */

static const struct simple_object_functions * const format_functions[] =
{
  &simple_object_elf_functions,
  &simple_object_mach_o_functions,
  &simple_object_coff_functions,
  &simple_object_xcoff_functions
};

/* Read data from a file using the simple_object error reporting
   conventions.  */

int
simple_object_internal_read (int descriptor, off_t offset,
			     unsigned char *buffer, size_t size,
			     const char **errmsg, int *err)
{
  if (lseek (descriptor, offset, SEEK_SET) < 0)
    {
      *errmsg = "lseek";
      *err = errno;
      return 0;
    }

  do
    {
      ssize_t got = read (descriptor, buffer, size);
      if (got == 0)
	break;
      else if (got > 0)
	{
	  buffer += got;
	  size -= got;
	}
      else if (errno != EINTR)
	{
	  *errmsg = "read";
	  *err = errno;
	  return 0;
	}
    }
  while (size > 0);

  if (size > 0)
    {
      *errmsg = "file too short";
      *err = 0;
      return 0;
    }

  return 1;
}

/* Write data to a file using the simple_object error reporting
   conventions.  */

int
simple_object_internal_write (int descriptor, off_t offset,
			      const unsigned char *buffer, size_t size,
			      const char **errmsg, int *err)
{
  if (lseek (descriptor, offset, SEEK_SET) < 0)
    {
      *errmsg = "lseek";
      *err = errno;
      return 0;
    }

  do
    {
      ssize_t wrote = write (descriptor, buffer, size);
      if (wrote == 0)
	break;
      else if (wrote > 0)
	{
	  buffer += wrote;
	  size -= wrote;
	}
      else if (errno != EINTR)
	{
	  *errmsg = "write";
	  *err = errno;
	  return 0;
	}
    }
  while (size > 0);

  if (size > 0)
    {
      *errmsg = "short write";
      *err = 0;
      return 0;
    }

  return 1;
}

/* Open for read.  */

simple_object_read *
simple_object_start_read (int descriptor, off_t offset,
			  const char *segment_name, const char **errmsg,
			  int *err)
{
  unsigned char header[SIMPLE_OBJECT_MATCH_HEADER_LEN];
  size_t len, i;

  if (!simple_object_internal_read (descriptor, offset, header,
				    SIMPLE_OBJECT_MATCH_HEADER_LEN,
				    errmsg, err))
    return NULL;

  len = sizeof (format_functions) / sizeof (format_functions[0]);
  for (i = 0; i < len; ++i)
    {
      void *data;

      data = format_functions[i]->match (header, descriptor, offset,
					 segment_name, errmsg, err);
      if (data != NULL)
	{
	  simple_object_read *ret;

	  ret = XNEW (simple_object_read);
	  ret->descriptor = descriptor;
	  ret->offset = offset;
	  ret->functions = format_functions[i];
	  ret->data = data;
	  return ret;
	}
    }

  *errmsg = "file not recognized";
  *err = 0;
  return NULL;
}

/* Find all sections.  */

const char *
simple_object_find_sections (simple_object_read *sobj,
			     int (*pfn) (void *, const char *, off_t, off_t),
			     void *data,
			     int *err)
{
  return sobj->functions->find_sections (sobj, pfn, data, err);
}

/* Internal data passed to find_one_section.  */

struct find_one_section_data
{
  /* The section we are looking for.  */
  const char *name;
  /* Where to store the section offset.  */
  off_t *offset;
  /* Where to store the section length.  */
  off_t *length;
  /* Set if the name is found.  */
  int found;
};

/* Internal function passed to find_sections.  */

static int
find_one_section (void *data, const char *name, off_t offset, off_t length)
{
  struct find_one_section_data *fosd = (struct find_one_section_data *) data;

  if (strcmp (name, fosd->name) != 0)
    return 1;

  *fosd->offset = offset;
  *fosd->length = length;
  fosd->found = 1;

  /* Stop iteration.  */
  return 0;
}

/* Find a section.  */

int
simple_object_find_section (simple_object_read *sobj, const char *name,
			    off_t *offset, off_t *length,
			    const char **errmsg, int *err)
{
  struct find_one_section_data fosd;

  fosd.name = name;
  fosd.offset = offset;
  fosd.length = length;
  fosd.found = 0;

  *errmsg = simple_object_find_sections (sobj, find_one_section,
					 (void *) &fosd, err);
  if (*errmsg != NULL)
    return 0;
  if (!fosd.found)
    return 0;
  return 1;
}

/* Callback to identify and rename LTO debug sections by name.
   Returns 1 if NAME is a LTO debug section, 0 if not.  */

static int
handle_lto_debug_sections (const char **name)
{
  /* ???  So we can't use .gnu.lto_ prefixed sections as the assembler
     complains about bogus section flags.  Which means we need to arrange
     for that to be fixed or .gnu.debuglto_ marked as SHF_EXCLUDE (to make
     fat lto object tooling work for the fat part).  */
  /* ???  For now this handles both .gnu.lto_ and .gnu.debuglto_ prefixed
     sections.  */
  /* Copy LTO debug sections and rename them to their non-LTO name.  */
  if (strncmp (*name, ".gnu.debuglto_", sizeof (".gnu.debuglto_") - 1) == 0)
    {
      *name = *name + sizeof (".gnu.debuglto_") - 1;
      return 1;
    }
  else if (strncmp (*name, ".gnu.lto_.debug_", sizeof (".gnu.lto_.debug_") -1) == 0)
    {
      *name = *name + sizeof (".gnu.lto_") - 1;
      return 1;
    }
  return 0;
}

/* Copy LTO debug sections.  */

const char *
simple_object_copy_lto_debug_sections (simple_object_read *sobj,
				       const char *dest, int *err)
{
  const char *errmsg;
  simple_object_write *dest_sobj;
  simple_object_attributes *attrs;
  int outfd;

  if (! sobj->functions->copy_lto_debug_sections)
    {
      *err = EINVAL;
      return "simple_object_copy_lto_debug_sections not implemented";
    }

  attrs = simple_object_fetch_attributes (sobj, &errmsg, err);
  if (! attrs)
    return errmsg;
  dest_sobj = simple_object_start_write (attrs, NULL, &errmsg, err);
  simple_object_release_attributes (attrs);
  if (! dest_sobj)
    return errmsg;

  errmsg = sobj->functions->copy_lto_debug_sections (sobj, dest_sobj,
						     handle_lto_debug_sections,
						     err);
  if (errmsg)
    {
      simple_object_release_write (dest_sobj);
      return errmsg;
    }

  outfd = creat (dest, 00777);
  if (outfd == -1)
    {
      *err = errno;
      simple_object_release_write (dest_sobj);
      return "open failed";
    }

  errmsg = simple_object_write_to_file (dest_sobj, outfd, err);
  close (outfd);
  if (errmsg)
    {
      simple_object_release_write (dest_sobj);
      return errmsg;
    }

  simple_object_release_write (dest_sobj);
  return NULL;
}

/* Fetch attributes.  */

simple_object_attributes *
simple_object_fetch_attributes (simple_object_read *sobj, const char **errmsg,
				int *err)
{
  void *data;
  simple_object_attributes *ret;

  data = sobj->functions->fetch_attributes (sobj, errmsg, err);
  if (data == NULL)
    return NULL;
  ret = XNEW (simple_object_attributes);
  ret->functions = sobj->functions;
  ret->data = data;
  return ret;
}

/* Release an simple_object_read.  */

void
simple_object_release_read (simple_object_read *sobj)
{
  sobj->functions->release_read (sobj->data);
  XDELETE (sobj);
}

/* Merge attributes.  */

const char *
simple_object_attributes_merge (simple_object_attributes *to,
				simple_object_attributes *from,
				int *err)
{
  if (to->functions != from->functions)
    {
      *err = 0;
      return "different object file format";
    }
  return to->functions->attributes_merge (to->data, from->data, err);
}

/* Release an attributes structure.  */

void
simple_object_release_attributes (simple_object_attributes *attrs)
{
  attrs->functions->release_attributes (attrs->data);
  XDELETE (attrs);
}

/* Start creating an object file.  */

simple_object_write *
simple_object_start_write (simple_object_attributes *attrs,
			   const char *segment_name, const char **errmsg,
			   int *err)
{
  void *data;
  simple_object_write *ret;

  data = attrs->functions->start_write (attrs->data, errmsg, err);
  if (data == NULL)
    return NULL;
  ret = XNEW (simple_object_write);
  ret->functions = attrs->functions;
  ret->segment_name = segment_name ? xstrdup (segment_name) : NULL;
  ret->sections = NULL;
  ret->last_section = NULL;
  ret->data = data;
  return ret;
}

/* Start creating a section.  */

simple_object_write_section *
simple_object_write_create_section (simple_object_write *sobj, const char *name,
				    unsigned int align,
				    const char **errmsg ATTRIBUTE_UNUSED,
				    int *err ATTRIBUTE_UNUSED)
{
  simple_object_write_section *ret;

  ret = XNEW (simple_object_write_section);
  ret->next = NULL;
  ret->name = xstrdup (name);
  ret->align = align;
  ret->buffers = NULL;
  ret->last_buffer = NULL;

  if (sobj->last_section == NULL)
    {
      sobj->sections = ret;
      sobj->last_section = ret;
    }
  else
    {
      sobj->last_section->next = ret;
      sobj->last_section = ret;
    }

  return ret;
}

/* Add data to a section.  */

const char *
simple_object_write_add_data (simple_object_write *sobj ATTRIBUTE_UNUSED,
			      simple_object_write_section *section,
			      const void *buffer,
			      size_t size, int copy,
			      int *err ATTRIBUTE_UNUSED)
{
  struct simple_object_write_section_buffer *wsb;

  wsb = XNEW (struct simple_object_write_section_buffer);
  wsb->next = NULL;
  wsb->size = size;

  if (!copy)
    {
      wsb->buffer = buffer;
      wsb->free_buffer = NULL;
    }
  else
    {
      wsb->free_buffer = (void *) XNEWVEC (char, size);
      memcpy (wsb->free_buffer, buffer, size);
      wsb->buffer = wsb->free_buffer;
    }

  if (section->last_buffer == NULL)
    {
      section->buffers = wsb;
      section->last_buffer = wsb;
    }
  else
    {
      section->last_buffer->next = wsb;
      section->last_buffer = wsb;
    }

  return NULL;
}

/* Write the complete object file.  */

const char *
simple_object_write_to_file (simple_object_write *sobj, int descriptor,
			     int *err)
{
  return sobj->functions->write_to_file (sobj, descriptor, err);
}

/* Release an simple_object_write.  */

void
simple_object_release_write (simple_object_write *sobj)
{
  simple_object_write_section *section;

  free (sobj->segment_name);

  section = sobj->sections;
  while (section != NULL)
    {
      struct simple_object_write_section_buffer *buffer;
      simple_object_write_section *next_section;

      buffer = section->buffers;
      while (buffer != NULL)
	{
	  struct simple_object_write_section_buffer *next_buffer;

	  if (buffer->free_buffer != NULL)
	    XDELETEVEC (buffer->free_buffer);
	  next_buffer = buffer->next;
	  XDELETE (buffer);
	  buffer = next_buffer;
	}

      next_section = section->next;
      free (section->name);
      XDELETE (section);
      section = next_section;
    }

  sobj->functions->release_write (sobj->data);
  XDELETE (sobj);
}