GELF_XLATETOF(3)

GELF_XLATETOF(3) | Library Functions Manual | GELF_XLATETOF(3)

# NAME

`elf32_xlate`, `elf64_xlate`, `gelf_xlate` —
translate data between files and memory

# LIBRARY

ELF Access Library (libelf, -lelf)

# SYNOPSIS

`#include <libelf.h>`

Elf_Data *
`elf32_xlatetof`(Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

Elf_Data *
`elf32_xlatetom`(Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

Elf_Data *
`elf64_xlatetof`(Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

Elf_Data *
`elf64_xlatetom`(Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

`#include <gelf.h>`

Elf_Data *
`gelf_xlatetof`(Elf *elf, Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

Elf_Data *
`gelf_xlatetom`(Elf *elf, Elf_Data *dst, Elf_Data *src, unsigned int file_encoding);

# DESCRIPTION

These functions translate between the file and memory representations of ELF data structures. The in-memory representation of an ELF data structure would conform to the byte ordering and data alignment restrictions dictated by the host processor. As described in elf(3), the file representation of this data structure could use a different byte ordering from that of the host, or could use a different layout within the file.

Functions `elf32_xlatetom`(), `elf64_xlatetom`(), and `gelf_xlatetom`() translate data from file representations to native, in-memory representations. Functions `elf32_xlatetof`(), `elf64_xlatetof`(), and `gelf_xlatetof`() translate data from in-memory representations to file representations.

Argument src denotes an Elf_Data descriptor describing the source to be translated. The following elements of the descriptor need to be set before invoking these functions:

d_buf
  Set to a valid pointer value denoting the beginning of the data area to be translated.
d_size
  Set to the total size in bytes of the source data area to be translated.
d_type
  Set to the type of the source data being translated. This value is one of the values defined in the Elf_Type enumeration. The Elf_Type enumeration is described in elf(3).
d_version
  Set to the version number of the ELF data structures being translated. Currently only version `EV_CURRENT` is supported.

Argument dst describes the destination buffer. The following elements of the Elf_Data descriptor need to be set before invoking these functions:

d_buf
  Set to a valid pointer value that denotes the start of the destination buffer that will hold translated data. This value may be the same as that of the source buffer, in which case an in-place conversion will be attempted.
d_size
  Set to the size of the destination buffer in bytes. This value will be modified if the function call succeeds.
d_version
  Set to the desired version number of the destination. Currently only version `EV_CURRENT` is supported.

These translations routines allow the source and destination buffers to coincide, in which case an in-place translation will be done if the destination is large enough to hold the translated data. Other kinds of overlap between the source and destination buffers are not permitted.

On successful completion of the translation request the following fields of the dst descriptor would be modified:

d_size
  Set to the size in bytes of the translated data.
d_type
  Set to the d_type value of the source data descriptor.

Argument file_encoding specifies the encoding in which the file objects are represented. It must be one of:

`ELFDATANONE`
  File objects use the library's native byte ordering.
`ELFDATA2LSB`
  File objects use a little-endian ordering.
`ELFDATA2MSB`
  File objects use a big-endian ordering.

The functions `gelf_xlatetof`() and `gelf_xlatetom`() select the appropriate translation scheme based on the properties of argument elf.

# RETURN VALUES

These functions return argument dst if successful, or `NULL` in case of an error.

# EXAMPLES

To translate a GElf_Rel structure to its LSB file representation use:

    Elf_Data dst, src;
    GElf_Rel rel;
    Elf *e;

    e = ...; /* See elf_begin(3). */

    /* Set up the 'src' descriptor. */
    memset(&src, 0, sizeof src);
    src.d_buf = &rel;
    src.d_size = sizeof(rel);
    src.d_type = ELF_T_REL;
    src.d_version = EV_CURRENT;

    /* Set up the 'dst' descriptor. */
    memset(&dst, 0, sizeof dst);
    dst.d_buf = filebuf;
    dst.d_size = gelf_fsize(e, ELF_T_REL, 1, EV_CURRENT);
    dst.d_version = EV_CURRENT;

    if (gelf_xlatetof(e, &dst, &src, ELFDATA2LSB) == NULL) {
    	printf("error: %s", elf_errmsg(0));
    }

# ERRORS

These functions may fail with the following errors:

[`ELF_E_ARGUMENT`]
  One of arguments src, dst or elf was `NULL`.
[`ELF_E_ARGUMENT`]
  Arguments src and dst were equal.
[`ELF_E_ARGUMENT`]
  The desired encoding parameter was not one of `ELFDATANONE`, `ELFDATA2LSB` or `ELFDATA2MSB`.
[`ELF_E_ARGUMENT`]
  The d_type field of argument src specified an unsupported type.
[`ELF_E_DATA`]
  The src argument specified a buffer size that was not an integral multiple of its underlying type.
[`ELF_E_DATA`]
  The dst argument specified a buffer size that was too small.
[`ELF_E_DATA`]
  Argument dst specified a destination buffer that overlaps with the source buffer.
[`ELF_E_DATA`]
  The destination buffer for a conversion to memory had an alignment inappropriate for the underlying ELF type.
[`ELF_E_DATA`]
  The source buffer for a conversion to file had an alignment inappropriate for the underlying ELF type.
[`ELF_E_UNIMPL`]
  The version numbers for arguments dst and src were not identical.
[`ELF_E_UNIMPL`]
  The argument src requested conversion for a type which is not currently supported.
[`ELF_E_VERSION`]
  Argument src specified an unsupported version number.

# SEE ALSO

elf(3), elf_getdata(3), gelf(3)

October 11, 2018 | NetBSD 10.1