elf.c File Reference

ELF image format. More...

#include <errno.h>
#include <elf.h>
#include <gpxe/uaccess.h>
#include <gpxe/segment.h>
#include <gpxe/image.h>
#include <gpxe/elf.h>

Go to the source code of this file.

Typedefs
typedef Elf32_Ehdr	Elf_Ehdr
typedef Elf32_Phdr	Elf_Phdr
typedef Elf32_Off	Elf_Off
Functions
	FILE_LICENCE (GPL2_OR_LATER)
static int	elf_load_segment (struct image *image, Elf_Phdr *phdr, Elf_Ehdr *ehdr)
	Load ELF segment into memory.
int	elf_load (struct image *image)
	Load ELF image into memory.

---

Detailed Description

ELF image format.

A "pure" ELF image is not a bootable image. There are various bootable formats based upon ELF (e.g. Multiboot), which share common ELF-related functionality.

Definition in file elf.c.

---

Typedef Documentation

typedef Elf32_Ehdr Elf_Ehdr

Definition at line 38 of file elf.c.

typedef Elf32_Phdr Elf_Phdr

Definition at line 39 of file elf.c.

typedef Elf32_Off Elf_Off

Definition at line 40 of file elf.c.

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static int elf_load_segment	(	struct image *	image,
		Elf_Phdr *	phdr,
		Elf_Ehdr *	ehdr
	)			[static]

Load ELF segment into memory.

Parameters:

	image	ELF file
	phdr	ELF program header
	ehdr	ELF executable header

Return values:

rc

Return status code

Definition at line 50 of file elf.c.

References image::data, DBGC, dest, Elf32_Ehdr::e_entry, ENOEXEC, image::len, memcpy_user(), Elf32_Phdr::p_filesz, Elf32_Phdr::p_memsz, Elf32_Phdr::p_offset, Elf32_Phdr::p_paddr, Elf32_Phdr::p_type, Elf32_Phdr::p_vaddr, image::phys, phys_to_user(), prep_segment(), image::priv, PT_LOAD, and strerror().

Referenced by elf_load().

                                               {
        physaddr_t dest;
        userptr_t buffer;
        unsigned long e_offset;
        int rc;

        /* Do nothing for non-PT_LOAD segments */
        if ( phdr->p_type != PT_LOAD )
                return 0;

        /* Check segment lies within image */
        if ( ( phdr->p_offset + phdr->p_filesz ) > image->len ) {
                DBGC ( image, "ELF %p segment outside image\n", image );
                return -ENOEXEC;
        }

        /* Find start address: use physical address for preference,
         * fall back to virtual address if no physical address
         * supplied.
         */
        dest = phdr->p_paddr;
        if ( ! dest )
                dest = phdr->p_vaddr;
        if ( ! dest ) {
                DBGC ( image, "ELF %p segment loads to physical address 0\n",
                       image );
                return -ENOEXEC;
        }
        buffer = phys_to_user ( dest );

        DBGC ( image, "ELF %p loading segment [%x,%x) to [%x,%x,%x)\n", image,
               phdr->p_offset, ( phdr->p_offset + phdr->p_filesz ),
               phdr->p_paddr, ( phdr->p_paddr + phdr->p_filesz ),
               ( phdr->p_paddr + phdr->p_memsz ) );

        /* Verify and prepare segment */
        if ( ( rc = prep_segment ( buffer, phdr->p_filesz,
                                   phdr->p_memsz ) ) != 0 ) {
                DBGC ( image, "ELF %p could not prepare segment: %s\n",
                       image, strerror ( rc ) );
                return rc;
        }

        /* Copy image to segment */
        memcpy_user ( buffer, 0, image->data, phdr->p_offset, phdr->p_filesz );

        /* Set execution address, if it lies within this segment */
        if ( ( e_offset = ( ehdr->e_entry - dest ) ) < phdr->p_filesz ) {
                image->priv.phys = ehdr->e_entry;
                DBGC ( image, "ELF %p found physical entry point at %lx\n",
                       image, image->priv.phys );
        } else if ( ( e_offset = ( ehdr->e_entry - phdr->p_vaddr ) )
                    < phdr->p_filesz ) {
                if ( ! image->priv.phys ) {
                        image->priv.phys = ( dest + e_offset );
                        DBGC ( image, "ELF %p found virtual entry point at %lx"
                               " (virt %lx)\n", image, image->priv.phys,
                               ( ( unsigned long ) ehdr->e_entry ) );
                }
        }

        return 0;
}

int elf_load

(

struct image *

image

)

Load ELF image into memory.

Parameters:

image

ELF file

Return values:

rc

Return status code

Definition at line 121 of file elf.c.

References assert, copy_from_user(), image::data, DBGC, Elf32_Ehdr::e_entry, Elf32_Ehdr::e_ident, Elf32_Ehdr::e_phentsize, Elf32_Ehdr::e_phnum, Elf32_Ehdr::e_phoff, EI_MAG0, elf_load_segment(), ELFMAG, ENOEXEC, image::len, memcmp(), NULL, image::phys, image::priv, SELFMAG, and image::type.

Referenced by elfboot_load(), and multiboot_load_elf().

                                     {
        Elf_Ehdr ehdr;
        Elf_Phdr phdr;
        Elf_Off phoff;
        unsigned int phnum;
        int rc;

        /* Image type must already have been set by caller */
        assert ( image->type != NULL );

        /* Read ELF header */
        copy_from_user ( &ehdr, image->data, 0, sizeof ( ehdr ) );
        if ( memcmp ( &ehdr.e_ident[EI_MAG0], ELFMAG, SELFMAG ) != 0 ) {
                DBGC ( image, "ELF %p has invalid signature\n", image );
                return -ENOEXEC;
        }

        /* Invalidate execution address */
        image->priv.phys = 0;

        /* Read ELF program headers */
        for ( phoff = ehdr.e_phoff , phnum = ehdr.e_phnum ; phnum ;
              phoff += ehdr.e_phentsize, phnum-- ) {
                if ( phoff > image->len ) {
                        DBGC ( image, "ELF %p program header %d outside "
                               "image\n", image, phnum );
                        return -ENOEXEC;
                }
                copy_from_user ( &phdr, image->data, phoff, sizeof ( phdr ) );
                if ( ( rc = elf_load_segment ( image, &phdr, &ehdr ) ) != 0 )
                        return rc;
        }

        /* Check for a valid execution address */
        if ( ! image->priv.phys ) {
                DBGC ( image, "ELF %p entry point %lx outside image\n",
                       image, ( ( unsigned long ) ehdr.e_entry ) );
                return -ENOEXEC;
        }

        return 0;
}