source: trunk/kernel/libk/elf.c @ 219

/*
 * elf.c - elf parser: find and map process CODE and DATA segments
 *
 * Authors   Alain Greiner    (2016)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH 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; version 2.0 of the License.
 *
 * ALMOS-MKH 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 ALMOS-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <kernel_config.h>
#include <hal_types.h>
#include <hal_uspace.h>
#include <printk.h>
#include <process.h>
#include <vseg.h>
#include <kmem.h>
#include <vfs.h>
#include <elf.h>
#include <syscalls.h>

///////////////////////////////////////////////////////////////////
// This static function checks the .elf header.
// - return true if legal header.
// - return false with an error message if illegal header.
///////////////////////////////////////////////////////////////////
static bool_t elf_isValidHeader(Elf32_Ehdr *header)
{
        if((header->e_ident[EI_CLASS] == ELFCLASS32)
           && (header->e_ident[EI_DATA] == ELFDATA2LSB)
           && (header->e_ident[EI_VERSION] == EV_CURRENT)
           && (header->e_ident[EI_OSABI] == ELFOSABI_NONE)
           && ((header->e_machine == EM_MIPS) ||
               (header->e_machine == EM_MIPS_RS3_LE) ||
               (header->e_machine == EM_X86_64))
           && (header->e_type == ET_EXEC))
                return true;

        if( header->e_ident[EI_CLASS] != ELFCLASS32 )
                printk("\n[ERROR] in %s : Elf is not 32-Binary\n", __FUNCTION__ );

        if( header->e_ident[EI_DATA] != ELFDATA2LSB )
                printk("\n[ERROR] in %s : Elf is not 2's complement, little endian\n", __FUNCTION__ );

        if( header->e_ident[EI_VERSION] != EV_CURRENT )
                printk("\n[ERROR] in %s : Elf is not in Current Version\n", __FUNCTION__);

        if( header->e_ident[EI_OSABI] != ELFOSABI_NONE )
                printk("\n[ERROR] in %s : Unexpected Elf ABI, need UNIX System V ABI\n", __FUNCTION__ );

        if( (header->e_machine == EM_MIPS) ||
            (header->e_machine == EM_MIPS_RS3_LE) ||
            (header->e_machine == EM_X86_64) )
                printk("\n[ERROR] in %s : unexpected core / accept only MIPS or x86_64\n", __FUNCTION__ );

        if( header->e_type == ET_EXEC )
                printk("\n[ERROR] in %s : Elf is not executable binary\n", __FUNCTION__ );

        return false;
}

///////////////////////////////////////////////////////////////////////////////////////
// This function loads the .elf header in the buffer allocated by the caller.
///////////////////////////////////////////////////////////////////////////////////////
// @ file   : extended pointer on the remote file descriptor.
// @ buffer : pointer on buffer allocated by the caller.
// @ size   : number of bytes to read.
///////////////////////////////////////////////////////////////////////////////////////
static error_t elf_header_load( xptr_t   file_xp,
                                void   * buffer,
                                uint32_t size )
{
        uint32_t  count;

        // load .elf header
        count = vfs_move( true ,
                          file_xp,
                          buffer,
                          size );

        if( count != size )
        {
                printk("\n[ERROR] in %s : failed to read ELF header\n", __FUNCTION__ );
                return -1;
        }

        Elf32_Ehdr * header = (Elf32_Ehdr *)buffer;

        if( (header->e_ident[EI_MAG0] != ELFMAG0) ||
            (header->e_ident[EI_MAG1] != ELFMAG1) ||
            (header->e_ident[EI_MAG2] != ELFMAG2) ||
            (header->e_ident[EI_MAG3] != ELFMAG3) )
        {
                printk("\n[ERROR] in %s : file %s not in ELF format\n", __FUNCTION__ );
                return -1;
        }

        if( !(elf_isValidHeader( header ) ) )
        {
                printk("\n[ERROR] in %s : not supported Elf\n", __FUNCTION__ );
                return -1;
        }
        return 0;

} // end elf_header_load()

///////////////////////////////////////////////////////////////////////////////////////
// This function registers in the process VMM the CODE and DATA segments.
///////////////////////////////////////////////////////////////////////////////////////
// @ file      : extended pointer on the remote file descriptor.
// @ segs_base : local pointer on buffer containing the segments descriptors array
// @ segs_nr   : number of segments in segment descriptors array.
// @ process   : local pointer on process descriptor.
///////////////////////////////////////////////////////////////////////////////////////
static error_t elf_segments_load( xptr_t       file_xp,
                                  void       * segs_base,
                                  uint32_t     nb_segs,
                                  process_t  * process )
{
        error_t      error;
        uint32_t     index;
        uint32_t     file_size;
        uint32_t     mem_size;
        intptr_t     start;
        uint32_t     type;
        uint32_t     flags;
        uint32_t     offset;
        vseg_t     * vseg;

        Elf32_Phdr * seg_ptr = (Elf32_Phdr *)segs_base;

        // loop on segments
        for( index = 0 ; index < nb_segs ; index++ , seg_ptr++ )
        {
                if( seg_ptr->p_type != PT_LOAD)
                        continue;

                // get segment attributes
                start     = seg_ptr->p_vaddr;
                offset    = seg_ptr->p_offset;
                file_size = seg_ptr->p_filesz;
                mem_size  = seg_ptr->p_memsz;
                flags     = seg_ptr->p_flags;

                // check alignment
                if( start & CONFIG_PPM_PAGE_MASK )
                {
                        printk("\n[WARNING] in %s : segment base not aligned = %x\n",
                               __FUNCTION__, start );
                }

                // check size
                if( file_size != mem_size )
                {
                        printk("\n[WARNING] in %s : base = %x / mem_size = %x / file_size = %x\n",
                               __FUNCTION__, start , mem_size , file_size);
                }

                // set seek on segment base in file
                error = vfs_lseek( file_xp,
                                   offset,
                                   SEEK_SET,
                                   NULL );

                if( error )
                {
                        printk("\n[ERROR] in %s : failed to seek\n", __FUNCTION__ );
                        return -1;
                }

                if( flags & PF_X ) // found CODE segment
                {
                        type                       = VSEG_TYPE_CODE;
                        process->vmm.code_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;

                        elf_dmsg("\n[INFO] %s found CODE vseg / base = %x / size = %x\n",
                                 __FUNCTION__ , start , mem_size );
                }
                else               // found DATA segment
                {
                        type                       = VSEG_TYPE_DATA;
                        process->vmm.data_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;

                        elf_dmsg("\n[INFO] %s found DATA vseg / base = %x / size = %x\n",
                                 __FUNCTION__, start , mem_size );
                }

                // register vseg in VMM
                vseg = (vseg_t *)vmm_create_vseg( process,
                                                  start,
                                                  mem_size,
                                                  type );
                if( vseg == NULL )
                {
                        printk("\n[ERROR] in %s : cannot map segment / base = %x / size = %x\n",
                               __FUNCTION__ , start , mem_size );
                        return -1;
                }

                vfs_file_count_up( file_xp );
        }

        return 0;

} // end elf_segments_load()

///////////////////////////////////////////////
error_t elf_load_process( char      * pathname,
                          process_t * process)
{
        kmem_req_t   req;              // kmem request for program header
        Elf32_Ehdr   header;           // local buffer for .elf header
        void       * segs_base;        // pointer on buffer for segment descriptors array
        uint32_t     segs_size;        // size of buffer for segment descriptors array
        xptr_t       file_xp;          // extended pointer on created file descriptor
        uint32_t     file_id;          // file descriptor index (unused)
        uint32_t     count;            // bytes counter
        error_t      error;

    elf_dmsg("\n[INFO] %s : enter for %s\n", __FUNCTION__ , pathname );

    // avoid GCC warning
        file_xp = XPTR_NULL;  
        file_id = -1;

        // open file
        error = vfs_open( process->vfs_cwd_xp,
                          pathname,
                          O_RDONLY,
                          0,
                          &file_xp,
                          &file_id );
        if( error )
        {
                printk("\n[ERROR] in %s : failed to open file %s\n", __FUNCTION__ , pathname );
                return -1;
        }

    elf_dmsg("\n[INFO] %s : file %s open\n", __FUNCTION__ , pathname );

        // load header in local buffer
        error = elf_header_load( file_xp ,
                                 &header,
                                 sizeof(Elf32_Ehdr) );
        if( error )
        {
                printk("\n[ERROR] in %s : cannot get header file %s\n", __FUNCTION__ , pathname );
                vfs_close( file_xp , file_id );
                return -1;
        }

        elf_dmsg("\n[INFO] %s : loaded elf header for %s\n", __FUNCTION__ , pathname );

        if( header.e_phnum == 0 )
        {
                printk("\n[ERROR] in %s : no segments found\n", __FUNCTION__ );
                vfs_close( file_xp , file_id );
                return -1;
        }

        // compute buffer size for segment descriptors array
        segs_size = sizeof(Elf32_Phdr) * header.e_phnum;

        // allocate memory for segment descriptors array
        req.type  = KMEM_GENERIC;
        req.size  = segs_size;
        req.flags = AF_KERNEL;
        segs_base = kmem_alloc( &req );

        if( segs_base == NULL )
        {
                printk("\n[ERROR] in %s : no memory for segment descriptors\n", __FUNCTION__ );
                vfs_close( file_xp , file_id );
                return -1;
        }

        // set seek pointer in file descriptor to access segment descriptors array
        error = vfs_lseek( file_xp , header.e_phoff, SEEK_SET , NULL );

        if( error )
        {
                printk("\n[ERROR] in %s : cannot seek for descriptors array\n", __FUNCTION__ );
                vfs_close( file_xp , file_id );
                req.ptr = segs_base;
                kmem_free( &req );
                return -1;
        }

        // load seg descriptors array to local buffer
        count = vfs_move( true,
                          file_xp,
                          segs_base,
                          segs_size );

        if( count != segs_size )
        {
                printk("\n[ERROR] in %s : cannot read segments descriptors\n", __FUNCTION__ );
                vfs_close( file_xp , file_id );
                req.ptr = segs_base;
                kmem_free( &req );
                return -1;
        }

        elf_dmsg("\n[INFO] %s loaded segments descriptors for %s \n", __FUNCTION__ , pathname );

        // register loadable segments in process VMM
        error = elf_segments_load( file_xp,
                                   segs_base,
                                   header.e_phnum,
                                   process );
        if( error )
        {
                vfs_close( file_xp , file_id );
                req.ptr = segs_base;
                kmem_free( &req );
                return -1;
        }

        // register process entry point in VMM
        process->vmm.entry_point = (intptr_t)header.e_entry;

        // register extended pointer on .elf file descriptor
        process->vfs_bin_xp = file_xp;

        // release allocated memory for program header
        req.ptr = segs_base;
        kmem_free(&req);

        elf_dmsg("\n[INFO] %s successfully completed / entry point = %x for %s]\n",
                 __FUNCTION__, (uint32_t) header.e_entry , pathname );

        return 0;

}  // end elf_load_process()