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source: trunk/kernel/libk/elf.c @ 36

Last change on this file since 36 was 23, checked in by alain, 8 years ago
Introduce syscalls.
File size: 10.9 KB

Rev	Line
[1]	1	/*
	2	* elf.c - elf parser: find and map process CODE and DATA segments
	3	*
	4	* Authors Alain Greiner (2016)
	5	*
	6	* Copyright (c) UPMC Sorbonne Universites
	7	*
	8	* This file is part of ALMOS-MKH.
	9	*
	10	* ALMOS-MKH is free software; you can redistribute it and/or modify it
	11	* under the terms of the GNU General Public License as published by
	12	* the Free Software Foundation; version 2.0 of the License.
	13	*
	14	* ALMOS-MKH is distributed in the hope that it will be useful, but
	15	* WITHOUT ANY WARRANTY; without even the implied warranty of
	16	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	17	* General Public License for more details.
	18	*
	19	* You should have received a copy of the GNU General Public License
	20	* along with ALMOS-MKH; if not, write to the Free Software Foundation,
	21	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	22	*/
	23
[14]	24	#include <kernel_config.h>
[1]	25	#include <hal_types.h>
	26	#include <hal_uspace.h>
	27	#include <printk.h>
	28	#include <process.h>
	29	#include <vseg.h>
	30	#include <kmem.h>
	31	#include <vfs.h>
	32	#include <elf.h>
[23]	33	#include <syscalls.h>
[1]	34
	35
	36	///////////////////////////////////////////////////////////////////
	37	// This static function checks the .elf header.
	38	// - return true if legal header.
	39	// - return false with an error message if illegal header.
	40	///////////////////////////////////////////////////////////////////
	41	static bool_t elf_isValidHeader(Elf32_Ehdr *header)
	42	{
	43	if((header->e_ident[EI_CLASS] == ELFCLASS32)
	44	&& (header->e_ident[EI_DATA] == ELFDATA2LSB)
	45	&& (header->e_ident[EI_VERSION] == EV_CURRENT)
	46	&& (header->e_ident[EI_OSABI] == ELFOSABI_NONE)
	47	&& ((header->e_machine == EM_MIPS) \|\|
	48	(header->e_machine == EM_MIPS_RS3_LE) \|\|
	49	(header->e_machine == EM_386))
	50	&& (header->e_type == ET_EXEC)) return true;
	51
	52	if( header->e_ident[EI_CLASS] != ELFCLASS32 )
	53	printk("\n[ERROR] in %s : Elf is not 32-Binary\n", __FUNCTION__ );
	54
	55	if( header->e_ident[EI_DATA] != ELFDATA2LSB )
	56	printk("\n[ERROR] in %s : Elf is not 2's complement, little endian\n", __FUNCTION__ );
	57
	58	if( header->e_ident[EI_VERSION] != EV_CURRENT )
	59	printk("\n[ERROR] in %s : Elf is not in Current Version\n", __FUNCTION__);
	60
	61	if( header->e_ident[EI_OSABI] != ELFOSABI_NONE )
	62	printk("\n[ERROR] in %s : Unexpected Elf ABI, need UNIX System V ABI\n", __FUNCTION__ );
	63
	64	if( (header->e_machine == EM_MIPS) \|\|
	65	(header->e_machine == EM_MIPS_RS3_LE) \|\|
	66	(header->e_machine == EM_386) )
	67	printk("\n[ERROR] in %s : unexpected core / accept only MIPS or 80386\n", __FUNCTION__ );
	68
	69	if( header->e_type == ET_EXEC )
	70	printk("\n[ERROR] in %s : Elf is not executable binary\n", __FUNCTION__ );
	71
	72	return false;
	73	}
	74
	75	///////////////////////////////////////////////////////////////////////////////////////
	76	// This function load the .elf header in the buffer allocated by the caller.
	77	// @ file : extended pointer on the remote file descriptor.
	78	// @ buffer : pointer on buffer allocated by the caller.
	79	// @ size : number of bytes to read.
	80	///////////////////////////////////////////////////////////////////////////////////////
	81	static error_t elf_header_read( xptr_t file_xp,
	82	void * buffer,
	83	uint32_t size )
	84	{
	85	uint32_t count;
	86
	87	// load .elf header
[23]	88	count = vfs_move( true ,
	89	file_xp,
	90	buffer,
	91	size );
[1]	92
	93	if( count != size )
	94	{
	95	printk("\n[ERROR] in %s : failed to read ELF header\n", __FUNCTION__ );
	96	return -1;
	97	}
	98
	99	Elf32_Ehdr * header = (Elf32_Ehdr *)buffer;
	100
	101	if( (header->e_ident[EI_MAG0] != ELFMAG0) \|\|
	102	(header->e_ident[EI_MAG1] != ELFMAG1) \|\|
	103	(header->e_ident[EI_MAG2] != ELFMAG2) \|\|
	104	(header->e_ident[EI_MAG3] != ELFMAG3) )
	105	{
	106	printk("\n[ERROR] in %s : file %s not in ELF format\n", __FUNCTION__ );
	107	return -1;
	108	}
	109
	110	if( !(elf_isValidHeader( header ) ) )
	111	{
	112	printk("\n[ERROR] in %s : not supported Elf\n", __FUNCTION__ );
	113	return -1;
	114	}
	115	return 0;
	116	} // end elf_header_read()
	117
	118	///////////////////////////////////////////////////////////////////////////////////////
	119	// This function registers in the process VMM the CODE and DATA segments.
	120	// @ file : extended pointer on the remote file descriptor.
	121	// @ segs_base : local pointer on buffer containing the segments descriptors array
	122	// @ segs_nr : number of segments in segment descriptors array.
	123	// @ process : local pointer on process descriptor.
	124	///////////////////////////////////////////////////////////////////////////////////////
	125	static error_t elf_segments_load( xptr_t file_xp,
	126	void * segs_base,
	127	uint32_t nb_segs,
	128	process_t * process )
	129	{
	130	error_t error;
	131	uint32_t index;
	132	uint32_t file_size;
	133	uint32_t mem_size;
	134	intptr_t start;
	135	uint32_t type;
	136	uint32_t flags;
	137	uint32_t offset;
	138	vseg_t * vseg;
	139
	140	Elf32_Phdr * seg_ptr = (Elf32_Phdr *)segs_base;
	141
	142	// loop on segments
	143	for( index = 0 ; index < nb_segs ; index++ , seg_ptr++ )
	144	{
	145	if( seg_ptr->p_type != PT_LOAD) continue;
	146
	147	// get segment attributes
	148	start = seg_ptr->p_vaddr;
	149	offset = seg_ptr->p_offset;
	150	file_size = seg_ptr->p_filesz;
	151	mem_size = seg_ptr->p_memsz;
	152	flags = seg_ptr->p_flags;
	153
	154	// check alignment
	155	if( start & CONFIG_PPM_PAGE_MASK )
	156	{
	157	printk("\n[WARNING] in %s : segment base not aligned = %x\n",
	158	__FUNCTION__, start );
	159	}
	160
	161	// check size
	162	if( file_size != mem_size )
	163	{
	164	printk("\n[WARNING] in %s : base = %x / mem_size = %x / file_size = %x\n",
	165	__FUNCTION__, start , mem_size , file_size);
	166	}
	167
	168	// set seek on segment base in file
[23]	169	error = vfs_lseek( file_xp,
	170	offset,
	171	SEEK_SET,
	172	NULL );
[1]	173
	174	if( error )
	175	{
	176	printk("\n[ERROR] in %s : failed to seek\n", __FUNCTION__ );
	177	return -1;
	178	}
	179
	180	if( flags & PF_X ) // found CODE segment
	181	{
	182	type = VSEG_TYPE_CODE;
	183	process->vmm.code_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;
	184
	185	elf_dmsg("\n[INFO] %s found CODE vseg / base = %x / size = %x\n",
	186	__FUNCTION__ , start , mem_size );
	187	}
	188	else // found DATA segment
	189	{
	190	type = VSEG_TYPE_DATA;
	191	process->vmm.data_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;
	192
	193	elf_dmsg("\n[INFO] %s found DATA vseg / base = %x / size = %x\n",
	194	__FUNCTION__, start , mem_size );
	195	}
	196
	197	// register vseg in VMM
	198	vseg = (vseg_t *)vmm_create_vseg( process,
	199	start,
	200	mem_size,
	201	type );
	202	if( vseg == NULL )
	203	{
	204	printk("\n[ERROR] in %s : cannot map segment / base = %x / size = %x\n",
	205	__FUNCTION__ , start , mem_size );
	206	return -1;
	207	}
	208
	209	vfs_file_count_up( file_xp );
	210	}
	211
	212	return 0;
	213	} // end elf_load_segments()
	214
	215	///////////////////////////////////////////////
	216	error_t elf_load_process( char * pathname,
	217	process_t * process)
	218	{
[23]	219	char path_copy[CONFIG_VFS_MAX_PATH_LENGTH];
[1]	220	kmem_req_t req; // kmem request for program header
	221	uint32_t length; // actual path length
	222	Elf32_Ehdr header; // local buffer for .elf header
	223	void * segs_base; // pointer on buffer for segment descriptors array
	224	uint32_t segs_size; // size of buffer for segment descriptors array
	225	xptr_t file_xp; // extended pointer on created file descriptor
[23]	226	uint32_t file_id; // file descriptor index (unused)
[1]	227	uint32_t count; // bytes counter
	228	error_t error;
	229
	230	// get path length from user space
	231	length = hal_strlen_from_uspace( pathname );
	232
[23]	233	if( length >= CONFIG_VFS_MAX_PATH_LENGTH )
[1]	234	{
	235	printk("\n[ERROR] in %s : pathname length too long\n", __FUNCTION__ );
	236	return -1;
	237	}
	238
	239	// make a local copy for pathname
	240	hal_copy_from_uspace( path_copy , pathname , length+1 );
	241
	242	// open file
	243	file_xp = XPTR_NULL; // avoid GCC warning
[23]	244	file_id = -1;
[1]	245
	246	error = vfs_open( process->vfs_cwd_xp,
	247	path_copy,
[23]	248	O_RDONLY,
	249	0,
	250	&file_xp,
	251	&file_id );
[1]	252	if( error )
	253	{
	254	printk("\n[ERROR] in %s : failed to open executable file %s\n",
	255	__FUNCTION__ , path_copy );
	256	return -1;
	257	}
	258
	259	// load header in local buffer
	260	error = elf_header_read( file_xp ,
	261	&header,
	262	sizeof(Elf32_Ehdr) );
	263	if( error )
	264	{
[23]	265	vfs_close( file_xp , file_id );
[1]	266	return -1;
	267	}
	268
	269	elf_dmsg("\n[INFO] %s loaded elf header for %s\n", __FUNCTION__ , path_copy );
	270
	271	if( header.e_phnum == 0 )
	272	{
	273	printk("\n[ERROR] in %s : no segments found\n", __FUNCTION__ );
[23]	274	vfs_close( file_xp , file_id );
[1]	275	return -1;
	276	}
	277
	278	// compute buffer size for segment descriptors array
	279	segs_size = sizeof(Elf32_Phdr) * header.e_phnum;
	280
	281	// allocate memory for segment descriptors array
	282	req.type = KMEM_GENERIC;
	283	req.size = segs_size;
	284	req.flags = AF_KERNEL;
	285	segs_base = kmem_alloc( &req );
	286
	287	if( segs_base == NULL )
	288	{
	289	printk("\n[ERROR] in %s : no memory for segment descriptors\n", __FUNCTION__ );
[23]	290	vfs_close( file_xp , file_id );
[1]	291	return -1;
	292	}
	293
	294	// set seek pointer in file descriptor to access segment descriptors array
[23]	295	error = vfs_lseek( file_xp , header.e_phoff, SEEK_SET , NULL );
[1]	296
	297	if( error )
	298	{
	299	printk("\n[ERROR] in %s : cannot seek for descriptors array\n", __FUNCTION__ );
[23]	300	vfs_close( file_xp , file_id );
[1]	301	req.ptr = segs_base;
	302	kmem_free( &req );
	303	return -1;
	304	}
	305
	306	// load seg descriptors array to local buffer
[23]	307	count = vfs_move( true,
	308	file_xp,
[1]	309	segs_base,
	310	segs_size );
	311
	312	if( count != segs_size )
	313	{
	314	printk("\n[ERROR] in %s : cannot read segments descriptors\n", __FUNCTION__ );
[23]	315	vfs_close( file_xp , file_id );
[1]	316	req.ptr = segs_base;
	317	kmem_free( &req );
	318	return -1;
	319	}
	320
	321	elf_dmsg("\n[INFO] %s loaded segments descriptors for %s \n", __FUNCTION__ , path_copy );
	322
	323	// register loadable segments in process VMM
	324	error = elf_segments_load( file_xp,
	325	segs_base,
	326	header.e_phnum,
	327	process );
	328	if( error )
	329	{
[23]	330	vfs_close( file_xp , file_id );
[1]	331	req.ptr = segs_base;
	332	kmem_free( &req );
	333	return -1;
	334	}
	335
	336	// register process entry point in VMM
	337	process->vmm.entry_point = (intptr_t)header.e_entry;
	338
	339	// register extended pointer on .elf file descriptor
	340	process->vfs_bin_xp = file_xp;
	341
	342	// release allocated memory for program header
	343	req.ptr = segs_base;
	344	kmem_free(&req);
	345
	346	elf_dmsg("\n[INFO] %s successfully completed / entry point = %x for %s]\n",
	347	__FUNCTION__, (uint32_t) header.e_entry , path_copy );
	348
	349	return 0;
	350	} // end elf_load_process()
	351

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