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source: trunk/kernel/libk/elf.c @ 12

Last change on this file since 12 was 1, checked in by alain, 8 years ago
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[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
	24	#include <almos_config.h>
	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>
	33
	34
	35	///////////////////////////////////////////////////////////////////
	36	// This static function checks the .elf header.
	37	// - return true if legal header.
	38	// - return false with an error message if illegal header.
	39	///////////////////////////////////////////////////////////////////
	40	static bool_t elf_isValidHeader(Elf32_Ehdr *header)
	41	{
	42	if((header->e_ident[EI_CLASS] == ELFCLASS32)
	43	&& (header->e_ident[EI_DATA] == ELFDATA2LSB)
	44	&& (header->e_ident[EI_VERSION] == EV_CURRENT)
	45	&& (header->e_ident[EI_OSABI] == ELFOSABI_NONE)
	46	&& ((header->e_machine == EM_MIPS) \|\|
	47	(header->e_machine == EM_MIPS_RS3_LE) \|\|
	48	(header->e_machine == EM_386))
	49	&& (header->e_type == ET_EXEC)) return true;
	50
	51	if( header->e_ident[EI_CLASS] != ELFCLASS32 )
	52	printk("\n[ERROR] in %s : Elf is not 32-Binary\n", __FUNCTION__ );
	53
	54	if( header->e_ident[EI_DATA] != ELFDATA2LSB )
	55	printk("\n[ERROR] in %s : Elf is not 2's complement, little endian\n", __FUNCTION__ );
	56
	57	if( header->e_ident[EI_VERSION] != EV_CURRENT )
	58	printk("\n[ERROR] in %s : Elf is not in Current Version\n", __FUNCTION__);
	59
	60	if( header->e_ident[EI_OSABI] != ELFOSABI_NONE )
	61	printk("\n[ERROR] in %s : Unexpected Elf ABI, need UNIX System V ABI\n", __FUNCTION__ );
	62
	63	if( (header->e_machine == EM_MIPS) \|\|
	64	(header->e_machine == EM_MIPS_RS3_LE) \|\|
	65	(header->e_machine == EM_386) )
	66	printk("\n[ERROR] in %s : unexpected core / accept only MIPS or 80386\n", __FUNCTION__ );
	67
	68	if( header->e_type == ET_EXEC )
	69	printk("\n[ERROR] in %s : Elf is not executable binary\n", __FUNCTION__ );
	70
	71	return false;
	72	}
	73
	74	///////////////////////////////////////////////////////////////////////////////////////
	75	// This function load the .elf header in the buffer allocated by the caller.
	76	// @ file : extended pointer on the remote file descriptor.
	77	// @ buffer : pointer on buffer allocated by the caller.
	78	// @ size : number of bytes to read.
	79	///////////////////////////////////////////////////////////////////////////////////////
	80	static error_t elf_header_read( xptr_t file_xp,
	81	void * buffer,
	82	uint32_t size )
	83	{
	84	uint32_t count;
	85
	86	// load .elf header
	87	count = vfs_read( file_xp , buffer , size );
	88
	89	if( count != size )
	90	{
	91	printk("\n[ERROR] in %s : failed to read ELF header\n", __FUNCTION__ );
	92	return -1;
	93	}
	94
	95	Elf32_Ehdr * header = (Elf32_Ehdr *)buffer;
	96
	97	if( (header->e_ident[EI_MAG0] != ELFMAG0) \|\|
	98	(header->e_ident[EI_MAG1] != ELFMAG1) \|\|
	99	(header->e_ident[EI_MAG2] != ELFMAG2) \|\|
	100	(header->e_ident[EI_MAG3] != ELFMAG3) )
	101	{
	102	printk("\n[ERROR] in %s : file %s not in ELF format\n", __FUNCTION__ );
	103	return -1;
	104	}
	105
	106	if( !(elf_isValidHeader( header ) ) )
	107	{
	108	printk("\n[ERROR] in %s : not supported Elf\n", __FUNCTION__ );
	109	return -1;
	110	}
	111	return 0;
	112	} // end elf_header_read()
	113
	114	///////////////////////////////////////////////////////////////////////////////////////
	115	// This function registers in the process VMM the CODE and DATA segments.
	116	// @ file : extended pointer on the remote file descriptor.
	117	// @ segs_base : local pointer on buffer containing the segments descriptors array
	118	// @ segs_nr : number of segments in segment descriptors array.
	119	// @ process : local pointer on process descriptor.
	120	///////////////////////////////////////////////////////////////////////////////////////
	121	static error_t elf_segments_load( xptr_t file_xp,
	122	void * segs_base,
	123	uint32_t nb_segs,
	124	process_t * process )
	125	{
	126	error_t error;
	127	uint32_t index;
	128	uint32_t file_size;
	129	uint32_t mem_size;
	130	intptr_t start;
	131	uint32_t type;
	132	uint32_t flags;
	133	uint32_t offset;
	134	vseg_t * vseg;
	135
	136	Elf32_Phdr * seg_ptr = (Elf32_Phdr *)segs_base;
	137
	138	// loop on segments
	139	for( index = 0 ; index < nb_segs ; index++ , seg_ptr++ )
	140	{
	141	if( seg_ptr->p_type != PT_LOAD) continue;
	142
	143	// get segment attributes
	144	start = seg_ptr->p_vaddr;
	145	offset = seg_ptr->p_offset;
	146	file_size = seg_ptr->p_filesz;
	147	mem_size = seg_ptr->p_memsz;
	148	flags = seg_ptr->p_flags;
	149
	150	// check alignment
	151	if( start & CONFIG_PPM_PAGE_MASK )
	152	{
	153	printk("\n[WARNING] in %s : segment base not aligned = %x\n",
	154	__FUNCTION__, start );
	155	}
	156
	157	// check size
	158	if( file_size != mem_size )
	159	{
	160	printk("\n[WARNING] in %s : base = %x / mem_size = %x / file_size = %x\n",
	161	__FUNCTION__, start , mem_size , file_size);
	162	}
	163
	164	// set seek on segment base in file
	165	error = vfs_lseek( file_xp , offset , VFS_SEEK_SET , NULL );
	166
	167	if( error )
	168	{
	169	printk("\n[ERROR] in %s : failed to seek\n", __FUNCTION__ );
	170	return -1;
	171	}
	172
	173	if( flags & PF_X ) // found CODE segment
	174	{
	175	type = VSEG_TYPE_CODE;
	176	process->vmm.code_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;
	177
	178	elf_dmsg("\n[INFO] %s found CODE vseg / base = %x / size = %x\n",
	179	__FUNCTION__ , start , mem_size );
	180	}
	181	else // found DATA segment
	182	{
	183	type = VSEG_TYPE_DATA;
	184	process->vmm.data_vpn_base = start >> CONFIG_PPM_PAGE_SHIFT;
	185
	186	elf_dmsg("\n[INFO] %s found DATA vseg / base = %x / size = %x\n",
	187	__FUNCTION__, start , mem_size );
	188	}
	189
	190	// register vseg in VMM
	191	vseg = (vseg_t *)vmm_create_vseg( process,
	192	start,
	193	mem_size,
	194	type );
	195	if( vseg == NULL )
	196	{
	197	printk("\n[ERROR] in %s : cannot map segment / base = %x / size = %x\n",
	198	__FUNCTION__ , start , mem_size );
	199	return -1;
	200	}
	201
	202	vfs_file_count_up( file_xp );
	203	}
	204
	205	return 0;
	206	} // end elf_load_segments()
	207
	208	///////////////////////////////////////////////
	209	error_t elf_load_process( char * pathname,
	210	process_t * process)
	211	{
	212	kmem_req_t req; // kmem request for program header
	213	char path_copy[256]; // local copy of pathname
	214	uint32_t length; // actual path length
	215	Elf32_Ehdr header; // local buffer for .elf header
	216	void * segs_base; // pointer on buffer for segment descriptors array
	217	uint32_t segs_size; // size of buffer for segment descriptors array
	218	xptr_t file_xp; // extended pointer on created file descriptor
	219	uint32_t count; // bytes counter
	220	error_t error;
	221
	222	// get path length from user space
	223	length = hal_strlen_from_uspace( pathname );
	224
	225	if( length > 255 )
	226	{
	227	printk("\n[ERROR] in %s : pathname length too long\n", __FUNCTION__ );
	228	return -1;
	229	}
	230
	231	// make a local copy for pathname
	232	hal_copy_from_uspace( path_copy , pathname , length+1 );
	233
	234	// open file
	235	file_xp = XPTR_NULL; // avoid GCC warning
	236
	237	error = vfs_open( process->vfs_cwd_xp,
	238	path_copy,
	239	VFS_O_RDONLY,
	240	&file_xp );
	241	if( error )
	242	{
	243	printk("\n[ERROR] in %s : failed to open executable file %s\n",
	244	__FUNCTION__ , path_copy );
	245	return -1;
	246	}
	247
	248	// load header in local buffer
	249	error = elf_header_read( file_xp ,
	250	&header,
	251	sizeof(Elf32_Ehdr) );
	252	if( error )
	253	{
	254	vfs_close( file_xp , &count );
	255	return -1;
	256	}
	257
	258	elf_dmsg("\n[INFO] %s loaded elf header for %s\n", __FUNCTION__ , path_copy );
	259
	260	if( header.e_phnum == 0 )
	261	{
	262	printk("\n[ERROR] in %s : no segments found\n", __FUNCTION__ );
	263	vfs_close( file_xp , &count );
	264	return -1;
	265	}
	266
	267	// compute buffer size for segment descriptors array
	268	segs_size = sizeof(Elf32_Phdr) * header.e_phnum;
	269
	270	// allocate memory for segment descriptors array
	271	req.type = KMEM_GENERIC;
	272	req.size = segs_size;
	273	req.flags = AF_KERNEL;
	274	segs_base = kmem_alloc( &req );
	275
	276	if( segs_base == NULL )
	277	{
	278	printk("\n[ERROR] in %s : no memory for segment descriptors\n", __FUNCTION__ );
	279	vfs_close( file_xp , &count );
	280	return -1;
	281	}
	282
	283	// set seek pointer in file descriptor to access segment descriptors array
	284	error = vfs_lseek( file_xp , header.e_phoff, VFS_SEEK_SET , NULL );
	285
	286	if( error )
	287	{
	288	printk("\n[ERROR] in %s : cannot seek for descriptors array\n", __FUNCTION__ );
	289	vfs_close( file_xp , &count );
	290	req.ptr = segs_base;
	291	kmem_free( &req );
	292	return -1;
	293	}
	294
	295	// load seg descriptors array to local buffer
	296	count = vfs_read( file_xp,
	297	segs_base,
	298	segs_size );
	299
	300	if( count != segs_size )
	301	{
	302	printk("\n[ERROR] in %s : cannot read segments descriptors\n", __FUNCTION__ );
	303	vfs_close( file_xp , &count );
	304	req.ptr = segs_base;
	305	kmem_free( &req );
	306	return -1;
	307	}
	308
	309	elf_dmsg("\n[INFO] %s loaded segments descriptors for %s \n", __FUNCTION__ , path_copy );
	310
	311	// register loadable segments in process VMM
	312	error = elf_segments_load( file_xp,
	313	segs_base,
	314	header.e_phnum,
	315	process );
	316	if( error )
	317	{
	318	vfs_close( file_xp , &count );
	319	req.ptr = segs_base;
	320	kmem_free( &req );
	321	return -1;
	322	}
	323
	324	// register process entry point in VMM
	325	process->vmm.entry_point = (intptr_t)header.e_entry;
	326
	327	// register extended pointer on .elf file descriptor
	328	process->vfs_bin_xp = file_xp;
	329
	330	// release allocated memory for program header
	331	req.ptr = segs_base;
	332	kmem_free(&req);
	333
	334	elf_dmsg("\n[INFO] %s successfully completed / entry point = %x for %s]\n",
	335	__FUNCTION__, (uint32_t) header.e_entry , path_copy );
	336
	337	return 0;
	338	} // end elf_load_process()
	339

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