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source: trunk/kernel/libk/elf.c @ 107

Last change on this file since 107 was 23, checked in by alain, 7 years ago
Introduce syscalls.
File size: 10.9 KB

Line
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 <kernel_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	#include <syscalls.h>
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
88	count = vfs_move( true ,
89	file_xp,
90	buffer,
91	size );
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
169	error = vfs_lseek( file_xp,
170	offset,
171	SEEK_SET,
172	NULL );
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	{
219	char path_copy[CONFIG_VFS_MAX_PATH_LENGTH];
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
226	uint32_t file_id; // file descriptor index (unused)
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
233	if( length >= CONFIG_VFS_MAX_PATH_LENGTH )
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
244	file_id = -1;
245
246	error = vfs_open( process->vfs_cwd_xp,
247	path_copy,
248	O_RDONLY,
249	0,
250	&file_xp,
251	&file_id );
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	{
265	vfs_close( file_xp , file_id );
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__ );
274	vfs_close( file_xp , file_id );
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__ );
290	vfs_close( file_xp , file_id );
291	return -1;
292	}
293
294	// set seek pointer in file descriptor to access segment descriptors array
295	error = vfs_lseek( file_xp , header.e_phoff, SEEK_SET , NULL );
296
297	if( error )
298	{
299	printk("\n[ERROR] in %s : cannot seek for descriptors array\n", __FUNCTION__ );
300	vfs_close( file_xp , file_id );
301	req.ptr = segs_base;
302	kmem_free( &req );
303	return -1;
304	}
305
306	// load seg descriptors array to local buffer
307	count = vfs_move( true,
308	file_xp,
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__ );
315	vfs_close( file_xp , file_id );
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	{
330	vfs_close( file_xp , file_id );
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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