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source: trunk/kernel/libk/elf.c @ 2

Last change on this file since 2 was 1, checked in by alain, 8 years ago
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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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