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source: trunk/kernel/libk/elf.c @ 408

Last change on this file since 408 was 407, checked in by alain, 7 years ago
First implementation of fork/exec.
File size: 11.1 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_special.h>
27	#include <hal_uspace.h>
28	#include <printk.h>
29	#include <process.h>
30	#include <thread.h>
31	#include <mapper.h>
32	#include <vseg.h>
33	#include <kmem.h>
34	#include <vfs.h>
35	#include <elf.h>
36	#include <syscalls.h>
37
38	///////////////////////////////////////////////////////////////////
39	// This static function checks the .elf header.
40	// - return true if legal header.
41	// - return false with an error message if illegal header.
42	///////////////////////////////////////////////////////////////////
43	static bool_t elf_isValidHeader(Elf_Ehdr *header)
44	{
45	if((header->e_ident[EI_CLASS] == ELFCLASS)
46	&& (header->e_ident[EI_DATA] == ELFDATA2LSB)
47	&& (header->e_ident[EI_VERSION] == EV_CURRENT)
48	/*
49	&& (header->e_ident[EI_OSABI] == ELFOSABI_NONE)
50	*/
51	&& ((header->e_machine == EM_MIPS) \|\|
52	(header->e_machine == EM_MIPS_RS3_LE) \|\|
53	(header->e_machine == EM_X86_64))
54	&& (header->e_type == ET_EXEC))
55	return true;
56
57	if( header->e_ident[EI_CLASS] != ELFCLASS )
58	printk("\n[ERROR] in %s : Elf is not 32/64-Binary\n", __FUNCTION__ );
59
60	if( header->e_ident[EI_DATA] != ELFDATA2LSB )
61	printk("\n[ERROR] in %s : Elf is not 2's complement, little endian\n", __FUNCTION__ );
62
63	if( header->e_ident[EI_VERSION] != EV_CURRENT )
64	printk("\n[ERROR] in %s : Elf is not in Current Version\n", __FUNCTION__);
65	/*
66	if( header->e_ident[EI_OSABI] != ELFOSABI_NONE )
67	printk("\n[ERROR] in %s : Unexpected Elf ABI, need UNIX System V ABI\n", __FUNCTION__ );
68	*/
69	if( (header->e_machine != EM_MIPS) &&
70	(header->e_machine != EM_MIPS_RS3_LE) &&
71	(header->e_machine != EM_X86_64) )
72	printk("\n[ERROR] in %s : unexpected core / accept only MIPS or x86_64\n", __FUNCTION__ );
73
74	if( header->e_type != ET_EXEC )
75	printk("\n[ERROR] in %s : Elf is not executable binary\n", __FUNCTION__ );
76
77	return false;
78	}
79
80	///////////////////////////////////////////////////////////////////////////////////////
81	// This function loads the .elf header in the buffer allocated by the caller.
82	///////////////////////////////////////////////////////////////////////////////////////
83	// @ file : extended pointer on the remote file descriptor.
84	// @ buffer : pointer on buffer allocated by the caller.
85	// @ size : number of bytes to read.
86	///////////////////////////////////////////////////////////////////////////////////////
87	static error_t elf_header_load( xptr_t file_xp,
88	void * buffer,
89	uint32_t size )
90	{
91	error_t error;
92	xptr_t buf_xp;
93
94	buf_xp = XPTR( local_cxy , buffer );
95
96	// load .elf header
97	error = vfs_kernel_move( true, // to_buffer
98	file_xp,
99	buf_xp,
100	size );
101
102	if( error )
103	{
104	printk("\n[ERROR] in %s : cannot read ELF header size : %d\n",
105	__FUNCTION__ , size );
106	return -1;
107	}
108
109	Elf_Ehdr * header = (Elf_Ehdr *)buffer;
110
111	if( (header->e_ident[EI_MAG0] != ELFMAG0) \|\|
112	(header->e_ident[EI_MAG1] != ELFMAG1) \|\|
113	(header->e_ident[EI_MAG2] != ELFMAG2) \|\|
114	(header->e_ident[EI_MAG3] != ELFMAG3) )
115	{
116	printk("\n[ERROR] in %s : file not in ELF format\n", __FUNCTION__ );
117	return -1;
118	}
119
120	if( !(elf_isValidHeader( header ) ) )
121	{
122	printk("\n[ERROR] in %s : not supported Elf\n", __FUNCTION__ );
123	return -1;
124	}
125	return 0;
126
127	} // end elf_header_load()
128
129	///////////////////////////////////////////////////////////////////////////////////////
130	// This function registers in the process VMM the CODE and DATA segments.
131	///////////////////////////////////////////////////////////////////////////////////////
132	// @ file : extended pointer on the remote file descriptor.
133	// @ segs_base : local pointer on buffer containing the segments descriptors array
134	// @ segs_nr : number of segments in segment descriptors array.
135	// @ process : local pointer on process descriptor.
136	///////////////////////////////////////////////////////////////////////////////////////
137	static error_t elf_segments_register( xptr_t file_xp,
138	void * segs_base,
139	uint32_t nb_segs,
140	process_t * process )
141	{
142	uint32_t index;
143	intptr_t file_size;
144	intptr_t mem_size;
145	intptr_t file_offset;
146	intptr_t vbase;
147	uint32_t type;
148	uint32_t flags;
149	vseg_t * vseg;
150
151	Elf_Phdr * seg_ptr = (Elf_Phdr *)segs_base;
152
153	// loop on segments
154	for( index = 0 ; index < nb_segs ; index++ , seg_ptr++ )
155	{
156	if( seg_ptr->p_type != PT_LOAD)
157	continue;
158
159	// get segment attributes
160	vbase = seg_ptr->p_vaddr; // vseg base vaddr
161	mem_size = seg_ptr->p_memsz; // actual vseg size
162	file_offset = seg_ptr->p_offset; // vseg offset in .elf file
163	file_size = seg_ptr->p_filesz; // vseg size in .elf file
164	flags = seg_ptr->p_flags;
165
166	if( flags & PF_X ) // found CODE segment
167	{
168	type = VSEG_TYPE_CODE;
169	process->vmm.code_vpn_base = vbase >> CONFIG_PPM_PAGE_SHIFT;
170	}
171	else // found DATA segment
172	{
173	type = VSEG_TYPE_DATA;
174	process->vmm.data_vpn_base = vbase >> CONFIG_PPM_PAGE_SHIFT;
175	}
176
177	// get .elf file descriptor cluster and local pointer
178	cxy_t file_cxy = GET_CXY( file_xp );
179	vfs_file_t * file_ptr = (vfs_file_t *)GET_PTR( file_xp );
180
181	// get local pointer on .elf file mapper
182	mapper_t * mapper_ptr = (mapper_t *)hal_remote_lpt( XPTR( file_cxy ,
183	&file_ptr->mapper ) );
184	// register vseg in VMM
185	vseg = (vseg_t *)vmm_create_vseg( process,
186	type,
187	vbase,
188	mem_size,
189	file_offset,
190	file_size,
191	XPTR( file_cxy , mapper_ptr ),
192	local_cxy );
193	if( vseg == NULL )
194	{
195	printk("\n[ERROR] in %s : cannot map segment / base = %x / size = %x\n",
196	__FUNCTION__ , vbase , mem_size );
197	return -1;
198	}
199
200	// update reference counter in file descriptor
201	vfs_file_count_up( file_xp );
202
203	elf_dmsg("\n[DBG] %s : found %s vseg / base = %x / size = %x\n"
204	" file_size = %x / file_offset = %x / mapper_xp = %l\n",
205	__FUNCTION__ , vseg_type_str(vseg->type) , vseg->min , vseg->max - vseg->min ,
206	vseg->file_size , vseg->file_offset , vseg->mapper_xp );
207	}
208
209	return 0;
210
211	} // end elf_segments_register()
212
213	///////////////////////////////////////////////
214	error_t elf_load_process( char * pathname,
215	process_t * process)
216	{
217	kmem_req_t req; // kmem request for program header
218	Elf_Ehdr header; // local buffer for .elf header
219	void * segs_base; // pointer on buffer for segment descriptors array
220	uint32_t segs_size; // size of buffer for segment descriptors array
221	xptr_t file_xp; // extended pointer on created file descriptor
222	uint32_t file_id; // file descriptor index (unused)
223	error_t error;
224
225	elf_dmsg("\n[DBG] %s : core[%x,%d] enter for <%s>\n",
226	__FUNCTION__ , local_cxy , CURRENT_THREAD->core->lid , pathname );
227
228	// avoid GCC warning
229	file_xp = XPTR_NULL;
230	file_id = -1;
231
232	// open file
233	error = vfs_open( process,
234	pathname,
235	O_RDONLY,
236	0,
237	&file_xp,
238	&file_id );
239	if( error )
240	{
241	printk("\n[ERROR] in %s : failed to open file %s\n", __FUNCTION__ , pathname );
242	return -1;
243	}
244
245	elf_dmsg("\n[DBG] %s : open file <%s>\n", __FUNCTION__ , pathname );
246
247	// load header in local buffer
248	error = elf_header_load( file_xp ,
249	&header,
250	sizeof(Elf_Ehdr) );
251	if( error )
252	{
253	printk("\n[ERROR] in %s : cannot get header file %s\n", __FUNCTION__ , pathname );
254	vfs_close( file_xp , file_id );
255	return -1;
256	}
257
258	elf_dmsg("\n[DBG] %s : loaded elf header for %s\n", __FUNCTION__ , pathname );
259
260	if( header.e_phnum == 0 )
261	{
262	printk("\n[ERROR] in %s : no segments found\n", __FUNCTION__ );
263	vfs_close( file_xp , file_id );
264	return -1;
265	}
266
267	// compute buffer size for segment descriptors array
268	segs_size = sizeof(Elf_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 , file_id );
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, 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 , file_id );
290	req.ptr = segs_base;
291	kmem_free( &req );
292	return -1;
293	}
294
295	elf_dmsg("\n[DBG] %s : segments array allocated for %s\n", __FUNCTION__ , pathname );
296
297	// load seg descriptors array to local buffer
298	error = vfs_kernel_move( true, // to_buffer
299	file_xp,
300	XPTR( local_cxy , segs_base ),
301	segs_size );
302
303	if( error )
304	{
305	printk("\n[ERROR] in %s : cannot read segments descriptors\n", __FUNCTION__ );
306	vfs_close( file_xp , file_id );
307	req.ptr = segs_base;
308	kmem_free( &req );
309	return -1;
310	}
311
312	elf_dmsg("\n[DBG] %s loaded segments descriptors for %s \n", __FUNCTION__ , pathname );
313
314	// register loadable segments in process VMM
315	error = elf_segments_register( file_xp,
316	segs_base,
317	header.e_phnum,
318	process );
319	if( error )
320	{
321	vfs_close( file_xp , file_id );
322	req.ptr = segs_base;
323	kmem_free( &req );
324	return -1;
325	}
326
327	// register process entry point in VMM
328	process->vmm.entry_point = (intptr_t)header.e_entry;
329
330	// register extended pointer on .elf file descriptor
331	process->vfs_bin_xp = file_xp;
332
333	// release allocated memory for program header
334	req.ptr = segs_base;
335	kmem_free(&req);
336
337	elf_dmsg("\n[DBG] %s : core[%x,%d] exit for <%s> / entry_point = %x\n",
338	__FUNCTION__ , local_cxy , CURRENT_THREAD->core->lid , pathname , header.e_entry );
339
340	return 0;
341
342	} // end elf_load_process()
343

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