source: trunk/kernel/syscalls/sys_exec.c @ 23

Last change on this file since 23 was 23, checked in by alain, 5 years ago

Introduce syscalls.

File size: 10.1 KB
Line 
1/*
2 * sys_exec.c - Kernel function implementing the "exec" system call.
3 *
4 * Authors   Alain Greiner (2016,2017)
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 <errno.h>
28#include <printk.h>
29#include <core.h>
30#include <vfs.h>
31#include <cluster.h>
32#include <process.h>
33#include <thread.h>
34#include <vmm.h>
35#include <ppm.h>
36#include <rpc.h>
37
38
39////////////////////////////////////////////////i//////////////////////////////////////
40// This static function is called by the sys_exec() function to register the .elf
41// pathname in the exec_info  structure, from a string stored in user space.
42////////////////////////////////////////////////i//////////////////////////////////////
43// @ exec_info : pointer on the exec_info structure.
44// @ pathname  : string containing the path to the .elf file (user space).
45// return 0 if success / non-zero if one string too long, or too many strings.
46///////////////////////////////////////////////////////////////////////////////////////
47static error_t process_exec_get_path( exec_info_t  * exec_info,
48                                      char         * pathname )
49{
50    uint32_t length;
51
52    // get string length
53        length = hal_strlen_from_uspace( pathname );
54
55        if( length >= CONFIG_VFS_MAX_PATH_LENGTH ) return EINVAL;
56
57    // copy string to exec_info
58    hal_copy_from_uspace( &exec_info->path[0] , pathname , length );
59
60    return 0;
61}
62
63////////////////////////////////////////////////i//////////////////////////////////////
64// This static function is called twice by the sys_exec() function :
65// - to register the main() arguments (args) in the exec_info structure.
66// - to register the environment variables (envs) in the exec_info structure.
67// In both cases the input is an array of string pointers in user space,
68// and a set of strings in user space.
69// We allocate one physical page to store a kernel copy of the array of pointers,
70// we allocate one or several physical pages to store the strings themselve,
71// and register these buffers and the number of strings in the exec_info structure.
72// The max number of strings is 1024 (for both args and envs). The numbers of pages
73// to store the (args) and (envs) strings are configuration parameters.
74///////////////////////////////////////////////////////////////////////////////////////
75// @ exec_info : pointer on the exec_info structure.
76// @ is_args   : true if called for (args) / false if called for (envs).
77// @ pointers  : array of pointers on the strings (in user space).
78// @ return 0 if success / non-zero if too many strings or no more memory.
79///////////////////////////////////////////////////////////////////////////////////////
80static error_t process_exec_get_strings( exec_info_t  * exec_info,
81                                         bool_t         is_args,
82                                                     char        ** u_pointers )
83{
84    uint32_t     index;       // string index
85    uint32_t     found_null;  // NULL pointer found in array of pointers
86    uint32_t     length;      // string length
87    kmem_req_t   req;         // kmem request
88    page_t     * page;        // page descriptor
89    uint32_t     order;       // ln2( number of pages to store strings )
90    char      ** k_pointers;  // base of kernel array of pointers
91    char       * k_buf_ptr;   // pointer on first empty slot in kernel strings buffer
92    char       * k_buf_base;  // base address of the kernel strings buffer
93
94    // compute ln2( number of pages for kernel strings buffer )
95    if( is_args ) order = bits_log2( CONFIG_VMM_ARGS_SIZE );
96    else          order = bits_log2( CONFIG_VMM_ENVS_SIZE );
97
98        req.type   = KMEM_PAGE;
99        req.flags  = AF_KERNEL | AF_ZERO;
100
101    // allocate one physical page for kernel array of pointers
102    req.type   = 0;
103    page       = kmem_alloc( &req );
104
105    if( page == NULL ) return ENOMEM;
106
107    k_pointers = ppm_page2base( page );
108   
109    // allocate several physical pages to store the strings themselve
110    req.type   = order;
111    page       = kmem_alloc( &req );
112
113    if( page == NULL ) return ENOMEM;
114
115    k_buf_base = ppm_page2base( page );
116   
117    // copy the array of pointers to kernel buffer
118    hal_copy_from_uspace( k_pointers, 
119                          u_pointers,
120                          CONFIG_PPM_PAGE_SIZE );
121
122    // scan kernel array of pointers to copy the strings
123    found_null = 0;
124    k_buf_ptr  = k_buf_base;
125    for( index = 0 ; index < 1024 ; index++ )
126    {
127        if( k_pointers[index] == NULL ) 
128        {
129            found_null = 1;
130            break;
131        }
132
133        // compute string length
134            length = hal_strlen_from_uspace( k_pointers[index] );
135 
136        // copy the user string to kernel buffer
137        hal_copy_from_uspace( k_buf_ptr,
138                              k_pointers[index],
139                              length );
140
141        // update k_pointer[index] entry
142        k_pointers[index] = k_buf_ptr;
143
144        // increment pointer on kernel strings buffer
145        k_buf_ptr += (length + 1);
146    }
147
148    // update into exec_info structure
149    if( found_null && is_args )
150    {
151        exec_info->args_pointers  =  k_pointers;
152        exec_info->args_buf_base  =  k_buf_base;
153        exec_info->args_nr        =  index;
154    }
155    else if( found_null && !is_args )
156    {
157        exec_info->envs_pointers  =  k_pointers;
158        exec_info->envs_buf_base  =  k_buf_base;
159        exec_info->envs_buf_free  =  k_buf_ptr;
160        exec_info->envs_nr        =  index;
161    }
162    else 
163    {
164        return EINVAL;
165    }
166
167    return 0;
168} // end process_exec_get_strings()
169
170/////////////////////////////////////////////////////////////////////////////////////////
171// Implementation note:
172// This function build an exec_info_t structure containing all informations
173// required to create the new process descriptor and the associated thread.
174// It calls the static process_exec_get_path() and process_exec_get_strings() functions
175// to copy the .elf pathname, the main() arguments and the environment variables from
176// user buffers to the exec_info_t structure, and call the process_make_exec() function.
177/////////////////////////////////////////////////////////////////////////////////////////
178int sys_exec( char  * filename,     // .elf file pathname
179              char ** args,         // process arguments
180              char ** envs )        // environment variables
181{
182    exec_info_t  exec_info;         // structure to pass to process_make_exec()
183        error_t      error;
184    paddr_t      paddr;
185
186    thread_t   * this    = CURRENT_THREAD;
187        process_t  * process = this->process;
188
189    // check argument fileme
190    error = vmm_v2p_translate( false , filename , &paddr );
191
192        if( error )
193    {
194        printk("\n[ERROR] in %s : filename unmapped\n", __FUNCTION__ );
195        this->errno = EINVAL;
196        return -1;
197    }
198
199    // check argument fileme
200    error = vmm_v2p_translate( false , args , &paddr );
201
202        if( error )
203    {
204        printk("\n[ERROR] in %s : args unmapped\n", __FUNCTION__ );
205        this->errno = EINVAL;
206        return -1;
207    }
208
209    // check argument fileme
210    error = vmm_v2p_translate( false , envs , &paddr );
211
212        if( error )
213    {
214        printk("\n[ERROR] in %s : envs unmapped\n", __FUNCTION__ );
215        this->errno = EINVAL;
216        return -1;
217    }
218
219    // compute client_cxy (local cluster) and server_cxy (target cluster)
220    cxy_t     cxy_server = CXY_FROM_PID( process->pid );
221    cxy_t     cxy_client = local_cxy;
222    bool_t    is_local   = (cxy_server == cxy_client);
223
224    exec_dmsg("\n[INFO] %s starts for process %x on core %d in cluster %x"
225                 " / target_cluster = %x / cycle %d\n",
226                 __FUNCTION__, process->pid , CURRENT_CORE->lid, 
227                 cxy_client, cxy_server, hal_time_stamp());
228
229    // initialize exec_info structure
230    exec_info.pid         = process->pid;
231    exec_info.ppid        = process->ppid;
232    exec_info.fd_array_xp = XPTR( local_cxy , &process->fd_array );
233    exec_info.vfs_root_xp = process->vfs_root_xp;
234    exec_info.vfs_cwd_xp  = process->vfs_cwd_xp;
235    exec_info.vfs_bin_xp  = process->vfs_bin_xp;
236
237        // check pathname and store it in exec_info structure
238        error = process_exec_get_path( &exec_info , filename );
239
240        if ( error )
241    {
242        printk("\n[ERROR] in %s : elf pathname too long\n", __FUNCTION__ );
243        this->errno = error;
244        return -1;
245    }
246
247        // check and store args in exec_info structure
248        error = process_exec_get_strings( &exec_info , true , args );
249
250        if( error ) 
251    {
252        printk("\n[ERROR] in %s : cannot access args\n", __FUNCTION__ );
253        this->errno = error;
254        return -1;
255    }
256       
257        // check and store envs in exec_info structure
258        error = process_exec_get_strings( &exec_info , false , envs );
259
260        if( error )
261    {
262        printk("\n[ERROR] in %s : cannot access envs\n", __FUNCTION__ );
263        this->errno = error;
264        return -1;
265    }
266       
267    exec_dmsg("\n[INFO] %s starts exec for process %x at cycle %d\n",
268              __FUNCTION__, process->pid, hal_time_stamp() );
269
270    if( is_local )  error = process_make_exec( &exec_info );
271    else            rpc_process_exec_client( cxy_server , &exec_info , &error );
272
273    if( error )
274    {
275        printk("\n[ERROR] in %s : cannot create new process %x\n",
276               __FUNCTION__ , process->pid );
277        this->errno = error;
278        return -1;
279    }
280
281    exec_dmsg("\n[INFO] %s completes exec for process %x at cycle %d\n",
282              __FUNCTION__, process->pid , hal_time_stamp() );
283
284    // delete the calling thread an process
285    thread_kill( CURRENT_THREAD );
286    process_kill( CURRENT_THREAD->process );
287
288    return 0;
289
290} // end sys_exec()
291
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