source: trunk/kernel/syscalls/sys_exec.c @ 407

Last change on this file since 407 was 407, checked in by alain, 5 years ago

First implementation of fork/exec.

File size: 9.1 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 twice by the sys_exec() function :
41// - to register the main() arguments (args) in the exec_info structure.
42// - to register the environment variables (envs) in the exec_info structure.
43// In both cases the input is an array of string pointers in user space,
44// and a set of strings in user space.
45// We allocate one physical page to store a kernel copy of the array of pointers,
46// we allocate one or several physical pages to store the strings themselve,
47// and register these buffers and the number of strings in the exec_info structure.
48// The max number of strings is 1024 (for both args and envs). The numbers of pages
49// to store the (args) and (envs) strings are configuration parameters.
50///////////////////////////////////////////////////////////////////////////////////////
51// @ exec_info   : pointer on the exec_info structure.
52// @ is_args     : true if called for (args) / false if called for (envs).
53// @ u_pointers  : array of pointers on the strings (in user space).
54// @ return 0 if success / non-zero if too many strings or no more memory.
55///////////////////////////////////////////////////////////////////////////////////////
56static error_t process_exec_get_strings( exec_info_t  * exec_info,
57                                         bool_t         is_args,
58                                         char        ** u_pointers )
59{
60    uint32_t     index;       // string index
61    uint32_t     found_null;  // NULL pointer found in array of pointers
62    uint32_t     length;      // string length
63    kmem_req_t   req;         // kmem request
64    page_t     * page;        // page descriptor
65    xptr_t       base_xp;     // extended pointer on page base
66    uint32_t     order;       // ln2( number of pages to store strings )
67    char      ** k_pointers;  // base of kernel array of pointers
68    char       * k_buf_ptr;   // pointer on first empty slot in kernel strings buffer
69    char       * k_buf_base;  // base address of the kernel strings buffer
70
71    // compute ln2( number of pages for kernel strings buffer )
72    if( is_args ) order = bits_log2( CONFIG_VMM_ARGS_SIZE );
73    else          order = bits_log2( CONFIG_VMM_ENVS_SIZE );
74
75    req.type   = KMEM_PAGE;
76    req.flags  = AF_KERNEL | AF_ZERO;
77
78    // allocate one physical page for kernel array of pointers
79    req.type   = 0;
80    page       = kmem_alloc( &req );
81
82    if( page == NULL ) return ENOMEM;
83
84    base_xp = ppm_page2base( XPTR( local_cxy , page ) );
85    k_pointers = (char **)GET_PTR( base_xp );
86
87    // allocate several physical pages to store the strings themselve
88    req.type   = order;
89    page       = kmem_alloc( &req );
90
91    if( page == NULL ) return ENOMEM;
92
93    base_xp = ppm_page2base( XPTR( local_cxy , page ) );
94    k_buf_base = (char *)GET_PTR( base_xp );
95
96    // copy the array of pointers to kernel buffer
97    hal_copy_from_uspace( k_pointers,
98                          u_pointers,
99                          CONFIG_PPM_PAGE_SIZE );
100
101    // scan kernel array of pointers to copy the strings
102    found_null = 0;
103    k_buf_ptr  = k_buf_base;
104    for( index = 0 ; index < 1024 ; index++ )
105    {
106        if( k_pointers[index] == NULL )
107        {
108            found_null = 1;
109            break;
110        }
111
112        // compute string length
113        length = hal_strlen_from_uspace( k_pointers[index] );
114
115        // copy the user string to kernel buffer
116        hal_copy_from_uspace( k_buf_ptr,
117                              k_pointers[index],
118                              length );
119
120        // update k_pointer[index] entry
121        k_pointers[index] = k_buf_ptr;
122
123        // increment pointer on kernel strings buffer
124        k_buf_ptr += (length + 1);
125    }
126
127    // update into exec_info structure
128    if( found_null && is_args )
129    {
130        exec_info->args_pointers  =  k_pointers;
131        exec_info->args_buf_base  =  k_buf_base;
132        exec_info->args_nr        =  index;
133    }
134    else if( found_null && !is_args )
135    {
136        exec_info->envs_pointers  =  k_pointers;
137        exec_info->envs_buf_base  =  k_buf_base;
138        exec_info->envs_buf_free  =  k_buf_ptr;
139        exec_info->envs_nr        =  index;
140    }
141    else
142    {
143        return EINVAL;
144    }
145
146    return 0;
147} // end process_exec_get_strings()
148
149/////////////////////////////////////////////////////////////////////////////////////////
150// Implementation note:
151// This function build an exec_info_t structure containing all informations
152// required to create the new process descriptor and the associated thread.
153// It calls the process_exec_get_strings() functions to copy the main() arguments and
154// the environment variables from user buffers to the exec_info_t structure, allocate
155// and call the process_make_exec() function.
156// Finally, it destroys the calling thread and process.
157// TODO : the args & envs arguments are not supported yet : both must be NULL
158/////////////////////////////////////////////////////////////////////////////////////////
159int sys_exec( char  * pathname,     // .elf file pathname
160              char ** args,         // process arguments
161              char ** envs )        // environment variables
162{
163    exec_info_t   exec_info;        // structure to pass to process_make_exec()
164    error_t       error;
165
166        uint64_t      tm_start;
167        uint64_t      tm_end;
168
169        tm_start = hal_get_cycles();
170
171    // get pointers on parent process and thread
172    thread_t   * this    = CURRENT_THREAD;
173    process_t  * process = this->process;
174    pid_t        pid     = process->pid;
175
176exec_dmsg("\n[DBG] %s : core[%x,%d] enters for process %x / cycle %d\n",
177__FUNCTION__, local_cxy, this->core->lid, pid, (uint32_t)hal_get_cycles() );
178
179sched_display( 0 );
180
181    // check pathname length
182    if( hal_strlen_from_uspace( pathname ) >= CONFIG_VFS_MAX_PATH_LENGTH )
183    {
184        printk("\n[ERROR] in %s : pathname too long\n", __FUNCTION__ );
185        this->errno = ENFILE;
186        return -1;
187    }
188
189    // copy pathname in exec_info structure (kernel space)
190    hal_strcpy_from_uspace( exec_info.path , pathname , CONFIG_VFS_MAX_PATH_LENGTH );
191    // check args argument
192    assert( (args == NULL) , __FUNCTION__ , 
193    "args not supported yet\n" );
194
195    // check envs argument
196    assert( (envs == NULL) , __FUNCTION__ , 
197    "args not supported yet\n" );
198
199    // compute client_cxy (local cluster) and server_cxy (target cluster)
200    cxy_t     cxy_server = CXY_FROM_PID( pid );
201    cxy_t     cxy_client = local_cxy;
202
203    // register parent process in exec_info
204    exec_info.parent_xp   = process->ref_xp;
205
206    // new process keep the parent process PID
207    exec_info.keep_pid   = true;
208
209    // check and store args in exec_info structure if required
210    if( args != NULL )
211    {
212        if( process_exec_get_strings( &exec_info , true , args ) )
213        {
214            printk("\n[ERROR] in %s : cannot access args\n", __FUNCTION__ );
215            this->errno = error;
216            return -1;
217        }
218    }
219
220    // check and store envs in exec_info structure if required
221    if( envs != NULL )
222    {
223        if( process_exec_get_strings( &exec_info , false , envs ) )
224        {
225            printk("\n[ERROR] in %s : cannot access envs\n", __FUNCTION__ );
226            this->errno = error;
227            return -1;
228        }
229    }
230
231    // call process_make_exec (local or remote)
232    if( cxy_server == cxy_client )
233    {
234        error = process_make_exec( &exec_info );
235    }
236    else
237    {
238        rpc_process_exec_client( cxy_server , &exec_info , &error );
239    }
240
241    if( error )
242    {
243        printk("\n[ERROR] in %s : cannot create new process %x in cluster %x\n",
244        __FUNCTION__, pid, cxy_server );
245        this->errno = error;
246        return -1;
247    }
248
249    // FIXME delete the local process descriptor
250    // process_kill( process );
251
252    tm_end = hal_get_cycles();
253
254exec_dmsg("\n[DBG] %s : core[%x,%d] exit for process %x / cycle %d\n"
255"     pathname = %s / cost = %d\n",
256__FUNCTION__, local_cxy, this->core->lid, pid, (uint32_t)tm_start,
257exec_info.path , (uint32_t)(tm_end - tm_start) );
258
259    return 0;
260
261} // end sys_exec()
262
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