source: trunk/kernel/syscalls/sys_exec.c @ 459

Last change on this file since 459 was 457, checked in by alain, 3 years ago

This version modifies the exec syscall and fixes a large number of small bugs.
The version number has been updated (0.1)

File size: 9.0 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_kernel_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 must be called by the main thread (thread 0 in owner cluster).
152// It build an exec_info_t structure containing all informations
153// required to initialize the new process descriptor and the associated thread.
154// It includes the new process main() arguments, the environment variables,
155// and the pathname to the new process .elf file.
156// It calls the process_exec_get_strings() functions to copy the main() arguments and
157// the environment variables from user buffers to the exec_info_t structure, allocate
158// and call the process_make_exec() function.
159// As it must destroy all process copies, and all othert threads in all clusters,
160// the process_make_exec() function must be executed in the owner cluster.
161//
162// TODO : the args & envs arguments are not supported yet : both must be NULL  [AG]
163/////////////////////////////////////////////////////////////////////////////////////////
164int sys_exec( char  * pathname,     // .elf file pathname
165              char ** args,         // process arguments
166              char ** envs )        // environment variables
167{
168    exec_info_t   exec_info;        // structure to pass to process_make_exec()
169    error_t       error;
170
171    // get calling thread, process, & pid
172    thread_t    * this    = CURRENT_THREAD;
173    process_t   * process = this->process;
174    pid_t         pid     = process->pid;
175
176    assert( (CXY_FROM_PID( pid ) == local_cxy) , __FUNCTION__ ,
177    "must be called in the owner cluster\n");
178
179    assert( (LTID_FROM_TRDID( this->trdid ) == 0) , __FUNCTION__ ,
180    "must be called by the main thread\n");
181
182    assert( (args == NULL) , __FUNCTION__ , 
183    "args not supported yet\n" );
184
185    assert( (envs == NULL) , __FUNCTION__ , 
186    "args not supported yet\n" );
187
188    // check pathname length
189    if( hal_strlen_from_uspace( pathname ) >= CONFIG_VFS_MAX_PATH_LENGTH )
190    {
191
192#if DEBUG_SYSCALLS_ERROR
193printk("\n[ERROR] in %s : pathname too long\n", __FUNCTION__ );
194#endif
195        this->errno = ENFILE;
196        return -1;
197    }
198
199    // copy pathname in exec_info structure (kernel space)
200    hal_strcpy_from_uspace( exec_info.path , pathname , CONFIG_VFS_MAX_PATH_LENGTH );
201
202#if DEBUG_SYS_EXEC
203uint64_t      tm_start;
204tm_start = hal_get_cycles();
205if( DEBUG_SYS_EXEC < tm_start )
206printk("\n[DBG] %s : thread %x in process %x enter for path <%s> / cycle = %d\n",
207__FUNCTION__, this->trdid, pid, exec_info.path, (uint32_t)tm_start );
208#endif
209
210    // check and store args in exec_info structure if required
211    if( args != NULL )
212    {
213        if( process_exec_get_strings( &exec_info , true , args ) )
214        {
215
216#if DEBUG_SYSCALLS_ERROR
217printk("\n[ERROR] in %s : thread %x in process %x cannot access args\n",
218__FUNCTION__ , this->trdid, pid );
219#endif
220            this->errno = EINVAL;
221            return -1;
222        }
223    }
224
225    // check and store envs in exec_info structure if required
226    if( envs != NULL )
227    {
228        if( process_exec_get_strings( &exec_info , false , envs ) )
229        {
230
231#if DEBUG_SYCALLS_ERROR
232printk("\n[ERROR] in %s : thread %x in process %x cannot access envs\n",
233__FUNCTION__ , this->trdid, pid );
234#endif
235            this->errno = EINVAL;
236            return -1;
237        }
238    }
239
240    // call relevant kernel function
241    error = process_make_exec( &exec_info );
242
243    if( error )
244    {
245
246#if DEBUG_SYSCALLS_ERROR
247printk("\n[ERROR] in %s : thread %x in process %x cannot create process for <%s>\n",
248__FUNCTION__, this->trdid, pid, exec_info.path );
249#endif
250        this->errno = error;
251        return -1;
252    }
253
254    assert( false , __FUNCTION__, "we should not execute this code" );
255
256    return 0; 
257
258} // end sys_exec()
259
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