source: trunk/kernel/syscalls/sys_lseek.c

/*
 * kern/sys_lseek.c - Kernel function implementing the lseek system call.
 * 
 * AUthor        Alain Greiner (2016,2017,2018,2019)
s
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-MKH is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <kernel_config.h>
#include <hal_kernel_types.h>
#include <hal_uspace.h>
#include <errno.h>
#include <vfs.h>
#include <vmm.h>
#include <thread.h>
#include <printk.h>
#include <process.h>

/////////////////////////////////
int sys_lseek ( uint32_t file_id,
                uint32_t offset,
                uint32_t whence )
{
        error_t    error;
    xptr_t     file_xp;
    uint32_t   new_offset;

        thread_t  * this    = CURRENT_THREAD;
        process_t * process = this->process;

#if (DEBUG_SYS_LSEEK || CONFIG_INSTRUMENTATION_SYSCALLS)
uint64_t     tm_start = hal_get_cycles();
#endif

#if DEBUG_SYS_LSEEK
if( DEBUG_SYS_LSEEK < tm_start )
printk("\n[%s] thread[%x,%x] enter / file_id %d / offset %d / cycle %d\n",
__FUNCTION__, process->pid, this->trdid, file_id, offset, (uint32_t)tm_start );
#endif

    // check file_id argument
        if( file_id >= CONFIG_PROCESS_FILE_MAX_NR )
        {

#if DEBUG_SYSCALLS_ERROR
printk("\n[ERROR] in %s : thread[%x,%x] illegal file descriptor index %d\n",
__FUNCTION__ , process->pid, this->trdid, file_id );
#endif
                this->errno = EBADFD;
                return -1;
        }

    // get extended pointer on remote file descriptor
    file_xp = process_fd_get_xptr_from_local( process , file_id );

    if( file_xp == XPTR_NULL )
    {

#if DEBUG_SYSCALLS_ERROR
printk("\n[ERROR] in %s : thread[%x,%x] undefined fd_id %d\n",
__FUNCTION__, process->pid, this->trdid, file_id );
#endif
                this->errno = EBADFD;
                return -1;
    }

// FIXME: file may be closed in parallel of seek/read/write/mmap ..etc 

    // call relevant VFS function
        error = vfs_lseek( file_xp , offset , whence , &new_offset );

        if( error )
        {

#if DEBUG_SYSCALLS_ERROR
printk("\n[ERROR] in %s : thread[%x,%x] cannot seek file_id %d\n",
__FUNCTION__, process->pid, this->trdid, file_id );
#endif
                this->errno = error;
                return -1;
        }

#if (DEBUG_SYS_LSEEK || CONFIG_INSTRUMENTATION_SYSCALLS)
uint64_t     tm_end = hal_get_cycles();
#endif

#if DEBUG_SYS_LSEEK
if( DEBUG_SYS_LSEEK < tm_end )
printk("\n[%s] thread[%x,%x] exit / cycle %d\n",
__FUNCTION__ , process->pid, this->trdid, (uint32_t)tm_end );
#endif

#if CONFIG_INSTRUMENTATION_SYSCALLS
hal_atomic_add( &syscalls_cumul_cost[SYS_LSEEK] , tm_end - tm_start );
hal_atomic_add( &syscalls_occurences[SYS_LSEEK] , 1 );
#endif
  
        return new_offset;
}