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/* uos.c.  Microkernel for Or1ksim

   Copyright (C) 2000 Damjan Lampret

   Copyright (C) 2010 Embecosm Limited

   Contributor Damjan Lampret <lampret@opencores.org>

   Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>

   This file is part of OpenRISC 1000 Architectural Simulator.

   This program 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; either version 3 of the License, or (at your option)

   any later version.

   This program 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 this program.  If not, see <http:  www.gnu.org/licenses/>.  */

/* ----------------------------------------------------------------------------

   This code is commented throughout for use with Doxygen.

   --------------------------------------------------------------------------*/

/* This file is part of test microkernel for OpenRISC 1000. */

#include "support.h"

#include "spr-defs.h"

#include "uos.h"

#include "ipc.h"

#include "int.h"

/* External functions prototypes */

int tick_init(unsigned long period, void (* inf)(void));

/* Pointers to contexts used by except_or32.S routines */

unsigned long *task_context;

unsigned long *kernel_context;

/* TCBs for all tasks in the system */

struct tcb tasks[MAX_TASKS+1];

/* Stacks for the tasks (stacks[0] is kernel stack) */

unsigned char stacks[MAX_TASKS+1][STACK_SIZE];

/* MCBs for IPC messages */

struct mcb msgs[MAX_MSGS];

/* Pointer to linked list of free MCBs. */

struct mcb *free_mcbs;

/* TID of the current user task */

tid_t curtask = 0;

/* Statistics */

int kernel_sched_cnt = 0;

int kernel_syscall_cnt = 0;

/* Timestamp via or1ksim (CPU cycle number). */

unsigned long timestamp()

{

        register unsigned long cycles asm("r3");

        asm("l.sys 201");

        return cycles;

}

/* Standard function for filling memory with a constant byte. */

void *memset(void *dst, int c, size_t size)

{

        char *tmp = dst;

        for(;tmp && (tmp < (char *)dst + size); tmp++)

                *(char *)tmp = (char)c;

        return dst;

}

/* Traverse linked list of MCBs and show individual messages. */

void kernel_show_mcbs(struct mcb *mcb)

{

        for(;mcb; mcb = mcb->next) {

                printf("MCB len=%u origintask=%u ", mcb->length, mcb->origin);

                printf("msg:%s\n", mcb->msg);

        }

}

/* Show all contexts. */

void kernel_show_contexts()

{

        int i;

        tid_t t;

        for(t = 1; t <= MAX_TASKS; t++) {

                printf("\ntask TID=%d: PC=0x%x ", t, (unsigned)tasks[t].regs.pc & ~0x3);

                printf("SP(r1)=0x%x ", (unsigned)tasks[t].regs.sp);

                printf("SR[IEE]=%d\n", (unsigned)tasks[t].regs.sr & SPR_SR_IEE);

                printf("SR[TEE]=%d\n", (unsigned)tasks[t].regs.sr & SPR_SR_TEE);

                printf("SR[SM]=%d\n", (unsigned)tasks[t].regs.sr & SPR_SR_SM);

                for(i = 1; i < GPRS; i++) {

                        if (i % 4 == 0)

                                printf("\n");

                        printf("r%d=0x%.8x ", i, (unsigned)tasks[t].regs.gprs[i]);

                }

                printf("\n");

                kernel_show_mcbs(tasks[t].waiting_msgs);

        }

        printf("\n");

}

/* Simple round-robin scheduler that directly calls dispatcher. It is

   called by low level external interrupt exception handler or by

   kernel_syscall if KERNEL_SYSCALL_SCHED is defined. */

void kernel_sched()

{

        if ((++curtask > MAX_TASKS) || !(tasks[curtask].regs.pc & ~0x3))

                curtask = 1;

        task_context = (unsigned long *)&tasks[curtask].regs;

#if KERNEL_OUTPUT

        printf("kernel_sched(): entry number %d, ", ++kernel_sched_cnt);

        printf("dispatching task TID=%d, time %u cycles", curtask, timestamp());

        kernel_show_contexts();

#endif

        dispatch();

}

/* System call uos_msgsnd. */

void

uos_msgsnd(tid_t desttask, char *buf, int len)

{

        asm("l.sys 1");

        asm("l.nop");

}

/* System call uos_msgrcv. */

void

uos_msgrcv(tid_t origintask, char *buf, int len)

{

        asm("l.sys 2");

        asm("l.nop");

}

/* Handles system call uos_msgsnd. */

void kernel_msgsnd(tid_t tid)

{

        struct mcb *mcb;

        struct mcb **dstmq;

        struct tcb *task;

        task = &tasks[tid];

        /* Sanity checks. */

        /* Does destination task exist? */

        if (!task->regs.gprs[1] || (task->regs.gprs[1] > MAX_TASKS)) {

        task->regs.gprs[9] = IPC_ENOTASK;

                return;

        }

        /* Are there any free MCBs? */

        if (!free_mcbs) {

                task->regs.gprs[9] = IPC_EOUTOFMCBS;

                return;

        }

        /* Is message too big to fit into MCB's message buffer? */

        if (task->regs.gprs[3] > MAX_MSGLEN) {

                task->regs.gprs[9] = IPC_ETOOBIG;

                return;

        }

        /* OK, send the message. */

        /* First, allocate MCB. */

        mcb = free_mcbs;

        free_mcbs = mcb->next;

        /* Second, copy message to the MCB. */

        memcpy(mcb->msg, (void *)task->regs.gprs[2], task->regs.gprs[3]);

        mcb->origin = tid;

        mcb->length = task->regs.gprs[3];

        mcb->next = NULL;

        /* Insert MCB into destination task's message queue at

           the end. */

        dstmq = &tasks[task->regs.gprs[1]].waiting_msgs;

        for(;*dstmq;)

                dstmq = &((*dstmq)->next);

        *dstmq = mcb;

        task->regs.gprs[9] = IPC_NOERR;

        return;

}

/* Handles system call uos_msgrcv. */

void kernel_msgrcv(tid_t tid)

{

        struct mcb *curmsg, **linkp;

        struct tcb *task;

        task = &tasks[tid];

        /* Sanity checks. */

        /* Does origin task exist? */

        if (task->regs.gprs[1] > MAX_TASKS) {

                task->regs.gprs[9] = IPC_ENOTASK;

                return;

        }

        /* Are there any messages waiting for reception? */

        if (!task->waiting_msgs) {

                task->regs.gprs[9] = IPC_ENOMSGS;

                return;

        }

        /* OK, receive the message. */

        /* Search waiting messages for one coming from origintask. If

           origintask is zero then grab the first message. */

        curmsg = task->waiting_msgs;

        linkp = &task->waiting_msgs;

        for(;task->regs.gprs[1] && curmsg->next && curmsg->origin != task->regs.gprs[1];) {

                linkp = &curmsg->next;

                curmsg = curmsg->next;

        }

        /* Is receive buffer too small for receiving message? */

        if (task->regs.gprs[3] < curmsg->length) {

                task->regs.gprs[9] = IPC_ETOOBIG;

                return;

        }

        /* Now copy the message from the MCB. */

        memcpy((void *)task->regs.gprs[2], curmsg->msg, task->regs.gprs[3]);

        /* Remove MCB from task's waiting queue and place it

           back into free MCBs queue. */

        *linkp = curmsg->next;

        curmsg->next = free_mcbs;

        free_mcbs = curmsg;

        task->regs.gprs[9] = IPC_NOERR;

        return;

}

/* Handles all uOS system calls. It is called by low level system call

   exception handler. */

void kernel_syscall()

{

        unsigned short syscall_num;

#if KERNEL_OUTPUT

        printf("kernel_syscall(): entry number %d, ", ++kernel_syscall_cnt);

        printf("current TID=%d, time %u cycles", curtask, timestamp());

        kernel_show_contexts();

#endif  

        syscall_num = *(unsigned short *)((tasks[curtask].regs.pc & ~0x3) - 6);

        switch(syscall_num) {

                case IPC_MSGSND:

                        kernel_msgsnd(curtask);

                        break;

                case IPC_MSGRCV:

                        kernel_msgrcv(curtask);

                        break;

                default:

                        printf("kernel_syscall(): unknown syscall (%u)\n", syscall_num);

        }

#if KERNEL_SYSCALL_SCHED

        kernel_sched();

#endif

        dispatch();

}

/* Called by reset exception handler to initialize the kernel and start

   rolling first task. */

void

kernel_init()

{

        tid_t t;

        int i;

        printf("Initializing kernel:\n");

        printf("  Clearing kernel structures...\n");

        memset(tasks, 0, sizeof(tasks));

        memset(stacks, 0, sizeof(stacks));

        memset(msgs, 0, sizeof(msgs));

        printf("  Initializing MCBs... %d MCB(s)\n", MAX_MSGS);

        for(i = 0; i < (MAX_MSGS - 1); i++)

                msgs[i].next = &msgs[i+1];

        free_mcbs = &msgs[0];

        printf("  Initializing TCBs... %d user task(s)\n", MAX_TASKS);

        tasks_entries();

        for(t = 0; t <= MAX_TASKS; t++) {

                tasks[t].regs.sp = (unsigned long)stacks[t] + STACK_SIZE - 4;

                /* Disable EXR for kernel context */

                tasks[t].regs.sr |= (t == 0 ? SPR_SR_SM : SPR_SR_TEE | SPR_SR_IEE);

                tasks[t].regs.gprs[1] = t;

        }

        /* First task runs in seprvisor mode */

        tasks[1].regs.sr |= SPR_SR_SM;

        /* TID=0 is reserved for kernel use */

        kernel_context = (unsigned long *)&tasks[0].regs;

        /* First task to be scheduled is task TID=1 */

        task_context = (unsigned long *)&tasks[1].regs;

        /* Initialize initrrupt controller */

        int_init();

        printf("  Exceptions will be enabled when first task is dispatched.\n");

        printf("Kernel initalized. Starting first user task.\n");

#if KERNEL_SYSCALL_SCHED

        kernel_sched();         /* Lets schedule and dispatch our first task */

#else

        tick_init(TICK_PERIOD, kernel_sched);

        kernel_sched();         /* Lets schedule and dispatch our first task */

#endif  

        /* ... */               /* We never get here */

}

int main ()

{

  kernel_init();

  return 0;

}