/*
 * hal_exception.c - implementation of exception handler for TSAR-MIPS32.
 * 
 * Author   Alain Greiner (2016, 2017)
 *
 * 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 <hal_types.h>
#include <hal_irqmask.h>
#include <hal_exception.h>
#include <thread.h>
#include <printk.h>
#include <chdev.h>
#include <vmm.h>
#include <errno.h>
#include <scheduler.h>
#include <core.h>
#include <signal.h>
#include <syscalls.h>
#include <remote_spinlock.h>
#include <mips32_uzone.h>


//////////////////////////////////////////////////////////////////////////////////////////
//  Extern global variables
//////////////////////////////////////////////////////////////////////////////////////////

extern   chdev_directory_t    chdev_dir;  // allocated in the kernel_init.c file.

//////////////////////////////////////////////////////////////////////////////////////////
// This enum defines the global exception types after analysis by the exception handler.
//////////////////////////////////////////////////////////////////////////////////////////

typedef enum
{
    EXCP_NON_FATAL,
    EXCP_USER_ERROR,
    EXCP_KERNEL_PANIC,
}
exception_handling_type_t;

//////////////////////////////////////////////////////////////////////////////////////////
// This enum defines the relevant subtypes for a MMU exception reported by the mips32.
//////////////////////////////////////////////////////////////////////////////////////////

typedef enum
{
    MMU_EXCP_PAGE_UNMAPPED,
    MMU_EXCP_USER_PRIVILEGE,
    MMU_EXCP_USER_EXEC,
    MMU_EXCP_USER_WRITE,
}
mmu_exception_subtype_t;

//////////////////////////////////////////////////////////////////////////////////////////
// This enum defines the relevant values for XCODE field in mips32 CP0_CR register.
//////////////////////////////////////////////////////////////////////////////////////////

typedef enum
{
    XCODE_ADEL = 0x4,        // Illegal address for data load 
    XCODE_ADES = 0x5,        // Illegal address for data store
    XCODE_IBE  = 0x6,        // Instruction MMU exception       (can be NON-FATAL)
    XCODE_DBE  = 0x7,        // Data MMU exception              (can be NON-FATAL)
    XCODE_RI   = 0xA,        // Reserved instruction exception
    XCODE_CPU  = 0xB,        // Coprocessor unusable exception  (can be NON-FATAl)
    XCODE_OVR  = 0xC,        // Arithmetic Overflow exception
}
xcode_values_t;

//////////////////////////////////////////////////////////////////////////////////////////
// This static function is called when a FPU Coprocessor Unavailable exception has been 
// detected for the calling thread. 
// It enables the FPU, It saves the current FPU context in the current owner thread 
// descriptor if required, and restore the FPU context from the calling thread descriptor.
//////////////////////////////////////////////////////////////////////////////////////////
// @ this     : pointer on faulty thread descriptor.
// @ return always EXCP_NON_FATAL
//////////////////////////////////////////////////////////////////////////////////////////
static error_t hal_fpu_exception( thread_t * this )
{
	core_t   * core = this->core; 

    // enable FPU  
	hal_fpu_enable();

    // save FPU context in current owner thread if required 
	if( core->fpu_owner != NULL )
    {
        if( core->fpu_owner != this )
	    {
		    hal_fpu_context_save ( core->fpu_owner->fpu_context );
        }
	}

    // attach the FPU to the requesting thread
	hal_fpu_context_restore( this->fpu_context );
	core->fpu_owner = this;

	return EXCP_NON_FATAL;

}  // end hal_fpu_exception()

//////////////////////////////////////////////////////////////////////////////////////////
// This static function is called when an MMU exception has been detected. 
// It get the relevant exception arguments from the MMU.
// It signal a fatal error in case of illegal access. In case of page unmapped
// it checks that the faulty address belongs to a registered vseg. It update the local
// vseg list from the reference cluster if required, and signal a fatal user error
// in case of illegal virtual address. Finally, it updates the local page table from the
// reference cluster.
//////////////////////////////////////////////////////////////////////////////////////////
// @ this     : pointer on faulty thread descriptor.
// @ return EXCP_NON_FATAL / EXCP_USER_ERROR / EXCP_KERNEL_PANIC
//////////////////////////////////////////////////////////////////////////////////////////
static error_t hal_mmu_exception( thread_t * this ) 
{
	vseg_t         * vseg;        // vseg containing the bad_vaddr
	process_t      * process;     // local process descriptor
    error_t          error;       // return value

    reg_t            mmu_ins_excp_code;
    reg_t            mmu_ins_bad_vaddr;
    reg_t            mmu_dat_excp_code;
    reg_t            mmu_dat_bad_vaddr;

    intptr_t         bad_vaddr;
    uint32_t         excp_code;
	
    process     = this->process;

    // get relevant values from MMU
	hal_get_mmu_excp( &mmu_ins_excp_code,
	                  &mmu_ins_bad_vaddr,
	                  &mmu_dat_excp_code, 
	                  &mmu_dat_bad_vaddr );

    // get exception code and faulty vaddr
    if( mmu_ins_excp_code )
    {
        excp_code = mmu_ins_excp_code;
        bad_vaddr = mmu_ins_bad_vaddr;
    }
    else if( mmu_dat_excp_code )
    {
        excp_code = mmu_dat_excp_code;
        bad_vaddr = mmu_dat_bad_vaddr;
    }
    else
    {
         return EXCP_NON_FATAL;
    }

	vmm_dmsg("\n[INFO] %s : enters for thread %x / process %x"
             " / bad_vaddr = %x / excep_code = %x\n", 
		     __FUNCTION__, this->trdid , process->pid , bad_vaddr , excp_code );

    // on TSAR, a kernel thread should not rise an MMU exception
	assert( (this->type != THREAD_USER) , __FUNCTION__ ,
    "thread %x is a kernel thread / vaddr = %x\n", this->trdid , bad_vaddr );
  
    // vaddr must be contained in a registered vseg
    error = vmm_get_vseg( process , bad_vaddr , &vseg );

	vmm_dmsg("\n[INFO] %s : found vseg for thread %x / vseg_min = %x / vseg_max = %x\n", 
			 __FUNCTION__ , this->trdid , vseg->min , vseg->max );

    // analyse exception code
    if( excp_code & MMU_EXCP_PAGE_UNMAPPED )
    {
        // enable IRQs before handling page fault
        hal_enable_irq( NULL );

        // try to map the unmapped PTE
        error = vmm_handle_page_fault( process, 
                                       vseg,
                                       bad_vaddr >> CONFIG_PPM_PAGE_SHIFT );  // vpn
        // disable IRQs
        hal_disable_irq( NULL );

        if( error )     // not enough memory
        {
            printk("\n[ERROR] in %s for thread %x : cannot map legal vaddr = %x\n",
               __FUNCTION__ , this->trdid , bad_vaddr );

		    return EXCP_USER_ERROR;
        } 
        else            // page fault successfully handled
        {
            vmm_dmsg("\n[INFO] %s : page fault handled for vaddr = %x in thread %x\n",
		             __FUNCTION__ , bad_vaddr , this->trdid );
  
            return EXCP_NON_FATAL;
        }
    }
    else if( excp_code & MMU_EXCP_USER_PRIVILEGE )
    {
        printk("\n[ERROR] in %s for thread %x : user access to kernel vseg at vaddr = %x\n",
               __FUNCTION__ , this->trdid , bad_vaddr );

        return EXCP_USER_ERROR;
    }
    else if( excp_code & MMU_EXCP_USER_EXEC )
    {
        printk("\n[ERROR] in %s for thread %x : access to non-exec vseg at vaddr = %x\n",
               __FUNCTION__ , this->trdid , bad_vaddr );

        return EXCP_USER_ERROR;
    }
    else if( excp_code & MMU_EXCP_USER_WRITE )
    {
        printk("\n[ERROR] in %s for thread %x : write to non-writable vseg at vaddr = %x\n",
               __FUNCTION__ , this->trdid , bad_vaddr );

        return EXCP_USER_ERROR;
    }

    else  // this is a kernel error => panic    
    {
        printk("\n[PANIC] in %s for thread %x : kernel exception = %x / vaddr = %x\n",
               __FUNCTION__ , this->trdid , excp_code , bad_vaddr );

        return EXCP_KERNEL_PANIC;
    }
  
} // end hal_mmu_exception()

//////////////////////////////////////////////////////////////////////////////////////////
// This static function prints on the kernel terminal the saved context (core registers)
// and the thread state of a faulty thread.
//////////////////////////////////////////////////////////////////////////////////////////
// @ this     : pointer on faulty thread descriptor.
// @ regs_tbl : pointer on register array.
// @ return always EXCP_NON_FATAL
//////////////////////////////////////////////////////////////////////////////////////////
static void hal_exception_dump( thread_t * this,
                                reg_t    * regs_tbl )
{
    uint32_t  save_sr;

    // get pointers on TXT0 chdev
    xptr_t    txt0_xp  = chdev_dir.txt[0];
    cxy_t     txt0_cxy = GET_CXY( txt0_xp );
    chdev_t * txt0_ptr = GET_PTR( txt0_xp );

    // get extended pointer on remote TXT0 chdev lock
    xptr_t  lock_xp = XPTR( txt0_cxy , &txt0_ptr->wait_lock );

    // get TXT0 lock in busy waiting mode
    remote_spinlock_lock_busy( lock_xp , &save_sr );

    if( this->type == THREAD_USER )
    nolock_printk("\n================= USER ERROR / cycle %d ====================\n",
           hal_time_stamp() );
    else
    nolock_printk("\n================= KERNEL PANIC / cycle %d ==================\n",
           hal_time_stamp() );

	nolock_printk("  thread type = %s / trdid = %x / pid %x / core[%x,%d]\n"
           "  local locks = %d / remote locks = %d / blocked_vector = %X\n\n",
           thread_type_str(this->type), this->trdid, this->process->pid, local_cxy,
           this->core->lid, this->local_locks, this->remote_locks, this->blocked );

	nolock_printk("CR    %X  EPC   %X  SR    %X  SP     %X\n",
		   regs_tbl[UZ_CR], regs_tbl[UZ_EPC], regs_tbl[UZ_SR], regs_tbl[UZ_SP]);

    nolock_printk("at_1  %X  v0_2  %X  v1_3  %X  a0_4   %X  a1_5   %X\n",
   	       regs_tbl[UZ_AT], regs_tbl[UZ_V0], regs_tbl[UZ_V1], regs_tbl[UZ_A0], regs_tbl[UZ_A1]);

    nolock_printk("a2_6  %X  a3_7  %X  t0_8  %X  t1_9   %X  t2_10  %X\n",
		   regs_tbl[UZ_A2],regs_tbl[UZ_A3],regs_tbl[UZ_T0],regs_tbl[UZ_T1],regs_tbl[UZ_T2]);
  
    nolock_printk("t3_11 %X  t4_12 %X  t5_13 %X  t6_14  %X  t7_15  %X\n",
		   regs_tbl[UZ_T3],regs_tbl[UZ_T4],regs_tbl[UZ_T5],regs_tbl[UZ_T6],regs_tbl[UZ_T7]);

    nolock_printk("t8_24 %X  t9_25 %X  gp_28 %X  c0_hi  %X  c0_lo  %X\n",
		   regs_tbl[UZ_T8],regs_tbl[UZ_T9],regs_tbl[UZ_GP],regs_tbl[UZ_HI],regs_tbl[UZ_LO]);

    nolock_printk("s0_16 %X  s1_17 %X  s2_18 %X  s3_19  %X  s4_20  %X\n",
		   regs_tbl[UZ_S0],regs_tbl[UZ_S1],regs_tbl[UZ_S2],regs_tbl[UZ_S3],regs_tbl[UZ_S4]);
  
    nolock_printk("s5_21 %X  s6_22 %X  s7_23 %X  s8_30  %X  ra_31  %X\n",
	       regs_tbl[UZ_S5],regs_tbl[UZ_S6],regs_tbl[UZ_S7],regs_tbl[UZ_S8],regs_tbl[UZ_RA]);

    // release the lock
    remote_spinlock_unlock_busy( lock_xp , save_sr );

}  // end hal_exception_dump()


///////////////////////////////////////////////////////////////////////////////
// TODO replace the hal_core_sleep() by the generic panic() function.
///////////////////////////////////////////////////////////////////////////////
void hal_do_exception( thread_t * this, 
                       reg_t    * regs_tbl )
{
	error_t             error;
	uint32_t            excCode;                  // 4 bits XCODE from CP0_CR

    // get 4 bits XCODE from CP0_CR register
	excCode        = (regs_tbl[UZ_CR] >> 2) & 0xF;

	switch(excCode)
	{
        case XCODE_DBE:     // can be non fatal
	    case XCODE_IBE:     // can be non fatal
        {
		    error = hal_mmu_exception( this );
        }
		break;

	    case XCODE_CPU:    // can be non fatal
        {
            if( ((regs_tbl[UZ_CR] >> 28) & 0x3) == 1 )  // unavailable FPU
            {
                error = hal_fpu_exception( this );
            }
            else
            {
		        error = EXCP_USER_ERROR;
            }
        }
		break;

        case XCODE_OVR:    // user fatal error
        case XCODE_RI:     // user fatal error
        case XCODE_ADEL:   // user fatal error
        case XCODE_ADES:   // user fatal error
        {
		    error = EXCP_USER_ERROR;
        }
	    break;

        default:
        {
		    error = EXCP_KERNEL_PANIC;
        }
	}
    
    // analyse error code
	if( error == EXCP_USER_ERROR )          //  user error => kill user process
	{
        hal_exception_dump( this , regs_tbl );
        sys_kill( this->process->pid , SIGKILL );
	}
    else if( error == EXCP_KERNEL_PANIC )   // kernel error => kernel panic
    {
        hal_exception_dump( this , regs_tbl );
        hal_core_sleep();
    }
}  // end hal_do_exception()


