| 1 | /* |
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| 2 | * Authors: Frédéric Pétrot and Denis Hommais |
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| 3 | * $Log: exception.s,v $ |
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| 4 | * Revision 1.1 2005/03/02 12:37:22 buchmann |
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| 5 | * Add "soft" directory. |
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| 6 | * It allows to generate MIPS binary using cross compiler. |
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| 7 | * |
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| 8 | * Revision 1.2 2003/07/18 16:21:30 fred |
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| 9 | * Now interprets the instruction that causes a DBE in order to print the |
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| 10 | * address responsible for the failure. |
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| 11 | * Cleaned up the code a little (mainly comments :) |
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| 12 | * |
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| 13 | * Revision 1.1 2003/03/10 13:39:07 fred |
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| 14 | * Adding the hardware dependent stuff to smoothly handle multi |
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| 15 | * architecture compilation of this kernel |
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| 16 | * |
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| 17 | * Revision 1.1.1.1 2002/02/28 12:58:55 disydent |
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| 18 | * Creation of Disydent CVS Tree |
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| 19 | * |
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| 20 | * Revision 1.1.1.1 2001/11/19 16:55:37 pwet |
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| 21 | * Changing the CVS tree structure of disydent |
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| 22 | * |
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| 23 | * Revision 1.3 2001/11/14 12:08:45 fred |
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| 24 | * Making the ldscript being generated for correct path accesses |
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| 25 | * Removing the syscall entry of the exception handler for now |
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| 26 | * |
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| 27 | * Revision 1.2 2001/11/09 14:51:03 fred |
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| 28 | * Remove the reset executable and make the assembler be piped through |
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| 29 | * cpp. |
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| 30 | * The ldscript is not usable. I have to think before going on |
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| 31 | * |
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| 32 | * $Id: exception.S,v 1.1 2003/03/10 13:39:07 fred Exp |
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| 33 | * Note : we do not check BD at any time yet! Beware, ... |
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| 34 | * Rev 0 : minimal handler to support syscall for system calls |
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| 35 | * implementation |
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| 36 | * Rev 1 : added correct exception/interruption detection and messages |
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| 37 | * Rev 2 : added mult and div interpretation in illegal instruction |
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| 38 | * Rev 3 : Makes it compliant with multi-thread/multi-processor |
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| 39 | * Stack is thread stack now (it must at least for preemptive |
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| 40 | * scheduling stuffs |
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| 41 | */ |
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| 42 | .rdata |
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| 43 | .align 2 |
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| 44 | msg : .ascii "An exception occurred with the following cause :\n\000" |
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| 45 | |
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| 46 | jmptable: |
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| 47 | .word Int |
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| 48 | .word Uimp |
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| 49 | .word Uimp |
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| 50 | .word Uimp |
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| 51 | .word AdEL |
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| 52 | .word AdES |
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| 53 | .word IBE |
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| 54 | .word DBE |
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| 55 | .word Sys |
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| 56 | .word Bp |
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| 57 | .word RI |
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| 58 | .word CpU |
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| 59 | .word Ovf |
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| 60 | .word Ukn |
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| 61 | .word Ukn |
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| 62 | |
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| 63 | .text |
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| 64 | .align 2 |
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| 65 | .ent excep |
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| 66 | excep: |
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| 67 | /* |
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| 68 | * Here I save the whole C compatible register context, which is a |
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| 69 | * waste of time if only assembly functions are to be used |
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| 70 | * A more optimized way to do things would be to check for critical |
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| 71 | * events (typically external interrupts) and do the saving only |
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| 72 | * when an other events took place |
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| 73 | * Note that this implies to check which registers to save according |
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| 74 | * to the interrupt handling routines, that are usually user defined! |
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| 75 | * |
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| 76 | * Reminder: $26 and $27 are kernel registers that need not be saved |
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| 77 | * This shall be executed in critical section since the stack pointer |
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| 78 | * is not properly set until the subu! |
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| 79 | */ |
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| 80 | .set noreorder |
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| 81 | /* Shall not touch $1 until it is saved */ |
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| 82 | .set noat |
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| 83 | |
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| 84 | subu $29, $29, 26*4 /* Load kernel stack addr + stack update */ |
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| 85 | sw $1, 1*4($29) /* save all temporaries*/ |
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| 86 | .set at |
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| 87 | sw $2, 2*4($29) /* others are saved when calling procedures*/ |
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| 88 | sw $3, 3*4($29) |
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| 89 | sw $4, 4*4($29) |
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| 90 | sw $5, 5*4($29) |
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| 91 | sw $6, 6*4($29) |
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| 92 | sw $7, 7*4($29) |
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| 93 | sw $8, 8*4($29) |
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| 94 | sw $9, 9*4($29) |
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| 95 | sw $10, 10*4($29) |
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| 96 | sw $11, 11*4($29) |
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| 97 | sw $12, 12*4($29) |
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| 98 | sw $13, 13*4($29) |
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| 99 | sw $14, 14*4($29) |
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| 100 | sw $15, 15*4($29) |
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| 101 | sw $24, 16*4($29) |
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| 102 | sw $25, 17*4($29) |
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| 103 | mfc0 $26, $14 /* load EPC into k0 (two cycles befor use)*/ |
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| 104 | sw $29, 18*4($29) |
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| 105 | sw $30, 19*4($29) |
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| 106 | sw $31, 20*4($29) |
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| 107 | sw $26, 21*4($29) /* and store it to be recallable*/ |
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| 108 | mfhi $26 |
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| 109 | sw $26, 22*4($29) |
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| 110 | mflo $26 |
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| 111 | sw $26, 23*4($29) |
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| 112 | |
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| 113 | /* Check the cause of the arrival in this code */ |
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| 114 | |
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| 115 | mfc0 $27, $13 /* load CAUSE into $27*/ |
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| 116 | nop |
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| 117 | andi $27, $27, 0x3c /* get the exception code (ExcCode)*/ |
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| 118 | beqz $27, Int /* Test if it is an interrupt. If so*/ |
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| 119 | sw $0, 24*4($29) /* return address is epc + 0 */ |
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| 120 | /* it's faster.*/ |
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| 121 | la $26, jmptable /* load the base of the jump table*/ |
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| 122 | /* get the exception code (ExcCode)*/ |
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| 123 | addu $26, $26, $27 /* load the offset in the table*/ |
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| 124 | lw $27, ($26) /* load the pointed value*/ |
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| 125 | li $26, 4 |
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| 126 | j $27 /* and jump there*/ |
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| 127 | sw $26, 24*4($29) /* faulty insn is at epc - 4 */ |
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| 128 | nop /* delayed slot too*/ |
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| 129 | |
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| 130 | /* |
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| 131 | * External interupts: |
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| 132 | * The meaning of these interupts is for sure system dependent, so |
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| 133 | * this routine must be adapted to each system particularities |
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| 134 | * |
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| 135 | * Right now we just find out what interrupt lead us here, and print |
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| 136 | * a small message about it. |
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| 137 | */ |
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| 138 | .rdata |
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| 139 | .align 2 |
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| 140 | .text |
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| 141 | Int : |
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| 142 | .set noat |
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| 143 | mfc0 $4, $13 /* load CAUSE into $27*/ |
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| 144 | mfc0 $26, $12 /* load STATUS into $26*/ |
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| 145 | andi $4, $4, 0xFF00 /* mask CAUSE to get the ITs only*/ |
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| 146 | and $4, $4, $26 /* keep only the enabled ITs*/ |
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| 147 | srl $4, $4, 8 /* and put them in the LSBees*/ |
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| 148 | beqz $4, _endit /* If none, then what are we doing here? */ |
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| 149 | nop |
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| 150 | |
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| 151 | .extern SwitchOnIt |
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| 152 | |
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| 153 | la $26, SwitchOnIt |
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| 154 | jal $26 |
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| 155 | nop |
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| 156 | |
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| 157 | _endit: |
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| 158 | j _return /* go back to user*/ |
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| 159 | nop |
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| 160 | .set at |
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| 161 | |
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| 162 | /* |
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| 163 | * Clearly fatal exceptions as far as we're concerned, ... |
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| 164 | */ |
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| 165 | .rdata |
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| 166 | .align 2 |
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| 167 | m2 : .ascii "Unimplemented TLB Exception!\n\000" |
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| 168 | m2k : .ascii "Reserved Exception!\n\000" |
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| 169 | m2o : .ascii "Integer Arithmetic Overflow!\n\000" |
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| 170 | |
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| 171 | .text |
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| 172 | .align 2 |
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| 173 | .set reorder |
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| 174 | Uimp : la $4, m2 /* load the appropriate message,...*/ |
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| 175 | j U /* */ |
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| 176 | Ukn : la $4, m2k /* */ |
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| 177 | j U /* */ |
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| 178 | Ovf : la $4, m2o /* */ |
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| 179 | U : la $2, uputs |
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| 180 | jal $2 /* and print it!*/ |
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| 181 | j _exit /* */ |
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| 182 | .set noreorder |
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| 183 | |
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| 184 | /* |
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| 185 | * Illegal instructions: |
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| 186 | * we interpret mult/div and lwl/lwr here, and exit on an other code |
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| 187 | * Before modifing this code think that NO REGISTER CONTENT should |
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| 188 | * be touched before the end of the register loading routine |
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| 189 | * This explains why some code seems duplicated (several mfc0) |
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| 190 | */ |
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| 191 | .rdata |
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| 192 | m2i : .ascii "Illegal or Reserved Instruction!\n\000" |
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| 193 | .text |
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| 194 | .set noat |
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| 195 | RI : mfc0 $26, $14 /* load EPC into $26*/ |
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| 196 | nop /* */ |
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| 197 | nop /* */ |
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| 198 | lw $26, ($26) /* $26 contains the faulty ins*/ |
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| 199 | lui $27, 0xFC00 /* mask for special*/ |
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| 200 | and $27, $26, $27 /* */ |
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| 201 | bne $27, $0, Ilg /* this is not a special trap*/ |
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| 202 | |
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| 203 | /* |
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| 204 | * I do not handle the mult/div trap, as we have added the |
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| 205 | * instructions in our R3000 model |
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| 206 | */ |
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| 207 | nop |
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| 208 | |
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| 209 | Ilg: la $4, m2i |
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| 210 | la $2, uputs |
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| 211 | jal $2 /* we got an illegal ins, so we quit*/ |
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| 212 | nop |
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| 213 | j _exit /* */ |
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| 214 | nop |
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| 215 | |
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| 216 | /* |
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| 217 | * Unaligned access: |
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| 218 | * Quite fatal, I'm afraid |
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| 219 | */ |
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| 220 | .rdata |
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| 221 | .align 2 |
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| 222 | m3 : .ascii "Unaligned/unallowed Access while %s address 0x%x at pc 0x%x!\n\000" |
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| 223 | m3l : .ascii "reading\000" |
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| 224 | m3e : .ascii "writing\000" |
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| 225 | |
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| 226 | .text |
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| 227 | .align 2 |
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| 228 | .set reorder |
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| 229 | AdEL : la $5, m3l |
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| 230 | j AdE |
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| 231 | AdES : la $5, m3e |
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| 232 | AdE : la $4, m3 |
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| 233 | .set noreorder |
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| 234 | mfc0 $6, $8 /* load BAR into thrid arg ($6)*/ |
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| 235 | mfc0 $7, $14 /* load EPC into fourth arg ($7)*/ |
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| 236 | la $2, uputs |
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| 237 | jal $2 /* print all that stuff*/ |
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| 238 | nop |
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| 239 | j _exit |
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| 240 | nop |
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| 241 | |
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| 242 | /* |
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| 243 | * Synchronous bus error |
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| 244 | */ |
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| 245 | .rdata |
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| 246 | .align 2 |
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| 247 | m4i: .ascii "Bus error while loading the instrunction at pc 0x%x!\n\000" |
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| 248 | m4d: .ascii "Bus error while loading the datum at pc 0x%x for addr 0x%x!\n\000" |
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| 249 | .data |
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| 250 | .text |
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| 251 | |
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| 252 | .align 2 |
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| 253 | .set reorder |
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| 254 | IBE : mfc0 $5, $14 /* load EPC */ |
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| 255 | la $4, m4i |
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| 256 | j BE |
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| 257 | .set noreorder |
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| 258 | DBE : la $4, m4d |
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| 259 | /* |
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| 260 | * The instruction at EPC must be interpreted to get the |
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| 261 | * address that caused the fault. |
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| 262 | * The register value must be reloaded from the stack, and |
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| 263 | * since the storage of the registers is quite exotic right |
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| 264 | * now, this will work only for registers 1 to 15! |
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| 265 | */ |
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| 266 | mfc0 $5, $14 /* load EPC */ |
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| 267 | lw $6, 0($5) /* load faulty insn */ |
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| 268 | andi $8, $6, 0xFFFF /* get the imm field of it */ |
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| 269 | srl $9, $6, 19 |
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| 270 | andi $9, $9, 0x7c /* get the rs register index times 4 */ |
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| 271 | add $9, $29, $9 /* compute the stack index of this register */ |
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| 272 | lw $9, 0($9) |
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| 273 | addu $6, $9, $8 /* get the address as computed */ |
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| 274 | |
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| 275 | BE : la $2, uputs |
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| 276 | jal $2 /* print all that stuff*/ |
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| 277 | nop |
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| 278 | j _exit |
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| 279 | nop |
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| 280 | |
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| 281 | /* |
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| 282 | * Syscall: simple and straightforward. |
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| 283 | * Even elegant : nothing's done at all anymore |
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| 284 | */ |
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| 285 | .rdata |
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| 286 | .align 2 |
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| 287 | m5 : .ascii "Syscall : no actions performed anymore\000" |
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| 288 | .text |
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| 289 | .align 2 |
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| 290 | Sys : |
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| 291 | la $4, m5 |
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| 292 | la $2, uputs |
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| 293 | jalr $2 |
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| 294 | nop |
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| 295 | j _ret_sys /* get back to caller */ |
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| 296 | nop |
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| 297 | #endif |
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| 298 | |
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| 299 | /* |
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| 300 | * |
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| 301 | * We just indicate we got a breakpoint |
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| 302 | * This shall be filled on a system per system basis |
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| 303 | * |
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| 304 | */ |
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| 305 | .rdata |
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| 306 | .align 2 |
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| 307 | m6 : .ascii "Breakpoint of code %d!\n\000" |
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| 308 | |
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| 309 | .text |
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| 310 | .align 2 |
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| 311 | Bp : la $4, m6 |
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| 312 | mfc0 $3, $14 /* load EPC*/ |
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| 313 | nop |
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| 314 | nop |
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| 315 | lw $5, ($3) /* load the 'break' instruction*/ |
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| 316 | li $3, 0xF /* filled delayed slot (load a mask)*/ |
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| 317 | srl $5, $5, 16 /* shift it*/ |
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| 318 | and $5, $5, $3 /* and get the code from the insn*/ |
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| 319 | la $2, uputs |
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| 320 | jal $2 /* print the string*/ |
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| 321 | nop |
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| 322 | j _return |
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| 323 | nop |
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| 324 | |
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| 325 | /* |
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| 326 | * |
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| 327 | * Kernel/user violation, or coprocessor unusable. |
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| 328 | * that's pretty fatal, ain't it ? |
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| 329 | * |
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| 330 | */ |
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| 331 | .rdata |
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| 332 | .align 2 |
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| 333 | m7 : .ascii "Unusable Coprocessor %d!\n\000" |
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| 334 | m70: .ascii "Trying to use a kernel instruction in user mode!\n\000" |
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| 335 | |
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| 336 | .text |
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| 337 | .align 2 |
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| 338 | CpU : mfc0 $3, $13 /* load CAUSE*/ |
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| 339 | nop |
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| 340 | li $2, 0x30000000/* */ |
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| 341 | and $2, $2, $3 /* mask to get the CE bits */ |
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| 342 | bnez $2, cun /* not zero, so it is a CUN*/ |
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| 343 | nop /* cannot put a 'la' here,...*/ |
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| 344 | .set reorder |
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| 345 | la $4, m70 /* here, it is a kernel violation*/ |
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| 346 | j C |
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| 347 | .set noreorder |
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| 348 | cun: la $4, m7 |
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| 349 | srl $5, $2, 28 /* LSByte contains now the copro number*/ |
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| 350 | C: la $2, uputs |
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| 351 | jal $2 |
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| 352 | nop |
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| 353 | j _exit |
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| 354 | nop |
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| 355 | |
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| 356 | _exit: li $2, 100000 |
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| 357 | _exit_l: bne $2, $0, _exit_l |
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| 358 | addiu $2, $2, -1 |
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| 359 | c0 00 |
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| 360 | nop |
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| 361 | |
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| 362 | _return : |
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| 363 | lw $2, 2*4($29) |
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| 364 | j tmp |
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| 365 | nop |
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| 366 | _ret_sys: /* Special case for syscall : $2 is not restored */ |
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| 367 | tmp: .set noat |
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| 368 | lw $1, 1*4($29) |
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| 369 | .set at |
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| 370 | lw $3, 3*4($29) |
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| 371 | lw $4, 4*4($29) |
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| 372 | lw $5, 5*4($29) |
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| 373 | lw $6, 6*4($29) |
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| 374 | lw $7, 7*4($29) |
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| 375 | lw $8, 8*4($29) |
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| 376 | lw $9, 9*4($29) |
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| 377 | lw $10, 10*4($29) |
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| 378 | lw $11, 11*4($29) |
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| 379 | lw $12, 12*4($29) |
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| 380 | lw $13, 13*4($29) |
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| 381 | lw $14, 14*4($29) |
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| 382 | lw $15, 15*4($29) |
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| 383 | lw $24, 16*4($29) |
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| 384 | lw $25, 17*4($29) |
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| 385 | lw $29, 18*4($29) |
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| 386 | lw $30, 19*4($29) |
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| 387 | lw $31, 20*4($29) |
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| 388 | |
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| 389 | /* Take care of hi and lo also */ |
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| 390 | lw $26, 22*4($29) |
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| 391 | mthi $26 |
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| 392 | lw $26, 23*4($29) |
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| 393 | mtlo $26 |
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| 394 | |
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| 395 | lw $26, 21*4($29) /* This is the epc of this context */ |
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| 396 | lw $27, 24*4($29) /* This is the offset: 4 excep, 0 int */ |
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| 397 | addu $29, $29, 26*4 /* Stack update : fill lw stall */ |
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| 398 | addu $26, $26, $27 /* Addr for return from excep */ |
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| 399 | j $26 /* Jump back where the exception occured*/ |
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| 400 | rfe /* And restore the original mode*/ |
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| 401 | .set reorder |
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| 402 | .end excep |
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