source: soft/giet_vm/giet_kernel/giet.s @ 295

Last change on this file since 295 was 267, checked in by cfuguet, 11 years ago
  • Adding new task context information: THREAD INDEX.

This value can be accessed by USER applications to get the
thread index of the current task. This thread index
corresponds to the index in a vspace.

The value of this index can be forced in the vspace part
of the XML description file using the trdid field in the
task description. When this value is missing, for each
task, a value from 0 to N-1 will be assigned, where N is
the number of task in the vspace.

The user application access this value through the
giet_thread_id() function defined in the stdio library
which uses the SYSCALL_THREAD_ID to access the task
context information.

  • Supporting mono TTY platforms

When the GIET_MONO_TTY constant defined in the giet_config
file, contains a value different than 0, all tasks will
share the TTY[0]. If this is the case, in the stdio
library, the giet_tty_printf() function will take the TTY
hardware lock before writing
  • Property svn:executable set to *
File size: 6.8 KB
Line 
1/************************************************************************************
2* GIET: Interruption/Exception/Trap Handler for MIPS32 processor
3*
4* The base address of the segment containing this code MUST be 0x80000000, in
5* order to have the entry point at address 0x80000180!!! All messages are
6* printed on the TTY corresponding to the task&processor identifiers.
7*
8* It uses two arrays of functions:
9* - the _cause_vector[16] array defines the 16 causes to enter the GIET
10*   it is initialized in th exc_handler.c file
11* - the _syscall_vector[64] array defines the 64 system calls entry points
12*   it is initialised in the sys_handler.c file
13***********************************************************************************/
14
15    .section .giet, "ax", @progbits
16    .space 0x180
17
18/*
19 * GIET Entry point (at address 0x80000180)
20 */
21
22    .func   _giet
23    .type   _giet, %function
24
25_giet:
26    mfc0    $27,    $13                 /* $27 <= Cause register */
27    la      $26,    _cause_vector       /* $26 <= _cause_vector */
28    andi    $27,    $27,    0x3c            /* $27 <= XCODE*4 */
29    addu    $26,    $26,    $27             /* $26 <= &_cause_vector[XCODE] */
30    lw      $26,    ($26)               /* $26 <=  _cause_vector[XCODE] */
31    jr      $26                         /* Jump indexed by XCODE */
32
33    .endfunc
34    .size _giet, .-_giet
35
36/*
37 * *** System Call Handler ***
38 *
39 * A system call is handled as a special function call.
40 *  - $2 contains the system call index (< 64).
41 *  - $3 is used to store the syscall address
42 *  - $4, $5, $6, $7 contain the arguments values.
43 *  - The return address (EPC) and the SR are saved in the stack.
44 *  - Interrupts are enabled before branching to the syscall.
45 *  - All syscalls must return to the syscall handler.
46 *  - $2, $3, $4, $5, $6, $7 as well as $26 & $27 can be modified.
47 *
48 * In case of undefined system call, an error message displays the value of EPC
49 * on the TTY corresponding to the processor, and the user program is killed.
50 */
51
52    .globl  _sys_handler
53    .func   _sys_handler
54    .type   _sys_handler, %function
55
56_sys_handler:
57    addiu   $29,    $29,    -24     /* 2 slots for SR&EPC, 4 slots for args passing */
58    mfc0    $26,    $12             /* load SR */
59    sw      $26,    16($29)         /* save it in the stack */
60    mfc0    $27,    $14             /* load EPC */
61    addiu   $27,    $27,    4       /* increment EPC for return address */
62    sw      $27,    20($29)         /* save it in the stack */
63
64    andi    $26,    $2,     0x3F    /* $26 <= syscall index (i < 64) */
65    sll     $26,    $26,    2       /* $26 <= index * 4 */
66    la      $27,    _syscall_vector /* $27 <= &_syscall_vector[0] */
67    addu    $27,    $27,    $26     /* $27 <= &_syscall_vector[i] */
68    lw      $3,     0($27)          /* $3  <= syscall address */
69
70    li      $27,    0xFFFFFFED      /* Mask for UM & EXL bits */
71    mfc0    $26,    $12             /* $26 <= SR */
72    and     $26,    $26,    $27     /* UM = 0 / EXL = 0 */
73    mtc0    $26,    $12             /* interrupt enabled */
74    jalr    $3                      /* jump to the proper syscall */
75    mtc0    $0,     $12             /* interrupt disbled */
76
77    lw      $26,    16($29)         /* load SR from stack */
78    mtc0    $26,    $12             /* restore SR */
79    lw      $26,    20($29)         /* load EPC from stack */
80    mtc0    $26,    $14             /* restore EPC */
81    addiu   $29,    $29,     24     /* restore stack pointer */
82    eret                            /* exit GIET */
83
84    .endfunc
85    .size _sys_handler, .-_sys_handler
86
87/*
88 * *** Interrupt Handler ***
89 *
90 * This simple interrupt handler cannot be interrupted.
91 *
92 * All non persistant registers, such as $1 to $15, and $24 to $25, as well as
93 * register $31 and EPC, are saved in the interrupted program stack, before
94 * calling the Interrupt Service Routine. These registers can be used by the
95 * ISR code.
96 */
97
98    .globl  _int_handler
99    .func   _int_handler
100    .type   _int_handler, %function
101
102_int_handler:
103    addiu   $29,    $29,    -25*4   /* stack space reservation (21 registers to
104                                       save and 4 free words to call function) */
105    .set noat
106    sw      $1,     4*4($29)        /* save $1 */
107    .set at
108    sw      $2,     5*4($29)        /* save $2 */
109    sw      $3,     6*4($29)        /* save $3 */
110    sw      $4,     7*4($29)        /* save $4 */
111    sw      $5,     8*4($29)        /* save $5 */
112    sw      $6,     9*4($29)        /* save $6 */
113    sw      $7,     10*4($29)       /* save $7 */
114    sw      $8,     11*4($29)       /* save $8 */
115    sw      $9,     12*4($29)       /* save $9 */
116    sw      $10,    13*4($29)       /* save $10 */
117    sw      $11,    14*4($29)       /* save $11 */
118    sw      $12,    15*4($29)       /* save $12 */
119    sw      $13,    16*4($29)       /* save $13 */
120    sw      $14,    17*4($29)       /* save $14 */
121    sw      $15,    18*4($29)       /* save $15 */
122    sw      $24,    19*4($29)       /* save $24 */
123    sw      $25,    20*4($29)       /* save $25 */
124    sw      $31,    21*4($29)       /* save $31 */
125    mflo    $26
126    sw      $26,    22*4($29)       /* save LO */
127    mfhi    $26
128    sw      $26,    23*4($29)       /* save HI */
129    mfc0    $27,    $14
130    sw      $27,    24*4($29)       /* save EPC */
131
132    la      $26,    _irq_demux
133    jalr    $26                     /* jump to a C function to find the proper ISR */
134
135restore:
136    .set noat
137    lw      $1,     4*4($29)        /* restore $1 */
138    .set at
139    lw      $2,     4*5($29)        /* restore $2 */
140    lw      $3,     4*6($29)        /* restore $3 */
141    lw      $4,     4*7($29)        /* restore $4 */
142    lw      $5,     4*8($29)        /* restore $5 */
143    lw      $6,     4*9($29)        /* restore $6 */
144    lw      $7,     4*10($29)       /* restore $7 */
145    lw      $8,     4*11($29)       /* restore $8 */
146    lw      $9,     4*12($29)       /* restore $9 */
147    lw      $10,    4*13($29)       /* restore $10 */
148    lw      $11,    4*14($29)       /* restore $11 */
149    lw      $12,    4*15($29)       /* restore $12 */
150    lw      $13,    4*16($29)       /* restore $13 */
151    lw      $14,    4*17($29)       /* restore $14 */
152    lw      $15,    4*18($29)       /* restore $15 */
153    lw      $24,    4*19($29)       /* restore $24 */
154    lw      $25,    4*20($29)       /* restore $25 */
155    lw      $31,    4*21($29)       /* restore $31 */
156    lw      $26,    4*22($29)
157    mtlo    $26                     /* restore LO */
158    lw      $26,    4*23($29)
159    mthi    $26                     /* restore HI */
160    lw      $27,    4*24($29)       /* return address (EPC) */
161    addiu   $29,    $29,    25*4    /* restore stack pointer */
162    mtc0    $27,    $14             /* restore EPC */
163    eret                            /* exit GIET */
164
165    .endfunc
166    .size _int_handler, .-_int_handler
167
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