source: soft/giet_vm/giet_kernel/giet.s @ 263

Last change on this file since 263 was 258, checked in by alain, 11 years ago

This is a major release, including a deep restructuration of code.
The main evolutions are

  • use of the Tsar preloader to load the GIET boot-loader from disk
  • introduction of a FAT32 file system library,
  • use of this fat32 library by the boot-loader to load the map.bin data structure, and the various .elf files
  • reorganisation of drivers (one file per peripheral).
  • introduction of drivers for new peripherals: vci_chbuf_dma and vci_multi_ahci.
  • introduction of a new physical memory allocator in the boot code.

This release has been tested on the tsar_generic_iob architecture,
for the two following mappings: 4c_1p_iob_four.xml and 4c_1p_iob_sort.xml
  • 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[32] array defines the 32 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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