mdw@git.distorted.org.uk Git - ssr/blob - StraySrc/Libraries/Sapphire/s/seh

   1 ;
   2 ; seh.s
   3 ;
   4 ; Structured Exception Handling, the Sapphire way
   5 ;
   6 ; © 1995-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's Sapphire library.
  12 ;
  13 ; Sapphire is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; Sapphire is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with Sapphire.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ;----- Standard header ------------------------------------------------------
  28
  29                 GET     libs:header
  30                 GET     libs:swis
  31
  32                 GET     libs:stream
  33
  34 ;----- External dependencies ------------------------------------------------
  35
  36                 GET     sapphire:except
  37                 GET     sapphire:msgs
  38                 GET     sapphire:sapphire
  39
  40 ;----- Main code ------------------------------------------------------------
  41
  42                 AREA    |Sapphire$$Code|,CODE,READONLY
  43
  44 ; --- seh_try ---
  45 ;
  46 ; On entry:     R0 == pointer to catch definition block
  47 ;
  48 ; On exit:      R13 dropped by a (small) amount
  49 ;
  50 ; Use:          Inserts an exception handler at the current position.
  51 ;               Exceptions are matched against those described in the catch
  52 ;               block.  If there is a handler for the exception, the
  53 ;               corresponding handler is called, and expected to resume
  54 ;               normally.  Otherwise the tidy-up routine is called and we
  55 ;               unwind the stack further to find an appropriate handler.
  56 ;
  57 ;               The catch block has the following format:
  58 ;
  59 ;               word    B to tidy-up routine
  60 ;               word    1st exception mask
  61 ;               word    1st B to catch routine
  62 ;               word    2nd exception mask
  63 ;               word    2nd B to catch routine
  64 ;               ...
  65 ;               word    0
  66 ;
  67 ;               An exception mask contains two halfwords.  Bits 16-31 are the
  68 ;               class to match, or -1 for all classes.  Bits 0-15 are the
  69 ;               subtype to match, or -1 for all subtypes.  You can do really
  70 ;               odd things if you set bits 16-31 to -1 and leave 0-15
  71 ;               matching specific subtypes -- do this at your own risk.
  72
  73                 EXPORT  seh_try
  74 seh_try         ROUT
  75
  76                 SUB     R13,R13,#16             ;Leave space for our record
  77                 STMFD   R13!,{R0,R12,R14}       ;Save some registers
  78
  79                 ; --- Save caller's R10 and R12 ---
  80
  81                 ADD     R14,R13,#16             ;Point to area in frame
  82                 STMIA   R14,{R0,R10,R12}        ;Save the registers away
  83
  84                 ; --- Now fiddle with the try list ---
  85
  86                 WSPACE  seh__wSpace             ;Find my workspace
  87                 LDR     R14,seh__currList       ;Find the current list
  88                 LDR     R0,[R14,#0]             ;Load the current value
  89                 STR     R0,[R13,#12]            ;Save that away nicely
  90                 ADD     R0,R13,#12              ;Point to the frame we made
  91                 STR     R0,[R14,#0]             ;This is the new list head
  92                 LDMFD   R13!,{R0,R12,PC}^       ;And return to caller
  93
  94                 LTORG
  95
  96 ; --- seh_unTry ---
  97 ;
  98 ; On entry:     --
  99 ;
 100 ; On exit:      R13 moved to position before corresponding seh_try
 101 ;
 102 ; Use:          Removes the try block marker in the stack at the current
 103 ;               position.  Note that the stack will be unwound to where it
 104 ;               was when seh_try was called.
 105
 106                 EXPORT  seh_unTry
 107 seh_unTry       ROUT
 108
 109                 STMFD   R13!,{R0,R1,R12,R14}    ;Save some registers
 110                 MOV     R1,R13                  ;Remember this stack frame
 111                 WSPACE  seh__wSpace             ;Find my workspace
 112                 LDR     R14,seh__currList       ;Find the current list
 113                 LDR     R13,[R14,#0]            ;Load the unwound stack ptr
 114                 LDR     R0,[R13],#16            ;Load the old list position
 115                 STR     R0,[R14,#0]             ;Store this away nicely
 116                 LDMIA   R1,{R0,R1,R12,PC}^      ;And return to caller
 117
 118                 LTORG
 119
 120 ; --- seh_throw ---
 121 ;
 122 ; On entry:     R0 == exception to match
 123 ;               R1-R3 == useful bits of information
 124 ;
 125 ; On exit:      Doesn't return, unless you've done something /really/ odd
 126 ;
 127 ; Use:          Throws an exception.  The stack is unwound until we find
 128 ;               a handler which can cope.  If there is no handler, we abort
 129 ;               the program.
 130
 131                 EXPORT  seh_throw
 132 seh_throw       ROUT
 133
 134                 WSPACE  seh__wSpace             ;Find my workspace
 135                 LDR     R9,seh__currList        ;Find the current list
 136
 137                 ; --- Now go through the list ---
 138
 139 05              LDR     R13,[R9,#0]             ;Get the top try block
 140                 CMP     R13,#0                  ;Have we run out of trys?
 141                 BEQ     %90seh_throw            ;Yes -- oh deary me
 142                 LDR     R14,[R13],#4            ;Load the previous pointer
 143                 STR     R14,[R9,#0]             ;And store it away
 144                 LDMIA   R13!,{R8,R10,R12}       ;Load useful things out
 145
 146                 ; --- Now find a matching catch ---
 147
 148                 MOV     R14,#&00FF              ;Build &FFFF
 149                 ORR     R14,R14,#&FF00          ;Because it's useful
 150
 151                 ADD     R7,R8,#4                ;Skip past tidy-up routine
 152 01              LDR     R6,[R7],#8              ;Load the exception mask
 153                 CMP     R6,#0                   ;Have we finished here?
 154                 BEQ     %10seh_throw            ;Yes -- deal with this then
 155                 MOV     R5,R6,LSL #16           ;Isolate the bottom half
 156                 CMP     R5,R14,LSL #16          ;Is it a wildcard?
 157                 CMPNE   R5,R0,LSL #16           ;Or does it match?
 158                 BNE     %b01                    ;No -- move on then
 159                 MOV     R5,R6,LSR #16           ;Isolate the top half
 160                 CMP     R5,R14                  ;Is it a wildcard?
 161                 CMPNE   R5,R0,LSR #16           ;Or does it match?
 162                 BNE     %b01                    ;No -- move on then
 163
 164                 SUB     PC,R7,#4                ;Go and do the exception
 165
 166 10seh_throw     MOV     R14,PC                  ;Set up return address
 167                 MOV     PC,R8                   ;So call tidy-up code
 168                 B       %b05                    ;And try another block
 169
 170                 ; --- No catch blocks found ---
 171                 ;
 172                 ; Oh dear.  Things go very badly now.
 173
 174 90seh_throw     MOV     R2,R0                   ;Get the exception type
 175                 LDR     R13,sapph_stackBase     ;Find a stack somewhere
 176                 ADR     R0,seh__noHandler       ;Point to the error block
 177                 BL      msgs_error              ;Translate it nicely
 178                 B       except_fatal            ;Report a fatal error
 179
 180 seh__noHandler  DCD     1
 181                 DCB     "sehNOHND",0
 182
 183                 LTORG
 184
 185 ; --- seh_throwErrors ---
 186 ;
 187 ; On entry:     --
 188 ;
 189 ; On exit:      --
 190 ;
 191 ; Use:          Sets up an except-style error handler to throw errors
 192 ;               as SEH exceptions.
 193
 194                 EXPORT  seh_throwErrors
 195 seh_throwErrors ROUT
 196
 197                 STMFD   R13!,{R0-R2,R14}        ;Save some registers
 198                 ADR     R0,seh__handler         ;Point to the handler
 199                 MOV     R1,#0                   ;Don't care about R12
 200                 MOV     R2,#0                   ;Don't even care about R13
 201                 BL      except_returnPt         ;Register that nicely
 202                 LDMFD   R13!,{R0-R2,PC}^        ;And return to caller
 203
 204 seh__handler    ADD     R0,PC,#0                ;Point to `resume point'
 205                 MOVS    PC,R14                  ;And return to except
 206
 207                 ADD     R1,R11,#4               ;Point to error message
 208                 MOV     R0,#&00010000           ;Exception number for error
 209                 B       seh_throw               ;Throw it to the handler
 210
 211                 LTORG
 212
 213 ; --- seh_setListBase ---
 214 ;
 215 ; On entry:     R0 == pointer to try block list base, or 0 to use global
 216 ;
 217 ; On exit:      --
 218 ;
 219 ; Use:          Sets the try block list base.  This should only be used by
 220 ;               coroutine providers, like coRoutine and thread.
 221
 222                 EXPORT  seh_setListBase
 223 seh_setListBase ROUT
 224
 225                 STMFD   R13!,{R12,R14}          ;Save some registers
 226                 WSPACE  seh__wSpace             ;Find my workspace
 227                 MOVS    R14,R0                  ;Get the value to save
 228                 ADREQ   R14,seh__tryList        ;If zero, use our pointer
 229                 STR     R14,seh__currList       ;Store away in the block
 230                 LDMFD   R13!,{R12,PC}^          ;And return to caller
 231
 232                 LTORG
 233
 234 ; --- seh_init ---
 235 ;
 236 ; On entry:     --
 237 ;
 238 ; On exit:      --
 239 ;
 240 ; Use:          Initialises SEH's facilities.
 241
 242                 EXPORT  seh_init
 243 seh_init        ROUT
 244
 245                 STMFD   R13!,{R12,R14}          ;Save some registers
 246                 WSPACE  seh__wSpace             ;Find my workspace
 247                 ADR     R14,seh__tryList        ;Find the global list
 248                 STR     R14,seh__currList       ;This is the current one
 249                 LDMFD   R13!,{R12,PC}^          ;And return to caller
 250
 251                 LTORG
 252
 253 seh__wSpace     DCD     0
 254
 255 ;----- Workspace ------------------------------------------------------------
 256
 257                 ^       0,R12
 258 seh__wStart     #       0
 259
 260 seh__tryList    #       4                       ;The global try list head
 261 seh__currList   #       4                       ;Address of current list
 262
 263 seh__wSize      EQU     {VAR}-seh__wStart
 264
 265                 AREA    |Sapphire$$LibData|,CODE,READONLY
 266
 267                 DCD     seh__wSize
 268                 DCD     seh__wSpace
 269                 DCD     0
 270                 DCD     seh_init
 271
 272 ;----- That's all, folks ----------------------------------------------------
 273
 274                 END