libffi/src/arm/gentramp.sh

   1 #!/bin/sh
   2
   3 # -----------------------------------------------------------------------
   4 #  gentramp.sh - Copyright (c) 2010, Plausible Labs Cooperative, Inc.
   5 #
   6 #  ARM Trampoline Page Generator
   7 #
   8 #  Permission is hereby granted, free of charge, to any person obtaining
   9 #  a copy of this software and associated documentation files (the
  10 #  ``Software''), to deal in the Software without restriction, including
  11 #  without limitation the rights to use, copy, modify, merge, publish,
  12 #  distribute, sublicense, and/or sell copies of the Software, and to
  13 #  permit persons to whom the Software is furnished to do so, subject to
  14 #  the following conditions:
  15 #
  16 #  The above copyright notice and this permission notice shall be included
  17 #  in all copies or substantial portions of the Software.
  18 #
  19 #  THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
  20 #  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  21 #  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  22 #  NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  23 #  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  24 #  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25 #  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  26 #  DEALINGS IN THE SOFTWARE.
  27 #  -----------------------------------------------------------------------
  28
  29 PROGNAME=$0
  30
  31 # Each trampoline is exactly 3 instructions, or 12 bytes. If any of these values change,
  32 # the entire arm trampoline implementation must be updated to match, too.
  33
  34 # Size of an individual trampoline, in bytes
  35 TRAMPOLINE_SIZE=12
  36
  37 # Page size, in bytes
  38 PAGE_SIZE=4096
  39
  40 # Compute the size of the reachable config page; The first 16 bytes of the config page
  41 # are unreachable due to our maximum pc-relative ldr offset.
  42 PAGE_AVAIL=`expr $PAGE_SIZE - 16`
  43
  44 # Compute the number of of available trampolines.
  45 TRAMPOLINE_COUNT=`expr $PAGE_AVAIL / $TRAMPOLINE_SIZE`
  46
  47 header () {
  48     echo "# GENERATED CODE - DO NOT EDIT"
  49     echo "# This file was generated by $PROGNAME"
  50     echo ""
  51
  52     # Write out the license header
  53 cat << EOF
  54 #  Copyright (c) 2010, Plausible Labs Cooperative, Inc.
  55 #
  56 #  Permission is hereby granted, free of charge, to any person obtaining
  57 #  a copy of this software and associated documentation files (the
  58 #  ``Software''), to deal in the Software without restriction, including
  59 #  without limitation the rights to use, copy, modify, merge, publish,
  60 #  distribute, sublicense, and/or sell copies of the Software, and to
  61 #  permit persons to whom the Software is furnished to do so, subject to
  62 #  the following conditions:
  63 #
  64 #  The above copyright notice and this permission notice shall be included
  65 #  in all copies or substantial portions of the Software.
  66 #
  67 #  THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
  68 #  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  69 #  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  70 #  NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  71 #  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  72 #  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  73 #  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  74 #  DEALINGS IN THE SOFTWARE.
  75 #  -----------------------------------------------------------------------
  76
  77 EOF
  78
  79     # Write out the trampoline table, aligned to the page boundary
  80     echo ".text"
  81     echo ".align 12"
  82     echo ".globl _ffi_closure_trampoline_table_page"
  83     echo "_ffi_closure_trampoline_table_page:"
  84 }
  85
  86
  87 # WARNING - Don't modify the trampoline code size without also updating the relevent libffi code
  88 trampoline () {
  89     cat << END
  90
  91     // trampoline
  92     // Save to stack
  93     stmfd sp!, {r0-r3}
  94
  95     // Load the context argument from the config page.
  96     // This places the first usable config value at _ffi_closure_trampoline_table-4080
  97     // This accounts for the above 4-byte stmfd instruction, plus 8 bytes constant when loading from pc.
  98     ldr r0, [pc, #-4092]
  99
 100     // Load the jump address from the config page.
 101     ldr pc, [pc, #-4092]
 102
 103 END
 104 }
 105
 106 main () {
 107     # Write out the header
 108     header
 109
 110     # Write out the trampolines
 111     local i=0
 112     while [ $i -lt ${TRAMPOLINE_COUNT} ]; do
 113         trampoline
 114         local i=`expr $i + 1`
 115     done
 116 }
 117
 118 main