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1 /*
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2
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3 Package: dyncall
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4 Library: dyncall
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5 File: dyncall/dyncall_call_arm32_thumb_gas.s
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6 Description: ARM Thumb call kernel implementation for GNU assembler.
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7 License:
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8
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9 Copyright (c) 2007-2011 Daniel Adler <dadler@uni-goettingen.de>,
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10 Tassilo Philipp <tphilipp@potion-studios.com>
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11
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12 Permission to use, copy, modify, and distribute this software for any
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13 purpose with or without fee is hereby granted, provided that the above
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14 copyright notice and this permission notice appear in all copies.
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15
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16 THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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17 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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18 MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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19 ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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20 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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21 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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22 OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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23
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24 */
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25
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26
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27 .text
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28 #if !defined(__thumb2__)
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29 .code 16 /* THUMB mode */
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30 #endif
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31
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32 .globl dcCall_arm32_thumb
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33
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34 /* Main dyncall call. */
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35 .thumb_func
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36 dcCall_arm32_thumb:
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37
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38 /* Prolog. This function never needs to spill inside its prolog, so just store the permanent registers. */
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39 push {%r4-%r7, %r14} /* Frame ptr, permanent registers, link register -> save area on stack. */
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40 mov %r7, %r13 /* Set frame ptr. */
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41
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42 /* Call. */
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43 mov %r4, %r0 /* Move 'fptr' to r4 (1st argument is passed in r0). */
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44
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45 /* Disable 'thumb' address forcing... */
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46
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47 /* mov %r0, #1 */ /* Assure that LSB is set to 1 (THUMB call). - Not Required and not useful for interworking calls */
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48 /* orr %r4, %r0 */
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49
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50 mov %r5, %r1 /* Move 'args' to r5 (2nd argument is passed in r1). */
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51 mov %r6, %r2 /* Move 'size' to r6 (3rd argument is passed in r2). */
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52
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53 cmp %r6, #16 /* Jump to call if no more than 4 arguments. */
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54 ble call
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55
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56 sub %r6, #16 /* Size of remaining arguments. */
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57 mov %r0, %r13 /* Set stack pointer to top of stack. */
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58 sub %r0, %r0, %r6
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59 lsr %r0, #3 /* Align stack on 8 byte boundaries. */
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60 lsl %r0, #3
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61 mov %r13, %r0
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62
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63 add %r1, #16 /* Let r1 point to remaining arguments. */
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64 mov %r2, #0 /* Init byte counter to 0. */
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65 .thumb_func
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66 pushArgs:
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67 ldrb %r3, [%r1, %r2] /* Load a byte into r3. */
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68 strb %r3, [%r0, %r2] /* Push byte onto stack. */
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69 add %r2, %r2, #1 /* Increment byte counter. */
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70 cmp %r2, %r6
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71 bne pushArgs
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72 .thumb_func
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73 call:
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74 ldmia %r5!, {%r0-%r3} /* Load first 4 arguments for new call into r0-r3. */
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75
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76 /* 'blx %r4' workaround for ARMv4t in THUMB: */
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77 mov %r6, %r15 /* Load PC+2 instructions from here */
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78 add %r6, #5 /* Increment by 2 instructions (Address of 'Epilog') and set bit 0 (THUMB) */
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79 mov %r14, %r6 /* Store in link register. */
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80 bx %r4 /* Branch and force THUMB-mode return (LR bit 0 set). */
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81
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82 /* Epilog. */
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83 mov %r13, %r7 /* Reset stack ptr. */
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84 pop {%r4-%r7, %r15} /* Restore permanent registers and program counter. (Force a stay in THUMB in ARMv4, whether ARMv5 can return in ARM or THUMB depending on the bit 0. */
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85
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