| nkeynes@812 | 1 | .section .text
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| nkeynes@812 | 2 | .code 32
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| nkeynes@812 | 3 | .align 0
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| nkeynes@812 | 4 | .global start
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| nkeynes@812 | 5 | .global ___exit
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| nkeynes@812 | 6 | .global _atexit
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| nkeynes@812 | 7 | start:
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| nkeynes@821 | 8 | b real_entry
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| nkeynes@821 | 9 | b exception_entry
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| nkeynes@821 | 10 | b exception_entry /* SWI - not used so jump to general exception */
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| nkeynes@821 | 11 | b exception_entry
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| nkeynes@821 | 12 | b exception_entry
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| nkeynes@821 | 13 | b exception_entry /* Not a vector, but if we ever get here... */
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| nkeynes@821 | 14 | b irq_entry
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| nkeynes@821 | 15 | b fiq_entry
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| nkeynes@812 | 16 |
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| nkeynes@812 | 17 | /* Start by setting up a stack */
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| nkeynes@821 | 18 | real_entry:
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| nkeynes@812 | 19 | /* Set up the stack pointer to a fixed value */
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| nkeynes@812 | 20 | ldr r3, .LC0
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| nkeynes@812 | 21 | mov sp, r3
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| nkeynes@812 | 22 | /* Setup a default stack-limit in-case the code has been
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| nkeynes@812 | 23 | compiled with "-mapcs-stack-check". Hard-wiring this value
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| nkeynes@812 | 24 | is not ideal, since there is currently no support for
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| nkeynes@812 | 25 | checking that the heap and stack have not collided, or that
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| nkeynes@812 | 26 | this default 64k is enough for the program being executed.
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| nkeynes@812 | 27 | However, it ensures that this simple crt0 world will not
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| nkeynes@812 | 28 | immediately cause an overflow event: */
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| nkeynes@812 | 29 | sub sl, sp, #64 << 10 /* Still assumes 256bytes below sl */
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| nkeynes@821 | 30 | b .LB0
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| nkeynes@812 | 31 |
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| nkeynes@821 | 32 | .syscall:
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| nkeynes@821 | 33 | .word -1 /* Syscall # */
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| nkeynes@821 | 34 | .word 0 /* Arguments */
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| nkeynes@821 | 35 | .word 0
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| nkeynes@821 | 36 | .word 0
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| nkeynes@821 | 37 |
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| nkeynes@821 | 38 | irq_counter:
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| nkeynes@821 | 39 | .word 0
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| nkeynes@821 | 40 | fiq_counter:
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| nkeynes@821 | 41 | .word 0
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| nkeynes@821 | 42 |
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| nkeynes@821 | 43 | .LB0:
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| nkeynes@812 | 44 | /* Zero-out the BSS segment */
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| nkeynes@812 | 45 | mov a2, #0 /* Second arg: fill value */
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| nkeynes@812 | 46 | mov fp, a2 /* Null frame pointer */
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| nkeynes@812 | 47 | mov r7, a2 /* Null frame pointer for Thumb */
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| nkeynes@812 | 48 |
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| nkeynes@812 | 49 | ldr a1, .LC1 /* First arg: start of memory block */
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| nkeynes@812 | 50 | ldr a3, .LC2
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| nkeynes@812 | 51 | sub a3, a3, a1 /* Third arg: length of block */
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| nkeynes@812 | 52 | bl memset
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| nkeynes@812 | 53 |
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| nkeynes@812 | 54 | /* Enter main with no arguments for now */
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| nkeynes@812 | 55 | mov r0, #0 /* no arguments */
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| nkeynes@812 | 56 | mov r1, #0 /* no argv either */
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| nkeynes@812 | 57 | bl main
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| nkeynes@812 | 58 |
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| nkeynes@812 | 59 | bl exit /* Should not return */
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| nkeynes@812 | 60 |
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| nkeynes@812 | 61 | /* For Thumb, constants must be after the code since only
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| nkeynes@812 | 62 | positive offsets are supported for PC relative addresses. */
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| nkeynes@821 | 63 |
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| nkeynes@821 | 64 | exception_entry:
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| nkeynes@821 | 65 | mov r13, #-2
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| nkeynes@821 | 66 | str r13, .syscall
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| nkeynes@821 | 67 | .die:
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| nkeynes@821 | 68 | b .die
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| nkeynes@812 | 69 |
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| nkeynes@821 | 70 | irq_entry:
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| nkeynes@821 | 71 | /* Increment IRQ counter and return */
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| nkeynes@821 | 72 | ldr r13, irq_counter
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| nkeynes@821 | 73 | add r13, r13, #1
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| nkeynes@821 | 74 | str r13, irq_counter
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| nkeynes@821 | 75 | subs r15, r14, #4
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| nkeynes@821 | 76 | fiq_entry:
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| nkeynes@821 | 77 | /* Increment FIQ counter and return */
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| nkeynes@821 | 78 | ldr r13, fiq_counter
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| nkeynes@821 | 79 | add r13, r13, #1
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| nkeynes@821 | 80 | str r13, fiq_counter
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| nkeynes@821 | 81 | subs r15, r14, #4
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| nkeynes@821 | 82 |
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| nkeynes@812 | 83 | .align 0
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| nkeynes@812 | 84 | .LC0:
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| nkeynes@812 | 85 | .word _stack
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| nkeynes@812 | 86 | .LC1:
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| nkeynes@812 | 87 | .word __bss_start
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| nkeynes@812 | 88 | .LC2:
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| nkeynes@812 | 89 | .word __bss_end
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| nkeynes@812 | 90 |
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| nkeynes@812 | 91 |
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lxdream 0.9.1