| 1 | #include "arm.h" |
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| 2 | |
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| 3 | .file "crt0.S" |
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| 4 | |
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| 5 | #define XGLUE(a,b) a##b |
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| 6 | #define GLUE(a,b) XGLUE(a,b) |
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| 7 | |
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| 8 | #ifdef __USER_LABEL_PREFIX__ |
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| 9 | #define SYM_NAME( name ) GLUE (__USER_LABEL_PREFIX__, name) |
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| 10 | #else |
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| 11 | #error __USER_LABEL_PREFIX is not defined |
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| 12 | #endif |
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| 13 | |
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| 14 | .text |
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| 15 | .syntax unified |
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| 16 | /* Setup the assembly entry point. */ |
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| 17 | #ifdef PREFER_THUMB |
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| 18 | .macro FUNC_START name |
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| 19 | .global \name |
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| 20 | .thumb_func |
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| 21 | \name: |
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| 22 | .endm |
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| 23 | .thumb |
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| 24 | #else |
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| 25 | .macro FUNC_START name |
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| 26 | .global \name |
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| 27 | \name: |
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| 28 | .endm |
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| 29 | .code 32 |
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| 30 | #endif |
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| 31 | FUNC_START SYM_NAME(_start) |
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| 32 | /* Unnecessary to set fp for v6-m/v7-m, which don't support |
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| 33 | ARM state. */ |
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| 34 | #if __ARM_ARCH_ISA_ARM |
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| 35 | mov fp, #0 /* Null frame pointer. */ |
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| 36 | #endif |
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| 37 | movs r7, #0 /* Null frame pointer for Thumb. */ |
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| 38 | |
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| 39 | /* Enable interrupts for gdb debugging. */ |
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| 40 | #ifdef PREFER_THUMB |
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| 41 | cpsie if |
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| 42 | #else |
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| 43 | mrs r0, cpsr |
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| 44 | bic r0, r0, #0xC0 |
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| 45 | msr cpsr, r0 |
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| 46 | #endif |
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| 47 | |
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| 48 | movs a2, #0 /* Second arg: fill value. */ |
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| 49 | ldr a1, .LC1 /* First arg: start of memory block. */ |
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| 50 | ldr a3, .LC2 |
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| 51 | subs a3, a3, a1 /* Third arg: length of block. */ |
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| 52 | |
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| 53 | #ifdef GCRT0 |
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| 54 | /* Zero out the bss without using memset. |
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| 55 | Using memset is bad because it may be instrumented for |
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| 56 | profiling, but at this point, the profiling data structures |
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| 57 | have not been set up. |
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| 58 | FIXME: This loop could be a lot more efficient. */ |
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| 59 | subs a3, a3, #0 |
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| 60 | beq 2f |
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| 61 | 1: strb a2, [a1] |
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| 62 | subs a3, a3, #1 |
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| 63 | add a1, a1, #1 |
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| 64 | bne 1b |
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| 65 | 2: |
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| 66 | /* Nothing to left to clear. */ |
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| 67 | #endif |
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| 68 | |
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| 69 | #if __thumb__ && !defined(PREFER_THUMB) |
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| 70 | /* Enter Thumb mode. */ |
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| 71 | add a4, pc, #1 /* Get the address of the Thumb block. */ |
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| 72 | bx a4 /* Go there and start Thumb decoding. */ |
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| 73 | |
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| 74 | .code 16 |
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| 75 | .global __change_mode |
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| 76 | .thumb_func |
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| 77 | __change_mode: |
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| 78 | #endif |
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| 79 | |
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| 80 | #ifndef GCRT0 |
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| 81 | bl SYM_NAME(memset) |
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| 82 | #endif |
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| 83 | bl SYM_NAME(__get_memtop) |
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| 84 | subs r0, r0, #32 |
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| 85 | mov sp, r0 |
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| 86 | |
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| 87 | #ifdef __USES_INITFINI__ |
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| 88 | /* Some arm/elf targets use the .init and .fini sections |
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| 89 | to create constructors and destructors, and for these |
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| 90 | targets we need to call the _init function and arrange |
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| 91 | for _fini to be called at program exit. */ |
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| 92 | ldr r0, .Lfini |
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| 93 | bl SYM_NAME (atexit) |
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| 94 | bl SYM_NAME (_init) |
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| 95 | #endif |
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| 96 | |
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| 97 | movs a1, #0 |
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| 98 | ldr a2, .LC3 |
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| 99 | movs a3, a2 |
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| 100 | bl SYM_NAME(main) |
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| 101 | 1: bl SYM_NAME(exit) |
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| 102 | b 1b |
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| 103 | .align 2 |
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| 104 | .LC1: |
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| 105 | .word __bss_start__ |
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| 106 | .LC2: |
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| 107 | .word __bss_end__ |
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| 108 | .LC3: |
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| 109 | .word 0 |
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| 110 | #ifdef __USES_INITFINI__ |
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| 111 | .Lfini: |
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| 112 | .word SYM_NAME(_fini) |
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| 113 | #endif |
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| 114 | #if 0 |
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| 115 | #ifdef __thumb__ |
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| 116 | .code 16 |
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| 117 | #endif |
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| 118 | .global SYM_NAME(__syscall) |
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| 119 | #ifdef __thumb__ |
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| 120 | .thumb_func |
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| 121 | #else |
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| 122 | .align 4 |
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| 123 | #endif |
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| 124 | SYM_NAME(__syscall): |
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| 125 | mov r12, lr |
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| 126 | #ifdef __thumb__ |
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| 127 | swi 0x18 |
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| 128 | #else |
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| 129 | swi 0x180001 |
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| 130 | #endif |
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| 131 | mov pc, r12 |
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| 132 | #endif |
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