112 lines
2.2 KiB
ArmAsm
112 lines
2.2 KiB
ArmAsm
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.file "crt0.S"
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#define XGLUE(a,b) a##b
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#define GLUE(a,b) XGLUE(a,b)
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#ifdef __USER_LABEL_PREFIX__
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#define SYM_NAME( name ) GLUE (__USER_LABEL_PREFIX__, name)
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#else
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#error __USER_LABEL_PREFIX is not defined
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#endif
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.text
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/* Setup the assembly entry point. */
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.code 32
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.globl SYM_NAME(start)
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.globl SYM_NAME(_start)
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SYM_NAME(start):
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SYM_NAME(_start):
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mov fp, #0 /* Null frame pointer. */
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mov r7, #0 /* Null frame pointer for Thumb. */
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/* Enable interrupts for gdb debugging. */
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mrs r0, cpsr
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bic r0, r0, #0xC0
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msr cpsr, r0
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mov a2, #0 /* Second arg: fill value. */
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ldr a1, .LC1 /* First arg: start of memory block. */
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ldr a3, .LC2
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sub a3, a3, a1 /* Third arg: length of block. */
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#ifdef GCRT0
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/* Zero out the bss without using memset.
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Using memset is bad because it may be instrumented for
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profiling, but at this point, the profiling data structures
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have not been set up.
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FIXME: This loop could be a lot more efficient. */
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subs a3, a3, #0
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beq 2f
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1: strb a2, [a1]
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subs a3, a3, #1
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add a1, a1, #1
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bne 1b
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2:
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/* Nothing to left to clear. */
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#endif
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#ifdef __thumb__ /* Enter Thumb mode. */
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add a4, pc, #1 /* Get the address of the Thumb block. */
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bx a4 /* Go there and start Thumb decoding. */
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.code 16
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.global __change_mode
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.thumb_func
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__change_mode:
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#endif
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#ifndef GCRT0
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bl SYM_NAME(memset)
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#endif
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bl SYM_NAME(__get_memtop)
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sub r0, r0, #32
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mov sp, r0
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#ifdef __USES_INITFINI__
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/* Some arm/elf targets use the .init and .fini sections
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to create constructors and destructors, and for these
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targets we need to call the _init function and arrange
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for _fini to be called at program exit. */
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ldr r0, .Lfini
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bl SYM_NAME (atexit)
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bl SYM_NAME (_init)
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#endif
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mov a1, #0
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ldr a2, .LC3
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mov a3, a2
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bl SYM_NAME(main)
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1: bl SYM_NAME(exit)
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b 1b
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.align 2
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.LC1:
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.word __bss_start__
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.LC2:
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.word __bss_end__
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.LC3:
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.word 0
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#ifdef __USES_INITFINI__
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.Lfini:
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.word SYM_NAME(_fini)
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#endif
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#if 0
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#ifdef __thumb__
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.code 16
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#endif
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.global SYM_NAME(__syscall)
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#ifdef __thumb__
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.thumb_func
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#else
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.align 4
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#endif
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SYM_NAME(__syscall):
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mov r12, lr
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#ifdef __thumb__
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swi 0x18
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#else
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swi 0x180001
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#endif
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mov pc, r12
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#endif
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