source: rtems/c/src/lib/libbsp/arm/armulator/start/start.S @ caf88699

#include "../startup/swi.h"

/* ANSI concatenation macros.  */
#define CONCAT(a, b) CONCAT2(a, b)
#define CONCAT2(a, b) a ## b

#ifdef __USER_LABEL_PREFIX__
#define FUNCTION( name ) CONCAT (__USER_LABEL_PREFIX__, name)
#else
#error __USER_LABEL_PREFIX is not defined
#endif

/* .text is used instead of .section .text so it works with arm-aout too.  */
        .text
        .code 32
        .align  0

        .global _mainCRTStartup
        .global _start
        .global start
start:
_start:
_mainCRTStartup:

/* Start by setting up a stack */
#ifdef ARM_RDP_MONITOR
        /*  Issue Demon SWI to read stack info */
        swi     SWI_GetEnv      /*  Returns command line in r0 */
        mov     sp,r1           /*  and the highest memory address in r1 */
        ldr     sl, .LC2        /*  stack limit is at end of data */
        add     sl, sl, #256    /*  allow slop for stack overflow handling */
                                /*  and small frames */
#else
#ifdef ARM_RDI_MONITOR
        /*  Issue Angel SWI to read stack info */
        mov     r0, #AngelSWI_Reason_HeapInfo
        adr     r1, .LC0        /*  point at ptr to 4 words to receive data */
        swi     AngelSWI_ARM    /*  We are always in ARM mode for startup */
        ldr     r0, .LC0        /*  point at values read */
        ldr     sp, [r0, #8]
        ldr     sl, [r0, #12]
        add     sl, sl, #256    /*  allow slop for stack overflow handling */
                                /*  and small frames */
#else
        /*  Set up the stack pointer to a fixed value */
        ldr     r3, .LC0
        mov     sp, r3
        /* Setup a default stack-limit in-case the code has been
           compiled with "-mapcs-stack-check".  Hard-wiring this value
           is not ideal, since there is currently no support for
           checking that the heap and stack have not collided, or that
           this default 64k is enough for the program being executed.
           However, it ensures that this simple crt0 world will not
           immediately cause an overflow event:  */
        sub     sl, sp, #64 << 10       /* Still assumes 256bytes below sl */
#endif
#endif
        mov     a2, #0                  /* Second arg: fill value */
        mov     fp, a2                  /* Null frame pointer */
        mov     r7, a2                  /* Null frame pointer for Thumb */
        
        ldr     a1, .LC1                /* First arg: start of memory block */
        ldr     a3, .LC2        
        sub     a3, a3, a1              /* Third arg: length of block */
        

#ifdef __thumb__                /* Enter Thumb mode.... */

        add     a4, pc, #1      /* Get the address of the Thumb block */
        bx      a4              /* Go there and start Thumb decoding  */

        .code 16
        .global __change_mode
        .thumb_func
__change_mode:  
#endif
        
        bl      FUNCTION (memset)
#if !defined (ARM_RDP_MONITOR) && !defined (ARM_RDI_MONITOR)
        mov     r0, #0          /*  no arguments  */
        mov     r1, #0          /*  no argv either */
#else
        /* Need to set up standard file handles */
        bl      FUNCTION (initialize_monitor_handles)
        
#ifdef ARM_RDP_MONITOR
        swi     SWI_GetEnv      /*  sets r0 to point to the command line */
        mov     r1, r0
#else
        mov     r0, #AngelSWI_Reason_GetCmdLine
        adr     r1, .LC30       /*  Space for command line */
        swi     AngelSWI
        ldr     r1, .LC30
#endif
        /*  Parse string at r1 */
        mov     r0, #0          /*  count of arguments so far */
.LC10:
/*  Skip leading blanks */
#ifdef __thumb__
        ldrb    r3, [r1]
        add     r1, #1
#else
        ldrb    r3, [r1], #1
#endif
        cmp     r3, #0
        beq     .LC12
        cmp     r3, #' '
        beq     .LC10

/*  See whether we are scanning a string */
        cmp     r3, #'"'
#ifdef __thumb__
        beq     .LC20
        cmp     r3, #'\''
        bne     .LC21
.LC20:
        mov     r2, r3
        b       .LC22

.LC21:
        mov     r2, #' '        /*  terminator type */
        sub     r1, r1, #1      /*  adjust back to point at start char */
.LC22:
#else
        cmpne   r3, #'\''
        moveq   r2, r3
        movne   r2, #' '        /*  terminator type */
        subne   r1, r1, #1      /*  adjust back to point at start char */
#endif

/*  Stack a pointer to the current argument */
#ifdef __thumb__
        push    {r1}
#else
        stmfd   sp!, {r1}
#endif
        add     r0, r0, #1
.LC11:
#ifdef __thumb__
        ldrb    r3, [r1]
        add     r1, #1
#else
        ldrb    r3, [r1], #1
#endif
        cmp     r3, #0
        beq     .LC12
        cmp     r2, r3          /*  reached terminator? */
        bne     .LC11
        mov     r2, #0
        sub     r3, r1, #1
        strb    r2, [r3]        /*  terminate the arg string */
        b       .LC10

.LC12:
        mov     r1, sp          /*  point at stacked arg pointers */
        /* We've now got the stacked args in order reverse the */
#ifdef __thumb__
        mov     r2, r0
        lsl     r2, #2
        add     r2, sp
        mov     r3, sp
.LC15:  cmp     r2, r3
        bls     .LC14
        sub     r2, #4
        ldr     r4, [r2]
        ldr     r5, [r3]
        str     r5, [r2]
        str     r4, [r3]
        add     r3, #4
        b       .LC15
.LC14:  
#else
        add     r2, sp, r0, LSL #2      /* End of args */
        mov     r3, sp                  /* Start of args */
.LC13:  cmp     r2, r3
        ldrhi   r4,[r2, #-4]            /* Reverse ends of list */
        ldrhi   r5, [r3]
        strhi   r5, [r2, #-4]!
        strhi   r4, [r3], #4
        bhi     .LC13
#endif

#endif
        bl      FUNCTION (main)

        bl      FUNCTION (exit)         /* Should not return */

#ifdef __thumb__
        /* Come out of Thumb mode... This code should be redundant...   */

        mov     a4, pc
        bx      a4

        .code 32
        .global change_back
change_back:
        /* Halt the execution.  This code should never be executed.  */
        /*
        ** With no debug monitor, this probably aborts (eventually).
        ** With a Demon debug monitor, this halts cleanly.
        ** With an Angel debug monitor, this will report 'Unknown SWI'.
        */
        swi     SWI_Exit
#endif
        
        /* For Thumb, constants must be after the code since only 
        positive offsets are supported for PC relative addresses. */
        
        .align 0
.LC0:
#ifdef ARM_RDI_MONITOR
        .word   HeapBase
#else
#ifndef ARM_RDP_MONITOR
#ifdef __pe__
        .word   0x800000
#else
/*      .word   0x80000 */              /* Top of RAM on the PIE board */
#endif
#endif
#endif
.LC1:
        .word   _clear_start
.LC2:
        .word   _clear_end

#ifdef ARM_RDI_MONITOR
.LC30:  .word   CommandLine

/*  Workspace for Angel calls. */
        .data
/*  Data returned by monitor SWI */
HeapBase:       .word   0
HeapLimit:      .word   0
StackBase:      .word   0
StackLimit:     .word   0
CommandLine:    .space  256,0   /*  Maximum length of 255 chars handled */
#endif
        
#ifdef __pe__
        .section .idata$3
        .long   0,0,0,0,0,0,0,0
#endif