source: trunk/libs/newlib/src/libgloss/arm/crt0.S @ 546

#include "newlib.h"
#include "arm.h"
#include "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

#ifdef HAVE_INITFINI_ARRAY
#define _init   __libc_init_array
#define _fini   __libc_fini_array
#endif

#if defined(__ARM_EABI__) && defined(__thumb__) && !defined(__thumb2__)
/* For Thumb1 we need to force the architecture to be sure that we get the
   correct attributes on the object file; otherwise the assembler will get
   confused and mark the object as being v6T2.  */
#if defined(__ARM_ARCH_4T__)
        .arch armv4t
#elif defined(__ARM_ARCH_5T__) || defined(__ARM_ARCH_5TE__)
        /* Nothing in this object requires higher than v5.  */
        .arch armv5t
#elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) \
        || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6Z__) \
        || defined(__ARM_ARCH_6ZK__)
        /* Nothing in this object requires higher than v6.  */
        .arch armv6
#elif defined(__ARM_ARCH_6M__)
#ifdef ARM_RDP_MONITOR
        /* Object file uses SVC, so mark as v6s-m.  */
        .arch armv6s-m
#else
        .arch armv6-m
#endif
#endif
#endif

/* .text is used instead of .section .text so it works with arm-aout too.  */
        .text
        .syntax unified
#ifdef PREFER_THUMB
        .thumb
.macro FUNC_START name
        .global \name
        .thumb_func
\name:
.endm
#else
        .code 32
.macro FUNC_START name
        .global \name
\name:
.endm
#endif

.macro indirect_call reg
#ifdef HAVE_CALL_INDIRECT
        blx \reg
#else
        mov     lr, pc
        mov     pc, \reg
#endif
.endm

        .align  0

        FUNC_START      _mainCRTStartup
        FUNC_START      _start
#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
        /* Annotation for EABI unwinding tables.  */
        .fnstart
#endif

        /* __ARM_ARCH_PROFILE is defined from GCC 4.8 onwards, however __ARM_ARCH_7A
        has been defined since 4.2 onwards, which is when v7-a support was added
        and hence 'A' profile support was added in the compiler.  Allow for this
        file to be built with older compilers.  We only call this for A profile
        cores.  */
#if defined (__ARM_ARCH_7A__) || (__ARM_ARCH_PROFILE == 'A')
/*  The init hook does not use the stack and is called before the stack has been set up.  */
#ifdef ARM_RDI_MONITOR
        bl      _rdimon_hw_init_hook
        .weak   FUNCTION (_rdimon_hw_init_hook)
#endif
#endif

/* 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 */

        /*  stack limit is at end of data */
        /*  allow slop for stack overflow handling and small frames */
#ifdef THUMB1_ONLY
        ldr     r0, .LC2
        adds    r0, #128
        adds    r0, #128
        mov     sl, r0
#else
        ldr     sl, .LC2
        add     sl, sl, #256
#endif
#else
#ifdef ARM_RDI_MONITOR
        /*  Issue Angel SWI to read stack info */
        movs    r0, #AngelSWI_Reason_HeapInfo
        adr     r1, .LC0        /*  point at ptr to 4 words to receive data */
#ifdef THUMB_VXM
        bkpt    AngelSWI
#elif defined(__thumb2__)
        /*  We are in thumb mode for startup on armv7 architectures. */
        AngelSWIAsm     AngelSWI
#else
        /*  We are always in ARM mode for startup on pre armv7 archs. */
        AngelSWIAsm     AngelSWI_ARM
#endif
        ldr     r0, .LC0        /*  point at values read */

        /* Set __heap_limit.  */
        ldr     r1, [r0, #4]
        cmp     r1, #0
        beq     .LC33
        ldr     r2, =__heap_limit
        str     r1, [r2]
.LC33:
        ldr     r1, [r0, #0]
        cmp     r1, #0
        bne     .LC32
        /* If the heap base value [r0, #0] is 0 then the heap base is actually 
           at the end of program data (i.e. __end__). See:
           http://infocenter.arm.com/help/topic/com.arm.doc.dui0471-/Bacbefaa.html
           for more information.  */
        ldr     r1, .LC31
        str     r1, [r0, #0]
.LC32:  
        ldr     r1, [r0, #8]
        ldr     r2, [r0, #12]
        /*  We skip setting sp/sl if 0 returned from semihosting. 
            - According to semihosting docs, if 0 returned from semihosting,
              the system was unable to calculate the real value, so it's ok
              to skip setting sp/sl to 0 here.
            - Considering M-profile processors, We might want to initialize
              sp by the first entry of vector table and return 0 to SYS_HEAPINFO
              semihosting call, which will be skipped here. */
        cmp     r1, #0
        beq     .LC26
        mov     sp, r1
.LC26:
        cmp     r2, #0
        beq     .LC27
        /*  allow slop for stack overflow handling and small frames */
#ifdef THUMB1_ONLY
        adds    r2, #128
        adds    r2, #128
        mov     sl, r2
#else
        add     sl, r2, #256
#endif
.LC27:
#else
        /*  Set up the stack pointer to a fixed value */
        /*  Changes by toralf:
            - Allow linker script to provide stack via __stack symbol - see
              defintion of .Lstack
            - Provide "hooks" that may be used by the application to add
              custom init code - see .Lhwinit and .Lswinit      
            - Go through all execution modes and set up stack for each of them.
              Loosely based on init.s from ARM/Motorola example code.
              Note: Mode switch via CPSR is not allowed once in non-privileged
                    mode, so we take care not to enter "User" to set up its sp,
                    and also skip most operations if already in that mode. */

        ldr     r3, .Lstack
        cmp     r3, #0
#ifdef __thumb2__
        it      eq
#endif  
#ifdef THUMB1_ONLY
        bne     .LC28
        ldr     r3, .LC0
.LC28:
#else
        ldreq   r3, .LC0
#endif
        /* Note: This 'mov' is essential when starting in User, and ensures we
                 always get *some* sp value for the initial mode, even if we 
                 have somehow missed it below (in which case it gets the same
                 value as FIQ - not ideal, but better than nothing.) */
        mov     sp, r3
#ifdef PREFER_THUMB
        /* XXX Fill in stack assignments for interrupt modes.  */
#else
        mrs     r2, CPSR
        tst     r2, #0x0F       /* Test mode bits - in User of all are 0 */
        beq     .LC23           /* "eq" means r2 AND #0x0F is 0 */
        msr     CPSR_c, #0xD1   /* FIRQ mode, interrupts disabled */
        mov     sp, r3
        sub     sl, sp, #0x1000 /* This mode also has its own sl (see below) */
        
        mov     r3, sl  
        msr     CPSR_c, #0xD7   /* Abort mode, interrupts disabled */
        mov     sp, r3
        sub     r3, r3, #0x1000

        msr     CPSR_c, #0xDB   /* Undefined mode, interrupts disabled */
        mov     sp, r3
        sub     r3, r3, #0x1000

        msr     CPSR_c, #0xD2   /* IRQ mode, interrupts disabled */
        mov     sp, r3
        sub     r3, r3, #0x2000
                
        msr     CPSR_c, #0xD3   /* Supervisory mode, interrupts disabled */

        mov     sp, r3
        sub     r3, r3, #0x8000 /* Min size 32k */
        bic     r3, r3, #0x00FF /* Align with current 64k block */
        bic     r3, r3, #0xFF00

        str     r3, [r3, #-4]   /* Move value into user mode sp without */ 
        ldmdb   r3, {sp}^       /* changing modes, via '^' form of ldm */ 
        orr     r2, r2, #0xC0   /* Back to original mode, presumably SVC, */
        msr     CPSR_c, r2      /* with FIQ/IRQ disable bits forced to 1 */
#endif  
.LC23:
        /* 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:  */
#ifdef THUMB1_ONLY
        movs    r2, #64
        lsls    r2, r2, #10
        subs    r2, r3, r2
        mov     sl, r2
#else
        sub     sl, r3, #64 << 10       /* Still assumes 256bytes below sl */
#endif
#endif
#endif
        /* Zero the memory in the .bss section.  */
        movs    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        
        subs    a3, a3, a1              /* Third arg: length of block */
        

#if __thumb__ && !defined(PREFER_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)
/* Changes by toralf: Taken from libgloss/m68k/crt0.S
 * initialize target specific stuff. Only execute these
 * functions it they exist.
 */
        ldr     r3, .Lhwinit
        cmp     r3, #0
        beq     .LC24
        indirect_call r3
.LC24:  
        ldr     r3, .Lswinit
        cmp     r3, #0
        beq     .LC25
        indirect_call r3

.LC25:  
        movs    r0, #0          /*  no arguments  */
        movs    r1, #0          /*  no argv either */
#else
        /* Need to set up standard file handles */
        bl      FUNCTION (initialise_monitor_handles)
        
#ifdef ARM_RDP_MONITOR
        swi     SWI_GetEnv      /*  sets r0 to point to the command line */
        movs    r1, r0
#else
        movs    r0, #AngelSWI_Reason_GetCmdLine
        ldr     r1, .LC30       /*  Space for command line */
        AngelSWIAsm     AngelSWI
        ldr     r1, .LC30
        ldr     r1, [r1]
#endif
        /*  Parse string at r1 */
        movs    r0, #0          /*  count of arguments so far */
        /* Push a NULL argument onto the end of the list.  */
#ifdef __thumb__
        push    {r0}
#else
        stmfd   sp!, {r0}
#endif
.LC10:
/*  Skip leading blanks */
#ifdef __thumb__
        ldrb    r3, [r1]
        adds    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:
        movs    r2, r3
        b       .LC22

.LC21:
        movs    r2, #' '        /*  terminator type */
        subs    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
        adds    r0, r0, #1
.LC11:
#ifdef __thumb__
        ldrb    r3, [r1]
        adds    r1, #1
#else
        ldrb    r3, [r1], #1
#endif
        cmp     r3, #0
        beq     .LC12
        cmp     r2, r3          /*  reached terminator? */
        bne     .LC11
        movs    r2, #0
        subs    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__
        movs    r2, r0
        lsls    r2, #2
        add     r2, sp
        mov     r3, sp
.LC15:  cmp     r2, r3
        bls     .LC14
        subs    r2, #4
        ldr     r4, [r2]
        ldr     r5, [r3]
        str     r5, [r2]
        str     r4, [r3]
        adds    r3, #4
        b       .LC15
.LC14:  
        /* Ensure doubleword stack alignment.  */
        mov     r4, sp
        movs    r5, #7
        bics    r4, r5
        mov     sp, r4
#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
        /* Ensure doubleword stack alignment.  */
        bic     sp, sp, #7
#endif
#endif

#ifdef __USES_INITFINI__
        /* Some arm/elf targets use the .init and .fini sections
           to create constructors and destructors, and for these
           targets we need to call the _init function and arrange
           for _fini to be called at program exit.  */
        movs    r4, r0
        movs    r5, r1
#ifdef _LITE_EXIT
        /* Make reference to atexit weak to avoid unconditionally pulling in
           support code.  Refer to comments in __atexit.c for more details.  */
        .weak   FUNCTION(atexit)
        ldr     r0, .Latexit
        cmp     r0, #0
        beq     .Lweak_atexit
#endif
        ldr     r0, .Lfini
        bl      FUNCTION (atexit)
.Lweak_atexit:
        bl      FUNCTION (_init)
        movs    r0, r4
        movs    r1, r5
#endif
        bl      FUNCTION (main)

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

#if __thumb__ && !defined(PREFER_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
        /* Changes by toralf: Provide alternative "stack" variable whose value
           may be defined externally; .Lstack will be used instead of .LC0 if
           it points to a non-0 value. Also set up references to "hooks" that
           may be used by the application to provide additional init code. */
        
#ifdef __pe__
        .word   0x800000
#else
        .word   0x80000                 /* Top of RAM on the PIE board.  */
#endif
.Lstack:        
        .word   __stack
.Lhwinit:       
        .word   FUNCTION (hardware_init_hook)
.Lswinit:
        .word   FUNCTION (software_init_hook)

        /* Set up defaults for the above variables in the form of weak symbols
           - so that application will link correctly, and get value 0 in
           runtime (meaning "ignore setting") for the variables, when the user
           does not provide the symbols. (The linker uses a weak symbol if,
           and only if, a normal version of the same symbol isn't provided
           e.g. by a linker script or another object file.) */  

        .weak __stack
        .weak FUNCTION (hardware_init_hook) 
        .weak FUNCTION (software_init_hook)
#endif
        
#endif
#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
        /* Protect against unhandled exceptions.  */
        .cantunwind
        .fnend
#endif
.LC1:
        .word   __bss_start__
.LC2:
        .word   __bss_end__
#ifdef __USES_INITFINI__
#ifdef _LITE_EXIT
.Latexit:
        .word   FUNCTION(atexit)

        /* Weak reference _fini in case of lite exit.  */
        .weak   FUNCTION(_fini)
#endif
.Lfini:
        .word   FUNCTION(_fini)
#endif
#ifdef ARM_RDI_MONITOR
.LC30:
        .word   AngelSWIArgs
.LC31:
        .word   __end__

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