source: trunk/libs/newlib/src/libgloss/sparc/libsys/libsys-crt0.S @ 548

! C run time start off

! This file supports:
!
! - both 32bit pointer and 64bit pointer environments (at compile time)
! - an imposed stack bias (of 2047) (at run time)
! - medium/low and medium/anywhere code models (at run time)

! Initial stack setup:
!
!    bottom of stack (higher memory address)
!       ...
!       text of environment strings
!       text of argument strings
!       envp[envc] = 0 (4/8 bytes)
!       ...
!       env[0] (4/8 bytes)
!       argv[argc] = 0 (4/8 bytes)
!       ...
!       argv[0] (4/8 bytes)
!       argc (4/8 bytes)
!       register save area (64 bits by 16 registers = 128 bytes)
!       top of stack (%sp)

! Stack Bias:
!
! It is the responsibility of the o/s to set this up.
! We handle both a 0 and 2047 value for the stack bias.

! Medium/Anywhere code model support:
!
! In this model %g4 points to the start of the data segment.
! The text segment can go anywhere, but %g4 points to the *data* segment.
! It is up to the compiler/linker to get this right.
!
! Since this model is statically linked the start of the data segment
! is known at link time.  Eg:
!
!       sethi   %hh(data_start), %g1
!       sethi   %lm(data_start), %g4
!       or      %g1, %hm(data_start), %g1
!       or      %g4, %lo(data_start), %g4
!       sllx    %g1, 32, %g1
!       or      %g4, %g1, %g4
!
! FIXME: For now we just assume 0.

! FIXME: if %g1 contains a non-zero value, atexit() should be invoked
! with this value.

#include "syscallasm.h"

#ifndef TARGET_PTR_SIZE
#define TARGET_PTR_SIZE 32
#endif

        TEXT_SECTION
        ALIGN (4)
        GLOBAL (ASM_PRIVATE_SYMBOL (start))
ASM_PRIVATE_SYMBOL (start):
        clr     %fp

! We use %g4 even if the code model is Medium/Low (simplifies the code).

        clr     %g4                     ! Medium/Anywhere base reg

! If there is a stack bias in effect, account for it in %g5.  Then always
! add %g5 to stack references below.  This way the code can be used with
! or without an imposed bias.

        andcc   %sp, 1, %g5
        bnz,a   .LHaveBias
        mov     2047, %g5
.LHaveBias:
        add     %sp, %g5, %sp

#if TARGET_PTR_SIZE == 32
        ! FIXME: We apparently assume here that there is no reserved word.
        ! This is probably correct, but try to verify it.
        ld      [%sp + 0x80], %o0       ! argc
        add     %sp, 0x84, %o1          ! argv
        add     %o0, 1, %o2
        sll     %o2, 2, %o2
#else /* TARGET_PTR_SIZE == 64 */
        ld      [%sp + 0x8c], %o0       ! argc.lo
        add     %sp, 0x90, %o1          ! argv
        add     %o0, 1, %o2
        sll     %o2, 3, %o2
#endif
        add     %o1, %o2, %o2           ! envp
        sethi   %hi (ASM_SYMBOL (environ)), %o3
        or      %o3, %lo (ASM_SYMBOL (environ)), %o3
#if TARGET_PTR_SIZE == 32
        st      %o2, [%o3 + %g4]
#else /* TARGET_PTR_SIZE == 64 */
        stx     %o2, [%o3 + %g4]
#endif

! Restore any stack bias before we call main() ...

        sub     %sp, %g5, %sp

        GLOBAL (ASM_SYMBOL (main))
        call    ASM_SYMBOL (main)

! FIXME: Not sure if this is needed anymore.
#if TARGET_PTR_SIZE == 32
        sub     %sp, 0x20, %sp          ! room to push args
#else /* TARGET_PTR_SIZE == 64 */
        sub     %sp, 0x30, %sp          ! room to push args
#endif

        GLOBAL (ASM_SYMBOL (exit))
        call    ASM_SYMBOL (exit)
        nop

        GLOBAL (ASM_SYMBOL (_exit))
        call    ASM_SYMBOL (_exit)
        nop

        set     SYS_exit, %g1
        ta      SYSCALL_TRAP            ! in case user redefines __exit

! If all the above methods fail to terminate the program, try an illegal insn.
! If that does not work, the o/s is hosed more than we are.

        WORD (0)