Subversion Repositories openrisc_me

! 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)