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! This file derived from the equivalent in newlib
!
! 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.
.text
.align 4
.globl _start
.type _start, @function
_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
bz,a .LNoBias
nop
mov 2047, %g5
.LNoBias:
add %sp, %g5, %g5
! On entry, the kernel leaves room for one register frame, but
! the C API wants more free space. Thus, we need to drop the stack
! pointer additionally.
#if TARGET_PTR_SIZE == 32
sub %sp, 32, %sp ! make room for incoming arguments
#else /* TARGET_PTR_SIZE == 64 */
sub %sp, 64, %sp ! make room for incoming arguments
#endif
! Set up pointers to the ELF data structure (argc, argv, ...)
! Pass as the first argument to __libc_init
#if TARGET_PTR_SIZE == 32
add %g5, 0x40, %o0
#else /* TARGET_PTR_SIZE == 64 */
add %g5, 0x80, %o0
#endif
call __libc_init
mov %g1, %o1 ! This is the "atexit" pointer;
! pass as the second argument to __libc_init
! If __libc_init returns, something is hosed. Try an illegal insn.
! If that does not work, the o/s is hosed more than we are.
.long 0
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