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{
This file is part of the Free Pascal run time library.
Copyright (c) 2005 by Michael Van Canneyt, Peter Vreman,
& Daniel Mantione, members of the Free Pascal development team.
See the file COPYING.FPC, included in this distribution,
for details about the copyright.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
**********************************************************************}
{
Linux ELF startup code for Free Pascal
Stack layout at program start:
nil
envn
....
.... ENVIRONMENT VARIABLES
env1
env0
nil
argn
....
.... COMMAND LINE OPTIONS
arg1
arg0
argc <--- esp
}
var
libc_environ: pchar; external name '__environ';
libc_fpu_control: word; external name '__fpu_control';
libc_init_proc: procedure; external name '_init';
libc_fini_proc: procedure; external name '_fini';
fpc_ret,fpc_ret_rbp : pointer;
procedure libc_atexit; external name '__libc_atexit';
procedure libc_exit; external name '__libc_exit';
procedure libc_init; external name '__libc_init';
procedure libc_setfpucw; external name '__setfpucw';
procedure libc_start_main; external name '__libc_start_main';
procedure PASCALMAIN; external name 'PASCALMAIN';
procedure main_stub; assembler; nostackframe;
asm
{ save return address }
popq %rax
// stack alignment
pushq %rax
movq %rax,fpc_ret
movq %rbp,fpc_ret_rbp
pushq %rax
{ Save initial stackpointer }
movq %rsp,__stkptr
{ start the program }
xorq %rbp,%rbp
call PASCALMAIN
hlt
end;
procedure ini_dummy; assembler; nostackframe
asm
ret
end;
{******************************************************************************
C library start/halt
******************************************************************************}
procedure _FPC_libc_start; assembler; nostackframe; public name '_start';
asm
{ Clear the frame pointer. The ABI suggests this be done, to mark
the outermost frame obviously. }
xorq %rbp, %rbp
{ Extract the arguments as encoded on the stack and set up
the arguments for __libc_start_main (int (*main) (int, char **, char **),
int argc, char *argv,
void (*init) (void), void (*fini) (void),
void (*rtld_fini) (void), void *stack_end).
The arguments are passed via registers and on the stack:
main: %rdi
argc: %rsi
argv: %rdx
init: %rcx
fini: %r8
rtld_fini: %r9
stack_end: stack. }
movq %rdx, %r9 { Address of the shared library termination
function. }
popq %rsi { Pop the argument count. }
movq %rsp, %rdx { argv starts just at the current stack top. }
movq %rsi,operatingsystem_parameter_argc
movq %rsp,operatingsystem_parameter_argv { argv starts just at the current stack top. }
leaq 8(,%rsi,8),%rax
addq %rsp,%rax
movq %rax,operatingsystem_parameter_envp
{ Align the stack to a 16 byte boundary to follow the ABI. }
andq $~15, %rsp
pushq %rax { Push garbage because we push 8 more bytes. }
{ Provide the highest stack address to the user code (for stacks
which grow downwards). }
pushq %rsp
{ Pass address of our own entry points to .fini and .init. }
movq $ini_dummy, %r8
movq $ini_dummy, %rcx
movq $main_stub, %rdi
{ Call the user's main function, and exit with its value.
But let the libc call main. }
call libc_start_main
hlt { Crash if somehow `exit' does return. }
{ We need this stuff to make gdb behave itself, otherwise
gdb will chokes with SIGILL when trying to debug apps.
}
.section ".note.ABI-tag", "a"
.align 4
.long 1f - 0f
.long 3f - 2f
.long 1
0: .asciz "GNU"
1: .align 4
2: .long 0
.long 2,4,0
3: .align 4
.section .note.GNU-stack,"",@progbits
end;
procedure _FPC_libc_haltproc; assembler; nostackframe; public name '_haltproc';
asm
movzwq operatingsystem_result,%rax { load and save exitcode }
movq ___fpc_ret,%rdx { return to libc }
movq ___fpc_ret_rbp,%rbp
pushq %rdx
ret
end;
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