cosmopolitan/libc/crt/crt.S
Justine Tunney 2d80bbc802 Get binaries closer to running without an o/s
blinkenlights now does a pretty good job emulating what happens when
binaries boot from BIOS into long mode. So it's been much easier to
debug the bare metal process and wrinkle out many issues.
2020-11-02 19:12:47 -08:00

69 lines
3 KiB
ArmAsm

/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify │
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License. │
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. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software │
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "libc/dce.h"
#include "libc/macros.h"
#include "libc/notice.inc"
#include "libc/runtime/internal.h"
.section .start,"ax",@progbits
.source __FILE__
nop
/ System Five userspace program entrypoint.
/
/ @param rsp is [n,argv₀..argvₙ₋₁,0,envp₀..,0,auxv₀..,0,..]
/ @note FreeBSD is special (see freebsd/lib/csu/amd64/...)
/ @noreturn
_start: test %rdi,%rdi
cmovnz %rdi,%rsp
jz 0f
movb $FREEBSD,hostos(%rip)
0: mov (%rsp),%ebx # argc
lea 8(%rsp),%rsi # argv
lea 24(%rsp,%rbx,8),%rdx # envp
.frame0
/ bofram 9f
.weak idata.iat
.weak idata.iatend
ezlea missingno,ax # make win32 imps noop
ezlea idata.iat,di
ezlea idata.iatend,cx
sub %rdi,%rcx
shr $3,%ecx
rep stosq
xor %eax,%eax # find end of environ
or $-1,%ecx
mov %rdx,%rdi
repnz scasq
mov %rdi,%rcx # auxv
mov %ebx,%edi
call _executive
9: ud2
.endfn _start,weak,hidden
/ Macintosh userspace program entrypoint.
/
/ @param rsp is [n,argv₀..argvₙ₋₁,0,envp₀..,0,auxv₀..,0,..]
/ @note FreeBSD is special (see freebsd/lib/csu/amd64/...)
/ @noreturn
_start_xnu:
movb $XNU,hostos(%rip)
jmp 0b
.endfn _start_xnu,weak,hidden