cosmopolitan/examples/tiny-raw-linux-tutorial.S

60 lines
3.3 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/macros.h"
/ Tiny Raw Linux Binary Tutorial
/
/ i.e. how to not use cosmopolitan runtimes at all
/ cosmopolitan basically abstracts this
/ except for all major platforms
/
/ make o//examples/raw-linux-hello.elf
/ o/examples/raw-linux-hello.elf # about 6kb
/
/ Next try C but with fancy build tuning
/
/ make -j8 -O \
/ MODE=tiny \
/ LDFLAGS+=-s \
/ CPPFLAGS+=-DIM_FEELING_NAUGHTY \
/ CPPFLAGS+=-DSUPPORT_VECTOR=0b00000001 \
/ o/tiny/examples/hello2.elf
/ o/tiny/examples/hello2.elf # about 8kb
/
/ @param rsp is [n,argv₀..argvₙ₋₁,0,envp₀..,0,auxv₀..,0,..]
/ @see also glibc static binaries which start at 800kb!!!
/ @see also go where interfaces sadly disempower ld prune
/ @see also the stl where bad linkage is due to tech debt
/ @note libc/elf/elf.lds can be tinier with page align off
/ @note gas is more powerful than nasm due to rms notation
/ @noreturn
_start: mov $12,%rdx # arg no. 3 is length
getstr "hello world\n",%rsi,%esi # arg no. 2 is memory
mov $1,%edi # arg no. 1 is stdout
mov $1,%eax # write()
syscall # libc/sysv/syscalls.sh
mov $0,%edi # arg no. 1 is success status
mov $0xE7,%eax # exit_group()
syscall # context switch
0: rep nop # basic blockading
jmp 0b
.endfn _start,globl
.source __FILE__