cosmopolitan/libc/crt/crt.S
Justine Tunney edd9297eba Support malloc() on bare metal
Your Actually Portable Executables now contains a simple virtual memory
that works similarly to the Linux Kernel in the sense that it maps your
physical memory to negative addresses. This is needed to support mmap()
and malloc(). This functionality has zero code size impact. For example
the MODE=tiny LIFE.COM executable is still only 12KB in size.

The APE bootloader code has also been simplified to improve readibility
and further elevate the elegance by which we're able to support so many
platforms thereby enhancing verifiability so that we may engender trust
in this bootloading process.
2021-02-24 00:53:24 -08:00

80 lines
3.2 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
Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
*/
#include "libc/dce.h"
#include "libc/macros.h"
#include "libc/notice.inc"
#include "libc/runtime/internal.h"
.section .start,"ax",@progbits
// 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:
#if SupportsFreebsd()
test %rdi,%rdi
cmovnz %rdi,%rsp
jz 0f
movb $FREEBSD,__hostos(%rip)
#endif
0: mov (%rsp),%ebx # argc
lea 8(%rsp),%rsi # argv
lea 16(%rsp,%rbx,8),%rdx # envp
.frame0
// bofram 9f
.weak ape_idata_iat
.weak ape_idata_iatend
ezlea missingno,ax # make win32 imps noop
ezlea ape_idata_iat,di
ezlea ape_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
#if SupportsXnu()
testb IsXnu()
jz 1f # polyfill xnu auxv
push $0 # auxv[1][1]=0
push $0 # auxv[1][0]=0
mov (%rcx),%rax # executable_path=BIN
lea 16(%rax),%rax # BIN
push %rax # auxv[0][0]=BIN
push $31 # auxv[0][0]=AT_EXECFN
mov %rsp,%rcx # auxv
#endif
1: mov %ebx,%edi
call cosmo
9: ud2
.endfn _start,weak,hidden
#if SupportsXnu()
// 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
_xnu: movb $XNU,__hostos(%rip)
jmp 0b
.endfn _xnu,weak,hidden
#endif