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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set et ft=asm ts=8 sw=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"
.source __FILE__
/*
besiyata
dishmaya
cosmopolitan § bell system five » system call support
*/
/ Performs System Five System Call.
/
/ Cosmopolitan is designed to delegate all function calls into the
/ Linux, FreeBSD, OpenBSD, and XNU kernels through this function,
/ with few exceptions. This function is intended to be called via
/ generated thunks in the libc/sysv/syscalls/ directory.
/
/ It's safe to call this function on Windows, where it'll always
/ return -1 w/ errno == ENOSYS. Further note that -1 is the only
/ return value that means error, a common anti-pattern is to check
/ for values less than 0 (which is more problematic on 32-bit).
/
/ It's important to consider that system calls are an order of a
/ magnitude more expensive than normal function calls. For example
/ getpid() on Linux usually takes 500ns, and cached i/o calls will
/ take 1µs or more.
/
/ @param %rax function ordinal supplied by jump slot
/ @param %rdi,%rsi,%rdx,%rcx,%r8,%r9 and rest on stack
/ @return %rax:%rdx is result, or -1 w/ errno on error
/ @clob %rcx,%r10,%r11
/ @see syscalls.sh
.initbss 300,_init_systemfive
hostos: .quad 0
.endobj hostos,globl,hidden
systemfive:
.quad 0
.endobj systemfive,globl,hidden
.previous
.Lanchorpoint:
systemfive.linux:
movswl %ax,%eax
test %eax,%eax
js systemfive.enosys
mov %rcx,%r10
push %rbp
mov %rsp,%rbp
syscall
pop %rbp
cmp $-4095,%rax
jae systemfive.error
ret
.endfn systemfive.linux,globl,hidden
systemfive.error:
neg %eax
/ 𝑠𝑙𝑖𝑑𝑒
.endfn systemfive.error,globl,hidden
systemfive.errno:
mov %eax,errno(%rip)
push $-1
pop %rax
stc
ret
.endfn systemfive.errno,globl,hidden
systemfive.enosys:
mov ENOSYS(%rip),%eax
jmp systemfive.errno
.endfn systemfive.enosys,globl,hidden
systemfive.openbsd:
shr $48,%rax
jmp systemfive.bsd
.endfn systemfive.openbsd,globl,hidden
systemfive.freebsd:
shr $32,%rax
movzwl %ax,%eax
/ 𝑠𝑙𝑖𝑑𝑒
.endfn systemfive.freebsd,globl,hidden
systemfive.bsd:
cmp $0xfff,%ax
jae systemfive.enosys
mov %rcx,%r10
push %rbp
mov %rsp,%rbp
syscall
pop %rbp
jc systemfive.errno
ret
.endfn systemfive.bsd
systemfive.xnu:
/ do this to rax
/ 0x????????2153????
/
/
/ 0x0000000002000153
mov %eax,%r11d
shr $4*7,%r11d
shl $4*6,%r11d
shl $4*1,%eax
shr $4*5,%eax
or %r11d,%eax
jmp systemfive.bsd
.endfn systemfive.xnu,globl,hidden
.previous
/ Initializes System Five system call support.
/
/ (1) Extracts parameters passed by kernel,
/ (2) Detects O/S without issuing system calls,
/ (3) Unpacks numbers.
/
/ @param %r15 is auxv
/ @note OpenBSD devs: let us know if you start using auxv
.init.start 300,_init_systemfive
push %rbx
push %rsi
testb $METAL,(%rdi) # @see ape/ape.S
jnz systemfive.init.metal
testb $XNU,(%rdi) # @see libc/crt/crt.S
jnz systemfive.init.xnu
testb $FREEBSD,(%rdi) # @see libc/crt/crt.S
jnz systemfive.init.freebsd
testb $WINDOWS,(%rdi) # @see libc/runtime/winmain.c
jnz systemfive.init.windows
cmpq $0,(%r15) # OpenBSD doesn't have auxv
je systemfive.init.openbsd
/ default state is safe state
/ 𝑠𝑙𝑖𝑑𝑒
systemfive.init.linux:
pushb systemfive.linux-.Lanchorpoint
push $LINUX
ezlea syscon.linux,si
jmp systemfive.init.os
systemfive.init.metal:
pushb systemfive.linux-.Lanchorpoint
push $METAL
ezlea syscon.linux,si
jmp systemfive.init.os
systemfive.init.windows:
pushb systemfive.enosys-.Lanchorpoint
push $WINDOWS
ezlea syscon.windows,si
jmp systemfive.init.os
systemfive.init.freebsd:
pushb systemfive.freebsd-.Lanchorpoint
push $FREEBSD
ezlea syscon.freebsd,si
jmp systemfive.init.os
systemfive.init.openbsd:
pushb systemfive.openbsd-.Lanchorpoint
push $OPENBSD
ezlea syscon.openbsd,si
jmp systemfive.init.os
systemfive.init.xnu:
pushb systemfive.xnu-.Lanchorpoint
push $XNU
ezlea syscon.xnu,si
/ 𝑠𝑙𝑖𝑑𝑒
systemfive.init.os:
ezlea .Lanchorpoint,cx
pop %rax
stosq # hostos
pop %rax
add %rcx,%rax
stosq # systemfive
push %rdi
ezlea syscon.start,di
ezlea syscon.end,bx
call systemfive.sleb128unpacker
pop %rdi
/ 𝑠𝑙𝑖𝑑𝑒
systemfive.init.done:
pop %rsi
pop %rbx
.init.end 300,_init_systemfive,globl,hidden
.text.startup
systemfive.sleb128unpacker:
.leafprologue
or $-1,%r9
2: cmp %rbx,%rdi
jnb 5f
xor %ecx,%ecx
xor %edx,%edx
3: lodsb
mov %rax,%r8
and $127,%r8d
sal %cl,%r8
add $7,%ecx
or %r8,%rdx
test %al,%al
js 3b
test $64,%al
je 4f
mov %r9,%rax
sal %cl,%rax
or %rax,%rdx
4: mov %rdx,%rax
cmpq $0,(%rdi) # don't change consts already set
cmovne (%rdi),%rax # @see WinMain() for example
stosq
jmp 2b
5: .leafepilogue
.previous
/ Sections for varint encoded numbers.
/
/ These sections are all ordered by (group_name, constant_name).
/ They're populated by modules simply referencing the symbols.
/
/ @see libc/sysv/consts.sh
/ @see libc/sysv/consts/syscon.h
.section .piro.bss.sort.syscon.1,"aw",@nobits
.align 8
syscon.start:/*
...decentralized quadwords...
*/.previous
.section .piro.bss.sort.syscon.3,"aw",@nobits
syscon.end:
.previous
.section .sort.rodata.syscon.linux.1,"a",@progbits
.align 1
syscon.linux:/*
...decentralized leb128...
*/.previous
.section .sort.rodata.syscon.xnu.1,"a",@progbits
.align 1
syscon.xnu:/*
...decentralized leb128...
*/.previous
.section .sort.rodata.syscon.freebsd.1,"a",@progbits
.align 1
syscon.freebsd:/*
...decentralized leb128...
*/.previous
.section .sort.rodata.syscon.openbsd.1,"a",@progbits
.align 1
syscon.openbsd:/*
...decentralized leb128...
*/.previous
.section .sort.rodata.syscon.windows.1,"a",@progbits
.align 1
syscon.windows:/*
...decentralized leb128...
*/.previous
.type syscon.start,@object
.type syscon.end,@object
.type syscon.linux,@object
.type syscon.xnu,@object
.type syscon.freebsd,@object
.type syscon.openbsd,@object
.type syscon.windows,@object
.globl syscon.start
.globl syscon.end
.globl syscon.linux
.globl syscon.xnu
.globl syscon.freebsd
.globl syscon.openbsd
.globl syscon.windows