mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
c843243322
- Support deterministic stacks on OpenBSD - Support OpenBSD system call origin verification - Fix overrun by one in chibicc string token allocator - Get all chibicc tests passing under Address Sanitizer
385 lines
15 KiB
ArmAsm
385 lines
15 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│vi: set et ft=asm ts=8 sw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/sysv/consts/nr.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/macros.h"
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.source __FILE__
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/* ▄▄▄
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╔────────────────────────────────────────────────────────────────────────────│─╗
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│ cosmopolitan § bell system five » system call support ─╬─│┼
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╚────────────────────────────────────────────────────────────────────────────│*/
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.initbss 300,_init_systemfive
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__hostos:
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.quad 0
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.endobj __hostos,globl,hidden
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/ Performs System Five System Call.
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/
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/ Cosmopolitan is designed to delegate all function calls into the
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/ Linux, FreeBSD, OpenBSD, and XNU kernels via this function, with
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/ few exceptions. This function should generally only be called by
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/ generated thunks in the libc/sysv/syscalls/ directory.
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/
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/ It's safe to call this function on Windows, where it will always
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/ return -1 with errno == ENOSYS. Further note that -1 is the only
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/ return value that means error, a common anti-pattern is to check
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/ for values less than 0 (which is more problematic on 32-bit).
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/
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/ It is important to consider that system calls are one order of a
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/ magnitude more expensive than normal function calls. For example
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/ getpid() on Linux usually takes 500ns, and cached i/o calls will
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/ take 1µs or more. So we don't need to inline them like Chromium.
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/
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/ Another thing to consider is that BSDs only loosely follow the
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/ System Five ABI for the SYSCALL instruction. For example Linux
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/ always follows the six argument limit but the FreeBSD sendfile
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/ system call accepts a seventh argument that is passed on stack
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/ and OpenBSD modifies functions like mmap so that the sixth arg
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/ is passed on the stack. There's also the carry flag convention
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/ that XNU, FreeBSD, and OpenBSD inherited from 386BSD aka Jolix
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/
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/ @param %rax function ordinal supplied by jump slot
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/ @param %rdi,%rsi,%rdx,%rcx,%r8,%r9 and rest on stack
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/ @return %rax:%rdx is result, or -1 w/ errno on error
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/ @clob %rcx,%r10,%r11
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/ @see syscalls.sh
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__systemfive:
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.quad 0
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.endobj __systemfive,globl,hidden
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.previous
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.text.syscall
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.Lanchorpoint:
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systemfive.linux:
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movswl %ax,%eax # gnu/systemd ordinal is first word
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test %eax,%eax # sign extend to optimize code size
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js systemfive.enosys # test for syscalls.sh ordinal ffff
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mov %rcx,%r10 # syscall instruction clobbers %rcx
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push %rbp # linux never reads args from stack
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mov %rsp,%rbp # having frame will help backtraces
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syscall # this is known as a context switch
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pop %rbp # next we check to see if it failed
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cmp $-4095,%rax # system five nexgen32e abi § A.2.1
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jae systemfive.error # encodes errno as neg return value
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ret
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.endfn systemfive.linux,globl,hidden
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systemfive.error:
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neg %eax
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/ 𝑠𝑙𝑖𝑑𝑒
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.endfn systemfive.error,globl,hidden
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systemfive.errno:
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mov %eax,errno(%rip) # normalize to c library convention
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push $-1 # negative one is only error result
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pop %rax # the push pop is to save code size
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ret
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.endfn systemfive.errno,globl,hidden
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systemfive.enosys:
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mov ENOSYS(%rip),%eax
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jmp systemfive.errno
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.endfn systemfive.enosys,globl,hidden
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systemfive.openbsd:
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shr $48,%rax
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jmp systemfive.bsd
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.endfn systemfive.openbsd,globl,hidden
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systemfive.freebsd:
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shr $32,%rax
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movzwl %ax,%eax
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/ 𝑠𝑙𝑖𝑑𝑒
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.endfn systemfive.freebsd,globl,hidden
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systemfive.bsd:
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cmp $0xfff,%ax
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jae systemfive.enosys
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mov %rcx,%r10 # note: we do not create a stack frame
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syscall # bsd will need arg on stack sometimes
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jc systemfive.errno # bsd sets carry flag if %rax is errno
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ret
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.endfn systemfive.bsd
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systemfive.xnu:
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/ 0x????????2153???? # how syscalls.sh encodes xnu ordinals
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/ │└┴┴─┐
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/ └┐ ├┬┐
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/ 0x0000000002000153 # how xnu wants ordinals to be encoded
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mov %eax,%r11d
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shr $4*7,%r11d
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shl $4*6,%r11d
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shl $4*1,%eax
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shr $4*5,%eax
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or %r11d,%eax
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jmp systemfive.bsd
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.endfn systemfive.xnu,globl,hidden
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.previous
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/ Initializes System Five system call support.
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/
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/ (1) Extracts parameters passed by kernel
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/ (2) Detects OS without issuing system calls
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/ (3) Unpacks magnums from libc/sysv/consts.sh
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/ (4) Replaces stack with one we control
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/
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/ @param %r15 is auxv
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/ @note OpenBSD devs: let us know if you start using auxv
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.init.start 300,_init_systemfive
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push %rbx
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push %rsi
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testb $METAL,(%rdi) # @see ape/ape.S
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jnz systemfive.init.metal
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testb $XNU,(%rdi) # @see libc/crt/crt.S
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jnz systemfive.init.xnu
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testb $FREEBSD,(%rdi) # @see libc/crt/crt.S
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jnz systemfive.init.freebsd
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testb $WINDOWS,(%rdi) # @see libc/runtime/winmain.c
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jnz systemfive.init.windows
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cmpq $0,(%r15) # OpenBSD doesn't have auxv
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je systemfive.init.openbsd
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/ default state is safe state
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/ 𝑠𝑙𝑖𝑑𝑒
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systemfive.init.linux:
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pushb systemfive.linux-.Lanchorpoint
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push $LINUX
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ezlea syscon.linux,si
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jmp systemfive.init.os
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systemfive.init.metal:
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pushb systemfive.linux-.Lanchorpoint
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push $METAL
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ezlea syscon.linux,si
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jmp systemfive.init.os
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systemfive.init.windows:
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pushb systemfive.enosys-.Lanchorpoint
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push $WINDOWS
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ezlea syscon.windows,si
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jmp systemfive.init.os
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systemfive.init.freebsd:
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pushb systemfive.freebsd-.Lanchorpoint
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push $FREEBSD
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ezlea syscon.freebsd,si
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jmp systemfive.init.os
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systemfive.init.openbsd:
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pushb systemfive.openbsd-.Lanchorpoint
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push $OPENBSD
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ezlea syscon.openbsd,si
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jmp systemfive.init.os
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systemfive.init.xnu:
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pushb systemfive.xnu-.Lanchorpoint
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push $XNU
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ezlea syscon.xnu,si
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/ 𝑠𝑙𝑖𝑑𝑒
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systemfive.init.os:
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ezlea .Lanchorpoint,cx
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pop %rax
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stosq #→ __hostos
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pop %rax
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add %rcx,%rax
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stosq #→ __systemfive
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/ 𝑠𝑙𝑖𝑑𝑒
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systemfive.init.magnums:
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push %rdi
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ezlea syscon.start,di
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ezlea syscon.end,bx
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or $-1,%r9
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2: cmp %rbx,%rdi
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jnb 5f
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xor %ecx,%ecx
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xor %edx,%edx
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3: lodsb # decodes sleb128
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mov %rax,%r8
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and $127,%r8d
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sal %cl,%r8
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add $7,%ecx
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or %r8,%rdx
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test %al,%al
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js 3b
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test $64,%al
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je 4f
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mov %r9,%rax
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sal %cl,%rax
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or %rax,%rdx
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4: mov %rdx,%rax
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cmpq $0,(%rdi) # dont change if set
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cmovne (%rdi),%rax # @see WinMain()
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stosq
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jmp 2b
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5: pop %rdi
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pop %rsi
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pop %rbx
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/ 𝑠𝑙𝑖𝑑𝑒
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#ifndef TINY
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systemfive.init.stack: # determinism ftw!
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testb IsWindows() # already did this
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jnz systemfive.init.done
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push %rdi
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push %rsi
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mov __NR_mmap,%eax
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mov $0x700000000000-STACKSIZE,%rdi
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mov $STACKSIZE,%esi
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mov $PROT_READ|PROT_WRITE,%edx
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mov $MAP_PRIVATE|MAP_FIXED,%r10d
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or MAP_ANONYMOUS,%r10d
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or $-1,%r8d
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xor %r9d,%r9d
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push %r9 # openbsd:pad
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push %r9 # openbsd:align
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testb IsOpenbsd()
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jz 0f
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syscall # openbsd:dubstack
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jc 1f
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mov __NR_mmap,%eax
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0: or MAP_GROWSDOWN,%r10d # openbsd:mapstack
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clc
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syscall
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pop %r9
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pop %r9
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jnc 2f
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1: mov %eax,%edi
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mov __NR_exit_group,%eax
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syscall
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2: test %rax,%rax
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js 1b
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.weak _mmi
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ezlea _mmi,cx
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test %rcx,%rcx
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jz 3f
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movb $1,(%rcx) # _mmi.i
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movl $(0x700000000000-STACKSIZE)>>16,8(%rcx) # _mmi.p[0].x
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movl $(0x700000000000-1)>>16,12(%rcx) # _mmi.p[0].y
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mov %edx,20(%rcx) # _mmi.p[0].prot
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mov %r10d,24(%rcx) # _mmi.p[0].flags
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3: pop %rsi
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pop %rdi
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leave
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pop %rcx
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lea STACKSIZE-16(%rax),%rsp # openbsd:stackbound
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push %rcx
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xor %ebp,%ebp
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push %rbp
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mov %rsp,%rbp
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/ 𝑠𝑙𝑖𝑑𝑒
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systemfive.init.syscall:
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mov __NR_msyscall,%eax # syscall origin protect
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test %eax,%eax # openbsd is pretty cool
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js systemfive.init.done
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push %rdi
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push %rsi
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.weak __text_syscall_addr
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.weak __text_syscall_size
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mov $__text_syscall_addr,%edi
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mov $__text_syscall_size,%esi
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syscall
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pop %rsi
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pop %rdi
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/ 𝑠𝑙𝑖𝑑𝑒
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#endif /* TINY */
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systemfive.init.done:
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nop
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.init.end 300,_init_systemfive,globl,hidden
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/ Sections for varint encoded magic numbers.
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/
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/ These sections are all ordered by (group_name, constant_name).
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/ They're populated by modules simply referencing the symbols.
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/
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/ @see libc/sysv/consts.sh
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/ @see libc/sysv/consts/syscon.h
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.section .piro.bss.sort.syscon.1,"aw",@nobits
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.align 8
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syscon.start:/*
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...decentralized quadwords...
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*/.previous
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.section .piro.bss.sort.syscon.3,"aw",@nobits
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syscon.end:
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.previous
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.section .sort.rodata.syscon.linux.1,"a",@progbits
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.align 1
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syscon.linux:/*
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...decentralized leb128...
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*/.previous
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.section .sort.rodata.syscon.xnu.1,"a",@progbits
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.align 1
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syscon.xnu:/*
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...decentralized leb128...
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*/.previous
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.section .sort.rodata.syscon.freebsd.1,"a",@progbits
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.align 1
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syscon.freebsd:/*
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...decentralized leb128...
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*/.previous
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.section .sort.rodata.syscon.openbsd.1,"a",@progbits
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.align 1
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syscon.openbsd:/*
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||
...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
|