/*-*- 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 │
│ │
│ 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/intrin/strace.internal.h"
#include "libc/dce.h"
#include "libc/macros.internal.h"
#include "libc/nexgen32e/macros.h"
#include "libc/sysv/consts/sig.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/sysv/consts/nr.h"
#define SIG_IGN 1
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╔────────────────────────────────────────────────────────────────────────────│─╗
│ cosmopolitan § bell system five » system call support ─╬─│┼
╚────────────────────────────────────────────────────────────────────────────│*/
.initbss 300,_init_systemfive
// Performs System Five System Call.
//
// Cosmopolitan is designed to delegate all function calls into the
// Linux, FreeBSD, OpenBSD, and XNU kernels via this function, with
// few exceptions. This function should generally only be called by
// generated thunks in the libc/sysv/syscalls/ directory.
//
// It's safe to call this function on Windows, where it will always
// return -1 with 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 is important to consider that system calls are one 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. So we don't need to inline them like Chromium.
//
// Another thing to consider is that BSDs only loosely follow the
// System Five ABI for the SYSCALL instruction. For example Linux
// always follows the six argument limit but the FreeBSD sendfile
// system call accepts a seventh argument that is passed on stack
// and OpenBSD modifies functions like mmap so that the sixth arg
// is passed on the stack. There's also the carry flag convention
// that XNU, FreeBSD, and OpenBSD inherited from 386BSD aka Jolix
//
// @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
__systemfive:
.quad 0
.endobj __systemfive,globl,hidden
__pid: .quad 0
.endobj __pid,globl,hidden
.previous
systemfive_cp:
push %rbp
mov %rsp,%rbp // so backtraces work
systemfive_cancellable: // our pthread_cancel() miracle code
cmpb $0,__tls_enabled(%rip) // inspired by the musl libc design!
je 1f // we handle linux and bsd together!
mov %fs:0,%r10 // CosmoTib::tib_self
mov 0x28(%r10),%r10 // CosmoTib::tib_pthread
test %r10,%r10 // is it a posix thread?
jz 1f // it's spawn() probably
testb $PT_NOCANCEL,0x00(%r10) // PosixThread::flags
jnz 1f // canceler no cancelling
#if IsModeDbg()
testb $PT_INCANCEL,0x00(%r10)
jz 5f
#endif
cmpl $0,0x04(%r10) // PosixThread::cancelled
jne systemfive_cancel // we will tail call below
1: mov %rcx,%r10 // move the fourth argument
clc // no cancellable system calls exist
syscall // that have 7+ args on the bsd OSes
systemfive_cancellable_end: // i/o calls park here for long time
pop %rbp
jnc 2f
neg %rax // turns bsd errno to system v errno
2: cmp $-4095,%rax // but we still check again on eintr
jae 3f // branch because system call failed
ret // done if the system call succeeded
3: neg %eax // now examine the nature of failure
cmp EINTR(%rip),%eax // did the SIGTHR cancel our IO call
jne systemfive_errno // werent interrupted by OnSigCancel
cmpb $0,__tls_enabled(%rip) // make sure it's safe to grab %fs:0
je systemfive_errno // tls is disabled we can't continue
mov %fs:0,%rcx // CosmoTib::tib_self
mov 0x28(%rcx),%rcx // CosmoTib::tib_pthread
test %rcx,%rcx // is it a posix thread?
jz systemfive_errno // it's spawn() probably
testb $PT_NOCANCEL,0x00(%rcx) // PosixThread::flags
jnz systemfive_errno // cancellation is disabled
cmpl $0,0x04(%rcx) // PosixThread::cancelled
je systemfive_errno // we aren't actually cancelled
jmp 4f // now we are in fact cancelled
systemfive_cancel: // SIGTHR will jump here too
pop %rbp
4: jmp _pthread_cancel_ack // tail call
.weak _pthread_cancel_ack // must be linked if we're cancelled
#if IsModeDbg()
not_a_cancellation_point: // need BEGIN/END_CANCELLATION_POINT
nop
.weak report_cancellation_point
5: ezlea report_cancellation_point,cx
test %rcx,%rcx
jz 6f
call *%rcx
6: ud2
nop
#endif
.globl systemfive_cancellable_end
.globl systemfive_cancellable
.globl systemfive_cancel
.endfn systemfive_cp
.Lanchorpoint:
#if SupportsLinux() || SupportsMetal()
systemfive_linux:
and $0xfff,%eax // remove nonlinux bits from ordinal
cmp $0xfff,%eax // checks if unsupported by platform
je systemfive_enosys // never taken branches cost nothing
btr $11,%eax // 0x800 means a call is cancellable
jc systemfive_cp // it is handled by the holiest code
mov %rcx,%r10 // syscall instruction clobbers %rcx
push %rbp // linux never reads args from stack
mov %rsp,%rbp // having frame will help backtraces
syscall // this is known as a context switch
pop %rbp // next we check to see if it failed
cmp $-4095,%rax // system five nexgen32e abi § a.2.1
jae systemfive_error // encodes errno as neg return value
ret
.endfn systemfive_linux,globl,hidden
systemfive_error:
neg %eax
// 𝑠𝑙𝑖𝑑𝑒
.endfn systemfive_error,globl,hidden
#endif
systemfive_errno:
xchg %eax,%ecx
.errno
mov %ecx,(%rax) // normalize to c library convention
push $-1 // negative one is only error result
pop %rax // the push pop is to save code size
ret
.endfn systemfive_errno,globl,hidden
systemfive_enosys:
mov ENOSYS(%rip),%eax
jmp systemfive_errno
.endfn systemfive_enosys,globl,hidden
#if SupportsNetbsd()
systemfive_netbsd:
shr $4*13,%rax
jmp systemfive_bsdscrub
.endfn systemfive_netbsd,globl,hidden
#endif
#if SupportsOpenbsd()
systemfive_openbsd:
shr $4*10,%rax
jmp systemfive_bsdscrub
.endfn systemfive_openbsd,globl,hidden
#endif
#if SupportsFreebsd()
systemfive_freebsd:
shr $4*7,%rax
movzwl %ax,%eax
// 𝑠𝑙𝑖𝑑𝑒
.endfn systemfive_freebsd,globl,hidden
#endif
#if SupportsBsd()
systemfive_bsdscrub:
and $0xfff,%eax
// 𝑠𝑙𝑖𝑑𝑒
.endfn systemfive_bsdscrub,globl,hidden
systemfive_bsd:
cmp $0xfff,%ax
je systemfive_enosys
btr $11,%eax // checks/reset the 800 cancellable bit
jc systemfive_cp
mov %rcx,%r10
syscall // bsd will need arg on stack sometimes
jc systemfive_errno // bsd sets carry flag if %rax is errno
ret
.endfn systemfive_bsd
#endif
#if SupportsXnu()
systemfive_xnu:
// 0x?????????2153??? // how syscalls.sh encodes xnu ordinals
// │└┴┴┐
// │ ├┬┐
// 0x0000000002000153 // how xnu wants ordinals to be encoded
mov %eax,%r11d
and $0x0f000000,%r11d
shl $8,%eax
shr $20,%eax
or %r11d,%eax
jmp systemfive_bsd
.endfn systemfive_xnu,globl,hidden
#endif
.previous
// Initializes System Five system call support.
//
// (1) Extracts parameters passed by kernel
// (2) Detects OS without issuing system calls
// (3) Unpacks magnums from libc/sysv/consts.sh
// (4) Replaces stack with one we control
//
// @param %r15 is auxv
// @note OpenBSD devs: let us know if you start using auxv
.init.start 300,_init_systemfive
push %rbx
push %rsi
// Detect the operating system.
mov __hostos(%rip),%eax
#if SupportsWindows() || SupportsXnu() || SupportsFreebsd()
// set by libc/ape.S for XNU
// set by libc/crt/crt.S for XNU/FreeBSD
// set by libc/nt/winmain.greg.c for New Technology
test %eax,%eax
jnz _init_systemfive_detected // os is already known
#endif
#if SupportsOpenbsd()
cmpq $0,(%r15) // OpenBSD has no auxv
jnz 0f
mov $_HOSTOPENBSD,%al
jmp _init_systemfive_detected
0:
#endif
#if SupportsNetbsd()
xor %ecx,%ecx
0: cmpq $2014,(%r15,%rcx,8) // NetBSD's AT_EXECFN
jne 1f
mov $_HOSTNETBSD,%al
jmp _init_systemfive_detected
1: cmpq $0,(%r15,%rcx,8)
lea 2(%ecx),%ecx
jnz 0b
2:
#endif
mov $_HOSTLINUX,%al
_init_systemfive_detected:
mov %eax,__hostos(%rip)
bsr %eax,%eax
mov $_init_systemfive_jmptab,%ebx
movzbl (%rbx,%rax),%eax
lea (%rbx,%rax),%eax
jmp *%rax
_init_systemfive_jmptab:
.byte _init_systemfive_linux-_init_systemfive_jmptab
.byte _init_systemfive_metal-_init_systemfive_jmptab
.byte _init_systemfive_windows-_init_systemfive_jmptab
.byte _init_systemfive_xnu-_init_systemfive_jmptab
.byte _init_systemfive_openbsd-_init_systemfive_jmptab
.byte _init_systemfive_freebsd-_init_systemfive_jmptab
.byte _init_systemfive_netbsd-_init_systemfive_jmptab
.endobj _init_systemfive_jmptab
_init_systemfive_linux:
#if SupportsLinux()
pushb systemfive_linux-.Lanchorpoint
mov $syscon_linux,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_linux
_init_systemfive_metal:
#if SupportsMetal()
pushb systemfive_enosys-.Lanchorpoint
mov $syscon_linux,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_metal
_init_systemfive_windows:
#if SupportsWindows()
pushb systemfive_enosys-.Lanchorpoint
mov $syscon_windows,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_windows
_init_systemfive_xnu:
#if SupportsXnu()
pushb systemfive_xnu-.Lanchorpoint
mov $syscon_xnu,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_xnu
_init_systemfive_openbsd:
#if SupportsOpenbsd()
pushb systemfive_openbsd-.Lanchorpoint
mov $syscon_openbsd,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_openbsd
_init_systemfive_freebsd:
#if SupportsFreebsd()
pushb systemfive_freebsd-.Lanchorpoint
mov $syscon_freebsd,%esi
jmp _init_systemfive_os
#endif
.endfn _init_systemfive_freebsd
_init_systemfive_netbsd:
#if SupportsNetbsd()
pushb systemfive_netbsd-.Lanchorpoint
mov $syscon_netbsd,%esi
// 𝑠𝑙𝑖𝑑𝑒
#endif
.endfn _init_systemfive_netbsd
_init_systemfive_os:
pop %rax
add $.Lanchorpoint,%eax
stosq #→ __systemfive
// 𝑠𝑙𝑖𝑑𝑒
.endfn _init_systemfive_os
_init_systemfive_magnums:
push %rdi
mov $syscon_start,%edi
2: cmp $syscon_end,%edi
jnb 5f
xor %ebx,%ebx
xor %ecx,%ecx
xor %edx,%edx
3: lodsb // decodes uleb128
movzbl %al,%edx
and $127,%dl
shl %cl,%rdx
or %rdx,%rbx
add $7,%cl
test $128,%al
jnz 3b
xchg %rbx,%rax
stosq
#ifdef SYSDEBUG
inc %r8d
#endif
jmp 2b
5: nop
#ifdef SYSDEBUG
push %rdi
push %rsi
push %r8
call __describe_os
mov %rax,%rdx
pop %r8
.weak __stracef
ezlea __stracef,ax
test %rax,%rax
jz 5f
ezlea .Llog,di
mov %r8d,%esi
push %rax
call *%rax
pop %rax
5: pop %rsi
pop %rdi
#endif /* DEBUGSYS */
pop %rdi
pop %rsi
pop %rbx
// 𝑠𝑙𝑖𝑑𝑒
.endfn _init_systemfive_magnums
#if SupportsSystemv()
_init_systemfive_pid:
ezlea __hostos,cx
mov (%rcx),%al
mov (%rdi),%eax
testb $_HOSTWINDOWS|_HOSTMETAL,(%rcx)
jnz 1f
mov __NR_getpid(%rip),%eax
syscall
1: stosq
.endfn _init_systemfive_pid
#endif
#if SupportsBsd() && !defined(TINY)
_init_systemfive_sigsys:
testb IsBsd() // BSDs will trap SIGSYS!
jz 1f // We want ENOSYS instead
push %rdi // XNU removed some calls
push %rsi // in past, so this makes
xor %eax,%eax // troubleshooting easier
push %rax // but it's non-essential
push %rax
push %rax
push %rax
push %rax
push $SIG_IGN // sigaction_meta size 48
mov __NR_sigaction(%rip),%eax // mag
mov SIGSYS,%edi // sig
mov %rsp,%rsi // new
xor %edx,%edx // old
mov $8,%r10d // for linux
xor %r8d,%r8d // for netbsd
syscall
add $6*8,%rsp
pop %rsi
pop %rdi
1: .endfn _init_systemfive_sigsys
#endif
_init_systemfive_done:
nop
.init.end 300,_init_systemfive,globl,hidden
#ifdef SYSDEBUG
.rodata.str1.1
.Llog: .ascii STRACE_PROLOGUE
.ascii "bell system five system call support"
.asciz " %'u magnums loaded on %s\n"
.previous
#endif /* DEBUGSYS */