cosmopolitan/libc/sysv/systemfive.S
Justine Tunney 957c61cbbf
Release Cosmopolitan v3.3
This change upgrades to GCC 12.3 and GNU binutils 2.42. The GNU linker
appears to have changed things so that only a single de-duplicated str
table is present in the binary, and it gets placed wherever the linker
wants, regardless of what the linker script says. To cope with that we
need to stop using .ident to embed licenses. As such, this change does
significant work to revamp how third party licenses are defined in the
codebase, using `.section .notice,"aR",@progbits`.

This new GCC 12.3 toolchain has support for GNU indirect functions. It
lets us support __target_clones__ for the first time. This is used for
optimizing the performance of libc string functions such as strlen and
friends so far on x86, by ensuring AVX systems favor a second codepath
that uses VEX encoding. It shaves some latency off certain operations.
It's a useful feature to have for scientific computing for the reasons
explained by the test/libcxx/openmp_test.cc example which compiles for
fifteen different microarchitectures. Thanks to the upgrades, it's now
also possible to use newer instruction sets, such as AVX512FP16, VNNI.

Cosmo now uses the %gs register on x86 by default for TLS. Doing it is
helpful for any program that links `cosmo_dlopen()`. Such programs had
to recompile their binaries at startup to change the TLS instructions.
That's not great, since it means every page in the executable needs to
be faulted. The work of rewriting TLS-related x86 opcodes, is moved to
fixupobj.com instead. This is great news for MacOS x86 users, since we
previously needed to morph the binary every time for that platform but
now that's no longer necessary. The only platforms where we need fixup
of TLS x86 opcodes at runtime are now Windows, OpenBSD, and NetBSD. On
Windows we morph TLS to point deeper into the TIB, based on a TlsAlloc
assignment, and on OpenBSD/NetBSD we morph %gs back into %fs since the
kernels do not allow us to specify a value for the %gs register.

OpenBSD users are now required to use APE Loader to run Cosmo binaries
and assimilation is no longer possible. OpenBSD kernel needs to change
to allow programs to specify a value for the %gs register, or it needs
to stop marking executable pages loaded by the kernel as mimmutable().

This release fixes __constructor__, .ctor, .init_array, and lastly the
.preinit_array so they behave the exact same way as glibc.

We no longer use hex constants to define math.h symbols like M_PI.
2024-02-20 13:27:59 -08:00

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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
vi: set noet 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/thread/pt.internal.h"
#define SIG_IGN 1
/*
besiyata
dishmaya
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 %gs:0x30,%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 %gs:0x30,%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
#if SYSDEBUG
inc %r8d
#endif
jmp 2b
5: nop
#if 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(%rip),%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
#if 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 */