cosmopolitan/libc/sysv/systemfive.S
Justine Tunney ec480f5aa0
Make improvements
- Every unit test now passes on Apple Silicon. The final piece of this
  puzzle was porting our POSIX threads cancelation support, since that
  works differently on ARM64 XNU vs. AMD64. Our semaphore support on
  Apple Silicon is also superior now compared to AMD64, thanks to the
  grand central dispatch library which lets *NSYNC locks go faster.

- The Cosmopolitan runtime is now more stable, particularly on Windows.
  To do this, thread local storage is mandatory at all runtime levels,
  and the innermost packages of the C library is no longer being built
  using ASAN. TLS is being bootstrapped with a 128-byte TIB during the
  process startup phase, and then later on the runtime re-allocates it
  either statically or dynamically to support code using _Thread_local.
  fork() and execve() now do a better job cooperating with threads. We
  can now check how much stack memory is left in the process or thread
  when functions like kprintf() / execve() etc. call alloca(), so that
  ENOMEM can be raised, reduce a buffer size, or just print a warning.

- POSIX signal emulation is now implemented the same way kernels do it
  with pthread_kill() and raise(). Any thread can interrupt any other
  thread, regardless of what it's doing. If it's blocked on read/write
  then the killer thread will cancel its i/o operation so that EINTR can
  be returned in the mark thread immediately. If it's doing a tight CPU
  bound operation, then that's also interrupted by the signal delivery.
  Signal delivery works now by suspending a thread and pushing context
  data structures onto its stack, and redirecting its execution to a
  trampoline function, which calls SetThreadContext(GetCurrentThread())
  when it's done.

- We're now doing a better job managing locks and handles. On NetBSD we
  now close semaphore file descriptors in forked children. Semaphores on
  Windows can now be canceled immediately, which means mutexes/condition
  variables will now go faster. Apple Silicon semaphores can be canceled
  too. We're now using Apple's pthread_yield() funciton. Apple _nocancel
  syscalls are now used on XNU when appropriate to ensure pthread_cancel
  requests aren't lost. The MbedTLS library has been updated to support
  POSIX thread cancelations. See tool/build/runitd.c for an example of
  how it can be used for production multi-threaded tls servers. Handles
  on Windows now leak less often across processes. All i/o operations on
  Windows are now overlapped, which means file pointers can no longer be
  inherited across dup() and fork() for the time being.

- We now spawn a thread on Windows to deliver SIGCHLD and wakeup wait4()
  which means, for example, that posix_spawn() now goes 3x faster. POSIX
  spawn is also now more correct. Like Musl, it's now able to report the
  failure code of execve() via a pipe although our approach favors using
  shared memory to do that on systems that have a true vfork() function.

- We now spawn a thread to deliver SIGALRM to threads when setitimer()
  is used. This enables the most precise wakeups the OS makes possible.

- The Cosmopolitan runtime now uses less memory. On NetBSD for example,
  it turned out the kernel would actually commit the PT_GNU_STACK size
  which caused RSS to be 6mb for every process. Now it's down to ~4kb.
  On Apple Silicon, we reduce the mandatory upstream thread size to the
  smallest possible size to reduce the memory overhead of Cosmo threads.
  The examples directory has a program called greenbean which can spawn
  a web server on Linux with 10,000 worker threads and have the memory
  usage of the process be ~77mb. The 1024 byte overhead of POSIX-style
  thread-local storage is now optional; it won't be allocated until the
  pthread_setspecific/getspecific functions are called. On Windows, the
  threads that get spawned which are internal to the libc implementation
  use reserve rather than commit memory, which shaves a few hundred kb.

- sigaltstack() is now supported on Windows, however it's currently not
  able to be used to handle stack overflows, since crash signals are
  still generated by WIN32. However the crash handler will still switch
  to the alt stack, which is helpful in environments with tiny threads.

- Test binaries are now smaller. Many of the mandatory dependencies of
  the test runner have been removed. This ensures many programs can do a
  better job only linking the the thing they're testing. This caused the
  test binaries for LIBC_FMT for example, to decrease from 200kb to 50kb

- long double is no longer used in the implementation details of libc,
  except in the APIs that define it. The old code that used long double
  for time (instead of struct timespec) has now been thoroughly removed.

- ShowCrashReports() is now much tinier in MODE=tiny. Instead of doing
  backtraces itself, it'll just print a command you can run on the shell
  using our new `cosmoaddr2line` program to view the backtrace.

- Crash report signal handling now works in a much better way. Instead
  of terminating the process, it now relies on SA_RESETHAND so that the
  default SIG_IGN behavior can terminate the process if necessary.

- Our pledge() functionality has now been fully ported to AARCH64 Linux.
2023-09-18 21:04:47 -07:00

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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
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
/*
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 %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
call *%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 */