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https://github.com/jart/cosmopolitan.git
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2278327eba
This change makes some miracle modifications to the System Five system call support, which lets us have safe, correct, and atomic handling of thread cancellations. It all turned out to be cheaper than anticipated because it wasn't necessary to modify the system call veneers. We were able to encode the cancellability of each system call into the magnums found in libc/sysv/syscalls.sh. Since cancellations are so waq, we are also supporting a lovely Musl Libc mask feature for raising ECANCELED.
70 lines
3.4 KiB
C
70 lines
3.4 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
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╚──────────────────────────────────────────────────────────────────────────────╝
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│ │
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│ Musl Libc │
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│ Copyright © 2005-2014 Rich Felker, et al. │
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│ │
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│ Permission is hereby granted, free of charge, to any person obtaining │
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│ a copy of this software and associated documentation files (the │
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│ "Software"), to deal in the Software without restriction, including │
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│ without limitation the rights to use, copy, modify, merge, publish, │
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│ distribute, sublicense, and/or sell copies of the Software, and to │
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│ permit persons to whom the Software is furnished to do so, subject to │
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│ the following conditions: │
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│ │
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│ The above copyright notice and this permission notice shall be │
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│ included in all copies or substantial portions of the Software. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
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│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
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│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
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│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
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│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
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│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
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│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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│ │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/calls/struct/flock.h"
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#include "libc/calls/weirdtypes.h"
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#include "libc/errno.h"
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#include "libc/sysv/consts/f.h"
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#include "libc/sysv/errfuns.h"
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#include "third_party/musl/lockf.h"
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asm(".ident\t\"\\n\\n\
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Musl libc (MIT License)\\n\
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Copyright 2005-2014 Rich Felker, et. al.\"");
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asm(".include \"libc/disclaimer.inc\"");
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// clang-format off
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/**
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* Locks file.
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*
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* @cancellationpoint when `op` is `F_LOCK`
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*/
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int lockf(int fd, int op, off_t size)
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{
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struct flock l = {
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.l_type = F_WRLCK,
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.l_whence = SEEK_CUR,
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.l_len = size,
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};
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switch (op) {
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case F_TEST:
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l.l_type = F_RDLCK;
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if (fcntl(fd, F_GETLK, &l) < 0)
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return -1;
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if (l.l_type == F_UNLCK || l.l_pid == getpid())
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return 0;
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return eacces();
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case F_ULOCK:
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l.l_type = F_UNLCK;
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case F_TLOCK:
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return fcntl(fd, F_SETLK, &l);
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case F_LOCK:
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return fcntl(fd, F_SETLKW, &l);
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}
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return einval();
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}
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