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59 lines
3 KiB
C
59 lines
3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 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/assert.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/strace.internal.h"
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#include "libc/nexgen32e/threaded.h"
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#include "libc/runtime/runtime.h"
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extern int __threadcalls_end[];
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extern int __threadcalls_start[];
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#pragma weak __threadcalls_start
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#pragma weak __threadcalls_end
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privileged void __enable_threads(void) {
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if (__threaded) return;
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STRACE("__enable_threads()");
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__morph_begin();
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/*
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* _NOPL("__threadcalls", func)
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*
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* The big ugly macro above is used by Cosmopolitan Libc to unser
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* locking primitive (e.g. flockfile, funlockfile) have zero impact on
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* performance and binary size when threads aren't actually in play.
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*
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* we have this
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*
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* 0f 1f 05 b1 19 00 00 nopl func(%rip)
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*
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* we're going to turn it into this
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*
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* 67 67 e8 b1 19 00 00 addr32 addr32 call func
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*
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* This is cheap and fast because the big ugly macro stored in the
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* binary the offsets of all the instructions we need to change.
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*/
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for (int *p = __threadcalls_start; p < __threadcalls_end; ++p) {
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_base[*p + 0] = 0x67;
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_base[*p + 1] = 0x67;
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_base[*p + 2] = 0xe8;
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}
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__morph_end();
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__threaded = gettid();
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}
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