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69f4152f38
We had previously not enabled TLS in MODE=tiny in order to keep the smallest example programs (e.g. life.com) just 16kb in size. But it was error prone doing that, so now we just always enable it because this change uses hacks to ensure it won't increase life.com's size. This change also fixes a bug on NetBSD, where signal handlers would break thread local storage if SA_SIGINFO was being used. This looks like it might be a bug in NetBSD, but it's got a simple workaround.
63 lines
3.1 KiB
C
63 lines
3.1 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 2020 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/syscall-sysv.internal.h"
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#include "libc/dce.h"
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#include "libc/nexgen32e/gettls.h"
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#include "libc/nexgen32e/threaded.h"
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/**
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* Returns current thread id.
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*
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* On Linux, and Linux only, this is guaranteed to be equal to getpid()
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* if this is the main thread. On NetBSD, gettid() for the main thread
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* is always 1.
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*
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* This function issues a system call. That stops being the case as soon
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* as __install_tls() is called. That'll happen automatically, when you
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* call clone() and provide the TLS parameter. We assume that when a TLS
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* block exists, then
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*
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* *(int *)(__get_tls() + 0x38)
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*
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* will contain the thread id. Therefore when issuing clone() calls, the
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* `CLONE_CHILD_SETTID` and `CLONE_CHILD_CLEARTID` flags should use that
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* index as its `ctid` memory.
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*
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* gettid (single threaded) l: 126𝑐 41𝑛𝑠
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* gettid (tls enabled) l: 2𝑐 1𝑛𝑠
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*
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* The TLS convention is important for reentrant lock performance.
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*
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* @return thread id greater than zero or -1 w/ errno
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* @asyncsignalsafe
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* @threadsafe
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*/
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int gettid(void) {
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int tid;
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if (__tls_enabled) {
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tid = *(int *)(__get_tls() + 0x38);
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if (tid > 0) {
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return tid;
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}
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}
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return sys_gettid();
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}
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