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https://github.com/jart/cosmopolitan.git
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2ab9e9f7fd
- Introduce portable sched_getcpu() api - Support GCC's __target_clones__ feature - Make fma() go faster on x86 in default mode - Remove some asan checks from core libraries - WinMain() now ensures $HOME and $USER are defined
71 lines
3.6 KiB
C
71 lines
3.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et 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/dce.h"
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#include "libc/macros.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/stdio/sysparam.h"
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#include "libc/sysv/consts/_posix.h"
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#include "libc/sysv/consts/limits.h"
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#include "libc/sysv/consts/rlimit.h"
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#define CTL_KERN 1
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#define KERN_ARGMAX 8
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/**
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* Returns expensive but more correct version of `ARG_MAX`.
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*/
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int __get_arg_max(void) {
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int res;
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if (IsLinux()) {
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// You might think that just returning a constant 128KiB (ARG_MAX)
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// would make sense, as this guy did:
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//
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// https://lkml.org/lkml/2017/11/15/813...
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//
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// I suspect a 128kB sysconf(_SC_ARG_MAX) is the sanest bet, simply
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// because of that "conservative is better than aggressive".
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//
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// Especially since _technically_ we're still limiting things to that
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// 128kB due to the single-string limit.
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//
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// Linus
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//
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// In practice that caused us trouble with toybox tests for xargs
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// edge cases. The tests assume that they can at least reach the
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// kernel's "minimum maximum" of 128KiB, but if we report 128KiB for
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// _SC_ARG_MAX and xargs starts subtracting the environment space
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// and so on from that, then xargs will think it's run out of space
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// when given 128KiB of data, which should always work. See this
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// thread for more:
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//
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// http://lists.landley.net/pipermail/toybox-landley.net/2019-November/011229.html
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//
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// So let's resign ourselves to tracking what the kernel actually
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// does. Right now (2019, Linux 5.3) that amounts to:
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uint64_t stacksz;
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stacksz = __get_rlimit(RLIMIT_STACK);
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res = MAX(MIN(stacksz / 4, 3 * (8 * 1024 * 1024) / 4), _ARG_MAX);
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} else if (IsBsd()) {
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res = __get_sysctl(CTL_KERN, KERN_ARGMAX);
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} else {
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res = _ARG_MAX;
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}
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return MAX(res, _POSIX_ARG_MAX);
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}
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