libutil: deal with Linux systems that do not implement close_range
Seems a little bit Rich that musl does not implement close_range because they suspect that the system call itself is a bad idea, so they uhhhh are considering not implementing a wrapper. Let's just fix the problem at hand by writing our own wrapper. Change-Id: I1f8e5858e4561d58a5450503d9c4585aded2b216
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2 changed files with 19 additions and 2 deletions
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@ -417,6 +417,11 @@ check_funcs = [
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'strsignal',
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'sysconf',
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]
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if target_machine.kernel() in ['linux', 'freebsd']
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# musl does not have close_range as of 2024-08-10
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# patch: https://www.openwall.com/lists/musl/2024/08/01/9
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check_funcs += [ 'close_range' ]
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endif
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foreach funcspec : check_funcs
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define_name = 'HAVE_' + funcspec.underscorify().to_upper()
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define_value = cxx.has_function(funcspec).to_int()
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@ -223,15 +223,27 @@ void closeExtraFDs()
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constexpr int MAX_KEPT_FD = 2;
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static_assert(std::max({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO}) == MAX_KEPT_FD);
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#if __linux__
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// Both Linux and FreeBSD support close_range.
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#if __linux__ || __FreeBSD__
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auto closeRange = [](unsigned int first, unsigned int last, int flags) -> int {
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// musl does not have close_range as of 2024-08-10
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// patch: https://www.openwall.com/lists/musl/2024/08/01/9
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#ifdef HAVE_CLOSE_RANGE
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return close_range(first, last, flags);
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#else
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return syscall(SYS_close_range, first, last, flags);
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#endif
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};
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// first try to close_range everything we don't care about. if this
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// returns an error with these parameters we're running on a kernel
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// that does not implement close_range (i.e. pre 5.9) and fall back
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// to the old method. we should remove that though, in some future.
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if (close_range(3, ~0U, 0) == 0) {
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if (closeRange(3, ~0U, 0) == 0) {
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return;
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}
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#endif
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#if __linux__
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try {
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for (auto & s : readDirectory("/proc/self/fd")) {
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auto fd = std::stoi(s.name);
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