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libutil: deal with Linux systems that do not implement close_range

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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
This commit is contained in:
jade 2024-08-10 01:10:35 -07:00
parent b15d5cc6ee
commit b9ed79c99a
2 changed files with 19 additions and 2 deletions
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5
meson.build
View file

@ -417,6 +417,11 @@ check_funcs = [
'strsignal',
'sysconf',
]
if target_machine.kernel() in ['linux', 'freebsd']
# musl does not have close_range as of 2024-08-10
# patch: https://www.openwall.com/lists/musl/2024/08/01/9
check_funcs += [ 'close_range' ]
endif
foreach funcspec : check_funcs
define_name = 'HAVE_' + funcspec.underscorify().to_upper()
define_value = cxx.has_function(funcspec).to_int()

16
src/libutil/file-descriptor.cc
View file

@ -223,15 +223,27 @@ void closeExtraFDs()
constexpr int MAX_KEPT_FD = 2;
static_assert(std::max({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO}) == MAX_KEPT_FD);
#if __linux__
// Both Linux and FreeBSD support close_range.
#if __linux__ || __FreeBSD__
auto closeRange = [](unsigned int first, unsigned int last, int flags) -> int {
// musl does not have close_range as of 2024-08-10
// patch: https://www.openwall.com/lists/musl/2024/08/01/9
#ifdef HAVE_CLOSE_RANGE
return close_range(first, last, flags);
#else
return syscall(SYS_close_range, first, last, flags);
#endif
};
// first try to close_range everything we don't care about. if this
// returns an error with these parameters we're running on a kernel
// that does not implement close_range (i.e. pre 5.9) and fall back
// to the old method. we should remove that though, in some future.
if (close_range(3, ~0U, 0) == 0) {
if (closeRange(3, ~0U, 0) == 0) {
return;
}
#endif
#if __linux__
try {
for (auto & s : readDirectory("/proc/self/fd")) {
auto fd = std::stoi(s.name);