Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 286 insertions, 0 deletions

diff --git a/vendor/rustix/src/weak.rs b/vendor/rustix/src/weak.rs
new file mode 100644
index 0000000..3cda8e6
--- /dev/null
+++ b/vendor/rustix/src/weak.rs
@@ -0,0 +1,286 @@
+// Implementation derived from `weak` in Rust's
+// library/std/src/sys/unix/weak.rs at revision
+// fd0cb0cdc21dd9c06025277d772108f8d42cb25f.
+//
+// Ideally we should update to a newer version which doesn't need `dlsym`,
+// however that depends on the `extern_weak` feature which is currently
+// unstable.
+
+#![cfg_attr(linux_raw, allow(unsafe_code))]
+
+//! Support for "weak linkage" to symbols on Unix
+//!
+//! Some I/O operations we do in libstd require newer versions of OSes but we
+//! need to maintain binary compatibility with older releases for now. In order
+//! to use the new functionality when available we use this module for
+//! detection.
+//!
+//! One option to use here is weak linkage, but that is unfortunately only
+//! really workable on Linux. Hence, use dlsym to get the symbol value at
+//! runtime. This is also done for compatibility with older versions of glibc,
+//! and to avoid creating dependencies on `GLIBC_PRIVATE` symbols. It assumes
+//! that we've been dynamically linked to the library the symbol comes from,
+//! but that is currently always the case for things like libpthread/libc.
+//!
+//! A long time ago this used weak linkage for the `__pthread_get_minstack`
+//! symbol, but that caused Debian to detect an unnecessarily strict versioned
+//! dependency on libc6 (#23628).
+
+// There are a variety of `#[cfg]`s controlling which targets are involved in
+// each instance of `weak!` and `syscall!`. Rather than trying to unify all of
+// that, we'll just allow that some unix targets don't use this module at all.
+#![allow(dead_code, unused_macros)]
+#![allow(clippy::doc_markdown)]
+
+use crate::ffi::CStr;
+use core::ffi::c_void;
+use core::ptr::null_mut;
+use core::sync::atomic::{self, AtomicPtr, Ordering};
+use core::{marker, mem};
+
+const NULL: *mut c_void = null_mut();
+const INVALID: *mut c_void = 1 as *mut c_void;
+
+macro_rules! weak {
+    ($vis:vis fn $name:ident($($t:ty),*) -> $ret:ty) => (
+        #[allow(non_upper_case_globals)]
+        $vis static $name: $crate::weak::Weak<unsafe extern fn($($t),*) -> $ret> =
+            $crate::weak::Weak::new(concat!(stringify!($name), '\0'));
+    )
+}
+
+pub(crate) struct Weak<F> {
+    name: &'static str,
+    addr: AtomicPtr<c_void>,
+    _marker: marker::PhantomData<F>,
+}
+
+impl<F> Weak<F> {
+    pub(crate) const fn new(name: &'static str) -> Self {
+        Self {
+            name,
+            addr: AtomicPtr::new(INVALID),
+            _marker: marker::PhantomData,
+        }
+    }
+
+    pub(crate) fn get(&self) -> Option<F> {
+        assert_eq!(mem::size_of::<F>(), mem::size_of::<usize>());
+        unsafe {
+            // Relaxed is fine here because we fence before reading through the
+            // pointer (see the comment below).
+            match self.addr.load(Ordering::Relaxed) {
+                INVALID => self.initialize(),
+                NULL => None,
+                addr => {
+                    let func = mem::transmute_copy::<*mut c_void, F>(&addr);
+                    // The caller is presumably going to read through this value
+                    // (by calling the function we've dlsymed). This means we'd
+                    // need to have loaded it with at least C11's consume
+                    // ordering in order to be guaranteed that the data we read
+                    // from the pointer isn't from before the pointer was
+                    // stored. Rust has no equivalent to memory_order_consume,
+                    // so we use an acquire fence (sorry, ARM).
+                    //
+                    // Now, in practice this likely isn't needed even on CPUs
+                    // where relaxed and consume mean different things. The
+                    // symbols we're loading are probably present (or not) at
+                    // init, and even if they aren't the runtime dynamic loader
+                    // is extremely likely have sufficient barriers internally
+                    // (possibly implicitly, for example the ones provided by
+                    // invoking `mprotect`).
+                    //
+                    // That said, none of that's *guaranteed*, and so we fence.
+                    atomic::fence(Ordering::Acquire);
+                    Some(func)
+                }
+            }
+        }
+    }
+
+    // Cold because it should only happen during first-time initialization.
+    #[cold]
+    unsafe fn initialize(&self) -> Option<F> {
+        let val = fetch(self.name);
+        // This synchronizes with the acquire fence in `get`.
+        self.addr.store(val, Ordering::Release);
+
+        match val {
+            NULL => None,
+            addr => Some(mem::transmute_copy::<*mut c_void, F>(&addr)),
+        }
+    }
+}
+
+// To avoid having the `linux_raw` backend depend on the libc crate, just
+// declare the few things we need in a module called `libc` so that `fetch`
+// uses it.
+#[cfg(linux_raw)]
+mod libc {
+    use core::ptr;
+    use linux_raw_sys::ctypes::{c_char, c_void};
+
+    #[cfg(all(target_os = "android", target_pointer_width = "32"))]
+    pub(super) const RTLD_DEFAULT: *mut c_void = -1isize as *mut c_void;
+    #[cfg(not(all(target_os = "android", target_pointer_width = "32")))]
+    pub(super) const RTLD_DEFAULT: *mut c_void = ptr::null_mut();
+
+    extern "C" {
+        pub(super) fn dlsym(handle: *mut c_void, symbol: *const c_char) -> *mut c_void;
+    }
+
+    #[test]
+    fn test_abi() {
+        assert_eq!(self::RTLD_DEFAULT, ::libc::RTLD_DEFAULT);
+    }
+}
+
+unsafe fn fetch(name: &str) -> *mut c_void {
+    let name = match CStr::from_bytes_with_nul(name.as_bytes()) {
+        Ok(c_str) => c_str,
+        Err(..) => return null_mut(),
+    };
+    libc::dlsym(libc::RTLD_DEFAULT, name.as_ptr().cast())
+}
+
+#[cfg(not(linux_kernel))]
+macro_rules! syscall {
+    (fn $name:ident($($arg_name:ident: $t:ty),*) via $_sys_name:ident -> $ret:ty) => (
+        unsafe fn $name($($arg_name: $t),*) -> $ret {
+            weak! { fn $name($($t),*) -> $ret }
+
+            if let Some(fun) = $name.get() {
+                fun($($arg_name),*)
+            } else {
+                libc_errno::set_errno(libc_errno::Errno(libc::ENOSYS));
+                -1
+            }
+        }
+    )
+}
+
+#[cfg(linux_kernel)]
+macro_rules! syscall {
+    (fn $name:ident($($arg_name:ident: $t:ty),*) via $sys_name:ident -> $ret:ty) => (
+        unsafe fn $name($($arg_name:$t),*) -> $ret {
+            // This looks like a hack, but `concat_idents` only accepts idents
+            // (not paths).
+            use libc::*;
+
+            trait AsSyscallArg {
+                type SyscallArgType;
+                fn into_syscall_arg(self) -> Self::SyscallArgType;
+            }
+
+            // Pass pointer types as pointers, to preserve provenance.
+            impl<T> AsSyscallArg for *mut T {
+                type SyscallArgType = *mut T;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+            impl<T> AsSyscallArg for *const T {
+                type SyscallArgType = *const T;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+
+            // Pass `BorrowedFd` values as the integer value.
+            impl AsSyscallArg for $crate::fd::BorrowedFd<'_> {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType {
+                    $crate::fd::AsRawFd::as_raw_fd(&self) as _
+                }
+            }
+
+            // Coerce integer values into `c_long`.
+            impl AsSyscallArg for i8 {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self.into() }
+            }
+            impl AsSyscallArg for u8 {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self.into() }
+            }
+            impl AsSyscallArg for i16 {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self.into() }
+            }
+            impl AsSyscallArg for u16 {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self.into() }
+            }
+            impl AsSyscallArg for i32 {
+                type SyscallArgType = ::libc::c_int;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+            impl AsSyscallArg for u32 {
+                type SyscallArgType = ::libc::c_uint;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+            impl AsSyscallArg for usize {
+                type SyscallArgType = ::libc::c_ulong;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self as _ }
+            }
+
+            // On 64-bit platforms, also coerce `i64` and `u64` since `c_long`
+            // is 64-bit and can hold those values.
+            #[cfg(target_pointer_width = "64")]
+            impl AsSyscallArg for i64 {
+                type SyscallArgType = ::libc::c_long;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+            #[cfg(target_pointer_width = "64")]
+            impl AsSyscallArg for u64 {
+                type SyscallArgType = ::libc::c_ulong;
+                fn into_syscall_arg(self) -> Self::SyscallArgType { self }
+            }
+
+            // `concat_idents` is [unstable], so we take an extra `sys_name`
+            // parameter and have our users do the concat for us for now.
+            //
+            // [unstable]: https://github.com/rust-lang/rust/issues/29599
+            /*
+            syscall(
+                concat_idents!(SYS_, $name),
+                $($arg_name.into_syscall_arg()),*
+            ) as $ret
+            */
+
+            syscall($sys_name, $($arg_name.into_syscall_arg()),*) as $ret
+        }
+    )
+}
+
+macro_rules! weakcall {
+    ($vis:vis fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
+        $vis unsafe fn $name($($arg_name: $t),*) -> $ret {
+            weak! { fn $name($($t),*) -> $ret }
+
+            // Use a weak symbol from libc when possible, allowing `LD_PRELOAD`
+            // interposition, but if it's not found just fail.
+            if let Some(fun) = $name.get() {
+                fun($($arg_name),*)
+            } else {
+                libc_errno::set_errno(libc_errno::Errno(libc::ENOSYS));
+                -1
+            }
+        }
+    )
+}
+
+/// A combination of `weakcall` and `syscall`. Use the libc function if it's
+/// available, and fall back to `libc::syscall` otherwise.
+macro_rules! weak_or_syscall {
+    ($vis:vis fn $name:ident($($arg_name:ident: $t:ty),*) via $sys_name:ident -> $ret:ty) => (
+        $vis unsafe fn $name($($arg_name: $t),*) -> $ret {
+            weak! { fn $name($($t),*) -> $ret }
+
+            // Use a weak symbol from libc when possible, allowing `LD_PRELOAD`
+            // interposition, but if it's not found just fail.
+            if let Some(fun) = $name.get() {
+                fun($($arg_name),*)
+            } else {
+                syscall! { fn $name($($arg_name: $t),*) via $sys_name -> $ret }
+                $name($($arg_name),*)
+            }
+        }
+    )
+}