1 files changed, 258 insertions, 0 deletions
diff --git a/vendor/rustix/src/backend/linux_raw/reg.rs b/vendor/rustix/src/backend/linux_raw/reg.rs
new file mode 100644
index 0000000..10f95a5
--- /dev/null
+++ b/vendor/rustix/src/backend/linux_raw/reg.rs
@@ -0,0 +1,258 @@
+//! Encapsulation for system call arguments and return values.
+//!
+//! The inline-asm code paths do some amount of reordering of arguments; to
+//! ensure that we don't accidentally misroute an argument or return value, we
+//! use distinct types for each argument index and return value.
+//!
+//! # Safety
+//!
+//! The `ToAsm` and `FromAsm` traits are unsafe to use; they should only be
+//! used by the syscall code which executes actual syscall machine
+//! instructions.
+
+#![allow(unsafe_code)]
+
+use super::c;
+use super::fd::RawFd;
+use core::marker::PhantomData;
+use core::ops::Range;
+
+pub(super) trait ToAsm: private::Sealed {
+    /// Convert `self` to a `usize` ready to be passed to a syscall
+    /// machine instruction.
+    ///
+    /// # Safety
+    ///
+    /// This should be used immediately before the syscall instruction, and the
+    /// returned value shouldn't be used for any other purpose.
+    #[must_use]
+    unsafe fn to_asm(self) -> *mut Opaque;
+}
+
+pub(super) trait FromAsm: private::Sealed {
+    /// Convert `raw` from a value produced by a syscall machine instruction
+    /// into a `Self`.
+    ///
+    /// # Safety
+    ///
+    /// This should be used immediately after the syscall instruction, and the
+    /// operand value shouldn't be used for any other purpose.
+    #[must_use]
+    unsafe fn from_asm(raw: *mut Opaque) -> Self;
+}
+
+/// To preserve provenance, syscall arguments and return values are passed as
+/// pointer types. They need a type to point to, so we define a custom private
+/// type, to prevent it from being used for anything else.
+#[repr(transparent)]
+pub(super) struct Opaque(c::c_void);
+
+// Argument numbers.
+pub(super) struct A0(());
+pub(super) struct A1(());
+pub(super) struct A2(());
+pub(super) struct A3(());
+pub(super) struct A4(());
+pub(super) struct A5(());
+#[cfg(any(target_arch = "mips", target_arch = "mips32r6"))]
+pub(super) struct A6(());
+#[cfg(target_arch = "x86")]
+pub(super) struct SocketArg;
+
+pub(super) trait ArgNumber: private::Sealed {}
+impl ArgNumber for A0 {}
+impl ArgNumber for A1 {}
+impl ArgNumber for A2 {}
+impl ArgNumber for A3 {}
+impl ArgNumber for A4 {}
+impl ArgNumber for A5 {}
+#[cfg(any(target_arch = "mips", target_arch = "mips32r6"))]
+impl ArgNumber for A6 {}
+#[cfg(target_arch = "x86")]
+impl ArgNumber for SocketArg {}
+
+// Return value numbers.
+pub(super) struct R0(());
+
+pub(super) trait RetNumber: private::Sealed {}
+impl RetNumber for R0 {}
+
+/// Syscall arguments use register-sized types. We use a newtype to
+/// discourage accidental misuse of the raw integer values.
+///
+/// This type doesn't implement `Clone` or `Copy`; it should be used exactly
+/// once. And it has a lifetime to ensure that it doesn't outlive any resources
+/// it might be pointing to.
+#[repr(transparent)]
+#[must_use]
+pub(super) struct ArgReg<'a, Num: ArgNumber> {
+    raw: *mut Opaque,
+    _phantom: PhantomData<(&'a (), Num)>,
+}
+
+impl<'a, Num: ArgNumber> ToAsm for ArgReg<'a, Num> {
+    #[inline]
+    unsafe fn to_asm(self) -> *mut Opaque {
+        self.raw
+    }
+}
+
+/// Syscall return values use register-sized types. We use a newtype to
+/// discourage accidental misuse of the raw integer values.
+///
+/// This type doesn't implement `Clone` or `Copy`; it should be used exactly
+/// once.
+#[repr(transparent)]
+#[must_use]
+pub(super) struct RetReg<Num: RetNumber> {
+    raw: *mut Opaque,
+    _phantom: PhantomData<Num>,
+}
+
+impl<Num: RetNumber> RetReg<Num> {
+    #[inline]
+    pub(super) fn decode_usize(self) -> usize {
+        debug_assert!(!(-4095..0).contains(&(self.raw as isize)));
+        self.raw as usize
+    }
+
+    #[inline]
+    pub(super) fn decode_raw_fd(self) -> RawFd {
+        let bits = self.decode_usize();
+        let raw_fd = bits as RawFd;
+
+        // Converting `raw` to `RawFd` should be lossless.
+        debug_assert_eq!(raw_fd as usize, bits);
+
+        raw_fd
+    }
+
+    #[inline]
+    pub(super) fn decode_c_int(self) -> c::c_int {
+        let bits = self.decode_usize();
+        let c_int_ = bits as c::c_int;
+
+        // Converting `raw` to `c_int` should be lossless.
+        debug_assert_eq!(c_int_ as usize, bits);
+
+        c_int_
+    }
+
+    #[inline]
+    pub(super) fn decode_c_uint(self) -> c::c_uint {
+        let bits = self.decode_usize();
+        let c_uint_ = bits as c::c_uint;
+
+        // Converting `raw` to `c_uint` should be lossless.
+        debug_assert_eq!(c_uint_ as usize, bits);
+
+        c_uint_
+    }
+
+    #[inline]
+    pub(super) fn decode_void_star(self) -> *mut c::c_void {
+        self.raw.cast()
+    }
+
+    #[cfg(target_pointer_width = "64")]
+    #[inline]
+    pub(super) fn decode_u64(self) -> u64 {
+        self.decode_usize() as u64
+    }
+
+    #[inline]
+    pub(super) fn decode_void(self) {
+        let ignore = self.decode_usize();
+        debug_assert_eq!(ignore, 0);
+    }
+
+    #[inline]
+    pub(super) fn decode_error_code(self) -> u16 {
+        let bits = self.raw as usize;
+
+        // `raw` must be in `-4095..0`. Linux always returns errors in
+        // `-4095..0`, and we double-check it here.
+        debug_assert!((-4095..0).contains(&(bits as isize)));
+
+        bits as u16
+    }
+
+    #[inline]
+    pub(super) fn is_nonzero(&self) -> bool {
+        !self.raw.is_null()
+    }
+
+    #[inline]
+    pub(super) fn is_negative(&self) -> bool {
+        (self.raw as isize) < 0
+    }
+
+    #[inline]
+    pub(super) fn is_in_range(&self, range: Range<isize>) -> bool {
+        range.contains(&(self.raw as isize))
+    }
+}
+
+impl<Num: RetNumber> FromAsm for RetReg<Num> {
+    #[inline]
+    unsafe fn from_asm(raw: *mut Opaque) -> Self {
+        Self {
+            raw,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+#[repr(transparent)]
+pub(super) struct SyscallNumber<'a> {
+    nr: usize,
+    _phantom: PhantomData<&'a ()>,
+}
+
+impl<'a> ToAsm for SyscallNumber<'a> {
+    #[inline]
+    unsafe fn to_asm(self) -> *mut Opaque {
+        self.nr as usize as *mut Opaque
+    }
+}
+
+/// Encode a system call argument as an `ArgReg`.
+#[inline]
+pub(super) fn raw_arg<'a, Num: ArgNumber>(raw: *mut Opaque) -> ArgReg<'a, Num> {
+    ArgReg {
+        raw,
+        _phantom: PhantomData,
+    }
+}
+
+/// Encode a system call number (a `__NR_*` constant) as a `SyscallNumber`.
+#[inline]
+pub(super) const fn nr<'a>(nr: u32) -> SyscallNumber<'a> {
+    SyscallNumber {
+        nr: nr as usize,
+        _phantom: PhantomData,
+    }
+}
+
+/// Seal our various traits using the technique documented [here].
+///
+/// [here]: https://rust-lang.github.io/api-guidelines/future-proofing.html
+mod private {
+    pub trait Sealed {}
+
+    // Implement for those same types, but no others.
+    impl<'a, Num: super::ArgNumber> Sealed for super::ArgReg<'a, Num> {}
+    impl<Num: super::RetNumber> Sealed for super::RetReg<Num> {}
+    impl<'a> Sealed for super::SyscallNumber<'a> {}
+    impl Sealed for super::A0 {}
+    impl Sealed for super::A1 {}
+    impl Sealed for super::A2 {}
+    impl Sealed for super::A3 {}
+    impl Sealed for super::A4 {}
+    impl Sealed for super::A5 {}
+    #[cfg(any(target_arch = "mips", target_arch = "mips32r6"))]
+    impl Sealed for super::A6 {}
+    #[cfg(target_arch = "x86")]
+    impl Sealed for super::SocketArg {}
+    impl Sealed for super::R0 {}
+}