Initial vendor packages

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

vendor/portable-atomic/src/imp/interrupt/armv4t.rs

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// Refs: https://developer.arm.com/documentation/ddi0406/cb/System-Level-Architecture/The-System-Level-Programmers--Model/ARM-processor-modes-and-ARM-core-registers/Program-Status-Registers--PSRs-?lang=en
+//
+// Generated asm:
+// - armv5te https://godbolt.org/z/Teh7WajMs
+
+#[cfg(not(portable_atomic_no_asm))]
+use core::arch::asm;
+
+// - 0x80 - I (IRQ mask) bit (1 << 7)
+// - 0x40 - F (FIQ mask) bit (1 << 6)
+// We disable only IRQs by default. See also https://github.com/taiki-e/portable-atomic/pull/28#issuecomment-1214146912.
+#[cfg(not(portable_atomic_disable_fiq))]
+macro_rules! mask {
+    () => {
+        "0x80"
+    };
+}
+#[cfg(portable_atomic_disable_fiq)]
+macro_rules! mask {
+    () => {
+        "0xC0" // 0x80 | 0x40
+    };
+}
+
+pub(super) type State = u32;
+
+/// Disables interrupts and returns the previous interrupt state.
+#[inline]
+#[instruction_set(arm::a32)]
+pub(super) fn disable() -> State {
+    let cpsr: State;
+    // SAFETY: reading CPSR and disabling interrupts are safe.
+    // (see module-level comments of interrupt/mod.rs on the safety of using privileged instructions)
+    unsafe {
+        asm!(
+            "mrs {prev}, cpsr",
+            concat!("orr {new}, {prev}, ", mask!()),
+            "msr cpsr_c, {new}",
+            prev = out(reg) cpsr,
+            new = out(reg) _,
+            // Do not use `nomem` and `readonly` because prevent subsequent memory accesses from being reordered before interrupts are disabled.
+            options(nostack, preserves_flags),
+        );
+    }
+    cpsr
+}
+
+/// Restores the previous interrupt state.
+///
+/// # Safety
+///
+/// The state must be the one retrieved by the previous `disable`.
+#[inline]
+#[instruction_set(arm::a32)]
+pub(super) unsafe fn restore(cpsr: State) {
+    // SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`,
+    //
+    // This clobbers the control field mask byte of CPSR. See msp430.rs to safety on this.
+    // (preserves_flags is fine because we only clobber the I, F, T, and M bits of CPSR.)
+    //
+    // Refs: https://developer.arm.com/documentation/dui0473/m/arm-and-thumb-instructions/msr--general-purpose-register-to-psr-
+    unsafe {
+        // Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled.
+        asm!("msr cpsr_c, {0}", in(reg) cpsr, options(nostack, preserves_flags));
+    }
+}
+
+// On pre-v6 ARM, we cannot use core::sync::atomic here because they call the
+// `__sync_*` builtins for non-relaxed load/store (because pre-v6 ARM doesn't
+// have Data Memory Barrier).
+//
+// Generated asm:
+// - armv5te https://godbolt.org/z/bMxK7M8Ta
+pub(crate) mod atomic {
+    #[cfg(not(portable_atomic_no_asm))]
+    use core::arch::asm;
+    use core::{cell::UnsafeCell, sync::atomic::Ordering};
+
+    macro_rules! atomic {
+        ($([$($generics:tt)*])? $atomic_type:ident, $value_type:ty, $asm_suffix:tt) => {
+            #[repr(transparent)]
+            pub(crate) struct $atomic_type $(<$($generics)*>)? {
+                v: UnsafeCell<$value_type>,
+            }
+
+            // Send is implicitly implemented for atomic integers, but not for atomic pointers.
+            // SAFETY: any data races are prevented by atomic operations.
+            unsafe impl $(<$($generics)*>)? Send for $atomic_type $(<$($generics)*>)? {}
+            // SAFETY: any data races are prevented by atomic operations.
+            unsafe impl $(<$($generics)*>)? Sync for $atomic_type $(<$($generics)*>)? {}
+
+            impl $(<$($generics)*>)? $atomic_type $(<$($generics)*>)? {
+                #[inline]
+                pub(crate) fn load(&self, order: Ordering) -> $value_type {
+                    let src = self.v.get();
+                    // SAFETY: any data races are prevented by atomic intrinsics and the raw
+                    // pointer passed in is valid because we got it from a reference.
+                    unsafe {
+                        let out;
+                        match order {
+                            Ordering::Relaxed => {
+                                asm!(
+                                    concat!("ldr", $asm_suffix, " {out}, [{src}]"),
+                                    src = in(reg) src,
+                                    out = lateout(reg) out,
+                                    options(nostack, preserves_flags, readonly),
+                                );
+                            }
+                            Ordering::Acquire | Ordering::SeqCst => {
+                                // inline asm without nomem/readonly implies compiler fence.
+                                // And compiler fence is fine because the user explicitly declares that
+                                // the system is single-core by using an unsafe cfg.
+                                asm!(
+                                    concat!("ldr", $asm_suffix, " {out}, [{src}]"),
+                                    src = in(reg) src,
+                                    out = lateout(reg) out,
+                                    options(nostack, preserves_flags),
+                                );
+                            }
+                            _ => unreachable!("{:?}", order),
+                        }
+                        out
+                    }
+                }
+
+                #[inline]
+                pub(crate) fn store(&self, val: $value_type, _order: Ordering) {
+                    let dst = self.v.get();
+                    // SAFETY: any data races are prevented by atomic intrinsics and the raw
+                    // pointer passed in is valid because we got it from a reference.
+                    unsafe {
+                        // inline asm without nomem/readonly implies compiler fence.
+                        // And compiler fence is fine because the user explicitly declares that
+                        // the system is single-core by using an unsafe cfg.
+                        asm!(
+                            concat!("str", $asm_suffix, " {val}, [{dst}]"),
+                            dst = in(reg) dst,
+                            val = in(reg) val,
+                            options(nostack, preserves_flags),
+                        );
+                    }
+                }
+            }
+        };
+    }
+
+    atomic!(AtomicI8, i8, "b");
+    atomic!(AtomicU8, u8, "b");
+    atomic!(AtomicI16, i16, "h");
+    atomic!(AtomicU16, u16, "h");
+    atomic!(AtomicI32, i32, "");
+    atomic!(AtomicU32, u32, "");
+    atomic!(AtomicIsize, isize, "");
+    atomic!(AtomicUsize, usize, "");
+    atomic!([T] AtomicPtr, *mut T, "");
+}