1 files changed, 92 insertions, 0 deletions
diff --git a/third_party/rust/crash-context/src/mac/guard.rs b/third_party/rust/crash-context/src/mac/guard.rs
new file mode 100644
index 0000000000..7caee5ffe3
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+++ b/third_party/rust/crash-context/src/mac/guard.rs
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+//! Contains types and helpers for dealing with `EXC_GUARD` exceptions.
+//!
+//! `EXC_GUARD` exceptions embed details about the guarded resource in the `code`
+//! and `subcode` fields of the exception
+//!
+//! See <https://github.com/apple-oss-distributions/xnu/blob/e7776783b89a353188416a9a346c6cdb4928faad/osfmk/kern/exc_guard.h>
+//! for the top level types that this module wraps.
+
+use mach2::exception_types::EXC_GUARD;
+
+/// The set of possible guard kinds
+#[derive(Copy, Clone, Debug)]
+#[repr(u8)]
+pub enum GuardKind {
+    /// Null variant
+    None = 0,
+    /// A `mach_port_t`
+    MachPort = 1,
+    /// File descriptor
+    Fd = 2,
+    /// Userland assertion
+    User = 3,
+    /// Vnode
+    Vnode = 4,
+    /// Virtual memory operation
+    VirtualMemory = 5,
+    /// Rejected system call trap
+    RejectedSyscall = 6,
+}
+
+#[inline]
+pub fn extract_guard_kind(code: u64) -> u8 {
+    ((code >> 61) & 0x7) as u8
+}
+
+#[inline]
+pub fn extract_guard_flavor(code: u64) -> u32 {
+    ((code >> 32) & 0x1fffffff) as u32
+}
+
+#[inline]
+pub fn extract_guard_target(code: u64) -> u32 {
+    code as u32
+}
+
+/// The extracted details of an `EXC_GUARD` exception
+pub struct GuardException {
+    /// One of [`GuardKind`]
+    pub kind: u8,
+    /// The specific guard flavor that was violated, specific to each `kind`
+    pub flavor: u32,
+    /// The resource that was guarded
+    pub target: u32,
+    /// Target specific guard information
+    pub identifier: u64,
+}
+
+/// Extracts the guard details from an exceptions code and subcode
+///
+/// code:
+/// +-------------------+----------------+--------------+
+/// |[63:61] guard type | [60:32] flavor | [31:0] target|
+/// +-------------------+----------------+--------------+
+///
+/// subcode:
+/// +---------------------------------------------------+
+/// |[63:0] guard identifier                            |
+/// +---------------------------------------------------+
+#[inline]
+pub fn extract_guard_exception(code: u64, subcode: u64) -> GuardException {
+    GuardException {
+        kind: extract_guard_kind(code),
+        flavor: extract_guard_flavor(code),
+        target: extract_guard_target(code),
+        identifier: subcode,
+    }
+}
+
+impl super::ExceptionInfo {
+    /// If this is an `EXC_GUARD` exception, retrieves the exception metadata
+    /// from the code, otherwise returns `None`
+    pub fn guard_exception(&self) -> Option<GuardException> {
+        if self.kind != EXC_GUARD {
+            return None;
+        }
+
+        Some(extract_guard_exception(
+            self.code,
+            self.subcode.unwrap_or_default(),
+        ))
+    }
+}