Rewrite Obj-C workflow in Rust

This is functionally equivalent to the previous workflow_objc, with the
following changes:
1. It mutates the `core.function.metaAnalysis` workflow rather than
   registering a new named workflow. The activities now all check for
   the presence of the Objective-C metadata added by `ObjCProcessor` to
   determine whether they should do work, rather than relying on
   `MachoView` to override the function workflow when Objective-C
   metadata is present. This fixes
   https://github.com/Vector35/binaryninja-api/issues/6779.
2. The auto-inlining of `objc_msgSend` selector stub functions is
   performed in a separate activity from the processing of
   `objc_msgSend` call sites. The selector stub inlining activity is
   configured so that it does not run in `DSCView` as the shared cache
   needs different behavior for stub functions more generally that
   `SharedCacheWorkflow` already provides.
3. The way that types like `id` and `SEL` are referenced is fixed so
   that they show up as `id` rather than `objc_struct*`.

This also replaces the Objective-C portion of the shared cache's
workflow, and incorporates several bug fixes that had been applied to it
but not the standalone Objective-C workflow.

1 files changed, 52 insertions, 0 deletions

diff --git a/plugins/workflow_objc/src/metadata/selector.rs b/plugins/workflow_objc/src/metadata/selector.rs
new file mode 100644
index 00000000..a48be14d
--- /dev/null
+++ b/plugins/workflow_objc/src/metadata/selector.rs
@@ -0,0 +1,52 @@
+use crate::Error;
+use binaryninja::binary_view::{BinaryView, BinaryViewBase as _, BinaryViewExt};
+
+pub struct Selector {
+    pub name: String,
+    pub addr: u64,
+}
+
+impl Selector {
+    pub fn from_address(bv: &BinaryView, addr: u64) -> Result<Self, Error> {
+        let name = if bv.offset_valid(addr) {
+            // Read the selector name from the binary view
+            read_cstring(bv, addr, 500)
+        } else {
+            // Look for the `sel_` symbols that ObjCProcessor adds to represent selectors
+            // whose backing regions have not yet been loaded into the view.
+            bv.symbol_by_address(addr)
+                .and_then(|sym| sym.raw_name().to_str().ok().map(|name| name.to_owned()))
+                .filter(|name| name.starts_with("sel_"))
+                .map(|name| name["sel_".len()..].to_string())
+        }
+        .ok_or(Error::InvalidSelector { address: addr })?;
+        Ok(Selector { name, addr })
+    }
+
+    pub fn argument_labels(&self) -> Vec<String> {
+        if !self.name.contains(':') {
+            return vec![];
+        }
+
+        self.name
+            .split(':')
+            .filter(|s| !s.is_empty())
+            .map(|s| s.to_string())
+            .collect()
+    }
+}
+
+// Read a null-terminated string from the view
+fn read_cstring(bv: &BinaryView, address: u64, max_len: usize) -> Option<String> {
+    let mut buffer = vec![0u8; max_len];
+    let bytes_read = bv.read(&mut buffer, address);
+    if bytes_read == 0 {
+        return None;
+    }
+
+    // Find the null terminator
+    let null_pos = buffer.iter().position(|&b| b == 0).unwrap_or(bytes_read);
+    buffer.truncate(null_pos);
+
+    String::from_utf8(buffer).ok()
+}