Add support for qOffsets packet

Adding support for this packet allows the stub to report section offsets
back to gdb so that debug symbols are resolved to the correct addresses if
the target performs any relocations

src/gdbstub_impl/mod.rs

@@ -237,6 +237,16 @@ impl<T: Target, C: Connection> GdbStubImpl<T, C> {
                 }
             }
             Command::vContQuestionMark(_) => res.write_str("vCont;c;s")?,
+            Command::qOffsets(_) => {
+                if let Some(sections) = target.get_section_offsets().maybe_missing_impl()? {
+                    res.write_str("TextSeg=")?;
+                    res.write_num(sections.text)?;
+                    if let Some(data) = sections.data {
+                        res.write_str(";DataSeg=")?;
+                        res.write_num(data)?;
+                    }
+                }
+            }
             Command::qXferFeaturesRead(cmd) => {
                 assert_eq!(cmd.annex, "target.xml");
                 match T::Arch::target_description_xml() {

src/protocol/commands.rs

@@ -97,6 +97,7 @@ commands! {
     "qRcmd" => _qRcmd::qRcmd<'a>,
     "qsThreadInfo" => _qsThreadInfo::qsThreadInfo,
     "qSupported" => _qSupported::qSupported<'a>,
+    "qOffsets" => _qOffsets::qOffsets,
     "qXfer:features:read" => _qXfer_features_read::qXferFeaturesRead<'a>,
     "s" => _s::s,
     "T" => _t_upcase::T,

src/protocol/commands/_qOffsets.rs

@@ -0,0 +1,13 @@
+use super::prelude::*;
+
+#[derive(PartialEq, Eq, Debug)]
+pub struct qOffsets;
+
+impl<'a> ParseCommand<'a> for qOffsets {
+    fn from_packet(buf: PacketBuf<'a>) -> Option<Self> {
+        if !buf.into_body().is_empty() {
+            return None;
+        }
+        Some(qOffsets)
+    }
+}

src/target.rs

@@ -273,6 +273,14 @@ pub trait Target {
         })?;
         Ok(found)
     }
+
+    /// (optional) Get section offsets that the target used when relocating the
+    /// downloaded image.
+    fn get_section_offsets(
+        &mut self,
+    ) -> OptResult<SectionOffsets<<Self::Arch as Arch>::Usize>, Self::Error> {
+        Err(MaybeUnimpl::no_impl())
+    }
 }
 
 /// The kind of watchpoint that should be set/removed.
@@ -359,6 +367,15 @@ impl Iterator for Actions<'_> {
     }
 }
 
+/// Describes the offset the target loaded the image sections at so the target
+/// can notify GDB that it needs to adjust the addresses of symbols
+pub struct SectionOffsets<U> {
+    /// The offset of the .text section
+    pub text: U,
+    /// The offset of the the .data section
+    pub data: Option<U>,
+}
+
 macro_rules! impl_dyn_target {
     ($type:ty) => {
         #[allow(clippy::type_complexity)]
@@ -454,6 +471,12 @@ macro_rules! impl_dyn_target {
             fn is_thread_alive(&mut self, tid: Tid) -> OptResult<bool, Self::Error> {
                 (**self).is_thread_alive(tid)
             }
+
+            fn get_section_offsets(
+                &mut self,
+            ) -> OptResult<SectionOffsets<<Self::Arch as Arch>::Usize>, Self::Error> {
+                (**self).get_section_offsets()
+            }
         }
     };
 }