Some small fixes

examples/armv4t/gdb/exec_file.rs

@@ -1,10 +1,11 @@
 use gdbstub::common::Pid;
 use gdbstub::target;
+use gdbstub::target::TargetResult;
 
 use crate::emu::Emu;
 
 impl target::ext::exec_file::ExecFile for Emu {
-    fn get_exec_file(&self, _pid: Option<Pid>) -> &[u8] {
-        b"/test.elf"
+    fn get_exec_file(&self, _pid: Option<Pid>) -> TargetResult<&[u8], Self> {
+        Ok(b"/test.elf")
     }
 }

examples/armv4t/gdb/host_io.rs

@@ -1,13 +1,13 @@
 use std::io::{Read, Seek, Write};
 
-use crate::TEST_PROGRAM_ELF;
 use gdbstub::target;
 use gdbstub::target::ext::host_io::{
     FsKind, HostIoErrno, HostIoError, HostIoOpenFlags, HostIoOpenMode, HostIoOutput, HostIoResult,
     HostIoStat, HostIoToken,
 };
 
 use crate::emu::Emu;
+use crate::TEST_PROGRAM_ELF;
 
 const FD_RESERVED: u32 = 1;
 
@@ -64,6 +64,10 @@ impl target::ext::host_io::HostIoOpen for Emu {
             return Err(HostIoError::Errno(HostIoErrno::ENOENT));
         }
 
+        // In this example, the test binary is compiled into the binary itself as the
+        // `TEST_PROGRAM_ELF` array using `include_bytes!`. As such, we must "spoof" the
+        // existence of a real file, which will actually be backed by the in-binary
+        // `TEST_PROGRAM_ELF` array.
         if filename == b"/test.elf" {
             return Ok(0);
         }

src/gdbstub_impl/ext/exec_file.rs

@@ -17,7 +17,7 @@ impl<T: Target, C: Connection> GdbStubImpl<T, C> {
 
         let handler_status = match command {
             ExecFile::qXferExecFileRead(cmd) => {
-                let filename = ops.get_exec_file(cmd.pid);
+                let filename = ops.get_exec_file(cmd.pid).handle_error()?;
                 res.write_binary_range(filename, cmd.offset, cmd.len)?;
                 HandlerStatus::Handled
             }

src/target/ext/exec_file.rs

@@ -1,13 +1,19 @@
 //! Provide exec-file path for the target.
-use crate::target::Target;
+use crate::target::{Target, TargetResult};
 
 use crate::common::Pid;
 
 /// Target Extension - Provide current exec-file.
+///
+/// NOTE: this extension is primarily intended to be used alongside the [`Host
+/// I/O Extensions`](crate::target::ext::host_io), which enables the GDB client
+/// to read the executable file directly from the target
 pub trait ExecFile: Target {
     /// Return the full absolute name of the file that was executed to create a
     /// process running on the remote system.
-    fn get_exec_file(&self, pid: Option<Pid>) -> &[u8];
+    /// If no `pid` is provided, return the filename corresponding to the
+    /// currently executing process.
+    fn get_exec_file(&self, pid: Option<Pid>) -> TargetResult<&[u8], Self>;
 }
 
 define_ext!(ExecFileOps, ExecFile);