Support read exec-file

Author: bet4it

README.md

@@ -77,6 +77,7 @@ Of course, most use-cases will want to support additional debugging features as
     -   Extend the GDB protocol with custom debug commands using GDB's `monitor` command
 -   Get target memory map
 -   Perform Host I/O operations
+-   Get target exec file
 
 _Note:_ GDB features are implemented on an as-needed basis by `gdbstub`'s contributors. If there's a missing GDB feature that you'd like `gdbstub` to implement, please file an issue and/or open a PR!
 

examples/armv4t/gdb/exec_file.rs

@@ -0,0 +1,10 @@
+use gdbstub::common::Pid;
+use gdbstub::target;
+
+use crate::emu::Emu;
+
+impl target::ext::exec_file::ExecFile for Emu {
+    fn get_exec_file(&self, _pid: Option<Pid>) -> &[u8] {
+        b"/test.elf"
+    }
+}

examples/armv4t/gdb/host_io.rs

@@ -1,5 +1,6 @@
 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,
@@ -8,6 +9,8 @@ use gdbstub::target::ext::host_io::{
 
 use crate::emu::Emu;
 
+const FD_RESERVED: u32 = 1;
+
 impl target::ext::host_io::HostIo for Emu {
     #[inline(always)]
     fn enable_open(&mut self) -> Option<target::ext::host_io::HostIoOpenOps<Self>> {
@@ -61,6 +64,10 @@ impl target::ext::host_io::HostIoOpen for Emu {
             return Err(HostIoError::Errno(HostIoErrno::ENOENT));
         }
 
+        if filename == b"/test.elf" {
+            return Ok(0);
+        }
+
         let path =
             std::str::from_utf8(filename).map_err(|_| HostIoError::Errno(HostIoErrno::ENOENT))?;
 
@@ -95,13 +102,17 @@ impl target::ext::host_io::HostIoOpen for Emu {
             }
         };
 
-        Ok(n as u32)
+        Ok(n as u32 + FD_RESERVED)
     }
 }
 
 impl target::ext::host_io::HostIoClose for Emu {
     fn close(&mut self, fd: u32) -> HostIoResult<(), Self> {
-        let file = match self.files.get_mut(fd as usize) {
+        if fd < FD_RESERVED {
+            return Ok(());
+        }
+
+        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
             Some(file) => file,
             _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
         };
@@ -122,7 +133,18 @@ impl target::ext::host_io::HostIoPread for Emu {
         offset: u32,
         output: HostIoOutput<'a>,
     ) -> HostIoResult<HostIoToken<'a>, Self> {
-        let file = match self.files.get_mut(fd as usize) {
+        if fd < FD_RESERVED {
+            if fd == 0 {
+                let len = TEST_PROGRAM_ELF.len();
+                return Ok(output.write(
+                    &TEST_PROGRAM_ELF[len.min(offset as usize)..len.min((offset + count) as usize)],
+                ));
+            } else {
+                return Err(HostIoError::Errno(HostIoErrno::EBADF));
+            }
+        }
+
+        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
             Some(Some(file)) => file,
             _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
         };
@@ -136,7 +158,11 @@ impl target::ext::host_io::HostIoPread for Emu {
 
 impl target::ext::host_io::HostIoPwrite for Emu {
     fn pwrite(&mut self, fd: u32, offset: u32, data: &[u8]) -> HostIoResult<u32, Self> {
-        let file = match self.files.get_mut(fd as usize) {
+        if fd < FD_RESERVED {
+            return Err(HostIoError::Errno(HostIoErrno::EACCES));
+        }
+
+        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
             Some(Some(file)) => file,
             _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
         };
@@ -149,7 +175,28 @@ impl target::ext::host_io::HostIoPwrite for Emu {
 
 impl target::ext::host_io::HostIoFstat for Emu {
     fn fstat(&mut self, fd: u32) -> HostIoResult<HostIoStat, Self> {
-        let metadata = match self.files.get(fd as usize) {
+        if fd < FD_RESERVED {
+            if fd == 0 {
+                return Ok(HostIoStat {
+                    st_dev: 0,
+                    st_ino: 0,
+                    st_mode: HostIoOpenMode::empty(),
+                    st_nlink: 0,
+                    st_uid: 0,
+                    st_gid: 0,
+                    st_rdev: 0,
+                    st_size: TEST_PROGRAM_ELF.len() as u64,
+                    st_blksize: 0,
+                    st_blocks: 0,
+                    st_atime: 0,
+                    st_mtime: 0,
+                    st_ctime: 0,
+                });
+            } else {
+                return Err(HostIoError::Errno(HostIoErrno::EBADF));
+            }
+        }
+        let metadata = match self.files.get((fd - FD_RESERVED) as usize) {
             Some(Some(file)) => file.metadata()?,
             _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
         };

examples/armv4t/gdb/mod.rs

@@ -16,6 +16,7 @@ use crate::emu::{Emu, Event};
 
 mod breakpoints;
 mod catch_syscalls;
+mod exec_file;
 mod extended_mode;
 mod host_io;
 mod memory_map;
@@ -100,6 +101,11 @@ impl Target for Emu {
     fn host_io(&mut self) -> Option<target::ext::host_io::HostIoOps<Self>> {
         Some(self)
     }
+
+    #[inline(always)]
+    fn exec_file(&mut self) -> Option<target::ext::exec_file::ExecFileOps<Self>> {
+        Some(self)
+    }
 }
 
 impl Emu {

examples/armv4t/main.rs

@@ -9,7 +9,7 @@ use gdbstub::{target::Target, ConnectionExt, DisconnectReason, GdbStub};
 
 pub type DynResult<T> = Result<T, Box<dyn std::error::Error>>;
 
-static TEST_PROGRAM_ELF: &[u8] = include_bytes!("test_bin/test.elf");
+pub static TEST_PROGRAM_ELF: &[u8] = include_bytes!("test_bin/test.elf");
 
 mod emu;
 mod gdb;

examples/armv4t/test_bin/.gdbinit

@@ -1,2 +1 @@
-file test.elf
 target extended-remote :9001

src/gdbstub_impl/ext/base.rs

@@ -115,6 +115,10 @@ impl<T: Target, C: Connection> GdbStubImpl<T, C> {
                     res.write_str(";qXfer:memory-map:read+")?;
                 }
 
+                if target.exec_file().is_some() {
+                    res.write_str(";qXfer:exec-file:read+")?;
+                }
+
                 HandlerStatus::Handled
             }
             Base::QStartNoAckMode(_) => {

src/gdbstub_impl/ext/exec_file.rs

@@ -0,0 +1,28 @@
+use super::prelude::*;
+use crate::protocol::commands::ext::ExecFile;
+
+impl<T: Target, C: Connection> GdbStubImpl<T, C> {
+    pub(crate) fn handle_exec_file(
+        &mut self,
+        res: &mut ResponseWriter<C>,
+        target: &mut T,
+        command: ExecFile,
+    ) -> Result<HandlerStatus, Error<T::Error, C::Error>> {
+        let ops = match target.exec_file() {
+            Some(ops) => ops,
+            None => return Ok(HandlerStatus::Handled),
+        };
+
+        crate::__dead_code_marker!("exec_file", "impl");
+
+        let handler_status = match command {
+            ExecFile::qXferExecFileRead(cmd) => {
+                let filename = ops.get_exec_file(cmd.pid);
+                res.write_binary_range(filename, cmd.offset, cmd.len)?;
+                HandlerStatus::Handled
+            }
+        };
+
+        Ok(handler_status)
+    }
+}

src/gdbstub_impl/ext/mod.rs

@@ -14,6 +14,7 @@ mod prelude {
 mod base;
 mod breakpoints;
 mod catch_syscalls;
+mod exec_file;
 mod extended_mode;
 mod host_io;
 mod memory_map;

src/gdbstub_impl/mod.rs

@@ -578,6 +578,7 @@ impl<T: Target, C: Connection> GdbStubImpl<T, C> {
             Command::ReverseStep(cmd) => self.handle_reverse_step(res, target, cmd),
             Command::MemoryMap(cmd) => self.handle_memory_map(res, target, cmd),
             Command::HostIo(cmd) => self.handle_host_io(res, target, cmd),
+            Command::ExecFile(cmd) => self.handle_exec_file(res, target, cmd),
         }
     }
 }