Support Host I/O operations

Author: bet4it

README.md

@@ -75,6 +75,8 @@ Of course, most use-cases will want to support additional debugging features as
     -   Get section/segment relocation offsets from the target
 -   Custom `monitor` Commands
     -   Extend the GDB protocol with custom debug commands using GDB's `monitor` command
+-   Get target memory map
+-   Perform Host I/O operations
 
 _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/host_io.rs

@@ -0,0 +1,35 @@
+use gdbstub::target;
+
+use crate::emu::Emu;
+
+impl target::ext::host_io::HostIo for Emu {
+    fn open(&self, filename: &[u8], _flags: u64, _mode: u64) -> i64 {
+        if filename == b"/proc/1/maps" {
+            1
+        } else {
+            -1
+        }
+    }
+
+    fn pread(&self, fd: usize, count: usize, offset: usize) -> &[u8] {
+        if fd == 1 {
+            let maps = b"0x55550000-0x55550078 r-x 0 0 0\n";
+            let len = maps.len();
+            &maps[offset.min(len)..(offset + count).min(len)]
+        } else {
+            b""
+        }
+    }
+
+    fn close(&self, fd: usize) -> i64 {
+        if fd == 1 {
+            0
+        } else {
+            -1
+        }
+    }
+
+    fn setfs(&self, _fd: usize) -> i64 {
+        0
+    }
+}

examples/armv4t/gdb/mod.rs

@@ -17,6 +17,7 @@ use crate::emu::{Emu, Event};
 mod breakpoints;
 mod catch_syscalls;
 mod extended_mode;
+mod host_io;
 mod memory_map;
 mod monitor_cmd;
 mod section_offsets;
@@ -94,6 +95,11 @@ impl Target for Emu {
     fn catch_syscalls(&mut self) -> Option<target::ext::catch_syscalls::CatchSyscallsOps<Self>> {
         Some(self)
     }
+
+    #[inline(always)]
+    fn host_io(&mut self) -> Option<target::ext::host_io::HostIoOps<Self>> {
+        Some(self)
+    }
 }
 
 impl Emu {

src/gdbstub_impl/ext/host_io.rs

@@ -0,0 +1,49 @@
+use super::prelude::*;
+use crate::protocol::commands::ext::HostIo;
+
+impl<T: Target, C: Connection> GdbStubImpl<T, C> {
+    pub(crate) fn handle_host_io(
+        &mut self,
+        res: &mut ResponseWriter<C>,
+        target: &mut T,
+        command: HostIo,
+    ) -> Result<HandlerStatus, Error<T::Error, C::Error>> {
+        let ops = match target.host_io() {
+            Some(ops) => ops,
+            None => return Ok(HandlerStatus::Handled),
+        };
+
+        crate::__dead_code_marker!("host_io", "impl");
+
+        let handler_status = match command {
+            HostIo::vFileOpen(cmd) => {
+                let ret = ops.open(cmd.filename, cmd.flags, cmd.mode);
+                res.write_str("F")?;
+                res.write_num(ret)?;
+                HandlerStatus::Handled
+            }
+            HostIo::vFileClose(cmd) => {
+                let ret = ops.close(cmd.fd);
+                res.write_str("F")?;
+                res.write_num(ret)?;
+                HandlerStatus::Handled
+            }
+            HostIo::vFilePread(cmd) => {
+                let data = ops.pread(cmd.fd, cmd.count, cmd.offset);
+                res.write_str("F")?;
+                res.write_num(data.len())?;
+                res.write_str(";")?;
+                res.write_binary(data)?;
+                HandlerStatus::Handled
+            }
+            HostIo::vFileSetfs(cmd) => {
+                let ret = ops.setfs(cmd.fd);
+                res.write_str("F")?;
+                res.write_num(ret)?;
+                HandlerStatus::Handled
+            }
+        };
+
+        Ok(handler_status)
+    }
+}

src/gdbstub_impl/ext/mod.rs

@@ -15,6 +15,7 @@ mod base;
 mod breakpoints;
 mod catch_syscalls;
 mod extended_mode;
+mod host_io;
 mod memory_map;
 mod monitor_cmd;
 mod reverse_exec;

src/gdbstub_impl/mod.rs

@@ -579,6 +579,7 @@ impl<T: Target, C: Connection> GdbStubImpl<T, C> {
             Command::ReverseCont(cmd) => self.handle_reverse_cont(res, target, cmd),
             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),
         }
     }
 }

src/protocol/commands.rs

@@ -223,6 +223,13 @@ commands! {
         "qXfer:memory-map:read" => _qXfer_memory_map::qXferMemoryMapRead,
     }
 
+    host_io use 'a{
+        "vFile:open" => _vFile_open::vFileOpen<'a>,
+        "vFile:close" => _vFile_close::vFileClose,
+        "vFile:pread" => _vFile_pread::vFilePread,
+        "vFile:setfs" => _vFile_setfs::vFileSetfs,
+    }
+
     catch_syscalls use 'a {
         "QCatchSyscalls" => _QCatchSyscalls::QCatchSyscalls<'a>,
     }

src/protocol/commands/_vFile_close.rs

@@ -0,0 +1,23 @@
+use super::prelude::*;
+
+#[derive(Debug)]
+pub struct vFileClose {
+    pub fd: usize,
+}
+
+impl<'a> ParseCommand<'a> for vFileClose {
+    fn from_packet(buf: PacketBuf<'a>) -> Option<Self> {
+        let body = buf.into_body();
+        if body.is_empty() {
+            return None;
+        }
+
+        match body {
+            [b':', body @ ..] => {
+                let fd = decode_hex(body).ok()?;
+                Some(vFileClose{fd})
+            },
+            _ => None,
+        }
+    }
+}

src/protocol/commands/_vFile_open.rs

@@ -0,0 +1,28 @@
+use super::prelude::*;
+
+#[derive(Debug)]
+pub struct vFileOpen<'a> {
+    pub filename: &'a [u8],
+    pub flags: u64,
+    pub mode: u64,
+}
+
+impl<'a> ParseCommand<'a> for vFileOpen<'a> {
+    fn from_packet(buf: PacketBuf<'a>) -> Option<Self> {
+        let body = buf.into_body();
+        if body.is_empty() {
+            return None;
+        }
+
+        match body {
+            [b':', body @ ..] => {
+                let mut body = body.splitn_mut_no_panic(3, |b| *b == b',');
+                let filename = decode_hex_buf(body.next()?).ok()?;
+                let flags= decode_hex(body.next()?).ok()?;
+                let mode= decode_hex(body.next()?).ok()?;
+                Some(vFileOpen{filename, flags, mode})
+            },
+            _ => None,
+        }
+    }
+}

src/protocol/commands/_vFile_pread.rs

@@ -0,0 +1,28 @@
+use super::prelude::*;
+
+#[derive(Debug)]
+pub struct vFilePread {
+    pub fd: usize,
+    pub count: usize,
+    pub offset: usize,
+}
+
+impl<'a> ParseCommand<'a> for vFilePread {
+    fn from_packet(buf: PacketBuf<'a>) -> Option<Self> {
+        let body = buf.into_body();
+        if body.is_empty() {
+            return None;
+        }
+
+        match body {
+            [b':', body @ ..] => {
+                let mut body = body.splitn_mut_no_panic(3, |b| *b == b',');
+                let fd = decode_hex(body.next()?).ok()?;
+                let count= decode_hex(body.next()?).ok()?;
+                let offset= decode_hex(body.next()?).ok()?;
+                Some(vFilePread{fd, count, offset})
+            },
+            _ => None,
+        }
+    }
+}

src/protocol/commands/_vFile_setfs.rs

@@ -0,0 +1,23 @@
+use super::prelude::*;
+
+#[derive(Debug)]
+pub struct vFileSetfs {
+    pub fd: usize,
+}
+
+impl<'a> ParseCommand<'a> for vFileSetfs {
+    fn from_packet(buf: PacketBuf<'a>) -> Option<Self> {
+        let body = buf.into_body();
+        if body.is_empty() {
+            return None;
+        }
+
+        match body {
+            [b':', body @ ..] => {
+                let fd = decode_hex(body).ok()?;
+                Some(vFileSetfs{fd})
+            },
+            _ => None,
+        }
+    }
+}

src/target/ext/host_io.rs

@@ -0,0 +1,19 @@
+//! Provide Host I/O operations for the target.
+use crate::target::Target;
+
+/// Target Extension - Perform I/O operations on host
+pub trait HostIo: Target {
+    /// Open a file at filename and return a file descriptor for it, or return
+    /// -1 if an error occurs.
+    fn open(&self, filename: &[u8], flags: u64, mode: u64) -> i64;
+    /// Close the open file corresponding to fd and return 0, or -1 if an error
+    /// occurs.
+    fn close(&self, fd: usize) -> i64;
+    /// Read data from the open file corresponding to fd.
+    fn pread(&self, fd: usize, count: usize, offset: usize) -> &[u8];
+    /// Select the filesystem on which vFile operations with filename arguments
+    /// will operate.
+    fn setfs(&self, fd: usize) -> i64;
+}
+
+define_ext!(HostIoOps, HostIo);

src/target/ext/mod.rs

@@ -260,6 +260,7 @@ pub mod base;
 pub mod breakpoints;
 pub mod catch_syscalls;
 pub mod extended_mode;
+pub mod host_io;
 pub mod memory_map;
 pub mod monitor_cmd;
 pub mod section_offsets;

src/target/mod.rs

@@ -358,6 +358,11 @@ pub trait Target {
     fn catch_syscalls(&mut self) -> Option<ext::catch_syscalls::CatchSyscallsOps<Self>> {
         None
     }
+
+    /// Support Host I/O operations.
+    fn host_io(&mut self) -> Option<ext::host_io::HostIoOps<Self>> {
+        None
+    }
 }
 
 macro_rules! impl_dyn_target {