From 12dc3b65d8c08139d193f8ace1ad7ae1b8fc0682 Mon Sep 17 00:00:00 2001
From: Victor Berger <victor.berger@m4x.org>
Date: Mon, 20 Feb 2017 22:32:03 +0100
Subject: [PATCH] shm: mmap logic

---
 Cargo.toml      |  1 +
 src/lib.rs      |  1 +
 src/shm/mod.rs  | 27 ++++++++++++---
 src/shm/pool.rs | 88 +++++++++++++++++++++++++++++++++++++++++++++----
 4 files changed, 106 insertions(+), 11 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 0e4ddf7..40217c4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,3 +5,4 @@ authors = ["Victor Berger <victor.berger@thalesgroup.com>"]
 
 [dependencies]
 wayland-server = "0.8.4"
+nix = "0.7.0"
diff --git a/src/lib.rs b/src/lib.rs
index f6df6e7..8ac17eb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,5 +2,6 @@
 
 #[macro_use]
 extern crate wayland_server;
+extern crate nix;
 
 pub mod shm;
diff --git a/src/shm/mod.rs b/src/shm/mod.rs
index ee9a7bd..3624c54 100644
--- a/src/shm/mod.rs
+++ b/src/shm/mod.rs
@@ -32,7 +32,7 @@ use std::sync::Arc;
 use wayland_server::{GlobalHandler, EventLoopHandle, Client, Init, Resource, Destroy, resource_is_registered};
 use wayland_server::protocol::{wl_shm, wl_shm_pool, wl_buffer};
 
-use self::pool::Pool;
+use self::pool::{Pool, ResizeError};
 
 mod pool;
 
@@ -156,9 +156,20 @@ impl Init for ShmHandler {
 }
 
 impl wl_shm::Handler for ShmHandler {
-    fn create_pool(&mut self, evqh: &mut EventLoopHandle, _client: &Client, _shm: &wl_shm::WlShm,
+    fn create_pool(&mut self, evqh: &mut EventLoopHandle, _client: &Client, shm: &wl_shm::WlShm,
                    pool: wl_shm_pool::WlShmPool, fd: RawFd, size: i32) {
-        let arc_pool = Box::new(Arc::new(Pool::new(fd, size)));
+        if size <= 0 {
+            shm.post_error(wl_shm::Error::InvalidFd as u32, "Invalid size for a new wl_shm_pool.".into());
+            return
+        }
+        let mmap_pool = match Pool::new(fd, size as usize) {
+            Ok(p) => p,
+            Err(()) => {
+                shm.post_error(wl_shm::Error::InvalidFd as u32, format!("Failed mmap of fd {}.", fd));
+                return
+            }
+        };
+        let arc_pool = Box::new(Arc::new(mmap_pool));
         evqh.register_with_destructor::<_, ShmHandler, ShmHandler>(&pool, self.my_id);
         pool.set_user_data(Box::into_raw(arc_pool) as *mut ());
     }
@@ -221,8 +232,14 @@ impl wl_shm_pool::Handler for ShmHandler {
               pool: &wl_shm_pool::WlShmPool, size: i32)
     {
         let arc_pool = unsafe { &*(pool.get_user_data() as *mut Arc<Pool>) };
-        if arc_pool.resize(size).is_err() {
-            pool.post_error(wl_shm::Error::InvalidFd as u32, "Invalid new size for a wl_shm_pool.".into())
+        match arc_pool.resize(size) {
+            Ok(()) => {},
+            Err(ResizeError::InvalidSize) => {
+                pool.post_error(wl_shm::Error::InvalidFd as u32, "Invalid new size for a wl_shm_pool.".into());
+            },
+            Err(ResizeError::MremapFailed) => {
+                pool.post_error(wl_shm::Error::InvalidFd as u32, "mremap failed.".into());
+            }
         }
     }
 }
diff --git a/src/shm/pool.rs b/src/shm/pool.rs
index 07a0198..4aa07f3 100644
--- a/src/shm/pool.rs
+++ b/src/shm/pool.rs
@@ -1,17 +1,93 @@
 use std::os::unix::io::RawFd;
+use std::sync::RwLock;
+use std::ptr;
 
-pub struct Pool;
+use nix::sys::mman;
+
+pub struct Pool {
+    map: RwLock<MemMap>
+}
+
+pub enum ResizeError {
+    InvalidSize,
+    MremapFailed
+}
 
 impl Pool {
-    pub fn new(fd: RawFd, size: i32) -> Pool {
-        unimplemented!()
+    pub fn new(fd: RawFd, size: usize) -> Result<Pool,()> {
+        let memmap = MemMap::new(fd, size)?;
+        Ok(Pool {
+            map: RwLock::new(memmap)
+        })
     }
 
-    pub fn resize(&self, newsize: i32) -> Result<(),()> {
-        unimplemented!()
+    pub fn resize(&self, newsize: i32) -> Result<(),ResizeError> {
+        let mut guard = self.map.write().unwrap();
+        if newsize <= 0 || guard.size() > (newsize as usize) {
+            return Err(ResizeError::InvalidSize)
+        }
+        guard.remap(newsize as usize).map_err(|()| ResizeError::MremapFailed)
     }
     
     pub fn with_data_slice<F: FnOnce(&[u8])>(&self, f: F) -> Result<(),()> {
-        unimplemented!()
+        // TODO: handle SIGBUS
+        let guard = self.map.read().unwrap();
+
+        let slice = guard.get_slice();
+        f(slice);
+
+        Ok(())
     }
 }
+
+struct MemMap {
+    ptr: *mut u8,
+    fd: RawFd,
+    size: usize
+}
+
+impl MemMap {
+    fn new(fd: RawFd, size: usize) -> Result<MemMap,()> {
+        Ok(MemMap {
+            ptr: map(fd, size)?,
+            fd: fd,
+            size: size
+        })
+    }
+
+    fn remap(&mut self, newsize: usize) -> Result<(),()> {
+        unmap(self.ptr, self.size)?;
+        self.ptr = map(self.fd, newsize)?;
+        self.size = newsize;
+        Ok(())
+    }
+
+    fn size(&self) -> usize {
+        self.size
+    }
+
+    fn get_slice(&self) -> &[u8] {
+        unsafe { ::std::slice::from_raw_parts(self.ptr, self.size) }
+    }
+}
+
+// mman::mmap should really be unsafe... why isn't it?
+#[allow(unused_unsafe)]
+fn map(fd: RawFd, size: usize) -> Result<*mut u8, ()> {
+    let ret = unsafe { mman::mmap(
+        ptr::null_mut(),
+        size,
+        mman::PROT_READ,
+        mman::MAP_SHARED,
+        fd,
+        0
+    ) };
+    ret.map(|p| p as *mut u8).map_err(|_| ())
+}
+
+// mman::munmap should really be unsafe... why isn't it?
+#[allow(unused_unsafe)]
+fn unmap(ptr: *mut u8, size: usize) -> Result<(),()> {
+    let ret = unsafe { mman::munmap(ptr as *mut _, size) };
+    ret.map_err(|_| ())
+}