firmware: use &CSlice for lists

artiq/firmware/ksupport/lib.rs

@@ -15,7 +15,7 @@ extern crate proto_artiq;
 extern crate riscv;
 
 use core::{mem, ptr, slice, str, convert::TryFrom};
-use cslice::{CSlice, AsCSlice};
+use cslice::CSlice;
 use io::Cursor;
 use dyld::Library;
 use board_artiq::{mailbox, rpc_queue};
@@ -190,13 +190,12 @@ fn terminate(exceptions: &'static [Option<eh_artiq::Exception<'static>>],
 }
 
 #[unwind(aborts)]
-extern fn cache_get<'a>(ret: &'a mut CSlice<i32>, key: &CSlice<u8>) -> &'a CSlice<'a, i32> {
+extern fn cache_get<'a>(key: &CSlice<u8>) -> *const CSlice<'a, i32> {
     send(&CacheGetRequest {
         key:   str::from_utf8(key.as_ref()).unwrap()
     });
     recv!(&CacheGetReply { value } => {
-        *ret = value.as_c_slice();
-        ret
+        value
     })
 }
 

artiq/firmware/libproto_artiq/kernel_proto.rs

@@ -1,4 +1,5 @@
 use core::fmt;
+use cslice::CSlice;
 use dyld;
 
 pub const KERNELCPU_EXEC_ADDRESS:    usize = 0x45000000;
@@ -53,7 +54,7 @@ pub enum Message<'a> {
     RpcFlush,
 
     CacheGetRequest { key: &'a str },
-    CacheGetReply   { value: &'static [i32] },
+    CacheGetReply   { value: *const CSlice<'static, i32> },
     CachePutRequest { key: &'a str, value: &'a [i32] },
     CachePutReply   { succeeded: bool },
 

artiq/firmware/libproto_artiq/rpc_proto.rs

@@ -70,16 +70,17 @@ unsafe fn recv_value<R, E>(reader: &mut R, tag: Tag, data: &mut *mut (),
         Tag::List(it) => {
             #[repr(C)]
             struct List { elements: *mut (), length: u32 }
-            consume_value!(List, |ptr| {
-                (*ptr).length = reader.read_u32()?;
-                let length = (*ptr).length as usize;
-
+            consume_value!(*mut List, |ptr| {
                 let tag = it.clone().next().expect("truncated tag");
                 let padding = if let Tag::Int64 | Tag::Float64 = tag { 4 } else { 0 };
-                let mut data = alloc(tag.size() * length + padding)?;
 
-                data = data.offset(alignment_offset(tag.alignment() as isize, data as isize));
+                let length = reader.read_u32()? as usize;
+                let data = alloc(tag.size() * length + padding + 8)? as *mut u8;
+                *ptr = data as *mut List;
+                let ptr = data as *mut List;
+                let mut data = data.offset(8 + alignment_offset(tag.alignment() as isize, data as isize)) as *mut ();
 
+                (*ptr).length = length as u32;
                 (*ptr).elements = data;
                 match tag {
                     Tag::Bool => {
@@ -221,11 +222,11 @@ unsafe fn send_value<W>(writer: &mut W, tag: Tag, data: &mut *const ())
         Tag::List(it) => {
             #[repr(C)]
             struct List { elements: *const (), length: u32 }
-            consume_value!(List, |ptr| {
-                let length = (*ptr).length as usize;
-                writer.write_u32((*ptr).length)?;
+            consume_value!(&List, |ptr| {
+                let length = (**ptr).length as usize;
+                writer.write_u32((**ptr).length)?;
                 let tag = it.clone().next().expect("truncated tag");
-                let mut data = (*ptr).elements;
+                let mut data = (**ptr).elements;
                 writer.write_u8(tag.as_u8())?;
                 match tag {
                     // we cannot use NativeEndian::from_slice_i32 as the data is not mutable,

artiq/firmware/runtime/cache.rs

@@ -1,27 +1,50 @@
 use alloc::{vec::Vec, string::String, collections::btree_map::BTreeMap};
+use cslice::{CSlice, AsCSlice};
+use core::mem::transmute;
 
-#[derive(Debug)]
 struct Entry {
     data: Vec<i32>,
+    slice: CSlice<'static, i32>,
     borrowed: bool
 }
 
-#[derive(Debug)]
+impl core::fmt::Debug for Entry {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.debug_struct("Entry")
+         .field("data", &self.data)
+         .field("borrowed", &self.borrowed)
+         .finish()
+    }
+}
+
 pub struct Cache {
-    entries: BTreeMap<String, Entry>
+    entries: BTreeMap<String, Entry>,
+    empty: CSlice<'static, i32>,
+}
+
+impl core::fmt::Debug for Cache {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.debug_struct("Cache")
+         .field("entries", &self.entries)
+         .finish()
+    }
 }
 
 impl Cache {
     pub fn new() -> Cache {
-        Cache { entries: BTreeMap::new() }
+        let empty_vec = vec![];
+        let empty = unsafe {
+            transmute::<CSlice<'_, i32>, CSlice<'static, i32>>(empty_vec.as_c_slice())
+        };
+        Cache { entries: BTreeMap::new(), empty }
     }
 
-    pub fn get(&mut self, key: &str) -> *const [i32] {
+    pub fn get(&mut self, key: &str) -> *const CSlice<'static, i32> {
         match self.entries.get_mut(key) {
-            None => &[],
+            None => &self.empty,
             Some(ref mut entry) => {
                 entry.borrowed = true;
-                &entry.data[..]
+                &entry.slice
             }
         }
     }
@@ -32,12 +55,21 @@ impl Cache {
             Some(ref mut entry) => {
                 if entry.borrowed { return Err(()) }
                 entry.data = Vec::from(data);
+                unsafe {
+                    entry.slice = transmute::<CSlice<'_, i32>, CSlice<'static, i32>>(
+                        entry.data.as_c_slice());
+                }
                 return Ok(())
             }
         }
 
+        let data = Vec::from(data);
+        let slice = unsafe {
+            transmute::<CSlice<'_, i32>, CSlice<'static, i32>>(data.as_c_slice())
+        };
         self.entries.insert(String::from(key), Entry {
-            data: Vec::from(data),
+            data,
+            slice,
             borrowed: false
         });
         Ok(())

artiq/firmware/runtime/session.rs

@@ -418,7 +418,7 @@ fn process_kern_message(io: &Io, aux_mutex: &Mutex,
                 kern_send(io, &kern::CacheGetReply {
                     // Zing! This transmute is only safe because we dynamically track
                     // whether the kernel has borrowed any values from the cache.
-                    value: unsafe { mem::transmute::<*const [i32], &'static [i32]>(value) }
+                    value: unsafe { mem::transmute(value) }
                 })
             }