Reduce boilerplate in wasmtime-wasi (#707)

This commit uses the `*.witx` files describing the current wasi API to
reduce the boilerplate used to define implementations in the
`wasmtime-wasi` crate. Eventually I'd like to remove lots of boilerplate
in the `wasi-common` crate too, but this should at least be a good start!

The boilerplate removed here is:

* No need to list each function to add it to the
  `wasmtime_runtime::Module` being created

* No need to list the signature of the function in a separate
  `syscalls.rs` file.

Instead the `*.witx` file is processed in a single-use macro inside the
`wasmtime-wasi` crate. This macro uses the signatures known from
`*.witx` to automatically register with the right type in the wasm
module as well as define a wrapper that the wasm module will call into.
Functionally this is all the same as before, it's just defined in a
different way now!

The shim generated by this macro which wasmtime calls into only uses
`i32`/`i64`/etc wasm types, and it internally uses `as` casts to convert
to the right wasi types when delegating into the `wasi-common` crate.

One change was necessary to get this implemented, however. The functions
in `wasi-common` sometimes took `WasiCtx` and sometimes took a slice of
memory. After this PR they uniformly all require both `WasiCtx` and
memory so the wrappers can be auto-generated. The arguments are ignored
if they weren't previously required.

crates/wasi-common/src/hostcalls/fs.rs

@@ -3,9 +3,9 @@ use crate::ctx::WasiCtx;
 use crate::{hostcalls_impl, wasi, wasi32};
 
 hostcalls! {
-    pub unsafe fn fd_close(wasi_ctx: &mut WasiCtx, fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
+    pub unsafe fn fd_close(wasi_ctx: &mut WasiCtx, memory: &mut [u8], fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
 
-    pub unsafe fn fd_datasync(wasi_ctx: &WasiCtx, fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
+    pub unsafe fn fd_datasync(wasi_ctx: &WasiCtx, memory: &mut [u8], fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
 
     pub unsafe fn fd_pread(
         wasi_ctx: &WasiCtx,
@@ -38,6 +38,7 @@ hostcalls! {
 
     pub unsafe fn fd_renumber(
         wasi_ctx: &mut WasiCtx,
+        memory: &mut [u8],
         from: wasi::__wasi_fd_t,
         to: wasi::__wasi_fd_t,
     ) -> wasi::__wasi_errno_t;
@@ -67,18 +68,20 @@ hostcalls! {
 
     pub unsafe fn fd_fdstat_set_flags(
         wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         fdflags: wasi::__wasi_fdflags_t,
     ) -> wasi::__wasi_errno_t;
 
     pub unsafe fn fd_fdstat_set_rights(
         wasi_ctx: &mut WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         fs_rights_base: wasi::__wasi_rights_t,
         fs_rights_inheriting: wasi::__wasi_rights_t,
     ) -> wasi::__wasi_errno_t;
 
-    pub unsafe fn fd_sync(wasi_ctx: &WasiCtx, fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
+    pub unsafe fn fd_sync(wasi_ctx: &WasiCtx, memory: &mut [u8], fd: wasi::__wasi_fd_t,) -> wasi::__wasi_errno_t;
 
     pub unsafe fn fd_write(
         wasi_ctx: &mut WasiCtx,
@@ -91,6 +94,7 @@ hostcalls! {
 
     pub unsafe fn fd_advise(
         wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         offset: wasi::__wasi_filesize_t,
         len: wasi::__wasi_filesize_t,
@@ -99,6 +103,7 @@ hostcalls! {
 
     pub unsafe fn fd_allocate(
         wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         offset: wasi::__wasi_filesize_t,
         len: wasi::__wasi_filesize_t,
@@ -179,6 +184,7 @@ hostcalls! {
 
     pub unsafe fn fd_filestat_set_times(
         wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         st_atim: wasi::__wasi_timestamp_t,
         st_mtim: wasi::__wasi_timestamp_t,
@@ -187,6 +193,7 @@ hostcalls! {
 
     pub unsafe fn fd_filestat_set_size(
         wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
         fd: wasi::__wasi_fd_t,
         st_size: wasi::__wasi_filesize_t,
     ) -> wasi::__wasi_errno_t;

crates/wasi-common/src/hostcalls/misc.rs

@@ -5,7 +5,7 @@ use log::trace;
 use wasi_common_cbindgen::wasi_common_cbindgen;
 
 #[wasi_common_cbindgen]
-pub unsafe fn proc_exit(rval: wasi::__wasi_exitcode_t) {
+pub unsafe fn proc_exit(_wasi_ctx: &WasiCtx, _memory: &mut [u8], rval: wasi::__wasi_exitcode_t) {
     trace!("proc_exit(rval={:?})", rval);
     // TODO: Rather than call std::process::exit here, we should trigger a
     // stack unwind similar to a trap.
@@ -51,18 +51,21 @@ hostcalls! {
     ) -> wasi::__wasi_errno_t;
 
     pub unsafe fn random_get(
+        wasi_ctx: &WasiCtx,
         memory: &mut [u8],
         buf_ptr: wasi32::uintptr_t,
         buf_len: wasi32::size_t,
     ) -> wasi::__wasi_errno_t;
 
     pub unsafe fn clock_res_get(
+        wasi_ctx: &WasiCtx,
         memory: &mut [u8],
         clock_id: wasi::__wasi_clockid_t,
         resolution_ptr: wasi32::uintptr_t,
     ) -> wasi::__wasi_errno_t;
 
     pub unsafe fn clock_time_get(
+        wasi_ctx: &WasiCtx,
         memory: &mut [u8],
         clock_id: wasi::__wasi_clockid_t,
         precision: wasi::__wasi_timestamp_t,
@@ -78,5 +81,8 @@ hostcalls! {
         nevents: wasi32::uintptr_t,
     ) -> wasi::__wasi_errno_t;
 
-    pub unsafe fn sched_yield() -> wasi::__wasi_errno_t;
+    pub unsafe fn sched_yield(
+        wasi_ctx: &WasiCtx,
+        memory: &mut [u8],
+    ) -> wasi::__wasi_errno_t;
 }