Auto merge of #2798 - LevitatingLion:master, r=oli-obk

Get Miri working on ARM

- Add a shim for `llvm.arm.hint`, which is required by `core::hint::spin_loop` on `arm` targets. The shim simply calls `yield_active_thread` on a YIELD hint, just like the shim for `llvm.aarch64.isb` that's already present.
- Change the signature of `miri_host_to_target_path` to use `c_char` instead of `i8`, to make it compatible with `CStr` on targets where `c_char` is unsigned. The implementation of `miri_host_to_target_path` accesses the memory as bytes and does not need to be adjusted.
- Enable ARM targets in CI. Specifically, `aarch64-unknown-linux-gnu` and `arm-unknown-linux-gnueabi` on the Linux host.

Since all tests also pass for `aarch64-unknown-linux-gnu` I took the liberty of adding that target to CI as well.

Fixes #2791

src/tools/miri/README.md

@@ -213,7 +213,9 @@ degree documented below):
 - The best-supported target is `x86_64-unknown-linux-gnu`. Miri releases are
   blocked on things working with this target. Most other Linux targets should
   also work well; we do run the test suite on `i686-unknown-linux-gnu` as a
-  32bit target and `mips64-unknown-linux-gnuabi64` as a big-endian target.
+  32bit target and `mips64-unknown-linux-gnuabi64` as a big-endian target, as
+  well as the ARM targets `aarch64-unknown-linux-gnu` and
+  `arm-unknown-linux-gnueabi`.
 - `x86_64-apple-darwin` should work basically as well as Linux. We also test
   `aarch64-apple-darwin`. However, we might ship Miri with a nightly even when
   some features on these targets regress.
@@ -590,7 +592,7 @@ extern "Rust" {
     /// `out` must point to at least `out_size` many bytes, and the result will be stored there
     /// with a null terminator.
     /// Returns 0 if the `out` buffer was large enough, and the required size otherwise.
-    fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
+    fn miri_host_to_target_path(path: *const std::ffi::c_char, out: *mut std::ffi::c_char, out_size: usize) -> usize;
 }
 ```
 

src/tools/miri/ci.sh

@@ -104,6 +104,7 @@ run_tests
 case $HOST_TARGET in
   x86_64-unknown-linux-gnu)
     MIRI_TEST_TARGET=i686-unknown-linux-gnu run_tests
+    MIRI_TEST_TARGET=aarch64-unknown-linux-gnu run_tests
     MIRI_TEST_TARGET=aarch64-apple-darwin run_tests
     MIRI_TEST_TARGET=i686-pc-windows-msvc run_tests
     MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple atomic data_race env/var
@@ -118,6 +119,7 @@ case $HOST_TARGET in
     MIRI_TEST_TARGET=x86_64-pc-windows-msvc run_tests
     ;;
   i686-pc-windows-msvc)
+    MIRI_TEST_TARGET=arm-unknown-linux-gnueabi run_tests
     MIRI_TEST_TARGET=x86_64-unknown-linux-gnu run_tests
     MIRI_TEST_TARGET=x86_64-pc-windows-gnu run_tests
     ;;

src/tools/miri/src/shims/foreign_items.rs

@@ -885,6 +885,19 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     }
                 }
             }
+            "llvm.arm.hint" if this.tcx.sess.target.arch == "arm" => {
+                let [arg] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
+                let arg = this.read_scalar(arg)?.to_i32()?;
+                match arg {
+                    // YIELD
+                    1 => {
+                        this.yield_active_thread();
+                    }
+                    _ => {
+                        throw_unsup_format!("unsupported llvm.arm.hint argument {}", arg);
+                    }
+                }
+            }
 
             // Platform-specific shims
             _ =>

src/tools/miri/test-cargo-miri/src/main.rs

@@ -23,7 +23,7 @@ fn main() {
     // (We rely on the test runner to always disable isolation when passing no arguments.)
     if std::env::args().len() <= 1 {
         fn host_to_target_path(path: String) -> PathBuf {
-            use std::ffi::{CStr, CString};
+            use std::ffi::{c_char, CStr, CString};
 
             let path = CString::new(path).unwrap();
             let mut out = Vec::with_capacity(1024);
@@ -31,8 +31,8 @@ fn main() {
             unsafe {
                 extern "Rust" {
                     fn miri_host_to_target_path(
-                        path: *const i8,
-                        out: *mut i8,
+                        path: *const c_char,
+                        out: *mut c_char,
                         out_size: usize,
                     ) -> usize;
                 }

src/tools/miri/test-cargo-miri/subcrate/main.rs

@@ -5,7 +5,7 @@ fn main() {
     println!("subcrate running");
 
     fn host_to_target_path(path: String) -> PathBuf {
-        use std::ffi::{CStr, CString};
+        use std::ffi::{c_char, CStr, CString};
 
         let path = CString::new(path).unwrap();
         let mut out = Vec::with_capacity(1024);
@@ -13,8 +13,8 @@ fn main() {
         unsafe {
             extern "Rust" {
                 fn miri_host_to_target_path(
-                    path: *const i8,
-                    out: *mut i8,
+                    path: *const c_char,
+                    out: *mut c_char,
                     out_size: usize,
                 ) -> usize;
             }

src/tools/miri/test-cargo-miri/subcrate/test.rs

@@ -8,7 +8,7 @@ fn main() {
     println!("subcrate testing");
 
     fn host_to_target_path(path: String) -> PathBuf {
-        use std::ffi::{CStr, CString};
+        use std::ffi::{c_char, CStr, CString};
 
         let path = CString::new(path).unwrap();
         let mut out = Vec::with_capacity(1024);
@@ -16,8 +16,8 @@ fn main() {
         unsafe {
             extern "Rust" {
                 fn miri_host_to_target_path(
-                    path: *const i8,
-                    out: *mut i8,
+                    path: *const c_char,
+                    out: *mut c_char,
                     out_size: usize,
                 ) -> usize;
             }

src/tools/miri/tests/pass-dep/shims/libc-fs.rs

@@ -5,7 +5,7 @@
 #![feature(io_error_uncategorized)]
 
 use std::convert::TryInto;
-use std::ffi::{CStr, CString};
+use std::ffi::{c_char, CStr, CString};
 use std::fs::{canonicalize, remove_dir_all, remove_file, File};
 use std::io::{Error, ErrorKind, Write};
 use std::os::unix::ffi::OsStrExt;
@@ -31,7 +31,11 @@ fn tmp() -> PathBuf {
 
     unsafe {
         extern "Rust" {
-            fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
+            fn miri_host_to_target_path(
+                path: *const c_char,
+                out: *mut c_char,
+                out_size: usize,
+            ) -> usize;
         }
         let ret = miri_host_to_target_path(path.as_ptr(), out.as_mut_ptr(), out.capacity());
         assert_eq!(ret, 0);

src/tools/miri/tests/pass-dep/shims/libc-misc.rs

@@ -7,7 +7,7 @@ use std::os::unix::io::AsRawFd;
 use std::path::PathBuf;
 
 fn tmp() -> PathBuf {
-    use std::ffi::{CStr, CString};
+    use std::ffi::{c_char, CStr, CString};
 
     let path = std::env::var("MIRI_TEMP")
         .unwrap_or_else(|_| std::env::temp_dir().into_os_string().into_string().unwrap());
@@ -17,7 +17,11 @@ fn tmp() -> PathBuf {
 
     unsafe {
         extern "Rust" {
-            fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
+            fn miri_host_to_target_path(
+                path: *const c_char,
+                out: *mut c_char,
+                out_size: usize,
+            ) -> usize;
         }
         let ret = miri_host_to_target_path(path.as_ptr(), out.as_mut_ptr(), out.capacity());
         assert_eq!(ret, 0);

src/tools/miri/tests/pass/shims/fs.rs

@@ -6,7 +6,7 @@
 #![feature(is_terminal)]
 
 use std::collections::HashMap;
-use std::ffi::OsString;
+use std::ffi::{c_char, OsString};
 use std::fs::{
     canonicalize, create_dir, read_dir, read_link, remove_dir, remove_dir_all, remove_file, rename,
     File, OpenOptions,
@@ -39,7 +39,11 @@ fn host_to_target_path(path: String) -> PathBuf {
 
     unsafe {
         extern "Rust" {
-            fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
+            fn miri_host_to_target_path(
+                path: *const c_char,
+                out: *mut c_char,
+                out_size: usize,
+            ) -> usize;
         }
         let ret = miri_host_to_target_path(path.as_ptr(), out.as_mut_ptr(), out.capacity());
         assert_eq!(ret, 0);