add more foreign items for linux/android

Author: Lander Brandt

src/helpers.rs

@@ -440,7 +440,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     /// Helper function used inside the shims of foreign functions to assert that the target OS
     /// is based on the Linux kernel. It panics showing a message with the `name` of the foreign function
     /// if this is not the case.
-    fn assert_linux_based_target_os(&self, name: &str) {
+    fn assert_target_os_is_linux_based(&self, name: &str) {
         assert!(
             matches!(self.eval_context_ref().tcx.sess.target.os.as_str(), "linux" | "android"),
             "`{}` is only available for supported Linux-based targets",

src/shims/posix/android/foreign_items.rs

@@ -1,6 +1,5 @@
 use rustc_middle::mir;
 use rustc_span::Symbol;
-use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi;
 
 use crate::*;

src/shims/posix/foreign_items.rs

@@ -60,6 +60,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let result = this.open(args)?;
                 this.write_scalar(Scalar::from_i32(result), dest)?;
             }
+            "openat" => {
+                // `open` is variadic, the third argument is only present when the second argument has O_CREAT (or on linux O_TMPFILE, but miri doesn't support that) set
+                this.check_abi_and_shim_symbol_clash(abi, Abi::C { unwind: false }, link_name)?;
+                let result = this.openat(args)?;
+                this.write_scalar(Scalar::from_i32(result), dest)?;
+            }
             "fcntl" => {
                 // `fcntl` is variadic. The argument count is checked based on the first argument
                 // in `this.fcntl()`, so we do not use `check_shim` here.