move randomness tests into a single file and share the getrandom implementation across unices

Author: RalfJung

ci/ci.sh

@@ -143,10 +143,10 @@ case $HOST_TARGET in
     # Partially supported targets (tier 2)
     VERY_BASIC="integer vec string btreemap" # common things we test on all of them (if they have std), requires no target-specific shims
     BASIC="$VERY_BASIC hello hashmap alloc align" # ensures we have the shims for stdout and basic data structures
-    MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC panic/panic concurrency/simple atomic threadname libc-getentropy libc-getrandom libc-misc fs env num_cpus
-    MIRI_TEST_TARGET=i686-unknown-freebsd   run_tests_minimal $BASIC panic/panic concurrency/simple atomic threadname libc-getentropy libc-getrandom libc-misc fs env num_cpus
+    MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal $BASIC panic/panic concurrency/simple atomic threadname libc-misc libc-random fs env num_cpus
+    MIRI_TEST_TARGET=i686-unknown-freebsd   run_tests_minimal $BASIC panic/panic concurrency/simple atomic threadname libc-misc libc-random fs env num_cpus
     MIRI_TEST_TARGET=aarch64-linux-android  run_tests_minimal $VERY_BASIC hello panic/panic
-    MIRI_TEST_TARGET=x86_64-unknown-illumos run_tests_minimal $VERY_BASIC hello panic/panic pthread-sync libc-misc
+    MIRI_TEST_TARGET=x86_64-unknown-illumos run_tests_minimal $VERY_BASIC hello panic/panic pthread-sync libc-misc libc-random
     # TODO fix solaris stack guard
     # MIRI_TEST_TARGET=x86_64-pc-solaris run_tests_minimal $VERY_BASIC hello panic/panic pthread-sync
     MIRI_TEST_TARGET=wasm32-wasi run_tests_minimal $VERY_BASIC wasm

src/shims/unix/foreign_items.rs

@@ -23,7 +23,7 @@ pub fn is_dyn_sym(name: &str, target_os: &str) -> bool {
         // well allow it in `dlsym`.
         "signal" => true,
         // needed at least on macOS to avoid file-based fallback in getrandom
-        "getentropy" => true,
+        "getentropy" | "getrandom" => true,
         // Give specific OSes a chance to allow their symbols.
         _ =>
             match target_os {
@@ -620,6 +620,24 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     this.write_scalar(Scalar::from_i32(0), dest)?;
                 }
             }
+            "getrandom" => {
+                // This function is non-standard but exists with the same signature and behavior on
+                // Linux, FreeBSD and Solaris/Illumos.
+                if !matches!(&*this.tcx.sess.target.os, "linux" | "freebsd" | "illumos" | "solaris") {
+                    throw_unsup_format!(
+                        "`getentropy` is not supported on {}",
+                        this.tcx.sess.target.os
+                    );
+                }
+                let [ptr, len, flags] =
+                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                let ptr = this.read_pointer(ptr)?;
+                let len = this.read_target_usize(len)?;
+                let _flags = this.read_scalar(flags)?.to_i32()?;
+                // We ignore the flags, just always use the same PRNG / host RNG.
+                this.gen_random(ptr, len)?;
+                this.write_scalar(Scalar::from_target_usize(len, this), dest)?;
+            }
 
             // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
             // These shims are enabled only when the caller is in the standard library.

src/shims/unix/freebsd/foreign_items.rs

@@ -20,11 +20,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         let this = self.eval_context_mut();
         match link_name.as_str() {
             // Threading
-            "pthread_attr_get_np" if this.frame_in_std() => {
-                let [_thread, _attr] =
-                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
-                this.write_null(dest)?;
-            }
             "pthread_set_name_np" => {
                 let [thread, name] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
@@ -75,27 +70,20 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             }
 
             // Miscellaneous
-            "getrandom" => {
-                let [ptr, len, flags] =
-                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
-                let ptr = this.read_pointer(ptr)?;
-                let len = this.read_target_usize(len)?;
-                let _flags = this.read_scalar(flags)?.to_i32()?;
-                // flags on freebsd does not really matter
-                // in practice, GRND_RANDOM does not particularly draw from /dev/random
-                // since it is the same as to /dev/urandom.
-                // GRND_INSECURE is only an alias of GRND_NONBLOCK, which
-                // does not affect the RNG.
-                // https://man.freebsd.org/cgi/man.cgi?query=getrandom&sektion=2&n=1
-                this.gen_random(ptr, len)?;
-                this.write_scalar(Scalar::from_target_usize(len, this), dest)?;
-            }
             "__error" => {
                 let [] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let errno_place = this.last_error_place()?;
                 this.write_scalar(errno_place.to_ref(this).to_scalar(), dest)?;
             }
 
+            // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
+            // These shims are enabled only when the caller is in the standard library.
+            "pthread_attr_get_np" if this.frame_in_std() => {
+                let [_thread, _attr] =
+                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                this.write_null(dest)?;
+            }
+
             _ => return Ok(EmulateItemResult::NotSupported),
         }
         Ok(EmulateItemResult::NeedsJumping)

src/shims/unix/linux/foreign_items.rs

@@ -11,7 +11,7 @@ use shims::unix::linux::mem::EvalContextExt as _;
 use shims::unix::linux::sync::futex;
 
 pub fn is_dyn_sym(name: &str) -> bool {
-    matches!(name, "getrandom" | "statx")
+    matches!(name, "statx")
 }
 
 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
@@ -152,11 +152,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             }
 
             // Miscellaneous
-            "getrandom" => {
-                let [ptr, len, flags] =
-                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
-                getrandom(this, ptr, len, flags, dest)?;
-            }
             "mmap64" => {
                 let [addr, length, prot, flags, fd, offset] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

tests/pass-dep/shims/libc-getentropy.rs

@@ -1,9 +1,29 @@
 //@ignore-target-windows: no libc
-//@ignore-target-apple: no getrandom
-
-use std::ptr;
+//@revisions: isolation no_isolation
+//@[no_isolation]compile-flags: -Zmiri-disable-isolation
 
 fn main() {
+    test_getentropy();
+    #[cfg(not(target_os = "macos"))]
+    test_getrandom();
+}
+
+fn test_getentropy() {
+    use libc::getentropy;
+
+    let mut buf1 = [0u8; 256];
+    let mut buf2 = [0u8; 257];
+    unsafe {
+        assert_eq!(getentropy(buf1.as_mut_ptr() as *mut libc::c_void, buf1.len()), 0);
+        assert_eq!(getentropy(buf2.as_mut_ptr() as *mut libc::c_void, buf2.len()), -1);
+        assert_eq!(std::io::Error::last_os_error().raw_os_error().unwrap(), libc::EIO);
+    }
+}
+
+#[cfg(not(target_os = "macos"))]
+fn test_getrandom() {
+    use std::ptr;
+
     let mut buf = [0u8; 5];
     unsafe {
         #[cfg(target_os = "linux")]