Auto merge of #3164 - devnexen:fbsd_upd3, r=RalfJung

freebsd adding getrandom interception.

note that os support was added in same time as getentropy.

Author: bors

ci.sh

@@ -108,7 +108,7 @@ case $HOST_TARGET in
     MIRI_TEST_TARGET=aarch64-unknown-linux-gnu run_tests
     MIRI_TEST_TARGET=aarch64-apple-darwin run_tests
     MIRI_TEST_TARGET=i686-pc-windows-gnu run_tests
-    MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthreads libc-getentropy atomic env/var
+    MIRI_TEST_TARGET=x86_64-unknown-freebsd run_tests_minimal hello integer vec panic/panic concurrency/simple pthreads libc-getentropy libc-getrandom atomic env/var
     MIRI_TEST_TARGET=aarch64-linux-android run_tests_minimal hello integer vec panic/panic
     MIRI_TEST_TARGET=wasm32-wasi run_tests_minimal no_std integer strings wasm
     MIRI_TEST_TARGET=wasm32-unknown-unknown run_tests_minimal no_std integer strings wasm

src/shims/unix/freebsd/foreign_items.rs

@@ -47,6 +47,21 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     this.read_scalar(len)?,
                 )?;
             }
+            "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)?;
+            }
 
             // errno
             "__error" => {

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

@@ -1,10 +1,12 @@
-//@only-target-linux
+//@ignore-target-windows: no libc
+//@ignore-target-apple: no getrandom
 
 use std::ptr;
 
 fn main() {
     let mut buf = [0u8; 5];
     unsafe {
+        #[cfg(target_os = "linux")]
         assert_eq!(
             libc::syscall(
                 libc::SYS_getrandom,
@@ -14,6 +16,7 @@ fn main() {
             ),
             0,
         );
+        #[cfg(target_os = "linux")]
         assert_eq!(
             libc::syscall(
                 libc::SYS_getrandom,