feat: Support fstat in linux

src/shims/unix/foreign_items.rs

@@ -345,6 +345,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.symlink(target, linkpath)?;
                 this.write_scalar(result, dest)?;
             }
+            "fstat" => {
+                let [fd, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
+                let result = this.fstat(fd, buf)?;
+                this.write_scalar(result, dest)?;
+            }
             "rename" => {
                 let [oldpath, newpath] = this.check_shim_sig(
                     shim_sig!(extern "C" fn(*const _, *const _) -> i32),

src/shims/unix/freebsd/foreign_items.rs

@@ -148,9 +148,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.macos_fbsd_solarish_lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
-            "fstat" | "fstat@FBSD_1.0" => {
+            "fstat@FBSD_1.0" => {
                 let [fd, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
-                let result = this.macos_fbsd_solarish_fstat(fd, buf)?;
+                let result = this.fstat(fd, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "readdir_r" | "readdir_r@FBSD_1.0" => {

src/shims/unix/fs.rs

@@ -118,7 +118,7 @@ impl UnixFileDescription for FileHandle {
 
 impl<'tcx> EvalContextExtPrivate<'tcx> for crate::MiriInterpCx<'tcx> {}
 trait EvalContextExtPrivate<'tcx>: crate::MiriInterpCxExt<'tcx> {
-    fn macos_fbsd_solarish_write_stat_buf(
+    fn write_stat_buf(
         &mut self,
         metadata: FileMetadata,
         buf_op: &OpTy<'tcx>,
@@ -130,7 +130,11 @@ trait EvalContextExtPrivate<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let (modified_sec, modified_nsec) = metadata.modified.unwrap_or((0, 0));
         let mode = metadata.mode.to_uint(this.libc_ty_layout("mode_t").size)?;
 
-        let buf = this.deref_pointer_as(buf_op, this.libc_ty_layout("stat"))?;
+        // We do *not* use `deref_pointer_as` here since determining the right pointee type
+        // is highly non-trivial: it depends on which exact alias of the function was invoked
+        // (e.g. `fstat` vs `fstat64`), and then on FreeBSD it also depends on the ABI level
+        // which can be different between the libc used by std and the libc used by everyone else.
+        let buf = this.deref_pointer(buf_op)?;
         this.write_int_fields_named(
             &[
                 ("st_dev", metadata.dev.into()),
@@ -141,8 +145,11 @@ trait EvalContextExtPrivate<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 ("st_gid", metadata.gid.into()),
                 ("st_rdev", 0),
                 ("st_atime", access_sec.into()),
+                ("st_atime_nsec", access_nsec.into()),
                 ("st_mtime", modified_sec.into()),
+                ("st_mtime_nsec", modified_nsec.into()),
                 ("st_ctime", 0),
+                ("st_ctime_nsec", 0),
                 ("st_size", metadata.size.into()),
                 ("st_blocks", 0),
                 ("st_blksize", 0),
@@ -153,9 +160,6 @@ trait EvalContextExtPrivate<'tcx>: crate::MiriInterpCxExt<'tcx> {
         if matches!(&this.tcx.sess.target.os, Os::MacOs | Os::FreeBsd) {
             this.write_int_fields_named(
                 &[
-                    ("st_atime_nsec", access_nsec.into()),
-                    ("st_mtime_nsec", modified_nsec.into()),
-                    ("st_ctime_nsec", 0),
                     ("st_birthtime", created_sec.into()),
                     ("st_birthtime_nsec", created_nsec.into()),
                     ("st_flags", 0),
@@ -550,7 +554,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             Err(err) => return this.set_last_error_and_return_i32(err),
         };
 
-        interp_ok(Scalar::from_i32(this.macos_fbsd_solarish_write_stat_buf(metadata, buf_op)?))
+        interp_ok(Scalar::from_i32(this.write_stat_buf(metadata, buf_op)?))
     }
 
     // `lstat` is used to get symlink metadata.
@@ -583,22 +587,17 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             Err(err) => return this.set_last_error_and_return_i32(err),
         };
 
-        interp_ok(Scalar::from_i32(this.macos_fbsd_solarish_write_stat_buf(metadata, buf_op)?))
+        interp_ok(Scalar::from_i32(this.write_stat_buf(metadata, buf_op)?))
     }
 
-    fn macos_fbsd_solarish_fstat(
-        &mut self,
-        fd_op: &OpTy<'tcx>,
-        buf_op: &OpTy<'tcx>,
-    ) -> InterpResult<'tcx, Scalar> {
+    fn fstat(&mut self, fd_op: &OpTy<'tcx>, buf_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
         let this = self.eval_context_mut();
 
-        if !matches!(&this.tcx.sess.target.os, Os::MacOs | Os::FreeBsd | Os::Solaris | Os::Illumos)
-        {
-            panic!(
-                "`macos_fbsd_solaris_fstat` should not be called on {}",
-                this.tcx.sess.target.os
-            );
+        if !matches!(
+            &this.tcx.sess.target.os,
+            Os::MacOs | Os::FreeBsd | Os::Solaris | Os::Illumos | Os::Linux
+        ) {
+            panic!("`fstat` should not be called on {}", this.tcx.sess.target.os);
         }
 
         let fd = this.read_scalar(fd_op)?.to_i32()?;
@@ -614,7 +613,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             Ok(metadata) => metadata,
             Err(err) => return this.set_last_error_and_return_i32(err),
         };
-        interp_ok(Scalar::from_i32(this.macos_fbsd_solarish_write_stat_buf(metadata, buf_op)?))
+        interp_ok(Scalar::from_i32(this.write_stat_buf(metadata, buf_op)?))
     }
 
     fn linux_statx(

src/shims/unix/linux/foreign_items.rs

@@ -53,7 +53,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.linux_statx(dirfd, pathname, flags, mask, statxbuf)?;
                 this.write_scalar(result, dest)?;
             }
-
             // epoll, eventfd
             "epoll_create1" => {
                 let [flag] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;

src/shims/unix/macos/foreign_items.rs

@@ -56,9 +56,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.macos_fbsd_solarish_lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
-            "fstat" | "fstat64" | "fstat$INODE64" => {
+            "fstat$INODE64" => {
                 let [fd, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
-                let result = this.macos_fbsd_solarish_fstat(fd, buf)?;
+                let result = this.fstat(fd, buf)?;
                 this.write_scalar(result, dest)?;
             }
             "opendir$INODE64" => {

src/shims/unix/solarish/foreign_items.rs

@@ -100,11 +100,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let result = this.macos_fbsd_solarish_lstat(path, buf)?;
                 this.write_scalar(result, dest)?;
             }
-            "fstat" | "fstat64" => {
-                let [fd, buf] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
-                let result = this.macos_fbsd_solarish_fstat(fd, buf)?;
-                this.write_scalar(result, dest)?;
-            }
             "readdir" => {
                 let [dirp] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
                 let result = this.readdir64("dirent", dirp)?;

tests/pass-dep/libc/libc-fs.rs

@@ -42,6 +42,7 @@ fn main() {
     test_posix_fallocate::<libc::off64_t>(libc::posix_fallocate64);
     #[cfg(target_os = "linux")]
     test_sync_file_range();
+    test_fstat();
     test_isatty();
     test_read_and_uninit();
     test_nofollow_not_symlink();
@@ -452,6 +453,41 @@ fn test_sync_file_range() {
     assert_eq!(result_2, 0);
 }
 
+fn test_fstat() {
+    use std::mem::MaybeUninit;
+    use std::os::unix::io::AsRawFd;
+
+    let path = utils::prepare_with_content("miri_test_libc_fstat.txt", b"hello");
+    let file = File::open(&path).unwrap();
+    let fd = file.as_raw_fd();
+
+    let mut stat = MaybeUninit::<libc::stat>::uninit();
+    let res = unsafe { libc::fstat(fd, stat.as_mut_ptr()) };
+    assert_eq!(res, 0);
+    let stat = unsafe { stat.assume_init_ref() };
+
+    assert_eq!(stat.st_size, 5);
+    assert_eq!(stat.st_mode & libc::S_IFMT, libc::S_IFREG);
+
+    // Check that all fields are initialized.
+    let _st_nlink = stat.st_nlink;
+    let _st_blksize = stat.st_blksize;
+    let _st_blocks = stat.st_blocks;
+    let _st_ino = stat.st_ino;
+    let _st_dev = stat.st_dev;
+    let _st_uid = stat.st_uid;
+    let _st_gid = stat.st_gid;
+    let _st_rdev = stat.st_rdev;
+    let _st_atime = stat.st_atime;
+    let _st_mtime = stat.st_mtime;
+    let _st_ctime = stat.st_ctime;
+    let _st_atime_nsec = stat.st_atime_nsec;
+    let _st_mtime_nsec = stat.st_mtime_nsec;
+    let _st_ctime_nsec = stat.st_ctime_nsec;
+
+    remove_file(&path).unwrap();
+}
+
 fn test_isatty() {
     // Testing whether our isatty shim returns the right value would require controlling whether
     // these streams are actually TTYs, which is hard.