add support for env::home_dir

and a bit of cleanup

Author: RalfJung

src/shims/unix/foreign_items.rs

@@ -228,16 +228,21 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let [name] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let name = this.read_scalar(name)?.to_i32()?;
 
-                let sysconfs = &[
-                    ("_SC_PAGESIZE", Scalar::from_int(PAGE_SIZE, this.pointer_size())),
-                    ("_SC_NPROCESSORS_CONF", Scalar::from_int(NUM_CPUS, this.pointer_size())),
-                    ("_SC_NPROCESSORS_ONLN", Scalar::from_int(NUM_CPUS, this.pointer_size())),
+                // FIXME: Which of these are POSIX, and which are GNU/Linux?
+                // At least the names seem to all also exist on macOS.
+                let sysconfs: &[(&str, fn(&MiriEvalContext<'_, '_>) -> Scalar<Provenance>)] = &[
+                    ("_SC_PAGESIZE", |this| Scalar::from_int(PAGE_SIZE, this.pointer_size())),
+                    ("_SC_NPROCESSORS_CONF", |this| Scalar::from_int(NUM_CPUS, this.pointer_size())),
+                    ("_SC_NPROCESSORS_ONLN", |this| Scalar::from_int(NUM_CPUS, this.pointer_size())),
+                    // 512 seems to be a reasonable default. The value is not critical, in
+                    // the sense that getpwuid_r takes and checks the buffer length.
+                    ("_SC_GETPW_R_SIZE_MAX", |this| Scalar::from_int(512, this.pointer_size()))
                 ];
                 let mut result = None;
                 for &(sysconf_name, value) in sysconfs {
                     let sysconf_name = this.eval_libc_i32(sysconf_name)?;
                     if sysconf_name == name {
-                        result = Some(value);
+                        result = Some(value(this));
                         break;
                     }
                 }
@@ -474,6 +479,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let ret = if complete { 0 } else { this.eval_libc_i32("ERANGE")? };
                 this.write_int(ret, dest)?;
             }
+            "getpid" => {
+                let [] = this.check_shim(abi, Abi::C { unwind: false}, link_name, args)?;
+                let result = this.getpid()?;
+                this.write_scalar(Scalar::from_i32(result), 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.
@@ -500,9 +510,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_null(dest)?;
             }
 
-            // Querying system information
-            "pthread_attr_getstack" => {
-                // We don't support "pthread_attr_setstack", so we just pretend all stacks have the same values here. Hence we can mostly ignore the input `attr_place`.
+            "pthread_attr_getstack"
+            if this.frame_in_std() => {
+                // We don't support "pthread_attr_setstack", so we just pretend all stacks have the same values here.
+                // Hence we can mostly ignore the input `attr_place`.
                 let [attr_place, addr_place, size_place] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let _attr_place = this.deref_operand(attr_place)?;
@@ -535,10 +546,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_null(dest)?;
             }
 
-            "getpid" => {
-                let [] = this.check_shim(abi, Abi::C { unwind: false}, link_name, args)?;
-                let result = this.getpid()?;
-                this.write_scalar(Scalar::from_i32(result), dest)?;
+            "getuid"
+            if this.frame_in_std() => {
+                let [] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                // FOr now, just pretend we always have this fixed UID.
+                this.write_int(super::UID, dest)?;
             }
 
             // Platform-specific shims

src/shims/unix/fs.rs

@@ -1091,31 +1091,35 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             ],
             &statxbuf,
         )?;
-        this.write_int_fields(
+        #[rustfmt::skip]
+        this.write_int_fields_named(
             &[
-                access_sec.into(),  // stx_atime.tv_sec
-                access_nsec.into(), // stx_atime.tv_nsec
+                ("tv_sec", access_sec.into()),
+                ("tv_nsec", access_nsec.into()),
             ],
             &this.mplace_field_named(&statxbuf, "stx_atime")?,
         )?;
-        this.write_int_fields(
+        #[rustfmt::skip]
+        this.write_int_fields_named(
             &[
-                created_sec.into(),  // stx_btime.tv_sec
-                created_nsec.into(), // stx_btime.tv_nsec
+                ("tv_sec", created_sec.into()),
+                ("tv_nsec", created_nsec.into()),
             ],
             &this.mplace_field_named(&statxbuf, "stx_btime")?,
         )?;
-        this.write_int_fields(
+        #[rustfmt::skip]
+        this.write_int_fields_named(
             &[
-                0.into(), // stx_ctime.tv_sec
-                0.into(), // stx_ctime.tv_nsec
+                ("tv_sec", 0.into()),
+                ("tv_nsec", 0.into()),
             ],
             &this.mplace_field_named(&statxbuf, "stx_ctime")?,
         )?;
-        this.write_int_fields(
+        #[rustfmt::skip]
+        this.write_int_fields_named(
             &[
-                modified_sec.into(),  // stx_mtime.tv_sec
-                modified_nsec.into(), // stx_mtime.tv_nsec
+                ("tv_sec", modified_sec.into()),
+                ("tv_nsec", modified_nsec.into()),
             ],
             &this.mplace_field_named(&statxbuf, "stx_mtime")?,
         )?;
@@ -1302,12 +1306,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
                 let file_type = this.file_type_to_d_type(dir_entry.file_type())?;
 
-                this.write_int_fields(
+                this.write_int_fields_named(
                     &[
-                        ino.into(),       // d_ino
-                        0,                // d_off
-                        size.into(),      // d_reclen
-                        file_type.into(), // d_type
+                        ("d_ino", ino.into()),
+                        ("d_off", 0),
+                        ("d_reclen", size.into()),
+                        ("d_type", file_type.into()),
                     ],
                     &MPlaceTy::from_aligned_ptr(entry, dirent64_layout),
                 )?;
@@ -1398,13 +1402,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
                 let file_type = this.file_type_to_d_type(dir_entry.file_type())?;
 
-                this.write_int_fields(
+                this.write_int_fields_named(
                     &[
-                        ino.into(),           // d_ino
-                        0,                    // d_seekoff
-                        0,                    // d_reclen
-                        file_name_len.into(), // d_namlen
-                        file_type.into(),     // d_type
+                        ("d_ino", ino.into()),
+                        ("d_seekoff", 0),
+                        ("d_reclen", 0),
+                        ("d_namlen", file_name_len.into()),
+                        ("d_type", file_type.into()),
                     ],
                     &entry_place,
                 )?;

src/shims/unix/linux/foreign_items.rs

@@ -155,6 +155,41 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_null(dest)?;
             }
 
+            "getpwuid_r" if this.frame_in_std() => {
+                let [uid, pwd, buf, buflen, result] =
+                    this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                this.check_no_isolation("`getpwuid_r`")?;
+
+                let uid = this.read_scalar(uid)?.to_u32()?;
+                let pwd = this.deref_operand(pwd)?;
+                let buf = this.read_pointer(buf)?;
+                let buflen = this.read_scalar(buflen)?.to_machine_usize(this)?;
+                let result = this.deref_operand(result)?;
+
+                // Must be for "us".
+                if uid != crate::shims::unix::UID {
+                    throw_unsup_format!("`getpwuid_r` on other users is not supported");
+                }
+
+                // Reset all fields to `uninit` to make sure nobody reads them.
+                this.write_uninit(&pwd.into())?;
+
+                // We only set the home_dir field.
+                #[allow(deprecated)]
+                let home_dir = std::env::home_dir().unwrap();
+                let (written, _) = this.write_path_to_c_str(&home_dir, buf, buflen)?;
+                let pw_dir = this.mplace_field_named(&pwd, "pw_dir")?;
+                this.write_pointer(buf, &pw_dir.into())?;
+
+                if written {
+                    this.write_pointer(pwd.ptr, &result.into())?;
+                    this.write_null(dest)?;
+                } else {
+                    this.write_null(&result.into())?;
+                    this.write_scalar(this.eval_libc("ERANGE")?, dest)?;
+                }
+            }
+
             _ => return Ok(EmulateByNameResult::NotSupported),
         };
 

src/shims/unix/mod.rs

@@ -10,3 +10,6 @@ mod linux;
 mod macos;
 
 pub use fs::{DirHandler, FileHandler};
+
+// Make up some constants.
+const UID: u32 = 1000;

src/shims/windows/foreign_items.rs

@@ -110,6 +110,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
             // Querying system information
             "GetSystemInfo" => {
+                // Also called from `page_size` crate.
                 let [system_info] =
                     this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
                 let system_info = this.deref_operand(system_info)?;

tests/pass/home.rs

@@ -0,0 +1,9 @@
+//@only-target-linux: home_dir is only supported on Linux
+//@compile-flags: -Zmiri-disable-isolation
+use std::env;
+
+fn main() {
+    env::remove_var("HOME"); // make sure we enter the interesting codepath
+    #[allow(deprecated)]
+    env::home_dir().unwrap();
+}