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feat: Support fstat in linux #4714

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5 changes: 5 additions & 0 deletions src/shims/unix/foreign_items.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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),
Expand Down
2 changes: 1 addition & 1 deletion src/shims/unix/freebsd/foreign_items.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -150,7 +150,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
}
"fstat" | "fstat@FBSD_1.0" => {
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@RalfJung RalfJung Nov 26, 2025

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Suggested change
"fstat" | "fstat@FBSD_1.0" => {
"fstat@FBSD_1.0" => {

As elsewhere, the "fstat" case should be removed here, since it is already handled in the "unix" handler now.

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" => {
Expand Down
28 changes: 13 additions & 15 deletions src/shims/unix/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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>,
Expand All @@ -141,8 +141,11 @@ 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),
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@RalfJung RalfJung Nov 26, 2025

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You are now writing these fields twice on macos and freebsd.

("st_size", metadata.size.into()),
("st_blocks", 0),
("st_blksize", 0),
Expand Down Expand Up @@ -550,7 +553,7 @@ 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.
Expand Down Expand Up @@ -583,22 +586,17 @@ 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()?;
Expand All @@ -614,7 +612,7 @@ 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(
Expand Down
6 changes: 5 additions & 1 deletion src/shims/unix/linux/foreign_items.rs
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Expand Up @@ -53,7 +53,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
let result = this.linux_statx(dirfd, pathname, flags, mask, statxbuf)?;
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)?;
}
Comment on lines +56 to +60
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@RalfJung RalfJung Nov 23, 2025

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As explained in the issue, this should be moved into src/shims/unix/foreign_items.rs, and then the corresponding blocks in the other unixes can be removed. (Some of them also make the function available under other names; those cannot be removed.)

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@hulxv hulxv Nov 24, 2025

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I tried to remove them from other unixes but it seems all of them are under different names

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@RalfJung RalfJung Nov 25, 2025

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You can add fstat64 here as well.

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@RalfJung RalfJung Nov 26, 2025

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You didn't yet add fstat64 here. What was your plan?

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@RalfJung RalfJung Nov 26, 2025

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Hm, if we are fstat64 we should probably use the stat64 type, not the stat type... but somehow this worked before? Not entirely sure what is happening. This might be related to the freebsd test failure.

// epoll, eventfd
"epoll_create1" => {
let [flag] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
Expand Down
4 changes: 2 additions & 2 deletions src/shims/unix/macos/foreign_items.rs
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Expand Up @@ -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" => {
Expand Down
2 changes: 1 addition & 1 deletion src/shims/unix/solarish/foreign_items.rs
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Expand Up @@ -102,7 +102,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
}
"fstat" | "fstat64" => {
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@RalfJung RalfJung Nov 26, 2025 •
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As I have already said twice, this match arm should be removed now. Please make sure you understand my comments before marking the PR as ready, and ask if anything is unclear. Do not just guess and update the PR. Only mark it as ready once you are confident everything is ready. It's a lot of extra work for me if I have to keep re-checking and repeating everything I already said.

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" => {
Expand Down
34 changes: 34 additions & 0 deletions tests/pass-dep/libc/libc-fs.rs
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Expand Up @@ -38,6 +38,7 @@ fn main() {
test_posix_fadvise();
#[cfg(target_os = "linux")]
test_sync_file_range();
test_fstat();
test_isatty();
test_read_and_uninit();
test_nofollow_not_symlink();
Expand Down Expand Up @@ -380,6 +381,39 @@ 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: libc::stat = unsafe { MaybeUninit::zeroed().assume_init() };
let res = unsafe { libc::fstat(fd, &mut stat) };
assert_eq!(res, 0);

assert_eq!(stat.st_size, 5);
assert_eq!(stat.st_mode & libc::S_IFMT, libc::S_IFREG);

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.
Expand Down
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