Add /proc/[pid]/cmdline support

kernel/aster-nix/src/fs/procfs/pid/cmdline.rs

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use crate::{
+    fs::{
+        procfs::template::{FileOps, ProcFileBuilder},
+        utils::Inode,
+    },
+    prelude::*,
+    Process,
+};
+
+/// Represents the inode at `/proc/[pid]/cmdline`.
+pub struct CmdlineFileOps(Arc<Process>);
+
+impl CmdlineFileOps {
+    pub fn new_inode(process_ref: Arc<Process>, parent: Weak<dyn Inode>) -> Arc<dyn Inode> {
+        ProcFileBuilder::new(Self(process_ref))
+            .parent(parent)
+            .build()
+            .unwrap()
+    }
+}
+
+impl FileOps for CmdlineFileOps {
+    fn data(&self) -> Result<Vec<u8>> {
+        let cmdline_output = if self.0.is_zombie() {
+            // Returns 0 characters for zombie process.
+            Vec::new()
+        } else {
+            let Ok(argv_cstrs) = self.0.vm().init_stack_reader().argv() else {
+                return Ok(Vec::new());
+            };
+            argv_cstrs
+                .into_iter()
+                .flat_map(|c_str| c_str.into_bytes_with_nul().into_iter())
+                .collect()
+        };
+        Ok(cmdline_output)
+    }
+}

kernel/aster-nix/src/fs/procfs/pid/comm.rs

@@ -1,6 +1,13 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::*;
+use crate::{
+    fs::{
+        procfs::template::{FileOps, ProcFileBuilder},
+        utils::Inode,
+    },
+    prelude::*,
+    Process,
+};
 
 /// Represents the inode at `/proc/[pid]/comm`.
 pub struct CommFileOps(Arc<Process>);

kernel/aster-nix/src/fs/procfs/pid/exe.rs

@@ -1,6 +1,13 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::*;
+use crate::{
+    fs::{
+        procfs::{ProcSymBuilder, SymOps},
+        utils::Inode,
+    },
+    prelude::*,
+    Process,
+};
 
 /// Represents the inode at `/proc/[pid]/exe`.
 pub struct ExeSymOps(Arc<Process>);

kernel/aster-nix/src/fs/procfs/pid/fd.rs

@@ -1,7 +1,18 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use super::*;
-use crate::fs::{file_handle::FileLike, file_table::FileDesc, inode_handle::InodeHandle};
+use crate::{
+    fs::{
+        file_handle::FileLike,
+        file_table::FileDesc,
+        inode_handle::InodeHandle,
+        procfs::{
+            pid::FdEvents, DirOps, Observer, ProcDir, ProcDirBuilder, ProcSymBuilder, SymOps,
+        },
+        utils::{DirEntryVecExt, Inode},
+    },
+    prelude::*,
+    Process,
+};
 
 /// Represents the inode at `/proc/[pid]/fd`.
 pub struct FdDirOps(Arc<Process>);

kernel/aster-nix/src/fs/procfs/pid/mod.rs

@@ -1,9 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use self::{comm::CommFileOps, exe::ExeSymOps, fd::FdDirOps};
-use super::template::{
-    DirOps, FileOps, ProcDir, ProcDirBuilder, ProcFileBuilder, ProcSymBuilder, SymOps,
-};
+use self::{cmdline::CmdlineFileOps, comm::CommFileOps, exe::ExeSymOps, fd::FdDirOps};
+use super::template::{DirOps, ProcDir, ProcDirBuilder};
 use crate::{
     events::Observer,
     fs::{
@@ -14,6 +12,7 @@ use crate::{
     process::Process,
 };
 
+mod cmdline;
 mod comm;
 mod exe;
 mod fd;
@@ -51,6 +50,7 @@ impl DirOps for PidDirOps {
             "exe" => ExeSymOps::new_inode(self.0.clone(), this_ptr.clone()),
             "comm" => CommFileOps::new_inode(self.0.clone(), this_ptr.clone()),
             "fd" => FdDirOps::new_inode(self.0.clone(), this_ptr.clone()),
+            "cmdline" => CmdlineFileOps::new_inode(self.0.clone(), this_ptr.clone()),
             _ => return_errno!(Errno::ENOENT),
         };
         Ok(inode)
@@ -70,6 +70,9 @@ impl DirOps for PidDirOps {
         });
         cached_children.put_entry_if_not_found("fd", || {
             FdDirOps::new_inode(self.0.clone(), this_ptr.clone())
-        })
+        });
+        cached_children.put_entry_if_not_found("cmdline", || {
+            CmdlineFileOps::new_inode(self.0.clone(), this_ptr.clone())
+        });
     }
 }