Resolve `semget01` failure by fixing key limit and adding `IPC_STAT`

docs/src/kernel/linux-compatibility/limitations-on-system-calls/inter-process-communication.md

@@ -7,7 +7,7 @@ futex, set_robust_list, and get_robust_list
 under this category.
 -->
 
-## `System V semaphore`
+## System V semaphore
 
 ### `semget`
 
@@ -80,10 +80,17 @@ semctl(
     semnum,
     cmd = GETVAL | GETPID | GETNCNT | GETZCNT
 );
+
+// Retrieve a copy of the `semid_ds` kernel structure for the specified semaphore set
+semctl(
+    semid,
+    semnum,
+    cmd = IPC_STAT,
+    arg
+);
 ```
 
 Unsupported commands:
-* `IPC_STAT`
 * `IPC_INFO`
 * `SEM_INFO`
 * `SEM_STAT`

kernel/src/ipc/semaphore/system_v/sem_set.rs

@@ -51,6 +51,37 @@ pub struct SemaphoreSet {
     sem_otime: AtomicU64,
 }
 
+// https://github.com/torvalds/linux/blob/master/include/uapi/asm-generic/ipcbuf.h
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Default, Pod)]
+pub struct IpcPerm {
+    key: u32,
+    uid: u32,
+    gid: u32,
+    cuid: u32,
+    cgid: u32,
+    mode: u16,
+    _pad1: u16,
+    seq: u16,
+    _pad2: u16,
+    _unused1: u64,
+    _unused2: u64,
+}
+
+// https://github.com/torvalds/linux/blob/master/arch/x86/include/uapi/asm/sembuf.h
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Default, Pod)]
+pub struct SemidDs {
+    sem_perm: IpcPerm,
+    sem_otime: u64,
+    _unused1: u64,
+    sem_ctime: u64,
+    _unused2: u64,
+    sem_nsems: u64,
+    _unused3: u64,
+    _unused4: u64,
+}
+
 #[derive(Debug)]
 pub(super) struct SemSetInner {
     /// Semaphores
@@ -196,6 +227,26 @@ impl SemaphoreSet {
             }),
         })
     }
+
+    pub fn semid_ds(&self) -> SemidDs {
+        let ipc_perm = IpcPerm {
+            key: self.permission.key() as u32,
+            uid: self.permission.uid().into(),
+            gid: self.permission.gid().into(),
+            cuid: self.permission.cuid().into(),
+            cgid: self.permission.cguid().into(),
+            mode: self.permission.mode(),
+            ..IpcPerm::default()
+        };
+
+        SemidDs {
+            sem_perm: ipc_perm,
+            sem_otime: self.sem_otime.load(Ordering::Relaxed),
+            sem_ctime: self.sem_ctime.load(Ordering::Relaxed),
+            sem_nsems: self.nsems as u64,
+            ..SemidDs::default()
+        }
+    }
 }
 
 impl Drop for SemaphoreSet {

kernel/src/syscall/semctl.rs

@@ -92,6 +92,12 @@ pub fn sys_semctl(
 
             return Ok(SyscallReturn::Return(cnt as isize));
         }
+        IpcControlCmd::IPC_STAT => {
+            check_and_ctl(semid, PermissionMode::READ, |sem_set| {
+                let semid_ds = sem_set.semid_ds();
+                ctx.user_space().write_val(arg as Vaddr, &semid_ds)
+            })?;
+        }
         _ => todo!("Need to support {:?} in SYS_SEMCTL", cmd),
     }
 

kernel/src/syscall/semget.rs

@@ -4,7 +4,7 @@ use super::SyscallReturn;
 use crate::{
     ipc::{
         semaphore::system_v::{
-            sem_set::{check_sem, create_sem_set, create_sem_set_with_id, SEMMSL},
+            sem_set::{check_sem, create_sem_set, create_sem_set_with_id, SEMMNI, SEMMSL},
             PermissionMode,
         },
         IpcFlags,
@@ -32,7 +32,7 @@ pub fn sys_semget(key: i32, nsems: i32, semflags: i32, ctx: &Context) -> Result<
 
     // Create a new semaphore set directly
     const IPC_NEW: i32 = 0;
-    if key == IPC_NEW {
+    if key == IPC_NEW || (key as usize > SEMMNI && flags.contains(IpcFlags::IPC_CREAT)) {
         if nsems == 0 {
             return_errno!(Errno::EINVAL);
         }

test/src/syscall/ltp/testcases/all.txt

@@ -1290,7 +1290,7 @@ select03
 # semctl08
 # semctl09
 
-# semget01
+semget01
 # semget02
 # semget05