feat(ipc/sem): add semaphore support for dragonOS - #2172
feat(ipc/sem): add semaphore support for dragonOS#2172mistcoversmyeyes wants to merge 5 commits into
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| let set = self | ||
| .get_by_semid_checked_mut(token.id) | ||
| .map_err(|_| SystemError::EIDRM)?; |
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当 prepare_setall() 检查权限后复制用户数组时，集合所有者可并发执行 IPC_SET 撤销调用者的写权限；这里重新加锁后只验证 ID 和长度，仍会提交全部新值。应在持锁修改 semval 前按当前权限再次执行写权限检查，避免权限撤销后的 TOCTOU 写入。
AGENTS.md reference: AGENTS.md:L9-L9
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| self.uid = make_kuid(user_ns, uid)?; | ||
| self.gid = make_kgid(user_ns, gid)?; |
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当信号量集的非特权所有者或创建者执行 IPC_SET 时，check_control_permission() 会放行，而该赋值逻辑接受任意可映射的 UID/GID，允许调用者把对象归属伪造成其他用户或自己不属于的组。Linux 仅允许无相应 capability 的调用者使用自身身份或所属组，因此应在写入前验证目标 UID/GID。
AGENTS.md reference: AGENTS.md:L9-L9
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| self.uid = make_kuid(user_ns, uid)?; | ||
| self.gid = make_kgid(user_ns, gid)?; |
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在用户命名空间中提交可映射的 UID 和不可映射的 GID 时，第一个赋值已经修改对象所有者，随后 make_kgid() 返回 EINVAL；因此失败的 IPC_SET 会留下部分更新，调用者甚至可能意外失去对象控制权。应先把两个映射结果保存到局部变量，全部成功后再一次性更新权限对象。
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| } | ||
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| fn get_by_index(&self, id: usize) -> Result<&KernelSemSet, SystemError> { | ||
| let idx = id & IpcIdAllocator::IPC_ID_IDX_MASK; |
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当 SEM_STAT 或 SEM_STAT_ANY 收到大于 IPC_ID_IDX_MASK 的索引时，这里静默截掉高位；只要低 15 位对应现有集合，诸如 0x8000 的无效索引就会错误返回索引 0 的对象，而不是 Linux 的 EINVAL。应先验证范围，再直接按原索引查表。
AGENTS.md reference: AGENTS.md:L9-L9
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| if changed { | ||
| break; |
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当队首有 B 个仍不可执行的等待者、其后有 W 个依次可执行且改变值的等待者时，这个 break 会在每次完成后从队首重新扫描；每次模拟还会分配 HashMap，并且全过程持有命名空间级自旋锁，形成 O(B×W) 的模拟和分配。等待者数量不受 SEMOPM 限制，非特权进程可借此造成整个 IPC 命名空间长时间停顿，应仅重新调度受值变化影响的条目或使用索引化等待队列。
AGENTS.md reference: AGENTS.md:L10-L10
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Related
Summary
semget,semctl,semop, andsemtimedop.Scope
SEM_UNDOis out of scope and currently returnsENOSYS.Acceptance
ENOSYS.semopandsemtimedopshare consistent operation semantics.IPC_RMID.Testing