feat(mm)：添加mlock系列的系统调用 #1619

kaleidoscope416 · 2026-01-08T05:26:40Z

概述

本 PR 实现了 Linux 兼容的 mlock/munlock/mlockall/munlockall 系列系统调用，用于防止关键内存页面被换出到交换空间。这是数据库、加密应用等需要保证内存持久性的场景的重要功能。

相关 Commits (按时间顺序):

faf59f0 - 设置 RLIMIT_MEMLOCK 默认值
5b55c44 - MADV_DONTNEED 与 VM_LOCKED 互斥检查等
3ea434d - 删去冗余接口和逻辑
48c854d - 完成锁定物理页的逻辑
913a80a - 加入单元测试
19581f7 - 减去一个锁
6894c04 - 单独定义常量

主要功能

核心系统调用

mlock(addr, len) - 锁定指定内存区域中已映射页面
mlock2(addr, len, flags) - 支持 MLOCK_ONFAULT 标志的锁定，锁定指定内存区域中已映射页面，延迟锁定指定内存区域中未映射页面
munlock(addr, len) - 解锁指定内存区域
mlockall(flags) - 锁定所有内存（支持 MCL_CURRENT 和 MCL_FUTURE）
munlockall() - 解锁所有内存

页面管理

页面级引用计数: 使用 Page::mlock_count 跟踪锁定次数
标志管理:
- PG_MLOCKED - 标记页面已锁定
- PG_UNEVICTABLE - 防止页面被换出
大页支持: 正确处理 2MB/1GB 大页的子页锁定

资源限制

RLIMIT_MEMLOCK 检查: 限制进程可锁定的内存总量
默认值: 64KB（与 Linux x86_64 一致）
CAP_IPC_LOCK: 框架已预留（TODO: 实现权限检查）

VMA 管理

VM_LOCKED 标志: 标记 VMA 中的页面应被锁定
VM_LOCKONFAULT 标志: 延迟锁定，仅在缺页时锁定
fork 语义: 正确实现 - 子进程不继承锁定状态

Note

Introduces Linux-compatible memory locking with proper accounting and limits.

Add kernel/src/mm/mlock.rs with mlock_page/munlock_page, page-table walking (incl. huge-page subpages), and can_do_mlock
New syscalls: mlock, mlock2 (MLOCK_ONFAULT), mlockall (MCL_CURRENT|MCL_FUTURE|MCL_ONFAULT), munlock, munlockall; validate ranges, align, CAP/RLIMIT checks
AddressSpace/VMA: track locked_vm and def_flags; implement mlock/munlock/mlockall/munlockall; apply VM_LOCKED/VM_LOCKONFAULT; do not inherit locks on fork
Page layer: add PG_MLOCKED, use PG_UNEVICTABLE, and per-page mlock_count
Fault handling: when VM_LOCKONFAULT set, lock anon pages on demand in do_anonymous_page
madvise: return EINVAL for MADV_DONTNEED on VM_LOCKED VMAs
mmap/mremap: enforce RLIMIT_MEMLOCK for MAP_LOCKED and locked VMA expansion, returning EPERM/EAGAIN/ENOMEM as appropriate
Process: set default RLIMIT_MEMLOCK to 64KB
Tests: add user/apps/c_unitest/test_mlock.c; whitelist mlock_test

^{Written by Cursor Bugbot for commit a4aa5ad. This will update automatically on new commits. Configure here.}

- 对已设置 VM_LOCKED 标志的 VMA 调用 MADV_DONTNEED 时返回 EINVAL - 符合 Linux 语义：已锁定内存不能通过 madvise 释放 2. sys_mlock.rs - RLIMIT_MEMLOCK 资源限制检查 - 添加 RLIMIT_MEMLOCK 限制检查 - 计算当前已锁定页面数和请求数 - 超过限制时返回 ENOMEM 3. sys_mmap.rs - MAP_LOCKED 标志的资源限制 - MAP_LOCKED 映射时进行 RLIMIT_MEMLOCK 检查 - 检查 can_do_mlock() 权限 - 超过限制时返回 EAGAIN 4. sys_mremap.rs - 扩展锁定 VMA 时的资源检查 - 扩展已锁定的 VMA 时检查额外需要的页面数 - 进行 RLIMIT_MEMLOCK 限制验证 5. ucontext.rs - Fork 语义和辅助函数 - 修正 fork 语义：子进程不应继承 locked_vm 计数（从 0 开始） - 修正 fork 语义：子进程不应继承 def_flags（mlockall 设置的默认标志） - 修正 fork 语义：子进程不应继承 VM_LOCKED 和 VM_LOCKONFAULT 标志 - 添加 vma_is_accessible() 辅助函数 - mlock 前检查 VMA 可访问性（PROT_NONE 应返回 ENOMEM） - 添加 locked_vm() getter 方法 - mmap 时应用 def_flags（支持 mlockall MCL_FUTURE）

fslongjin · 2026-01-08T05:30:02Z

bugbot run

kernel/src/mm/ucontext.rs

cursor · 2026-01-08T05:36:45Z

kernel/src/mm/ucontext.rs

 use ida::IdAllocator;
 use log::warn;
 use system_error::SystemError;
+use x86::current;


Unused import x86::current accidentally added

Low Severity

The import use x86::current; is added but never used anywhere in the file. The current() calls in this file refer to AddressSpace::current() and self.is_current() methods, not the x86 crate's current module. This appears to be accidentally committed code.

kernel/src/mm/syscall/sys_mlock2.rs

kernel/src/mm/syscall/sys_mlockall.rs

kernel/src/mm/syscall/sys_mmap.rs

kernel/src/mm/syscall/sys_mlockall.rs

kaleidoscope416 · 2026-01-08T06:16:50Z

bugbot run

cursor · 2026-01-08T06:16:52Z

Skipping Bugbot: Unable to authenticate your request. Please make sure Bugbot is properly installed and configured for this repository.

fslongjin · 2026-01-08T11:47:04Z

bugbot run

kernel/src/mm/ucontext.rs

kernel/src/mm/mlock.rs

kernel/src/mm/syscall/sys_mlock.rs

kaleidoscope416 · 2026-01-14T03:57:36Z

bugbot run

cursor · 2026-01-14T03:57:37Z

Skipping Bugbot: Unable to authenticate your request. Please make sure Bugbot is properly installed and configured for this repository.

kaleidoscope416 · 2026-01-14T04:03:33Z

https://github.com/codex review

kaleidoscope416 · 2026-01-14T04:03:45Z

@codex review

chatgpt-codex-connector · 2026-01-14T04:03:50Z

To use Codex here, create a Codex account and connect to github.

kaleidoscope416 · 2026-01-14T04:07:18Z

@codex review

chatgpt-codex-connector · 2026-01-14T04:07:23Z

To use Codex here, create a Codex account and connect to github.

fslongjin · 2026-01-14T05:26:09Z

@claude review

dragonos-community-ai-pr-reviewer · 2026-01-14T05:26:22Z

Claude finished @fslongjin's task in 8m 46s —— View job

Code Review for PR #1619: feat(mm): 添加mlock系列的系统调用

I'm reviewing the mlock system call implementation. Let me examine the changes and provide feedback.

Todo List:

Analyze PR description and existing review comments
Examine key implementation files
Check for bugs and issues mentioned in previous reviews
Review new mlock.rs module
Review syscall implementations
Review VMA and page management changes
Test integration and edge cases
Provide comprehensive review feedback

Summary

This PR implements Linux-compatible mlock, mlock2, munlock, mlockall, and munlockall system calls with proper resource accounting, page locking, and RLIMIT_MEMLOCK enforcement. The implementation is comprehensive and follows Linux semantics.

Bug Fix Status

I've examined the 15 issues identified by Cursor Bugbot. Most have been addressed in the current code:

✅ Fixed issues:

mlockall fails to update locked_vm counter - Now updates locked_vm with VMA size
munlock unconditionally decrements causing potential underflow - Checks was_locked before decrementing
mlock double-counts already-locked pages - Checks was_locked before incrementing
Unused import x86::current - Appears removed
mlock2 syscall missing RLIMIT_MEMLOCK enforcement - Now includes RLIMIT check
mlockall syscall missing RLIMIT_MEMLOCK enforcement - Includes RLIMIT check for MCL_CURRENT
mmap with MAP_LOCKED fails to update locked_vm - Now updates locked_vm and checks RLIMIT
mlockall accepts empty flags - Validates at least MCL_CURRENT or MCL_FUTURE
TOCTOU race condition in VMA flag update - Mitigated by holding address space write lock
Huge page locking uses wrong physical address offset - Fixed with offset_in_entry
Missing address page alignment - Fixed in mlock, mlock2, and munlock
mlock2 missing address alignment - Now includes alignment logic
mlockall locked_vm accounting uses wrong count - Uses VMA size not mapped page count
Missing RLIMIT check for MCL_FUTURE mmap locking - RLIMIT check added for def_flags
munlock_page never clears PG_UNEVICTABLE flag - Now checks map_count() == 0

Code Quality

The implementation is well-documented with Linux references, follows Rust safety patterns, and includes comprehensive error handling. The use of atomic counters, proper locking, and page table walking is correct.

Suggestions

Error propagation: Some syscall handlers return SystemError but could benefit from more specific error codes in edge cases.
Edge case testing: While test_mlock.c is comprehensive, consider adding tests for:
- Concurrent mlock/munlock operations
- RLIMIT_MEMLOCK exhaustion scenarios
- MCL_FUTURE with subsequent mmap failures
Page flag consistency: Ensure PG_UNEVICTABLE is always cleared when page is unmapped and mlock_count reaches zero.
Potential unwrap panics: The few unwrap() calls after entry.present() checks are safe, but consider using expect() with descriptive messages.

Overall

This is a high-quality implementation of a critical OS feature. The code addresses the previously identified security and correctness issues. The PR is ready for merge pending successful CI tests.

Recommended action: Approve after CI passes.

CI Status: All checks passed ✅ (branch: feat/mlock)

Review performed by Claude via Claude Code

fslongjin · 2026-01-14T05:28:14Z

这个pr有太多代码冗余了，并且封装程度也不够。
还有，在ucontext原有函数里面，加了一大段相对独立的内容，这种也要提取出来。
并且ucontext.rs太长了，最好把你在里面新增的逻辑提取到mlock.rs

kaleidoscope416 added 9 commits January 4, 2026 20:53

初步完成mlock

8281b18

设置 RLIMIT_MEMLOCK 默认值

faf59f0

删去冗余接口和逻辑

3ea434d

完成锁定物理页的逻辑

48c854d

加入单元测试

913a80a

减去一个锁

19581f7

单独定义常量

6894c04

fmt

1951aa1

fmt

c97ebd5

cursor bot reviewed Jan 8, 2026

View reviewed changes

kaleidoscope416 added 9 commits January 8, 2026 13:39

fmt并启用测试

55bcc91

fix: 在mlockall后增加locked_vm的对应值保证rlimt准确

9e5b43e

fix：在munlock中增加标志位的检查，正确减去解锁页面

ce78f2c

fix：修复mlock中对已锁定页面多次计数的问题

5bb1026

fix：增加mlock2和mlockall中对rlimit的检查

53bc828

fix：修复mmap锁定时未增加locked_vm的问题

ae1c72a

fix：强制要求mlockall指定cur或future

723b7d7

fmt

5a2c884

可变性

8082e31

fmt

3f9c91e

cursor bot reviewed Jan 8, 2026

View reviewed changes

kernel/src/mm/ucontext.rs Show resolved Hide resolved

kernel/src/mm/mlock.rs Show resolved Hide resolved

kernel/src/mm/syscall/sys_mlock.rs Outdated Show resolved Hide resolved

kaleidoscope416 added 4 commits January 8, 2026 20:49

fix: 修复mlock_page静默失败的问题&mlock的竞态条件的问题

1a76ad2

增加对CAP_IPC_LOCK的检查

756afbc

修复大页中页表遍历的问题

8e6f8be

增加对起始地址的向下对齐

5e835e0

kaleidoscope416 added 7 commits January 12, 2026 18:25

在munmap中减去对于locked_vm

5cdc2c8

把locked_vm也降为usize

1da191c

去掉没有必要返回值

6ee7246

修复mlock_count递减逻辑的下溢问题

ee666fa

在对页面锁定时持有page manager guard 防止页面被回收

9e90dad

fmt

2c34ff8

toutoc

e8609b4

kaleidoscope416 force-pushed the feat/mlock branch from 082f756 to a9152ac Compare January 13, 2026 06:09

kaleidoscope416 added 3 commits January 13, 2026 18:18

mremap正确更新locked_vm

156f427

fmt

6447bc2

1

447fbf9

kaleidoscope416 force-pushed the feat/mlock branch from a9152ac to 447fbf9 Compare January 13, 2026 10:49

kaleidoscope416 marked this pull request as ready for review January 14, 2026 03:39

kaleidoscope416 added 3 commits January 14, 2026 11:55

Merge branch 'master' into feat/mlock

6cbba87

改锁

1a59067

fmt

eaccfc6

kaleidoscope416 and others added 2 commits January 14, 2026 12:11

Merge branch 'master' into feat/mlock

6622500

1

f3ef017

github-actions bot added the enhancement New feature or request label Jan 14, 2026

kaleidoscope416 marked this pull request as draft January 14, 2026 09:07

Uh oh!

feat(mm)：添加mlock系列的系统调用 #1619

Are you sure you want to change the base?

feat(mm)：添加mlock系列的系统调用 #1619

Uh oh!

Conversation

kaleidoscope416 commented Jan 8, 2026 • edited by cursor bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

fslongjin commented Jan 8, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

cursor bot Jan 8, 2026

Choose a reason for hiding this comment

Unused import x86::current accidentally added

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

kaleidoscope416 commented Jan 8, 2026

Uh oh!

cursor bot commented Jan 8, 2026

Uh oh!

fslongjin commented Jan 8, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

kaleidoscope416 commented Jan 14, 2026

Uh oh!

cursor bot commented Jan 14, 2026

Uh oh!

kaleidoscope416 commented Jan 14, 2026

Uh oh!

kaleidoscope416 commented Jan 14, 2026

Uh oh!

chatgpt-codex-connector bot commented Jan 14, 2026

Uh oh!

kaleidoscope416 commented Jan 14, 2026

Uh oh!

chatgpt-codex-connector bot commented Jan 14, 2026

Uh oh!

fslongjin commented Jan 14, 2026

Uh oh!

dragonos-community-ai-pr-reviewer bot commented Jan 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Code Review for PR #1619: feat(mm): 添加mlock系列的系统调用

Summary

Bug Fix Status

Code Quality

Suggestions

Overall

Uh oh!

fslongjin commented Jan 14, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

kaleidoscope416 commented Jan 8, 2026 •

edited by cursor bot

Loading

dragonos-community-ai-pr-reviewer bot commented Jan 14, 2026 •

edited

Loading