feat(vfs): 实现 SYS_PWRITEV 系统调用

[mistcoversmyeyes]

• 实现了 SYS_PWRITEV 系统调用
• 为 SYS_PWRITEV 系统调用添加 C Unit test

---

Note

Implements SYS_PWRITEV (vectorized positional write) and updates gVisor write test blocklist annotations.

• VFS Syscalls:
  • sys_pwritev: Add handler SysPwriteVHandle to read user IoVecs, gather buffers, and perform positional writes via do_pwritev -> file.pwrite.
  • Wire into syscall table: add mod sys_pwritev in vfs/syscall/mod.rs and declare_syscall!(SYS_PWRITEV, ...).
• Tests:
  • Update user/apps/tests/syscall/gvisor/blocklists/write_test with entries/comments for failing write-related cases and kernel error notes.

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[Copilot]

Pull Request Overview

This PR implements the SYS_PWRITEV system call for vectorized positional writing to files in the VFS (Virtual File System).

• Implements the SYS_PWRITEV system call that allows writing from multiple buffers to a file at a specified offset
• Adds comprehensive C unit tests covering basic functionality, edge cases, and error handling
• Integrates the new system call into the VFS module structure

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
user/apps/c_unitest/test_pwritev.c	Complete test suite with 6 test cases covering basic pwritev functionality, EOF scenarios, error handling, and offset preservation
kernel/src/filesystem/vfs/syscall/sys_pwritev.rs	Implementation of SysPwriteVHandle struct with system call handling and do_pwritev function
kernel/src/filesystem/vfs/syscall/mod.rs	Module declaration to include the new pwritev system call

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[fslongjin]

要格式化代码

[fslongjin]

看看这俩测例，在有了这个pr之后，能不能通过测试？
blocklist里面删掉他们，然后编译测试套件看看？

https://code.dragonos.org.cn/xref/DragonOS/user/apps/tests/syscall/gvisor/blocklists/write_test?r=7f1a7eff4859f56bb9b91b010ef2af036384b653

测例代码
https://cnb.cool/DragonOS-Community/gvisor/-/tree/dragonos/release-20250616.0/test/syscalls/linux

[mistcoversmyeyes]

Ok，预计下周找个时间使用 gVisor测试一下。最近几天有别的事情。

[mistcoversmyeyes]

测试进度

通过 write_test 所有测试

在系统根目录下使用 `make test-syscall` 能够通过 write_test

问题

进入 DragonOS gvisor 文件夹手动测试完成，退出测试的时候会出现段错误，表现如下：

/opt/tests/gvisor # ./tests/write_test 
[ WARN ] (src/syscall/mod.rs:391)        SYS_RSEQ has not yet been implemented
[==========] Running 12 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 12 tests from WriteTest
[ RUN      ] WriteTest.WriteNoExceedsRLimit
[       OK ] WriteTest.WriteNoExceedsRLimit (12 ms)
[ RUN      ] WriteTest.WriteExceedsRLimit
[ WARN ] (src/syscall/mod.rs:449)        SYS_RT_SIGTIMEDWAIT has not yet been implemented
[  FAILED  ] WriteTest.WriteExceedsRLimit (28 ms)
[ RUN      ] WriteTest.WriteIncrementOffset
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WriteIncrementOffset (28 ms)
[ RUN      ] WriteTest.WriteIncrementOffsetSeek
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WriteIncrementOffsetSeek (24 ms)
[ RUN      ] WriteTest.WriteIncrementOffsetAppend
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WriteIncrementOffsetAppend (20 ms)
[ RUN      ] WriteTest.WriteIncrementOffsetEOF
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WriteIncrementOffsetEOF (24 ms)
[ RUN      ] WriteTest.PwriteNoChangeOffset
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.PwriteNoChangeOffset (16 ms)
[ RUN      ] WriteTest.WriteWithOpath
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WriteWithOpath (16 ms)
[ RUN      ] WriteTest.WritevWithOpath
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.WritevWithOpath (16 ms)
[ RUN      ] WriteTest.PwriteWithOpath
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[       OK ] WriteTest.PwriteWithOpath (16 ms)
[ RUN      ] WriteTest.PartialWriteSIGSEGV
[ WARN ] (src/filesystem/vfs/open.rs:64)         do_fchmodat: not implemented yet

[ ERROR ] (src/arch/x86_64/mm/fault.rs:319)      vma access error, error_code: (empty), address: 0x95a000
Segmentation fault

[fslongjin]

可是，pwritev应该是去看pwritev_test吧

[mistcoversmyeyes]

回复

gvisor 自动测试忘记取消对于以下两个测试的屏蔽，导致在 DragonOS 根目录下运行 make test-syscall 的时候一切正常，但是手动进行测试的时候出现 ERROR

• WriteTest.PartialWriteSIGSEGV
• WriteTest.PartialWriteSIGBUS

新的错误定位（简单描述见最新提交）

计划

这两个 Error 都能稳定复现，计划调试内核详细定位问题

• 理解 DragonOS mm 模块实现方式
• 调试定位具体错误位置
• 修复 mm 模块问题

[sparkzky]

可以去cnb看看测例内容

[fslongjin]

这里为什么要改为4gb? 原本的2gb应该是很空余的