fix(vfs):调整 lseek 行为 —— 禁止 procfs SEEK_END，目录 SEEK_END 返回 MAX_LFS_FILESIZE

[kaleidoscope416]

vfs: 调整 lseek 行为 —— 禁止 procfs SEEK_END，目录 SEEK_END 返回 MAX_LFS_FILESIZE

• 在 lseek 中加入对 procfs 私有数据的检查：若为 procfs 的伪文件，拒绝 SEEK_END 和无效的 seek 模式，返回 EINVAL。
• 对目录类型在 SEEK_END 的处理采用常见 Linux 语义：返回 MAX_LFS_FILESIZE (0x7fffffffffffffff)。测试允许返回该值或 EINVAL，选择返回 MAX_LFS_FILESIZE 以通过现有测试。
• 保持 SEEK_CUR 按当前 offset 计算位置（使用 self.offset.load(Ordering::SeqCst)）。
• 目的：使 DragonOS 在 procfs/目录与 lseek 相关行为上与 Linux 更一致，修复测试套件对这些情形的期望。
• 按照 POSIX / Linux lseek 语义，对于目标偏移为负的情况应返回 EINVAL。
• 将lseek加入whitelist并添加屏蔽测试

注意：

• 该变更为局部修复；更完善的方式是对不同文件类型（procfs、设备、目录等）在 inode/drivers 层实现或分发 llseek，或做更大的 FileDescription 重构以统一文件描述符语义。
• 建议在合并后运行 lseek 测试用例与 procfs 相关测试以验证行为。

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Note

Refines lseek to reject procfs SEEK_END, return MAX_LFS_FILESIZE for directory SEEK_END, treat negative results as EINVAL, and enables gVisor lseek_test with targeted blocklists.

• VFS (kernel/src/filesystem/vfs/file.rs):
  • Procfs: disallow SEEK_END and Invalid in lseek, return EINVAL.
  • Directories: SEEK_END returns MAX_LFS_FILESIZE.
  • Negative resulting positions now return EINVAL.
• Tests:
  • Enable lseek_test in user/apps/tests/syscall/gvisor/whitelist.txt.
  • Add blocklisted cases in user/apps/tests/syscall/gvisor/blocklists/lseek_test: LseekTest.ProcStatTwice, LseekTest.EtcPasswdDup, LseekTest.SeekDataAndSeekHole.

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[Copilot]

Pull Request Overview

This PR adds support for the lseek syscall test from gvisor, with implementation improvements to handle edge cases for procfs files and directories.

• Added lseek_test to the gvisor test whitelist with a corresponding blocklist for unsupported test cases
• Enhanced lseek implementation to handle procfs files and directories correctly
• Fixed error code from EOVERFLOW to EINVAL for negative seek positions
• Removed extraneous blank lines in syscall handler code

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
user/apps/tests/syscall/gvisor/whitelist.txt	Enabled lseek_test in the test suite
user/apps/tests/syscall/gvisor/blocklists/lseek_test	Created blocklist for 3 unsupported lseek test cases
kernel/src/filesystem/vfs/syscall/sys_lseek.rs	Removed unnecessary blank lines for code cleanup
kernel/src/filesystem/vfs/file.rs	Added procfs and directory-specific lseek handling, fixed error code for negative positions

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[Copilot]

Use the imported SeekFrom type directly instead of the fully qualified path crate::driver::base::block::SeekFrom. The type is already imported at line 11, so you can simplify to SeekFrom::SeekEnd(_) and SeekFrom::Invalid.

Suggested change

	crate::driver::base::block::SeekFrom::SeekEnd(_) => {
	return Err(SystemError::EINVAL);
	}
	crate::driver::base::block::SeekFrom::Invalid => {
	SeekFrom::SeekEnd(_) => {
	return Err(SystemError::EINVAL);
	}
	SeekFrom::Invalid => {

[Copilot]

The magic number 0x7fffffffffffffff should use a more explicit representation. Consider using i64::MAX instead of the hex literal for better readability and maintainability.

Suggested change

	const MAX_LFS_FILESIZE: i64 = 0x7fffffffffffffff;
	const MAX_LFS_FILESIZE: i64 = i64::MAX;

[fslongjin]

SeekFrom::SeekEnd(_) | SeekFrom::Invalid

可以这样合并测试条件。不然太啰嗦了

[fslongjin]

在全局声明。

[fslongjin]

还有，需要修改pr标题