[lldb][windows] _wsopen_s does not accept bits other than `_S_IREAD | _S_IWRITE`

[yshui]

Summary

When sending file from a Linux host to a Windows remote, Linux host will try to copy the source file's permission bits, which will contain _S_I?GRP and _S_I?OTH bits. Those bits are rejected by _wsopen_s, causing it to return EINVAL.

This patch masks out the rejected bits.

GitHub issue: #64313

[jasonmolenda]

LGTM.

[DavidSpickett]

I just commented on the issue, thanks for the fix!

What exactly are the other bits in the mode here, are we losing something important potentially? I guess it can't be that important if Windows rejects them.

[DavidSpickett]

Also please put [lldb][Windows] at the start of the commit title.

lldb/source/Host/windows/FileSystem.cpp

104

Nitpick: comments are usually on the line before.

[yshui]

In D156817#4553045, @DavidSpickett wrote:

What exactly are the other bits in the mode here, are we losing something important potentially? I guess it can't be that important if Windows rejects them.

I don't think so, group and other permission bits don't really make sense on Windows anyways, unless we use ACL or something.

[DavidSpickett]

I think this could be tested with an lldb-server test, but it would likely go in lldb/test/API/tools/lldb-server/TestGdbRemotePlatformFile.py which has every test marked as skipped on Windows. For reasons lost to time.

If you feel like trying to re-enable them, great, otherwise I'm ok for such a simple fix to go in as is. Thanks again!

[mstorsjo]

I noticed this review is accepted but not committed. If you don't have commit access, what's your preferred git identity, i.e. Real Name <email@address>?

[yshui]

In D156817#4620998, @mstorsjo wrote:

I noticed this review is accepted but not committed. If you don't have commit access, what's your preferred git identity, i.e. Real Name <email@address>?

"Yuxuan Shui <[e-mail]>"

Thanks.

lldb/source/Host/windows/FileSystem.cpp

if (_wfopen_s(&file, wpath.c_str(), wmode.c_str()) != 0)
     return nullptr;
   return file;
 }
 
 int FileSystem::Open(const char *path, int flags, int mode) {
   std::wstring wpath;
   if (!llvm::ConvertUTF8toWide(path, wpath))
     return -1;
+  // All other bits are rejected by _wsopen_s
+  mode = mode & (_S_IREAD | _S_IWRITE);
   int result;
   ::_wsopen_s(&result, wpath.c_str(), flags, _SH_DENYNO, mode);
   return result;
 }