[NEW FEATURE] make git-for-windows supports posix file mode bits in WSL's way

.github/workflows/nano-server.yml

@@ -0,0 +1,76 @@
+name: Windows Nano Server tests
+
+on:
+  workflow_dispatch:
+
+env:
+  DEVELOPER: 1
+
+jobs:
+  test-nano-server:
+    runs-on: windows-2022
+    env:
+      WINDBG_DIR: "C:/Program Files (x86)/Windows Kits/10/Debuggers/x64"
+      IMAGE: mcr.microsoft.com/powershell:nanoserver-ltsc2022
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: git-for-windows/setup-git-for-windows-sdk@v1
+      - name: build Git
+        shell: bash
+        run: make -j15
+      - name: pull nanoserver image
+        shell: bash
+        run: docker pull $IMAGE
+      - name: run nano-server test
+        shell: bash
+        run: |
+          docker run \
+            --user "ContainerAdministrator" \
+            -v "$WINDBG_DIR:C:/dbg" \
+            -v "$(cygpath -aw /mingw64/bin):C:/mingw64-bin" \
+            -v "$(cygpath -aw .):C:/test" \
+            $IMAGE pwsh.exe -Command '
+              # Extend the PATH to include the `.dll` files in /mingw64/bin/
+              $env:PATH += ";C:\mingw64-bin"
+
+              # For each executable to test pick some no-operation set of
+              # flags/subcommands or something that should quickly result in an
+              # error with known exit code that is not a negative 32-bit
+              # number, and set the expected return code appropriately.
+              #
+              # Only test executables that could be expected to run in a UI
+              # less environment.
+              #
+              # ( Executable path, arguments, expected return code )
+              # also note space is required before close parenthesis (a
+              # powershell quirk when defining nested arrays like this)
+
+              $executables_to_test = @(
+                  ("C:\test\git.exe", "", 1 ),
+                  ("C:\test\scalar.exe", "version", 0 )
+              )
+
+              foreach ($executable in $executables_to_test)
+              {
+                  Write-Output "Now testing $($executable[0])"
+                  &$executable[0] $executable[1]
+                  if ($LASTEXITCODE -ne $executable[2]) {
+                      # if we failed, run the debugger to find out what function
+                      # or DLL could not be found and then exit the script with
+                      # failure The missing DLL or EXE will be referenced near
+                      # the end of the output
+
+                      # Set a flag to have the debugger show loader stub
+                      # diagnostics. This requires running as administrator,
+                      # otherwise the flag will be ignored.
+                      C:\dbg\gflags -i $executable[0] +SLS
+
+                      C:\dbg\cdb.exe -c "g" -c "q" $executable[0] $executable[1]
+
+                      exit 1
+                  }
+              }
+
+              exit 0
+            '

Documentation/config/core.txt

@@ -749,3 +749,9 @@ core.abbrev::
 	If set to "no", no abbreviation is made and the object names
 	are shown in their full length.
 	The minimum length is 4.
+
+core.WSLCompat::
+	Tells Git whether to enable wsl compatibility mode.
+	The default value is false. When set to true, Git will set the mode
+	bits of the file in the way of wsl, so that the executable flag of
+	files can be set or read correctly.

compat/mingw.c

@@ -26,6 +26,7 @@
 #include "win32/fscache.h"
 #include "../attr.h"
 #include "../string-list.h"
+#include "win32/wsl.h"
 
 #define HCAST(type, handle) ((type)(intptr_t)handle)
 
@@ -810,6 +811,11 @@ int mingw_open (const char *filename, int oflags, ...)
 
 	fd = open_fn(wfilename, oflags, mode);
 
+	if ((oflags & O_CREAT) && fd >= 0 && are_wsl_compatible_mode_bits_enabled()) {
+		_mode_t wsl_mode = S_IFREG | (mode&0777);
+		set_wsl_mode_bits_by_handle((HANDLE)_get_osfhandle(fd), wsl_mode);
+	}
+
 	if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) {
 		DWORD attrs = GetFileAttributesW(wfilename);
 		if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY))
@@ -1097,6 +1103,11 @@ int mingw_lstat(const char *file_name, struct stat *buf)
 		filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
 		filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
 		filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
+		if (S_ISREG(buf->st_mode) &&
+		    are_wsl_compatible_mode_bits_enabled()) {
+			copy_wsl_mode_bits_from_disk(wfilename, -1,
+						     &buf->st_mode);
+		}
 		return 0;
 	}
 
@@ -1148,6 +1159,8 @@ static int get_file_info_by_handle(HANDLE hnd, struct stat *buf)
 	filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
 	filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
 	filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
+	if (are_wsl_compatible_mode_bits_enabled())
+	    get_wsl_mode_bits_by_handle(hnd, &buf->st_mode);
 	return 0;
 }
 

compat/win32/fscache.c

@@ -8,6 +8,7 @@
 #include "config.h"
 #include "../../mem-pool.h"
 #include "ntifs.h"
+#include "wsl.h"
 
 static volatile long initialized;
 static DWORD dwTlsIndex;
@@ -237,6 +238,10 @@ static struct fsentry *fseentry_create_entry(struct fscache *cache,
 			     &(fse->u.s.st_mtim));
 	filetime_to_timespec((FILETIME *)&(fdata->CreationTime),
 			     &(fse->u.s.st_ctim));
+	if (fdata->EaSize > 0 && are_wsl_compatible_mode_bits_enabled()) {
+		copy_wsl_mode_bits_from_disk(fdata->FileName,
+			fdata->FileNameLength / sizeof(wchar_t), &fse->st_mode);
+	}
 
 	return fse;
 }

compat/win32/wsl.c

@@ -0,0 +1,139 @@
+#include "../../git-compat-util.h"
+#include "../win32.h"
+#include "../../repository.h"
+#include "config.h"
+#include "ntifs.h"
+#include "wsl.h"
+
+int are_wsl_compatible_mode_bits_enabled(void)
+{
+	/* default to `false` during initialization */
+	static const int fallback = 0;
+	static int enabled = -1;
+
+	if (enabled < 0) {
+		/* avoid infinite recursion */
+		if (!the_repository)
+			return fallback;
+
+		if (the_repository->config &&
+		    the_repository->config->hash_initialized &&
+		    git_config_get_bool("core.wslcompat", &enabled) < 0)
+			enabled = 0;
+	}
+
+	return enabled < 0 ? fallback : enabled;
+}
+
+int copy_wsl_mode_bits_from_disk(const wchar_t *wpath, ssize_t wpathlen,
+				 _mode_t *mode)
+{
+	int ret = -1;
+	HANDLE h;
+	if (wpathlen >= 0) {
+		/*
+		 * It's caller's duty to make sure wpathlen is reasonable so
+		 * it does not overflow.
+		 */
+		wchar_t *fn2 = (wchar_t*)alloca((wpathlen + 1) * sizeof(wchar_t));
+		memcpy(fn2, wpath, wpathlen * sizeof(wchar_t));
+		fn2[wpathlen] = 0;
+		wpath = fn2;
+	}
+	h = CreateFileW(wpath, FILE_READ_EA | SYNCHRONIZE,
+			FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+			NULL, OPEN_EXISTING,
+			FILE_FLAG_BACKUP_SEMANTICS |
+				FILE_FLAG_OPEN_REPARSE_POINT,
+			NULL);
+	if (h != INVALID_HANDLE_VALUE) {
+		ret = get_wsl_mode_bits_by_handle(h, mode);
+		CloseHandle(h);
+	}
+	return ret;
+}
+
+#define LX_FILE_METADATA_HAS_UID 0x1
+#define LX_FILE_METADATA_HAS_GID 0x2
+#define LX_FILE_METADATA_HAS_MODE 0x4
+#define LX_FILE_METADATA_HAS_DEVICE_ID 0x8
+#define LX_FILE_CASE_SENSITIVE_DIR 0x10
+typedef struct _FILE_STAT_LX_INFORMATION {
+	LARGE_INTEGER FileId;
+	LARGE_INTEGER CreationTime;
+	LARGE_INTEGER LastAccessTime;
+	LARGE_INTEGER LastWriteTime;
+	LARGE_INTEGER ChangeTime;
+	LARGE_INTEGER AllocationSize;
+	LARGE_INTEGER EndOfFile;
+	uint32_t FileAttributes;
+	uint32_t ReparseTag;
+	uint32_t NumberOfLinks;
+	ACCESS_MASK EffectiveAccess;
+	uint32_t LxFlags;
+	uint32_t LxUid;
+	uint32_t LxGid;
+	uint32_t LxMode;
+	uint32_t LxDeviceIdMajor;
+	uint32_t LxDeviceIdMinor;
+} FILE_STAT_LX_INFORMATION, *PFILE_STAT_LX_INFORMATION;
+
+/*
+ * This struct is extended from the original FILE_FULL_EA_INFORMATION of
+ * Microsoft Windows.
+ */
+struct wsl_full_ea_info_t {
+	uint32_t NextEntryOffset;
+	uint8_t Flags;
+	uint8_t EaNameLength;
+	uint16_t EaValueLength;
+	char EaName[7];
+	char EaValue[4];
+	char Padding[1];
+};
+
+enum {
+	FileStatLxInformation = 70,
+};
+__declspec(dllimport) NTSTATUS WINAPI
+	NtQueryInformationFile(HANDLE FileHandle,
+			       PIO_STATUS_BLOCK IoStatusBlock,
+			       PVOID FileInformation, ULONG Length,
+			       uint32_t FileInformationClass);
+__declspec(dllimport) NTSTATUS WINAPI
+	NtSetInformationFile(HANDLE FileHandle, PIO_STATUS_BLOCK IoStatusBlock,
+			     PVOID FileInformation, ULONG Length,
+			     uint32_t FileInformationClass);
+__declspec(dllimport) NTSTATUS WINAPI
+	NtSetEaFile(HANDLE FileHandle, PIO_STATUS_BLOCK IoStatusBlock,
+		    PVOID EaBuffer, ULONG EaBufferSize);
+
+int set_wsl_mode_bits_by_handle(HANDLE h, _mode_t mode)
+{
+	uint32_t value = mode;
+	struct wsl_full_ea_info_t ea_info;
+	IO_STATUS_BLOCK iob;
+	/* mode should be valid to make WSL happy */
+	assert(S_ISREG(mode) || S_ISDIR(mode));
+	ea_info.NextEntryOffset = 0;
+	ea_info.Flags = 0;
+	ea_info.EaNameLength = 6;
+	ea_info.EaValueLength = sizeof(value); /* 4 */
+	strlcpy(ea_info.EaName, "$LXMOD", sizeof(ea_info.EaName));
+	memcpy(ea_info.EaValue, &value, sizeof(value));
+	ea_info.Padding[0] = 0;
+	return NtSetEaFile(h, &iob, &ea_info, sizeof(ea_info));
+}
+
+int get_wsl_mode_bits_by_handle(HANDLE h, _mode_t *mode)
+{
+	FILE_STAT_LX_INFORMATION fxi;
+	IO_STATUS_BLOCK iob;
+	if (NtQueryInformationFile(h, &iob, &fxi, sizeof(fxi),
+				   FileStatLxInformation) == 0) {
+		if (fxi.LxFlags & LX_FILE_METADATA_HAS_MODE)
+			*mode = (_mode_t)fxi.LxMode;
+		return 0;
+	}
+	return -1;
+}

compat/win32/wsl.h

@@ -0,0 +1,12 @@
+#ifndef COMPAT_WIN32_WSL_H
+#define COMPAT_WIN32_WSL_H
+
+int are_wsl_compatible_mode_bits_enabled(void);
+
+int copy_wsl_mode_bits_from_disk(const wchar_t *wpath, ssize_t wpathlen,
+				 _mode_t *mode);
+
+int get_wsl_mode_bits_by_handle(HANDLE h, _mode_t *mode);
+int set_wsl_mode_bits_by_handle(HANDLE h, _mode_t mode);
+
+#endif

config.mak.uname

@@ -488,7 +488,7 @@ endif
 		compat/win32/path-utils.o \
 		compat/win32/pthread.o compat/win32/syslog.o \
 		compat/win32/trace2_win32_process_info.o \
-		compat/win32/dirent.o compat/win32/fscache.o
+		compat/win32/dirent.o compat/win32/fscache.o compat/win32/wsl.o
 	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DDETECT_MSYS_TTY -DENSURE_MSYSTEM_IS_SET -DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
 	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO
 	# invalidcontinue.obj allows Git's source code to close the same file
@@ -679,7 +679,7 @@ ifeq ($(uname_S),MINGW)
 		compat/win32/flush.o \
 		compat/win32/path-utils.o \
 		compat/win32/pthread.o compat/win32/syslog.o \
-		compat/win32/dirent.o compat/win32/fscache.o
+		compat/win32/dirent.o compat/win32/fscache.o compat/win32/wsl.o
 	BASIC_CFLAGS += -DWIN32
 	EXTLIBS += -lws2_32
 	GITLIBS += git.res

contrib/buildsystems/CMakeLists.txt

@@ -306,6 +306,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
 		compat/win32/syslog.c
 		compat/win32/trace2_win32_process_info.c
 		compat/win32/dirent.c
+		compat/win32/wsl.c
 		compat/nedmalloc/nedmalloc.c
 		compat/strdup.c
 		compat/win32/fscache.c)