[Support] Provide linux/magic.h fallback for older kernels

The function for distinguishing local and remote files added in r295768
unconditionally uses linux/magic.h header to provide necessary
filesystem magic numbers. However, in kernel headers predating 2.6.18
the magic numbers are spread throughout multiple include files.
Furthermore, LLVM did not require kernel headers being installed so far.

To increase the portability across different versions of Linux kernel
and different Linux systems, add CMake header checks for linux/magic.h
and -- if it is missing -- the linux/nfs_fs.h and linux/smb.h headers
which contained the numbers previously.

Furthermore, since the numbers are static and the feature does not seem
critical enough to make LLVM require kernel headers at all, add fallback
constants for the case when none of the necessary headers is available.

Differential Revision: https://reviews.llvm.org/D30261

llvm-svn: 295854

llvm/cmake/config-ix.cmake

@@ -88,6 +88,15 @@ if(APPLE)
     HAVE_CRASHREPORTER_INFO)
 endif()
 
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+  check_include_file(linux/magic.h HAVE_LINUX_MAGIC_H)
+  if(NOT HAVE_LINUX_MAGIC_H)
+    # older kernels use split files
+    check_include_file(linux/nfs_fs.h HAVE_LINUX_NFS_FS_H)
+    check_include_file(linux/smb.h HAVE_LINUX_SMB_H)
+  endif()
+endif()
+
 # library checks
 if( NOT PURE_WINDOWS )
   check_library_exists(pthread pthread_create "" HAVE_LIBPTHREAD)

llvm/lib/Support/Unix/Path.inc

@@ -76,7 +76,16 @@
 #include <sys/param.h>
 #include <sys/mount.h>
 #elif defined(__linux__)
+#if defined(HAVE_LINUX_MAGIC_H)
 #include <linux/magic.h>
+#else
+#if defined(HAVE_LINUX_NFS_FS_H)
+#include <linux/nfs_fs.h>
+#endif
+#if defined(HAVE_LINUX_SMB_H)
+#include <linux/smb.h>
+#endif
+#endif
 #include <sys/vfs.h>
 #else
 #include <sys/mount.h>
@@ -346,6 +355,12 @@ std::error_code remove(const Twine &path, bool IgnoreNonExisting) {
 
 static bool is_local_impl(struct STATVFS &Vfs) {
 #if defined(__linux__)
+#ifndef NFS_SUPER_MAGIC
+#define NFS_SUPER_MAGIC 0x6969
+#endif
+#ifndef SMB_SUPER_MAGIC
+#define SMB_SUPER_MAGIC 0x517B
+#endif
 #ifndef CIFS_MAGIC_NUMBER
 #define CIFS_MAGIC_NUMBER 0xFF534D42
 #endif